Different visual manipulations have similar effects on quasi-static and dynamic balance responses of young and older people

Fear-related visual stimuli do not promote internal focus of attention in older adults

BACKGROUND

The influence of internal focus (IF) on postural balance needs to be determined when assessing fall risk in older adults. Moreover, the mechanism through which IF is triggered should be elucidated.

RESEARCH QUESTION

Does fear unrelated to threats to postural balance modulate IF during postural control?

METHODS

The participants were 16 community-dwelling older adults. We generated visual stimuli for neutral and fear conditions using the International Affective Picture System. Participants were assessed for postural control while standing on a stabilometer and looking at projected images. The IF allocated to postural control during task was assessed immediately after the task using the Conscious Movement Processing subscale of the Movement-Specific Reinvestment Scale (MSRS-CMP). Sympathetic activity was assessed using the mean low-frequency/high-frequency ratio (LF/HF), and posture was evaluated using the root mean square area (RMS-A), anteroposterior mean power frequency (MPF-AP), mediolateral MPF, and co-contraction index. Differences (Δ) in the MSRS-CMP, RMS-A and MPF between the neutral/fear conditions and control condition were calculated. Each index was also compared among the control, neutral, and fear conditions. The correlations between ΔMSRS-CMP and postural measures were evaluated. Equivalence tests were conducted to determine whether change of IF was different among conditions.

RESULTS

The MSRS-CMP score did not differ significantly among conditions; equivalence was observed. The LF/HF and MPF-AP in the fear condition were higher than in the other conditions. The RMS-A in the fear condition was lower than in the neutral condition. ΔMSRS-CMP and ΔMPF-AP were significantly negatively correlated.

SIGNIFICANCE

The results of this study suggest that feelings of fear affect postural control but not the IF of attention. Taken together with previous research, the findings of this study suggest that consideration of the fear-inducing context may be useful in assessments of, and interventions for, older adults with a fall risk.

The impact of additional visual tasks in physical exercise on balance ability among 9-10-year-old children: the mediating effect of visual acuity

Purpose

This study aimed to explore the effects of additional visual tasks in physical exercise on the vision and balance ability of children, and to verify whether children's vision mediated the influence of physical exercise on their balance ability.

Methods

The study randomly selected 86 students aged 9-10 years old from a school in Suzhou city, dividing them into an experimental group (n = 43) and a control group (n = 43). The experimental group participated in physical exercise with additional visual tasks, while the control group engaged in routine physical exercise. The experiment lasted for 16 weeks, with kinetic visual acuity (KVA), uncorrected distance visual acuity (UDVA), static balance, and dynamic balance measured before and after the experiment.

Results

The results showed that after the experiment, the experimental group had significantly improved kinetic visual acuity (KVA), uncorrected distance visual acuity (UDVA), static balance, and dynamic balance. In contrast, the control group had significantly decreased kinetic visual acuity, no significant improvement in uncorrected distance visual acuity, and no significant difference in dynamic balance and static balance. In the experimental group, there was a moderate positive correlation between kinetic visual acuity and uncorrected distance visual acuity, and a moderate positive correlation between uncorrected distance visual acuity and both static and dynamic balance. The study also found that uncorrected distance visual acuity partially mediated the effect of additional visual tasks during physical exercise on static and dynamic balance among children.

Conclusion

In conclusion, adding visual tasks to physical exercise had a positive effect on improving children's vision and balance ability. Kinetic visual acuity and uncorrected distance visual acuity were positively correlated, and uncorrected distance visual acuity was positively correlated with both static and dynamic balance. Uncorrected distance visual acuity partially mediated the effect of physical exercise on children's balance ability.

Anticipatory Postural Adjustments and Compensatory Postural Responses to Multidirectional Perturbations-Effects of Medication and Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease

BACKGROUND

Postural instability is one of the most restricting motor symptoms for patients with Parkinson's disease (PD). While medication therapy only shows minor effects, it is still unclear whether medication in conjunction with deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves postural stability. Hence, the aim of this study was to investigate whether PD patients treated with medication in conjunction with STN-DBS have superior postural control compared to patients treated with medication alone.

METHODS

Three study groups were tested: PD patients on medication (PD-MED), PD patients on medication and on STN-DBS (PD-MED-DBS), and healthy elderly subjects (HS) as a reference. Postural performance, including anticipatory postural adjustments (APA) prior to perturbation onset and compensatory postural responses (CPR) following multidirectional horizontal perturbations, was analyzed using force plate and electromyography data.

RESULTS

Regardless of the treatment condition, both patient groups showed inadequate APA and CPR with early and pronounced antagonistic muscle co-contractions compared to healthy elderly subjects. Comparing the treatment conditions, study group PD-MED-DBS only showed minor advantages over group PD-MED. In particular, group PD-MED-DBS showed faster postural reflexes and tended to have more physiological co-contraction ratios.

CONCLUSION

medication in conjunction with STN-DBS may have positive effects on the timing and amplitude of postural control.

Characteristics of the postural stability of the lower limb in different visual states of undergraduate students with moderate myopia

Objective: To explore the characteristics of lower limb postural stability in undergraduates with moderate myopia in three different visual states. Methods: Twenty male undergraduate students were recruited to complete respectively the static and dynamic postural stability tests under eyes-closed, myopia (taking off their glasses immediately) and corrected vision conditions. A three-dimensional force platform (Bertec, United States) was used to test static postural stability, which calculated the total path length of the Center of Pressure (COP), path length in the antero-posterior (A/P) and medio-lateral (M/L) directions, COP area, SampleEntropy (SampEn), and low-, medium-, and high-frequency spectrum energies. Dynamic postural stability was tested using the Y-balance test, and the Y-balance test scores were calculated. The Vicon three-dimensional motion capture system (Oxford, United Kingdom) measured the maximum flexion angles of the ankle, knee, and hip joints. The electromyography (EMG) root mean square (RMS) and integral EMG (iEMG) of the tibialis anterior and lateral gastrocnemius of the lower extremity were simultaneously measured using wireless surface electromyography (Noraxon, United States). Results: The SampEn-A/P and SampEn-M/L of corrected vision state higher than myopia and eyes-closed states, and myopia state larger than eyes-closed state (χ² = 51.631, p < .001). The original and standard scores of the anterior, postero-medial and comprehensive values of the three visual states had significant differences (F = 32.125, p < .001). The original and standard values of postero-lateral corrected vision and myopia were larger than those of eyes-closed states (F = 37.972, p < .001). The maximum flexion angles of the ankle and knee joints were in the following order: corrected vision, myopia and eyes-closed (F = 10.93, p < .001). The iEMG and RMS had significant differences in the three different states (χ² = 12.700, p < .001) in the all directions of YBT. Conclusion: Compared with corrected vision, the stability of static posture in the state of myopia was decreased, and the postural regularity was more regular. The dynamic postural stability in the state of myopia was also lower than that corrected vision, and the activation and work of ankle muscles were also increased.

Postural Balance in Relation with Vision and Physical Activity in Healthy Young Adults

Postural balance is an essential part of a wide range of activities, from daily living tasks to sports. Regularly repeated physical and/or sport activities improve both the postural performance and the postural strategy. The aim of our study was to evaluate if the physical activity level is a factor that influences postural balance performance, including the impact of vision and gender, in healthy young adults. Postural balance was assessed in 78 subjects (38 males and 40 females, aged 20.64 ± 1.18 years) by using the PoData system, in open (EO) and closed (EC) eye conditions. Based on the physical activity level, subjects were classified in two groups—low physical activity level (n = 36, 46.15%) and moderate physical activity level (n = 42, 53.85%). A group significant difference was found only for the average centre of pressure (CoP) deviations on the latero-lateral axis (CoP_X), with a higher lateral deviation of the CoP (toward right) in the low physical activity group (F = 4.005, p = 0.04). CoP path length, the 90% confidence ellipse and maximum CoP speed were significantly increased in EC conditions. A statistically significant interaction effect (vision × physical activity) was observed for the CoP path length (F = 7.9, p = 0.006).