Vision provides important sensory input to postural control. Medical conditions and aging affect sensory—Central Nervous System (CNS) interactions, causing mismatches. Virtual Reality (VR) may address these by promoting recalibration from vision to other systems. Twenty-eight young adults (17 males, mean age 25.3 years) and 25 older adults (14 males, mean age 74.8 years) were included. Electromyography (EMG) was recorded while the participants performed, while standing, 2 control tests in quiet stance with eyes open and closed and thereafter repeatedly five times watching the same 120-second VR simulation of a rollercoaster ride. The older group watched a less challenging rollercoaster ride. Muscle activation patterns in four postural muscles; gluteus medius, medial gastrocnemius, tibialis anterior, and peroneus longus. were recorded bilaterally. The first VR session produced a marked stability challenge, reflected by significantly increased mean (p ≤ 0.008) and SD (p < 0.001) EMG amplitudes in both young and older adults in all four muscles. Both mean (p < 0.001) and SD (p < 0.001) EMG amplitudes increased more among the older adults than in young adults in all four muscles. Repeated VR sessions led to progressively decreased mean (p < 0.001) and SD (p ≤ 0.003) EMG amplitudes compare to the first VR session in both young and older adults in all muscle groups. Both age groups could quickly reduce the effects of the VR challenges when allowed to familiarize themselves with the situation during repeated sessions. Postural control adaptations enabled modulation of both the degree of muscle activation measured with EMG amplitudes and muscle group activity patterns to address stability challenges.

Immersive visual environment can deceive our interoceptive perception of how we move relative to our environment. If the visual environment or a high reliance on vision produces straining work conditions, motion sickness or is associated with a medical disorder, the causes merit addressing. Therefore, the purpose of this study was to investigate whether postural control adapts to challenging visual environments from VR by adjusting postural stability and muscle co-contractions responses and investigate associations between stability measures and postural muscle co-contractions during VR-stimulation and control tests in quiet stance. Twenty-eight young adults participated (mean age 25.3 years, SD 4.6 years). In five sessions, they watched a VR simulation of a roller coast ride while a force platform recorded postural stability and electromyography recorded muscle co-contractions in leg muscles. Two control tests (quiet stance with eyes open and eyes closed), were performed before the VR sessions. The first VR session significantly increased the postural stability energy (p ≤ 0.002) and the muscle co-contraction levels (p ≤ 0.008) compared with the eyes open control test. Repeated VR sessions produced an adaptation that decreased postural stability energy (p ≤ 0.033) and muscle co-contraction levels (p ≤ 0.028). VR-stimulation made the association between postural stability responses and muscle co-contractions more prominent. Immersive visual environments can produce marked challenges to postural control, but the repeated experiences can also initiate sensory reweighting increasing resilience to visual disturbance.

Objective: To evaluate psychometric properties of newly developed hand and wrist proprioception tests.

Design: Cross-sectional and test-retest comparisons.

Subjects/patients: Twenty-six individuals (mean age 40 years) with wrist disability (> 3 months) due to traumatic injury or general instability.

Methods: Pointing acuity (with eyes open and closed), active joint position sense (in extension, flexion, radial- and ulnar deviation) and grip force reproduction were measured by 1 rater on 2 occasions, 1 week apart. The mean absolute error was calculated for each test. Discriminative validity (affected vs non-affected hand/wrist) was evaluated by paired t-test and test-retest reliability with Intraclass Correlation Coefficient (ICC).

Results: The pointing acuity test with eyes closed gave higher errors for the affected hand/wrist (p = 0.08) and good ICCs (0.80–0.85), while the test with eyes open had poor discriminative ability (p = 0.32) and test-retest reliability (ICC 0.13–0.16). The active joint position sense test showed higher error in flexion for the affected wrist (p = 0.03), and the ICC was moderate (0.51). The remaining joint directions and the grip force reproduction test had poor discriminative ability (p = 0.21–0.94) and poor to moderate ICCs (0.00–0.65).

Conclusion: The pointing acuity test with eyes closed and the active joint position test in flexion show-ed promising results but need further evaluation in larger samples.

Sensorimotor disturbances such as disturbed cervical joint position sense (JPS) and reduced reaction time and velocity in fast cervical movements have been demonstrated in people with neck pain. While these sensorimotor functions have been assessed mainly in movement science laboratories, new sensor technology enables objective assessments in the clinic. The aim was to investigate concurrent validity of a VR-based JPS test and a new cervical reaction acuity (CRA) test. Twenty participants, thirteen asymptomatic and seven with neck pain, participated in this cross-sectional study. The JPS test, including outcome measures of absolute error (AE), constant error (CE), and variable error (VE), and the CRA test, including outcome measures of reaction time and maximum velocity, were performed using a VR headset and compared to a gold standard optical motion capture system. The mean bias (assessed with the Bland–Altman method) between VR and the gold standard system ranged from 0.0° to 2.4° for the JPS test variables. For the CRA test, reaction times demonstrated a mean bias of −19.9 milliseconds (ms), and maximum velocity a mean bias of −6.5 degrees per seconds (°/s). The intraclass correlation coefficients (ICCs) between VR and gold standard were good to excellent (ICC 0.835–0.998) for the JPS test, and excellent (ICC 0.931–0.954) for reaction time and maximum velocity for the CRA test. The results show acceptable concurrent validity for the VR technology for assessment of JPS and CRA. A slightly larger bias was observed in JPS left rotation which should be considered in future research.

Background: Postural control is dependent on the central nervous system’s accurate interpretation of sensory information to formulate and execute adequate motor actions. Research has shown that cognitive functions are associated with both postural control and fall risk, but specific associations are not established. The aim of this study was to explore how specific components of everyday postural control tasks are associated with both general and specific cognitive functions.

Methods: Forty-six community-dwelling older adults reported their age, sex, physical activity level, falls and fall-related concerns. The following cognitive aspects were assessed: global cognition, executive functions, processing speed and intraindividual variability. Postural control was quantified by measuring postural sway in quiet stance, walking at a self-selected pace, and walking while performing a concurrent arithmetical task. Separate orthogonal projections of latent structures models were generated for each postural control outcome using descriptive and cognitive variables as explanatory variables.

Results: Longer step length and faster gait speed were related to faster processing speed and less intraindividual variability in the choice reaction test. Moreover, longer step length was also related to less fall-related concerns and less severe fall-related injuries, while faster gait speed was also related to female sex and poorer global cognition. Lower dual-task cost for gait speed was explained by the executive function inhibition and faster processing speed. Postural sway in quiet stance was not explained by cognitive functions.

Conclusions: Cognitive functions explained gait speed and step length during normal walking, as well as the decrease of gait speed while performing a concurrent cognitive task. The results suggest that different cognitive processes are important for different postural control aspects. Postural sway in quiet stance, step time and gait variability seem to depend more on physical and automatic processes rather than higher cognitive functions among physically active older people. The relationships between cognitive functions and postural control likely vary depending on the specific tasks and the characteristics of different populations.

Background: Proprioception is vital for motor control and can be disturbed, for example, due to fatigue or injury. Clinical feasible, reliable and valid tests of shoulder proprioception are warranted. The aim was to investigate the effects of local fatigue on shoulder proprioception and the reliability of a feasible joint position sense test using an experimental repeated measures design.

Method: Forty participants repeated a shoulder joint position sense test to assess test–retest reliability. The test was then utilized on a subgroup of handball players who were subjected to five bouts of a repeated throwing task with the dominant hand. The effect of local fatigue was investigated by comparing the fatigued with the non-fatigued shoulder.

Results: There was a significant interaction for the arm × bout (p = 0.028, ηp2 = 0.20) and a significant effect for the arm (p = 0.034, ηp2 = 0.35) with a significant decrease in joint position sense for the throwing arm compared to the non-throwing arm. The intraclass correlation coefficient was 0.78 (95% CI = [0.57; 0.89]). The standard error of measurement between trials was 0.70° (range: 0.57°–0.90°).

Discussion: The results indicate that repeated throwing to fatigue disturbs shoulder joint position sense. Assessment with the modified test showed acceptable reliability and can be a valuable assessment tool in the clinic.

Reduced cervical range of motion (ROM) and movement velocity are often seen in people with neck pain. Objective assessment of movement characteristics is important to identify dysfunction, to inform tailored interventions, and for the evaluation of the treatment effect. The purpose of this study was to investigate the concurrent validity of a newly developed VR technology for the assessment of cervical ROM and movement velocity. VR technology was compared against a gold-standard three-dimensional optical motion capture system. Consequently, 20 people, 13 without and 7 with neck pain, participated in this quantitative cross-sectional study. ROM was assessed according to right/left rotation, flexion, extension, right/left lateral flexion, and four diagonal directions. Velocity was assessed according to fast cervical rotation to the right and left. The correlations between VR and the optical system for cervical ROM and velocity were excellent, with intraclass correlation coefficient (ICC) values > 0.95. The mean biases between VR and the optical system were ≤ 2.1° for the ROM variables, <12°/s for maximum velocity, and ≤3.0°/s for mean velocity. In conclusion, VR is a useful assessment device for ROM and velocity measurements with clinically acceptable biases. It is a feasible tool for the objective measurement of cervical kinematics in the clinic.

Background

Chronic obstructive pulmonary disease (COPD) is considered a heterogenic syndrome with systemic effects, including muscle dysfunction. There is evidence of postural control impairments among individuals with COPD, partly related to muscle weakness. However, research is scarce regarding the other underlying systems of postural control, such as the visual, somatosensory and vestibular system. The aim was to compare postural control, as well as the motor and sensory systems, between individuals with and without COPD.

Methods

Twenty-two participants with COPD (mean age 74.0 ±6.2 years) and 34 non-obstructive references (mean age 74.9 ±4.9 years) participated in this cross-sectional study. Postural control was assessed with center of pressure trajectory of postural sway in quiet as well as a limits of stability test, calculating mediolateral and anteroposterior amplitudes for each test. Assessment of function in the motor system included maximum hand grip strength, as well as maximum strength in muscles around the hip, knee and ankle joints. Visual acuity, pressure sensibility, proprioception, vestibular screening, and reaction time were also included. Data was compared between groups, and significant differences in postural control were further analyzed with an orthogonal projection of latent structures regression model.

Results

There was a significantly increased sway amplitude in the mediolateral direction in quiet stance on soft surface with eyes open (p = 0.014) as well as a smaller anteroposterior amplitude in the limits of stability test (p = 0.019) in the COPD group. Regression models revealed that the mediolateral amplitude was related to visual acuity and the burden of tobacco smoking assessed as pack-years. Further, muscle strength associated with anteroposterior amplitude in limits of stability test in the COPD group, and with age and ankle dorsal flexion strength among the referents. Besides for lower ankle plantar flexion strength in the COPD group, there were however no significant differences in muscle strength.

Conclusions

Individuals with COPD had a decreased postural control and several factors were associated with the impairments. The findings imply that the burden of tobacco smoking and reduced visual acuity relate to increased postural sway in quiet stance, and that muscle weakness is related to decreased limits of stability, among individuals with COPD.

Background: Aging is associated with a decline in postural control and an increased risk of falls. The Center of Pressure (CoP) trajectory analysis is a commonly used method to assess balance. In this study, we proposed a new method to identify balance impairments in older adults by analyzing their CoP trajectory frequency components, sensory inputs, reaction time, motor functions, and Fall-related Concerns (FrC).

Methods: The study includes 45 older adults aged 75.2(±4.5)75.2(±4.5) years who were assessed for sensory and motor functions. FrC and postural control in a quiet stance with open and closed eyes on stable and unstable surfaces. A Discrete Wavelet Transform (DWT) was used to detect features in frequency scales, followed by the K-means algorithm to detect different clusters. The multinomial logistic model was used to identify and predict the association of each group with the sensorimotor tests and FrC.

Results: The study results showed that by DWT, three distinct groups of subjects could be revealed. Group 2 exhibited the broadest use of frequency scales, less decline in sensorimotor functions, and lowest FrC. The study also found that a decline in sensorimotor functions and fall-related concern may cause individuals to rely on either very low-frequency scales (group 1) or higher-frequency scales (group 3) and that those who use lower-frequency scales (group 1) can manage their balance more successfully than group 3.

Conclusions: Our study provides a new, cost-effective method for detecting balance impairments in older adults. This method can be used to identify people at risk and develop interventions and rehabilitation strategies to prevent falls in this population.