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  • 1.
    Bortolan, Lorenzo
    et al.
    Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; CeRiSM, Sport Mountain and Health Research Centre, University of Verona, Rovereto, Italy.
    Savoldelli, Aldo
    Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; CeRiSM, Sport Mountain and Health Research Centre, University of Verona, Rovereto, Italy.
    Pellegrini, Barbara
    Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; CeRiSM, Sport Mountain and Health Research Centre, University of Verona, Rovereto, Italy.
    Modena, Roberto
    Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; CeRiSM, Sport Mountain and Health Research Centre, University of Verona, Rovereto, Italy.
    Sacchi, Massimiliano
    Oberalp S.p.A., Bolzano, Italy.
    Holmberg, Hans-Christer
    Luleå University of Technology, Department of Health, Learning and Technology, Health, Medicine and Rehabilitation.
    Supej, Matej
    Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia.
    Ski Mountaineering: Perspectives on a Novel Sport to Be Introduced at the 2026 Winter Olympic Games2021In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 12, article id 737249Article in journal (Refereed)
    Abstract [en]

    Ski mountaineering is a rapidly growing winter sport that involves alternately climbing and descending slopes and various racing formats that differ in length and total vertical gain, as well as their distribution of downhill and uphill sections. In recent years, both participation in and media coverage of this sport have increased dramatically, contributing, at least in part, to its inclusion in the 2026 Winter Olympics in Milano-Cortina. Here, our aim has been to briefly describe the major characteristics of ski mountaineering, its physiological and biomechanical demands, equipment, and training/testing, as well as to provide some future perspectives. Despite its popularity, research on this discipline is scarce, but some general characteristics are already emerging. Pronounced aerobic capacity is an important requirement for success, as demonstrated by positive correlations between racing time and maximal oxygen uptake and oxygen uptake at the second ventilatory threshold. Moreover, due to the considerable mechanical work against gravity on demanding uphill terrain, the combined weight of the athlete and equipment is inversely correlated with performance, prompting the development of both lighter and better equipment in recent decades. In ski mountaineering, velocity uphill is achieved primarily by more frequent (rather than longer) strides due primarily to high resistive forces. The use of wearable technologies, designed specifically for analysis in the field (including at elevated altitudes and cold temperatures) and more extensive collaboration between researchers, industrial actors, and coaches/athletes, could further improve the development of this sport.

     

  • 2.
    Calbet, Jose A. L.
    et al.
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain; IUIBS, Res Inst Biomed & Hlth Sci, Las Palmas Gran Canaria, Spain.
    Ponce-Gonzalez, Jesus G.
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain.
    de la Calle-Herrero, Jaime
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain.
    Perez-Suarez, Ismael
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain; IUIBS, Res Inst Biomed & Hlth Sci, Las Palmas Gran Canaria, Spain..
    Martin-Rincon, Marcos
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain; IUIBS, Res Inst Biomed & Hlth Sci, Las Palmas Gran Canaria, Spain.
    Santana, Alfredo
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain; IUIBS, Res Inst Biomed & Hlth Sci, Las Palmas Gran Canaria, Spain.
    Morales-Alamo, David
    Univ Las Palmas Gran Canaria, Dept Phys Educ, Las Palmas Gran Canaria, Spain; IUIBS, Res Inst Biomed & Hlth Sci, Las Palmas Gran Canaria, Spain.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Exercise Preserves Lean Mass and Performance during Severe Energy Deficit: The Role of Exercise Volume and Dietary Protein Content2017In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 8, article id 483Article in journal (Refereed)
    Abstract [en]

    The loss of fat-free mass (FFM) caused by very-low-calorie diets (VLCD) can be attenuated by exercise. The aim of this study was to determine the role played by exercise and dietary protein content in preserving the lean mass and performance of exercised and non-exercised muscles, during a short period of extreme energy deficit (similar to 23 MJ deficit/day). Fifteen overweight men underwent three consecutive experimental phases: baseline assessment (PRE), followed by 4 days of caloric restriction and exercise (CRE) and then 3 days on a control diet combined with reduced exercise (CD). During CRE, the participants ingested a VLCD and performed 45 min of one-arm cranking followed by 8 h walking each day. The VLCD consisted of 0.8 g/kg body weight/day of either whey protein (PRO, n = 8) or sucrose (SU, n = 7). FFM was reduced after CRE (P < 0.001), with the legs and the exercised arm losing proportionally less FFM than the control arm [57% (P < 0.05) and 29% (P = 0.05), respectively]. Performance during leg pedaling, as reflected by the peak oxygen uptake and power output (Wpeak), was reduced after CRE by 15 and 12%, respectively (P < 0.05), and recovered only partially after CD. The deterioration of cycling performance was more pronounced in the whey protein than sucrose group (P < 0.05). Wpeak during arm cranking was unchanged in the control arm, but improved in the contralateral arm by arm cranking. There was a linear relationship between the reduction in whole-body FFM between PRE and CRE and the changes in the cortisol/free testosterone ratio (C/FT), serum isoleucine, leucine, tryptophan, valine, BCAA, and EAA (r = -0.54 to -0.71, respectively, P < 0.05). C/FT tended to be higher in the PRO than the SU group following CRE (P = 0.06). In conclusion, concomitant low-intensity exercise such as walking or arm cranking even during an extreme energy deficit results in remarkable preservation of lean mass. The intake of proteins alone may be associated with greater cortisol/free testosterone ratio and is not better than the ingestion of only carbohydrates for preserving FFM and muscle performance in interventions of short duration.

  • 3.
    Cardinale, Daniele A.
    et al.
    Swedish Sch Sport & Hlth Sci, Stockholm.
    Larsen, Filip J.
    Swedish Sch Sport & Hlth Sci, Stockholm.
    Schiffer, Tomas A.
    Karolinska Inst, Stockholm.
    Morales-Alamo, David
    Univ Las Palmas Gran Canaria, Las Palmas Gran Canaria, Spain; Res Inst Biomed & Hlth Sci IUIBS, Las Palmas De Gran Canad, Gran Canaria, Spain.
    Ekblom, Bjorn
    Swedish Sch Sport & Hlth Sci, Stockholm.
    Calbet, Jose A. L.
    Univ Las Palmas Gran Canaria, Las Palmas Gran Canaria, Spain; Res Inst Biomed & Hlth Sci IUIBS, Las Palmas De Gran Canad, Gran Canaria, Spain; Univ British Columbia, Vancouver, BC, Canada.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Boushel, Robert
    Univ British Columbia, Vancouver, BC, Canada.
    Superior Intrinsic Mitochondria Respiration in Women Than in Men2018In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 9, no AUG, article id 1133Article in journal (Refereed)
    Abstract [en]

    Sexual dimorphism is apparent in humans, however, to date no studies have investigated mitochondria! function focusing on intrinsic mitochondrial respiration (i.e., mitochondrial respiration for a given amount of mitochondrial protein) and mitochondrial oxygen affinity (p50(mito)) in relation to biological sex in human. A skeletal muscle biopsy was donated by nine active women, and ten men matched for maximal oxygen consumption (VO2max) and by nine endurance trained men. Intrinsic mitochondrial respiration, assessed in isolated mitochondria, was higher in women compared to men when activating complex I (Cl-p) and complex I+II(Cl+IIp) (p < 0.05), and was similar to trained men (Cl-p, p = 0.053; Cl+IIp, p = 0.066). Proton leak and p50(mito) to were higher in women compared to men independent of VO2max. In conclusion, significant novel differences in mitochondrial oxidative function, intrinsic mitochondrial respiration and p50(mito) to exist between women and men. These findings may represent an adaptation in the oxygen cascade in women to optimize muscle oxygen uptake to compensate for a lower oxygen delivery during exercise.

  • 4.
    Dueking, Peter
    et al.
    Univ Wurzburg, Inst Sport Sci, Dept Sports Sci, Integrat & Expt Training Sci, D-97070 Wurzburg, Germany.
    Hotho, Andreas
    Univ Wurzburg, Data Min & Informat Retrieval Grp, Comp Sci Artificial Intelligence & Appl Comp Sci, D-97070 Wurzburg, Germany.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Fuss, Franz Konstantin
    RMIT Univ, Sch Engn, Dept Mech & Automot Engn, Melbourne, Vic, Australia.
    Sperlich, Billy
    Univ Wurzburg, Inst Sport Sci, Dept Sports Sci, Integrat & Expt Training Sci, D-97070 Wurzburg, Germany.
    Comparison of Non-Invasive Individual Monitoring of the Training and Health of Athletes with Commercially Available Wearable Technologies2016In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 7, article id 71Article, review/survey (Refereed)
    Abstract [en]

    Athletes adapt their training daily to optimize performance, as well as avoid fatigue, overtraining and other undesirable effects on their health. To optimize training load, each athlete must take his/her own personal objective and subjective characteristics into consideration and an increasing number of wearable technologies (wearables) provide convenient monitoring of various parameters. Accordingly, it is important to help athletes decide which parameters are of primary interest and which wearables can monitor these parameters most effectively. Here, we discuss the wearable technologies available for non-invasive monitoring of various parameters concerning an athlete's training and health. On the basis of these considerations, we suggest directions for future development. Furthermore, we propose that a combination of several wearables is most effective for accessing all relevant parameters, disturbing the athlete as little as possible, and optimizing performance and promoting health.

  • 5.
    Düking, Peter
    et al.
    Julius Maximilians Univ, Wurzburg, Germany.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Sperlich, Billy
    Julius Maximilians Univ, Wurzburg, Germany.
    Instant biofeedback provided by wearable sensor technology can help to optimize exercise and prevent injury and overuse2017In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 8, no APR, article id 167Article in journal (Refereed)
  • 6.
    Düking, Peter
    et al.
    University of Würzburg, Würzburg, Germany.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Sperlich, Billy
    University of Würzburg, Würzburg, Germany.
    The potential usefulness of virtual reality systems for athletes: A short SWOT analysis2018In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 9, no MAR, article id 128Article in journal (Refereed)
  • 7.
    Ekenros, Linda
    et al.
    Department of Neurobiology, Care Sciences and Society, Division of Physiotherapy Karolinska Institutet, Huddinge, Sweden.
    von Rosen, Philip
    Department of Neurobiology, Care Sciences and Society, Division of Physiotherapy Karolinska Institutet, Huddinge, Sweden.
    Solli, Guro Strøm
    School of Sport Sciences, UiT, the Arctic University of Norway, Tromsø, Norway; Department of Sports Science and Physical Education, Nord University, Bodø, Norway.
    Sandbakk, Øyvind
    School of Sport Sciences, UiT, the Arctic University of Norway, Tromsø, Norway; Department of Neuromedicine and Movement Science, Centre for Elite Sports Research, Norwegian University of Science and Technology, Trondheim, Norway.
    Holmberg, Hans-Christer
    Luleå University of Technology, Department of Health, Learning and Technology, Health, Medicine and Rehabilitation. Department of Physiology and Pharmacology, Biomedicum C5, Karolinska Institutet, Stockholm, Sweden.
    Hirschberg, Angelica Lindén
    Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden; Department of Gynecology and Reproductive Medicine, Karolinska University Hospital, Stockholm, Sweden.
    Fridén, Cecilia
    Department of Neurobiology, Care Sciences and Society, Division of Physiotherapy Karolinska Institutet, Huddinge, Sweden; Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden.
    Perceived impact of the menstrual cycle and hormonal contraceptives on physical exercise and performance in 1,086 athletes from 57 sports2022In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 13, article id 954760Article in journal (Refereed)
    Abstract [en]

    Female athletes train and compete under the potential influence of hormonal fluctuations during the menstrual cycle or during use of various hormonal contraceptives. Dysmenorrhea and premenstrual symptoms are common in the general population, as well as side effects of hormonal contraceptives. More detailed knowledge concerning prevalence and perceived impact of these symptoms on training and performance in different sports is required. The aim of the study was to 1) characterize perceptions of training and performance during the menstrual cycle phases and by hormonal contraceptive use in a large population of female athletes; 2) explore whether symptoms experienced are related to perceived performance; and 3) examine potential differences in these factors between athletes at different levels of performance. The study was based on self-reported data from 1,086 athletes from 57 sports at different performance levels via a web-based questionnaire. Thirty-seven percent (n = 407) of the athletes did not use hormonal contraceptives. In this group, menstrual cycle related symptoms were common across all athlete levels, particularly dysmenorrhea (74%, n = 300) and premenstrual symptoms (78%, n = 318), which also influenced perceived performance of aerobic fitness, muscle strength, mental sharpness, balance, and sleep quality. Sixty-three percent (n = 679) of the athletes used various hormonal contraceptives and 40% (n = 272) perceived a variety of side-effects. Physical performance was experienced equally independent of time-point of the pill-chart except for the period of inactive pills, which was associated with more negative impact. Nonetheless, only 18% (n = 191) of the athletes considered menstrual cycle or hormonal contraceptive issues when planning their training or competitions. These results indicate that greater focus is needed to identify and effectively treat different menstrual cycle and hormonal contraceptive related symptoms on an individual level.

  • 8.
    Gejl, Kasper D.
    et al.
    Department of Sports Science and Clinical Biomechanics, Faculty of Health Sciences, University of Southern Denmark, Denmark.
    Hvid, Lars G.
    Section for Sports Science, Department of Public Health, Faculty of Health, Aarhus University, Denmark.
    Andersson, Erik P.
    Swedish Winter Sports Research Centre, Mid Sweden University, Sweden; School of Sport Sciences, Faculty of Health Sciences, UiT the Arctic University of Norway, Norway.
    Jensen, Rasmus
    Department of Sports Science and Clinical Biomechanics, Faculty of Health Sciences, University of Southern Denmark, Denmark.
    Holmberg, Hans-Christer
    Luleå University of Technology, Department of Health, Learning and Technology, Health, Medicine and Rehabilitation. Swedish Winter Sports Research Centre, Mid Sweden University, Sweden; Department of Physiology and Pharmacology, Karolinska Institutet, Sweden.
    Ørtenblad, Niels
    Department of Sports Science and Clinical Biomechanics, Faculty of Health Sciences, University of Southern Denmark, Denmark.
    Contractile Properties of MHC I and II Fibers From Highly Trained Arm and Leg Muscles of Cross-Country Skiers2021In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 12, article id 682943Article in journal (Refereed)
    Abstract [en]

    Little is known about potential differences in contractile properties of muscle fibers of the same type in arms and legs. Accordingly, the present study was designed to compare the force-generating capacity and Ca2+ sensitivity of fibers from arm and leg muscles of highly trained cross-country skiers. Method: Single muscle fibers of m. vastus lateralis and m. triceps brachii of 8 highly trained cross-country skiers were analyzed with respect to maximal Ca2+-activated force, specific force and Ca2+ sensitivity. Result: The maximal Ca2+-activated force was greater for MHC II than MHC I fibers in both the arm (+62 %, P < 0.001) and leg muscle (+77 %, P < 0.001), with no differences between limbs for each MHC isoform. In addition, the specific force of MHC II fibers was higher than that of MHC I fibers in both arms (+41 %, P = 0.002) and legs (+95 %, P < 0.001). The specific force of MHC II fibers was the same in both limbs, whereas MHC I fibers from the m. triceps brachii were, on average, 39% stronger than fibers of the same type from the m. vastus lateralis (P = 0.003). pCa50 was not different between MHC I and II fibers in neither arms nor legs, but the MHC I fibers of m. triceps brachii demonstrated higher Ca2+ sensitivity than fibers of the same type from m. vastus lateralis (P = 0.007). Conclusion: Comparison of muscles in limbs equally well trained revealed that MHC I fibers in the arm muscle exhibited a higher specific force-generating capacity and greater Ca2+ sensitivity than the same type of fiber in the leg, with no such difference in the case of MHC II fibers. These distinct differences in the properties of fibers of the same type in equally well-trained muscles open new perspectives in muscle physiology.

  • 9.
    Gejl, Kasper Degn
    et al.
    Univ Southern Denmark, Dept Sports Sci & Clin Biomech, Odense, Denmark..
    Andersson, Erik P.
    Mittuniversitetet, Institutionen för hälsovetenskap.
    Nielsen, Joachim
    Univ Southern Denmark, Dept Sports Sci & Clin Biomech, Odense, Denmark..
    Holmberg, Hans-Christer
    Mittuniversitetet, Institutionen för hälsovetenskap.
    Ortenblad, Niels
    Univ Southern Denmark, Dept Sports Sci & Clin Biomech, Odense, Denmark..
    Effects of Acute Exercise and Training on the Sarcoplasmic Reticulum Ca(2+)Release and Uptake Rates in Highly Trained Endurance Athletes2020In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 11, article id 810Article in journal (Refereed)
    Abstract [en]

    Little is presently known about the effects of acute high-intensity exercise or training on release and uptake of Ca(2+)by the sarcoplasmic reticulum (SR). The aims here were to characterize this regulation in highly trained athletes following (1) repeated bouts of high-intensity exercise and (2) a period of endurance training including high-intensity sessions. Eleven cross-country skiers (25 +/- 4 years, 65 +/- 4 mL O-2.kg(-1).min(-1)) performed four self-paced sprint time-trials (STT 1-4) lasting approximate to 4 min each (STT 1-4) and separated by 45 min of recovery; while 19 triathletes and road cyclists (25 +/- 4 years, 65 +/- 5 mL O-2.kg(-1).min(-1)) completed 4 weeks of endurance training in combination with three sessions of high-intensity interval cycling per week. Release (mu mol.g(-1)prot.min(-1)) and uptake [tau (s)] of Ca(2+)by SR vesicles isolated from m.triceps brachiiand m.vastus lateraliswere determined before and after STT 1 and 4 in the skiers and in m.vastus lateralisbefore and after the 4 weeks of training in the endurance athletes. The Ca(2+)release rate was reduced by 17-18% in both limbs already after STT 1 (arms: 2.52 +/- 0.74 to 2.08 +/- 0.60; legs: 2.41 +/- 0.45 to 1.98 +/- 0.51,P< 0.0001) and attenuated further following STT 4 (arms: 2.24 +/- 0.67 to 1.95 +/- 0.45; legs: 2.13 +/- 0.51 to 1.83 +/- 0.36,P< 0.0001). Also, there was a tendency toward an impairment in the SR Ca(2+)uptake from pre STT1 to post STT4 in both arms and legs (arms: from 22.0 +/- 3.7 s to 25.3 +/- 6.0 s; legs: from 22.5 +/- 4.7 s to 25.5 +/- 7.7 s,P= 0.05). Endurance training combined with high-intensity exercise increased the Ca(2+)release rate by 9% (1.76 +/- 0.38 to 1.91 +/- 0.44,P= 0.009), without altering the Ca(2+)uptake (29.6 +/- 7.0 to 29.1 +/- 8.7 s;P= 0.98). In conclusion, the Ca(2+)release and uptake rates by SR in exercising limbs of highly trained athletes declines gradually by repetitive bouts of high-intensity exercise. We also demonstrate, for the first time, that the SR Ca(2+)release rate can be enhanced by a specific program of training in highly trained athletes, which may have important implications for performance parameters.

  • 10.
    Gilgien, Matthias
    et al.
    Norwegian Sch Sport Sci, Oslo, Norway; Norwegian Ski Federat, Alpine Skiing, Oslo, Norway.
    Reid, Robert
    Norwegian Ski Federat, Alpine Skiing, Oslo, Norway.
    Raschner, Christian
    Univ Innsbruck, Olymp Training Ctr, Innsbruck, Austria.
    Supej, Matej
    Univ Ljubljana, Ljubljana, Slovenia.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    The Training of Olympic Alpine Ski Racers2018In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 9, article id 1772Article in journal (Refereed)
    Abstract [en]

    Alpine combined was the only alpine ski racing event at the first Winter Olympic Games in 1936, but since then, slalom, giant slalom, super-G, downhill, and team events have also become Olympic events. Substantial improvements in slope preparation, design of courses, equipment, and the skills of Olympic alpine skiers have all helped this sport attain its present significance. Improved snow preparation has resulted in harder surfaces and improved equipment allows a more direct interaction between the skier and snow. At the same time, courses have become more challenging, with technical disciplines requiring more pronounced patterns of loading - unloading, with greater ground reaction forces. Athletes have adapted their training to meet these new demands, but little is presently known about these adaptations. Here, we describe how Olympic athletes from four of the major alpine ski racing nations prepared for the Olympic Games in South Korea in 2018. This overview describes their typical exercise programs with respect to physical conditioning, ski training and periodization, based on interviews with the coaching staff. Alpine ski racing requires mastery of a broad spectrum of physical, technical, mental, and social skills. We describe how athletes and teams deal with the multifactorial nature of the training required. Special emphasis is placed on sport-specific aspects, such as the combination of stimuli that interfere with training, training with chronic injury, training at altitude and in cold regions, the efficiency and effectiveness of ski training and testing, logistic challenges and their effects on fatigue, including the stress of frequent traveling. Our overall goal was to present as complete a picture of the training undertaken by Olympic alpine skiers as possible and on the basis of these findings propose how training for alpine ski racing might be improved.

  • 11.
    Kunz, Philipp
    et al.
    University of Würzburg, Würzburg, Germany.
    Zinner, Christoph
    University of Applied Sciences for Police and Administration of Hesse, Wiesbaden, Germany.
    Holmberg, Hans-Christer
    Mittuniversitetet, Institutionen för hälsovetenskap.
    Sperlich, Billy
    University of Würzburg, Würzburg, Germany.
    Intra- and Post-match Time-Course of Indicators Related to Perceived and Performance Fatigability and Recovery in Elite Youth Soccer Players2019In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 10, article id 1383Article in journal (Refereed)
    Abstract [en]

    Purpose: Our aims were to examine (i) the internal load during simulated soccer match-play by elite youth players; and (ii) the time-course of subsequent recovery from perceived and performance fatigability. Methods: Eleven male youth players (16 ± 1 years, 178 ± 7 cm, 67 ± 7 kg) participated in a 2 × 40-min simulated soccer match, completing 30 rounds (160 s each) with every round including multidirectional and linear sprinting (LS20m), jumping (CMJ) and running at different intensities. During each round, LS20m, CMJ, agility, heart rate (HR), oxygen uptake (VO2), energy expenditure (EE), substrate utilization and perceived exertion RPE were assessed. In addition, the blood level of lactate (Lac) was obtained after each of the five rounds. Creatine kinase (CK) concentration, maximal voluntary isometric knee extension and flexion, CMJ, number of skippings in 30 s, and subjective ratings on the Acute Recovery and Stress Scale (ARSS) were examined before and immediately, 24 and 48 h after the simulation. Results: During the game %HRpeak (p &lt; 0.05, d = 1.08), %VO2peak (p &lt; 0.05; d = 0.68), Lac (p &lt; 0.05, d = 2.59), RPEtotal (p &lt; 0.05, d = 4.59), and RPElegs (p &lt; 0.05, d = 4.45) all increased with time during both halves (all p &lt; 0.05). Agility improved (p &lt; 0.05, d = 0.70) over the time-course of the game, with no changes in LS20m (p ≥ 0.05, d = 0.34) or CMJ (p ≥ 0.05, d = 0.27). EE was similar during both halves (528 ± 58 vs. 514 ± 61 kcal; p = 0.60; d = 0.23), with 62% (second half: 65%) carbohydrate, 9% (9%) protein and 26% (27%) fat utilization. With respect to recovery, maximal voluntary knee extension (p ≥ 0.05, d = 0.50) and flexion force (p ≥ 0.05, d = 0.19), CMJ (p ≥ 0.05, d = 0.13), number of ground contacts (p ≥ 0.05, d = 0.57) and average contact time (p ≥ 0.05, d = 0.39) during 30-s of skipping remained unaltered 24 and 48 h after the game. Most ARSS dimensions of load (p &lt; 0.05, d = 3.79) and recovery (p &lt; 0.05, d = 3.22) returned to baseline levels after 24 h of recovery. Relative to baseline values, CK was elevated immediately and 24 h after (p &lt; 0.05, d = 2.03) and normalized 48 h later. Conclusion: In youth soccer players the simulated match evoked considerable circulatory, metabolic and perceptual load, with an EE of 1042 ± 118 kcal. Among the indicators of perceived and performance fatigability examined, the level of CK and certain subjective ratings differed considerably immediately following or 24–48 h after a 2 × 40-min simulated soccer match in comparison to baseline. Accordingly, monitoring these variables may assist coaches in assessing a U17 player’s perceived and performance fatigability in connection with scheduling training following a soccer match. 

  • 12.
    Laaksonen, Marko
    et al.
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Jonsson, Malin
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    The Olympic biathlon – Recent advances and perspectives after Pyeongchang2018In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 9, no JUL, article id 796Article in journal (Refereed)
    Abstract [en]

    The biathlon, combining cross-country ski skating with rifle marksmanship, has been an Olympic event since the Winter Games in Squaw Valley, United States, in 1960. As a consequence of replacing the classical with the skating technique in the 1980s, as well as considerable improvements in equipment and preparation of ski tracks and more effective training, the average biathlon skiing speed has increased substantially. Moreover, the mass-start, pursuit, and sprint races have been introduced. Indeed, two of the four current individual Olympic biathlon competitions involve mass-starts, where tactics play a major role and the outcome is often decided during the last round of shooting or final sprint. Biathlon is a demanding endurance sport requiring extensive aerobic capacity. The wide range of speeds and slopes involved requires biathletes to alternate continuously between and adapt different skating sub-techniques duringraces, a technical complexity that places a premium on efficiency. Although the relative amounts of endurance training at different levels of intensity have remained essentially constant during recent decades, today’s biathletes perform more specific endurance training on roller skis on terrain similar to that used for competition, with more focus on the upper-body, systematic strength and power training and skiing at higher speeds. Success in the biathlon also requires accurate and rapid shooting while simultaneously recovering from high-intensity skiing. Many different factors, including body sway, triggering behavior, and even psychology, influence the shooting performance. Thus, the complexity of biathlon deserves a greater research focus on areas such as race tactics, skating techniques, or shooting process.

  • 13.
    Marsland, Finn
    et al.
    Univ Canberra, Canberra, ACT, Australia; Australian Inst Sport, Canberra, ACT, Australia.
    Anson, Judith
    Univ Canberra, Canberra, ACT, Australia.
    Waddington, Gordon
    Univ Canberra, Canberra, ACT, Australia.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Chapman, Dale W.
    Univ Canberra, Canberra, ACT, Australia; Australian Inst Sport, Canberra, ACT, Australia.
    Macro-Kinematic Differences Between Sprint and Distance Cross-Country Skiing Competitions Using the Classical Technique2018In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 9, no MAY, article id 570Article in journal (Refereed)
    Abstract [en]

    We compare the macro-kinematics of six elite female cross-country skiers competing in 1.1-km Sprint and 10.5-km Distance classical technique events on consecutive days under similar weather and track conditions. The relative use of double pole (DP), kick-double pole (KDP), diagonal stride (DS), tucking (Tuck) and turning (Turn) sub-techniques, plus each technique's respective velocities, cycle lengths and cycle rates were monitored using a single micro-sensor unit worn by each skier during the Sprint qualification, semi-final and finals, and multiple laps of the Distance race. Over a 1.0-km section of track common to both Sprint and Distance events, the mean race velocity, cyclical sub-technique velocities, and cycle rates were higher during the Sprint race, while Tuck and Turn velocities were similar. Velocities with KDP and DS on the common terrain were higher in the Sprint (KDP +12%, DS +23%) due to faster cycle rates (KDP +8%, DS +11 %) and longer cycle lengths (KDP +5%, DS +10%), while the DP velocity was higher (+8%) with faster cycle rate (+16%) despite a shorter cycle length (-9%). During the Sprint the percentage of total distance covered using DP was greater (+15%), with less use of Tuck (-19%). Across all events and rounds, DP was the most used sub-technique in terms of distance, followed by Tuck, DS, Turn and KDP. KDP was employed relatively little, and during the Sprint by only half the participants. Tuck was the fastest sub-technique followed by Turn, DP, KDP, and DS, These findings reveal differences in the macro-kinematic characteristics and strategies utilized during Sprint and Distance events, confirm the use of higher cycle rates in the Sprint, and increase our understanding of the performance demands of cross-country skiing competition.

  • 14.
    McGawley, Kerry
    et al.
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Juudas, Elisabeth
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Kazior, Zuzanna
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Ström, Kristoffer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Blomstrand, Eva
    Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden.
    Hansson, Ola
    Lunds Universitet.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    No additional benefits of block-over evenly-distributed high-intensity interval training within a polarized microcycle2017In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 8, no JUN, p. 1-12, article id 413Article in journal (Refereed)
    Abstract [en]

    Introduction: The current study aimed to investigate the responses to block- versus evenly-distributed high-intensity interval training (HIT) within a polarized microcycle. Methods: Twenty well-trained junior cross-country skiers (10 males, age 17.6 ± 1.5 and 10 females, age 17.3 ± 1.5) completed two, 3-week periods of training (EVEN and BLOCK) in a randomized, crossover-design study. In EVEN, 3 HIT sessions (5 × 4-min of diagonal-stride roller-skiing) were completed at a maximal sustainable intensity each week while low-intensity training (LIT) was distributed evenly around the HIT. In BLOCK, the same 9 HIT sessions were completed in the second week while only LIT was completed in the first and third weeks. Heart rate (HR), session ratings of perceived exertion (sRPE), and perceived recovery (pREC) were recorded for all HIT and LIT sessions, while distance covered was recorded for each HIT interval. The recovery-stress questionnaire for athletes (RESTQ-Sport) was completed weekly. Before and after EVEN and BLOCK, resting saliva and muscle samples were collected and an incremental test and 600-m time-trial (TT) were completed. Results: Pre- to post-testing revealed no significant differences between EVEN and BLOCK for changes in resting salivary cortisol, testosterone, or IgA, or for changes in muscle capillary density, fiber area, fiber composition, enzyme activity (CS, HAD, and PFK) or the protein content of VEGF or PGC-1α. Neither were any differences observed in the changes in skiing economy, VO2max or 600-m time-trial performance between interventions. These findings were coupled with no significant differences between EVEN and BLOCK for distance covered during HIT, summated HR zone scores, total sRPE training load, overall pREC or overall recovery-stress state. However, 600-m TT performance improved from pre- to post-training, irrespective of intervention (P = 0.003), and a number of hormonal and muscle biopsy markers were also significantly altered post-training (P < 0.05). Discussion: The current study shows that well-trained junior cross-country skiers are able to complete 9 HIT sessions within 1 week without compromising total work done and without experiencing greater stress or reduced recovery over a 3-week polarized microcycle. However, the findings do not support block-distributed HIT as a superior method to a more even distribution of HIT in terms of enhancing physiological or performance adaptions.

  • 15.
    Ogrin, J.
    et al.
    Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia.
    Šarabon, N.
    Faculty of Health Sciences, University of Primorska, Izola, Slovenia; S2P, Science to Practice, Ltd., Laboratory for Motor Control and Motor Behavior, Ljubljana, Slovenia.
    Madsen, M. K.
    Department of Health Science and Technology, Sport Sciences – Performance and Technology, Aalborg University, Aalborg, Denmark.
    Kersting, U.
    Department of Health Science and Technology, Sport Sciences – Performance and Technology, Aalborg University, Aalborg, Denmark; Institute of Biomechanics and Orthopedics, German Sport University Cologne, Cologne, Germany.
    Holmberg, Hans-Christer
    Department of Physiology and Pharmacology, Biomedicum C5, Karolinska Institute, Stockholm, Sweden; China Institute of Sport and Health Science, Beijing Sport University, Beijing, China.
    Supej, Matej
    Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia; Swedish Winter Sports Research Centre, Mid Sweden University, Östersund, Sweden.
    Asymmetries in Ground Reaction Forces During Turns by Elite Slalom Alpine Skiers Are Not Related to Asymmetries in Muscular Strength2021In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 12, article id 577698Article in journal (Refereed)
    Abstract [en]

    The ground reaction forces (GRF) associated with competitive alpine skiing, which are relatively large, might be asymmetric during left and right turns due to asymmetries in the strength of the legs and torso and the present investigation was designed to evaluate this possibility. While skiing a symmetrical, 20-gate slalom course, the asymmetries of 9 elite alpine skiers were calculated on the basis of measurements provided by inertial motion units (IMU), a Global Navigation Satellite System and pressure insoles. In addition, specialized dynamometers were utilized to assess potential asymmetry in the strength of their legs and torso in the laboratory. In total, seven variables related to GRF were assessed on-snow and eight related to strength of the legs and torso in the laboratory. The asymmetries in these parameters between left and right turns on snow were expressed in terms of the symmetry (SI) and Jaccard indices (JI), while the asymmetries between the left and right sides of the body in the case of the laboratory measurements were expressed as the SIs. The three hypotheses to be tested were examined using multivariable regression models. Our findings resulted in rejection of all three hypotheses: The asymmetries in total GRF (H1), as well as in the GRF acting on the inside and outside legs (H2) and on the rear- and forefeet GRF (H3) during left and right turns were not associated with asymmetries in parameters related to muscular strength. Nevertheless, this group of elite slalom skiers exhibited significant asymmetry between their right and left legs with respect to MVC during ankle flexion (0.53 ± 0.06 versus 0.60 ± 0.07 Nm/kg, respectively) and hip extension (2.68 ± 0.39 versus 2.17 ± 0.26 Nm/kg), as well as with respect to the GRFs on the inside leg while skiing (66.8 ± 7.39 versus 76.0 ± 10.0 %BW). As indicated by the JI values, there were also large asymmetries related to GRF as measured by pressure insoles (range: 42.7–56.0%). In conclusion, inter-limb asymmetries in GRFs during elite alpine skiing are not related to corresponding asymmetries in muscular strength. Although our elite athletes exhibited relatively small inter-limb asymmetries in strength, their asymmetries in GRF on-snow were relatively large. 

  • 16.
    Ortenblad, Niels
    et al.
    Univ Southem Denmark, Odense, Denmark; Univ British Columbia, Vancouver, BC, Canada.
    Nielsen, Joachim
    Univ Southem Denmark, Odense, Denmark.
    Boushel, Robert
    Univ British Columbia, Vancouver, BC, Canada.
    Söderlund, Karin
    Swedish Sch Sport & Hlth Sci, Astrand Lab, Stockholm.
    Saltin, Bengt
    Copenhagen Muscle Res Ctr, Copenhagen, Denmark.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    The Muscle Fiber Profiles, Mitochondrial Content, and Enzyme Activities of the Exceptionally Well-Trained Arm and Leg Muscles of Elite Cross-Country Skiers2018In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 9, no AUG, article id 1031Article in journal (Refereed)
    Abstract [en]

    As one of the most physically demanding sports in the Olympic Games, cross-country skiing poses considerable challenges with respect to both force generation and endurance during the combined upper-and lower-body effort of varying intensity and duration. The isoforms of myosin in skeletal muscle have long been considered not only to define the contractile properties, but also to determine metabolic capacities. The current investigation was designed to explore the relationship between these isoforms and metabolic profiles in the arms (triceps brachii) and legs (vastus lateralis) as well as the range of training responses in the muscle fibers of elite cross-country skiers with equally and exceptionally well-trained upper and lower bodies. The proportion of myosin heavy chain (MHC)-1 was higher in the leg (58 +/- 2% [34-69%]) than arm (40 +/- 3% [24-57%]), although the mitochondrial volume percentages [8.6 +/- 1.6 (leg) and 9.0 +/- 2.0 (arm)], and average number of capillaries per fiber [5.8 +/- 0.8 (leg) and 6.3 +/- 0.3 (arm)] were the same. In these comparable highly trained leg and arm muscles, the maximal citrate synthase (CS) activity was the same. Still, 3-hydroxy-acyl-CoA-dehydrogenase (HAD) capacity was 52% higher (P < 0.05) in the leg compared to arm muscles, suggesting a relatively higher capacity for lipid oxidation in leg muscle, which cannot be explained by the different fiber type distributions. For both limbs combined, HAD activity was correlated with the content of MHC-1 (r(2) = 0.32, P = 0.011), whereas CS activity was not. Thus, in these highly trained cross-country skiers capillarization of and mitochondrial volume in type 2 fiber can be at least as high as in type 1 fibers, indicating a divergence between fiber type pattern and aerobic metabolic capacity. The considerable variability in oxidative metabolism with similar MHC profiles provides a new perspective on exercise training. Furthermore, the clear differences between equally well-trained arm and leg muscles regarding HAD activity cannot be explained by training status or MHC distribution, thereby indicating an intrinsic metabolic difference between the upper and lower body. Moreover, trained type 1 and type 2A muscle fibers exhibited similar aerobic capacity regardless of whether they were located in an arm or leg muscle.

  • 17.
    Pellegrini, Barbara
    et al.
    CeRiSM Res Ctr Mt Sport & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Stöggl, Thomas Leonhard
    Univ Salzburg, Salzburg, Austria.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Developments in the Biomechanics and Equipment of Olympic Cross-Country Skiers2018In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 9, no JUL, article id 976Article in journal (Refereed)
    Abstract [en]

    Here, our aim was to describe the major changes in cross-country (XC) skiing in recent decades, as well as potential future developments. XC skiing has been an Olympic event since the very first Winter Games in Chamonix, France, in 1924. Over the past decades, considerable developments in skiing techniques and improvements in equipment and track preparation have increased skiing speed. In contrast to the numerous investigations on the physiological determinants of successful performance, key biomechanical factors have been less explored. Today's XC skier must master a wide range of speeds, terrains, and race distances and formats (e.g., distance races with individual start, mass-start or pursuit; knock-out and team-sprint; relays), continuously adapting by alternating between various sub-techniques. Moreover, several of the new events in which skiers compete head-to-head favor technical and tactical flexibility and encourage high-speed techniques (including more rapid development of propulsive force and higher peak forces), as well as appropriate training. Moreover, the trends toward more extensive use of double poling and skiing without grip wax in classical races have given rise to regulations in connection with Olympic distances that appear to have preserved utilization of the traditional classical sub-techniques. In conclusion, although both XC equipment and biomechanics have developed significantly in recent decades, there is clearly room for further improvement. In this context as well, for analyzing performance and optimizing training, sensor technology has a potentially important role to play.

  • 18.
    Sandbakk, Øyvind
    et al.
    Norwegian University of Science and Technology, Trondheim, Norway.
    Perl, Rilana
    Swiss Federal Institute of Sport, Magglingen, Switzerland.
    Holmberg, Hans-Christer
    Mittuniversitetet, Institutionen för hälsovetenskap.
    Steiner, Thomas
    Swiss Federal Institute of Sport, Magglingen, Switzerland.
    Energetic Cost and Kinematics of Pushing a Stroller on Flat and Uphill Terrain2020In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 11, article id 574Article in journal (Refereed)
    Abstract [en]

    During early parenthood, walking and/or running while pushing a stroller is a common form of endurance exercise among both recreationally active individuals and athletes. Here, we investigate how pushing a stroller influences the energetic cost, gross efficiency (GE), and kinematic behavior of well-trained men and women while walking or running on flat and uphill incline. Eight men and nine women, all recreationally active, performed three 5-min submaximal tests of walking or running during four different testing sessions, in randomized order: with and without pushing a 24.3-kg stroller on a flat (1%; 6, 8/9, and 11/12 km/h for women/men) and uphill (10%; 5, 6.5/7.5, and 7.5/8.5 km/h for women/men) incline. Respiratory parameters, heart rate (HR), blood lactate concentration, and rating of perceived exertion (RPE) were determined and video-based kinematic analysis was performed in connection with all these tests. Except while walking on the flat incline, pushing a stroller increased the energetic cost of walking/running under all conditions (all p < 0.05). This was associated with shorter and more rapid strides on both inclines (all p < 0.05); however, GE was higher when pushing the stroller (p < 0.05). The increase in energetic cost of pushing the stroller was approximately threefold higher uphill than on the flat incline, and women were influenced more than men when running uphill at the highest speed (all p < 0.05). Here, we provide novel insights on the energetic cost and kinematic behavior of pushing a stroller while walking or running on flat and uphill inclines. The energetic cost of pushing a stroller was clearly higher than for unloaded exercise, coincided by shorter and more rapid strides, and especially pronounced on uphill terrain where also women were more influenced than men. 

  • 19.
    Sperlich, B
    et al.
    University of Würzburg.
    De Clerck, Ine
    Artevelde University College Ghent, Ghent, Belgium.
    Zinner, Christoph
    Department of Sport, University of Applied Sciences for Police and Administration of Hesse, Wiesbaden, Germany.
    Holmberg, Hans-Christer
    Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden.
    Wallmann-Sperlich, Birgit
    University of Würzburg.
    Prolonged Sitting Interrupted by 6-Min of High-Intensity Exercise: Circulatory, Metabolic, Hormonal, Thermal, Cognitive, and Perceptual Responses2018In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 9, article id 1279Article in journal (Refereed)
    Abstract [en]

    The aim was to examine certain aspects of circulatory, metabolic, hormonal,

    thermoregulatory, cognitive, and perceptual responses while sitting following a brief

    session of high-intensity interval exercise. Twelve students (five men; age, 22

    2 years) performed two trials involving either simply sitting for 180 min (SIT) or sitting for this same period with a 6-min session of high-intensity exercise after 60 min (SIT CHIIT).

    At T0 (after 30 min of resting), T1 (after a 20-min breakfast), T2 (after sitting for 1 h),

    T3 (immediately after the HIIT), T4, T5, T6, and T7 (30, 60, 90, and 120 min after

    the HIIT), circulatory, metabolic, hormonal, thermoregulatory, cognitive, and perceptual

    responses were assessed. The blood lactate concentration (at T3–T5), heart rate (at

    T3–T6), oxygen uptake (at T3–T7), respiratory exchange ratio, and sensations of heat

    (T3–T5), sweating (T3, T4) and odor (T3), as well as perception of vigor (T3–T6), were

    higher and the respiratory exchange ratio (T4–T7) and mean body and skin temperatures

    (T3) lower in the SITCHIIT than the SIT trial. Levels of blood glucose and salivary cortisol,

    cerebral oxygenation, and feelings of anxiety/depression, fatigue or hostility, as well as

    the variables of cognitive function assessed by the Stroop test did not differ between

    SIT and SITCHIIT. In conclusion, interruption of prolonged sitting with a 6-min session

    of HIIT induced more pronounced circulatory and metabolic responses and improved

    certain aspects of perception, without affecting selected hormonal, thermoregulatory or

    cognitive functions.

  • 20.
    Sperlich, B
    et al.
    University of Ljubljana, Ljubljana, Slovenia.
    Ogrin, J
    University of Ljubljana, Ljubljana, Slovenia.
    Holmberg, Hans-Christer
    UiT Arctic University of Norway; University of British Columbia, Vancouver, BC, Canada; Karolinska Institutet, Stockholm, Sweden.
    Whole-Body Vibrations Associated With Alpine Skiing: A Risk Factor for Low Back Pain?2018In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 9, article id 204Article in journal (Refereed)
    Abstract [en]

    Alpine skiing, both recreational and competitive, is associated with high rates of injury. Numerous studies have shown that occupational exposure to whole-body vibrations is strongly related to lower back pain and some suggest that, in particular, vibrations of lower frequencies could lead to overuse injuries of the back in connection with alpine ski racing. However, it is not yet known which forms of skiing involve stronger vibrations and whether these exceed safety thresholds set by existing standards and directives. Therefore, this study was designed to examine whole-body vibrations connected with different types of skiing and the associated potential risk of developing low back pain. Eight highly skilled ski instructors, all former competitive ski racers and equipped with five accelerometers and a Global Satellite Navigation System to measure vibrations and speed, respectively, performed six different forms of skiing: straight running, plowing, snow-plow swinging, basic swinging, short swinging, and carved turns. To estimate exposure to periodic, random and transient vibrations the power spectrum density (PSD) and standard ISO 2631-1:1997 parameters [i.e., the weighted root-mean-square acceleration (RMS), crest factor, maximum transient vibration value and the fourth-power vibration dose value (VDV)] were calculated. Ground reaction forces were estimated from data provided by accelerometers attached to the pelvis. The major novel findings were that all of the forms of skiing tested produced whole-body vibrations, with highest PSD values of 1.5–8 Hz. Intensified PSD between 8.5 and 35 Hz was observed only when skidding was involved. The RMS values for 10 min of short swinging or carved turns, as well as all 10-min equivalent VDV values exceeded the limits set by European Directive 2002/44/EC for health and safety. Thus, whole-body vibrations, particularly in connection with high ground reaction forces, contribute to a high risk for low back pain among active alpine skiers.

  • 21.
    Sperlich, Billy
    et al.
    University of Würzburg, Würzburg, Germany.
    Aminian, Kamiar
    Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
    Düking, Peter
    University of Würzburg, Würzburg, Germany.
    Holmberg, Hans-Christer
    Mittuniversitetet, Institutionen för hälsovetenskap.
    Editorial: Wearable Sensor Technology for Monitoring Training Load and Health in the Athletic Population2020In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 10, article id 1520Article in journal (Refereed)
  • 22.
    Sperlich, Billy
    et al.
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Hahn, Lea-Sofie
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Edel, Antonia
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Behr, Tino
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Helmprobst, Julian
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Leppich, Robert
    Univ Wurzburg, Inst Sport Sci, Integrat & Expt Exercise Sci & Training, Wurzburg, Germany.
    Wallmann-Sperlich, Birgit
    Univ Wurzburg, Inst Sport Sci, Wurzburg, Germany.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    A 4-Week Intervention Involving Mobile-Based Daily 6-Minute Micro-Sessions of Functional High-Intensity Circuit Training Improves Strength and Quality of Life, but Not Cardio-Respiratory Fitness of Young Untrained Adults2018In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 9, article id e423Article in journal (Refereed)
    Abstract [en]

    The present study was designed to assess the psycho-physiological responses of physically untrained individuals to mobile-based multi-stimulating, circuit-like, multiplejoint conditioning (CircuitHiu) performed either once (IxCircuitmu) or twice (2xCircuitHiu) daily for 4 weeks. In this single-center, two-arm randomized, controlled study, 24 men and women (age: 25 +/- 5 years) first received no training instructions for 4 weeks and then performed 4 weeks of either IxCircuitnirr or 2xCircuitHiu (5 men and 7 women in each group) daily. The IxCircuitnirr and 2xCircuitHiu participants carried out 90.7 and 85.7% of all planned training sessions, respectively, with average heart rates during the 6-min sessions of 74.3 and 70.8% of maximal heart rate. Body, fat and fat-free mass, and metabolic rate at rest did not differ between the groups or between time-points of measurement. Heart rate while running at 6 km h(-1) declined after the intervention in both groups. Submaximal and peak oxygen uptake, the respiratory exchange ratio and heart rate recovery were not altered by either intervention. The maximal numbers of push-ups, leg-levers, burpees, 45 degrees-one-legged squats and 30-s skipping, as well as perception of general health improved in both groups. Our IxCircuitHiu or 2xCircuitHiiT interventions improved certain parameters of functional strength and certain dimensions of quality of life in young untrained individuals. However, they were not sufficient to enhance cardio-respiratory fitness, in particular peak oxygen uptake.

  • 23.
    Sperlich, Billy
    et al.
    University of Wurzburg, Germany.
    Wallman-Sperlich, Birgit
    University of Wurzburg, Germany.
    Zinner, Christoph
    University of Wurzburg, Germany.
    Von Stauffenberg, Valerie
    University of Wurzburg, Germany.
    Losert, Helena
    University of Wurzburg, Tyskland.
    Holmberg, Hans-Christer
    School of Sport Sciences, University of Tromsø, Norway.
    Functional High-Intensity Circuit Training Improves Body Composition, Peak Oxygen Uptake, Strength, and Alters Certain Dimensions of Quality of Life in Overweight Women2017In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 8, article id 172Article in journal (Refereed)
    Abstract [en]

    The effects of circuit-like functional high-intensity training (CircuitHIIT) alone or in combination with high-volume low-intensity exercise (Circuitcombined) on selected cardio-respiratory and metabolic parameters, body composition, functional strength and the quality of life of overweight women were compared. In this single-center, two-armed randomized, controlled study, overweight women performed 9-weeks (3 sessions·wk-1) of either CircuitHIIT (n = 11), or Circuitcombined (n = 8). Peak oxygen uptake and perception of physical pain were increased to a greater extent (p < 0.05) by CircuitHIIT, whereas Circuitcombined improved perception of general health more (p < 0.05). Both interventions lowered body mass, body-mass-index, waist-to-hip ratio, fat mass, and enhanced fat-free mass; decreased ratings of perceived exertion during submaximal treadmill running; improved the numbers of push-ups, burpees, one-legged squats, and 30-s skipping performed, as well as the height of counter-movement jumps; and improved physical and social functioning, role of physical limitations, vitality, role of emotional limitations, and mental health to a similar extent (all p < 0.05). Either forms of these multi-stimulating, circuit-like, multiple-joint training can be employed to improve body composition, selected variables of functional strength, and certain dimensions of quality of life in overweight women. However, CircuitHIIT improves peak oxygen uptake to a greater extent, but with more perception of pain, whereas Circuitcombined results in better perception of general health.

  • 24.
    Supej, Matej
    et al.
    Univ Ljubljana, Ljubljana, Slovenia.
    Holmberg, Hans-Christer
    Mittuniversitetet, Institutionen för hälsovetenskap.
    Recent Kinematic and Kinetic Advances in Olympic Alpine Skiing: Pyeongchang and Beyond2019In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 10, no FEB, article id 111Article in journal (Refereed)
    Abstract [en]

    Alpine skiing has been an Olympic event since the first Winter Games in 1936. Nowadays, skiers compete in four main events: slalom, giant slalom, super-G and downhill. Here, we present an update on the biomechanics of alpine ski racers and their equipment. The technical and tactical ability of today's world-class skiers have adapted substantially to changes in equipment, snow conditions and courses. The wide variety of terrain, slopes, gate setups and snow conditions involved in alpine skiing requires skiers to continuously adapt, alternating between the carving and skidding turning techniques. The technical complexity places a premium on minimizing energy dissipation, employing strategies and ski equipment that minimize ski-snow friction and aerodynamic drag. Access to multiple split times along the racing course, in combination with analysis of the trajectory and speed provide information that can be utilized to enhance performance. Peak ground reaction forces, which can be as high as five times body weight, serve as a measure of the external load on the skier and equipment. Although the biomechanics of alpine skiing have significantly improved, several questions concerning optimization of skiers' performance remain to be investigated. Recent advances in sensor technology that allow kinematics and kinetics to be monitored can provide detailed information about the biomechanical factors related to success in competitions. Moreover, collection of data during training and actual competitions will enhance the quality of guidelines for training future Olympic champions. At the same time, the need to individualize training and skiing equipment for each unique skier will motivate innovative scientific research for years to come.

  • 25.
    Verdel, Nina
    et al.
    Swedish Winter Sports Research Centre, Mid Sweden University, Sundsvall, Sweden; Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia.
    Hjort, Klas
    Department of Materials Science and Engineering, Uppsala University, Uppsala, Sweden.
    Sperlich, Billy
    Integrative and Experimental Exercise Science and Training, Institute of Sport Science, University of Würzburg, Würzburg, Germany.
    Holmberg, Hans-Christer
    Luleå University of Technology, Department of Health, Learning and Technology, Health, Medicine and Rehabilitation. Department of Physiology and Pharmacology, Biomedicum C5, Karolinska Institutet, Stockholm, Sweden.
    Supej, Matej
    Swedish Winter Sports Research Centre, Mid Sweden University, Sundsvall, Sweden; Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia.
    Use of smart patches by athletes: A concise SWOT analysis2023In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 14, article id 1055173Article in journal (Refereed)
    Download full text (pdf)
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  • 26.
    Zinner, Christoph
    et al.
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Morales-Alamo, David
    Univ Las Palmas Gran Canaria, Las Palmas Gran Canaria, Spain.
    Örtenblad, Niels
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Larsen, Filip J.
    Swedish Sch Sport & Hlth Sci, Stockholm.
    Schiffer, Tomas A.
    Linköping Univ, Dept Med & Hlth Sci, Linköping.
    Willis, Sarah J.
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Gelabert-Rebato, Miriam
    Univ British Columbia, Sch Kinesiol, Vancouver, BC, Canada.
    Perez-Valera, Mario
    Univ Las Palmas Gran Canaria, Las Palmas Gran Canaria, Spain.
    Boushel, Robert
    Univ British Columbia, Sch Kinesiol, Vancouver, BC, Canada.
    Calbet, Jose A. L.
    Univ British Columbia, Sch Kinesiol, Vancouver, BC, Canada; Univ Las Palmas Gran Canaria, Las Palmas Gran Canaria, Spain.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    The Physiological Mechanisms of Performance Enhancement with Sprint Interval Training Differ between the Upper and Lower Extremities in Humans2016In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 7, no SEP, article id 426Article in journal (Refereed)
    Abstract [en]

    To elucidate the mechanisms underlying the differences in adaptation of arm and leg muscles to sprint training, over a period of 11 days 16 untrained men performed six sessions of 4-6 x 30-s all-out sprints (SIT) with the legs and arms, separately, with a 1-h interval of recovery. Limb-specific VO(2)peak, sprint performance (two 30-s Wingate tests with 4-min recovery), muscle efficiency and time-trial performance (TT, 5-min all-out) were assessed and biopsies from the m. vastus lateralis and m. triceps brachii taken before and after training. VO(2)peak and Wmax increased 3-11% after training, with a more pronounced change in the arms (P < 0.05). Gross efficiency improved for the arms (+8.8%, P < 0.05), but not the legs (-0.6%). Wingate peak and mean power outputs improved similarly for the arms and legs, as did TT performance. After training, VO2 during the two Wingate tests was increased by 52 and 6% for the arms and legs, respectively (P < 0.001). In the case of the arms, VO2 was higher during the first than second Wingate test (64 vs. 44%, P < 0.05). During the TT, relative exercise intensity, HR, VO2, VCO2, V-E, and V-t were all lower during arm-cranking than leg-pedaling, and oxidation of fat was minimal, remaining so after training. Despite the higher relative intensity, fat oxidation was 70% greater during leg-pedaling (P = 0.017). The aerobic energy contribution in the legs was larger than for the arms during the Wingate tests, although VO2 for the arms was enhanced more by training, reducing the O-2 deficit after SIT. The levels of muscle glycogen, as well as the myosin heavy chain composition were unchanged in both cases, while the activities of 3-hydroxyacyl-CoA-dehydrogenase and citrate synthase were elevated only in the legs and capillarization enhanced in both limbs. Multiple regression analysis demonstrated that the variables that predict TT performance differ for the arms and legs. The primary mechanism of adaptation to SIT by both the arms and legs is enhancement of aerobic energy production. However, with their higher proportion of fast muscle fibers, the arms exhibit greater plasticity.

  • 27.
    Zoppirolli, Chiara
    et al.
    CeRiSM Res Ctr Sport Mt & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Bortolan, Lorenzo
    CeRiSM Res Ctr Sport Mt & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Stella, Federico
    CeRiSM Res Ctr Sport Mt & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Boccia, Gennaro
    Univ Turin, NeuroMuscularFunct Res Grp, Turin, Italy.
    Holmberg, Hans-Christer
    Mittuniversitetet, Avdelningen för hälsovetenskap.
    Schena, Federico
    CeRiSM Res Ctr Sport Mt & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Pellegrini, Barbara
    CeRiSM Res Ctr Sport Mt & Hlth, Rovereto, Italy; Univ Verona, Verona, Italy.
    Following a Long-Distance Classical Race the Whole-Body Kinematics of Double Poling by Elite Cross-Country Skiers Are Altered2018In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 9, no JUL, article id 978Article in journal (Refereed)
    Abstract [en]

    Introduction: Although short-term (approximately 10-min) fatiguing DP has been reported not to alter the joint kinematics or displacement of the centre of mass (COM) of high-level skiers, we hypothesize that prolonged DP does change these kinematics, since muscular strength is impaired following endurance events lasting longer than 2 h. Methods: During the 58-km Marcialonga race in 2017, the fastest 15 male skiers were videofilmed (100 fps, FHD resolution in the sagittal plane) on two 20-m sections (inclines: 0.7 +/- 0.1 degrees) 48 km apart (i.e., 7 and 55 km from the start), approximating 50-km Olympic races. The cameras were positioned perpendicular to and about 40 m from the middle of each section and spatial dimensions adjusted for each individual track skied. Pole and joint kinematics, as well as displacement of the COM during two DP cycles were assessed. Results: The 10 skiers who fulfilled our inclusion criteria finished the race in 2 h 09 min 19 s +/- 28 s. Displacements of the joints and COM were comparable to previous observations on skiers roller skiing on a flat treadmill at similar speeds in the laboratory. 55 km after the start, cycle velocity and length were lower (P < 0.001 and P = 0.002, respectively) and the angular range of elbow joint flexion during the initial part of the poling phase reduced, while shoulder angle was greater during the first 35% of the DP cycle (all P < 0.05). Moreover, the ankle angle was increased and forward displacement of the COM reduced during the first 80% of the cycle. Conclusion: Prolonged DP reduced the forward displacement of the COM and altered arm kinematics during the early poling phase. The inefficient utilization of COM observed after 2 h of competition together with potential impairment of the stretch-shortening of arm extensor muscles probably attenuated generation of poling force. To minimize these effects of fatigue, elite skiers should focus on maintaining optimal elbow and ankle kinematics and an effective forward lean during the propulsive phase of DP.

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