Effects of four days hiking on postural control

Cortical activity associated with the maintenance of balance during unstable stances

Background

Humans continuously maintain and adjust posture during gait, standing, and sitting. The difficulty of postural control is reportedly increased during unstable stances, such as unipedal standing and with closed eyes. Although balance is slightly impaired in healthy young adults in such unstable stances, they rarely fall. The brain recognizes the change in sensory inputs and outputs motor commands to the musculoskeletal system. However, such changes in cortical activity associated with the maintenance of balance following periods of instability require further clarified.

Methods

In this study, a total of 15 male participants performed two postural control tasks and the center of pressure displacement and electroencephalogram were simultaneously measured. In addition, the correlation between amplitude of center of pressure displacement and power spectral density of electroencephalogram was analyzed.

Results

The movement of the center of pressure was larger in unipedal standing than in bipedal standing under both eye open and eye closed conditions. It was also larger under the eye closed condition compared with when the eyes were open in unipedal standing. The amplitude of high-frequency bandwidth (1-3 Hz) of the center of pressure displacement was larger during more difficult postural tasks than during easier ones, suggesting that the continuous maintenance of posture was required. The power spectral densities of the theta activity in the frontal area and the gamma activity in the parietal area were higher during more difficult postural tasks than during easier ones across two postural control tasks, and these correlate with the increase in amplitude of high-frequency bandwidth of the center of pressure displacement.

Conclusions

Taken together, specific activation patterns of the neocortex are suggested to be important for the postural maintenance during unstable stances.

Persistent cancer-related fatigue after breast cancer treatment predicts postural sway and post-exertional changes in sit-to-stand strategy

Background

Chemotherapy-induced peripheral neuropathy (CIPN) is considered a primary mechanism of imbalance among women diagnosed with breast cancer. Recent evidence, however, suggests that cancer-related fatigue (CRF) may also influence balance.

Purpose

Examine the contributions of CRF and CIPN to static and dynamic balance before and after a period of fatiguing exercise.

Methods

This is a secondary analysis of data examining functional differences between women with breast cancer with and without persistent CRF. Postural sway was measured during static standing and the rising phase of an instrumented sit-to-stand (ISTS) before and after exercise. Regression analyses were performed to determine how CRF and severity of CIPN predicted sway and how much variance was attributable to each.

Results

Greater CRF predicted increased pre-, p=.04, and post-exertional, p=.02, static sway in the anterior-posterior plane. CRF accounted for 10.5% and 9.5% of the variance in pre- and post-exertional sway (respectively) compared to the 0.9% and 1.4% accounted for by CIPN severity which was not a significant predictor. After exercise, greater CRF predicted smaller, more conservative, anterior weight shifting during the ISTS, p=.01, and accounted for 6.6% of the variance in sway compared to 3% attributed to CIPN which was not a significant predictor.

Limitations

This analysis is limited by its small and demographically homogenous sample.

Conclusions

These results suggest that CRF may influence balance independent of CIPN symptoms. While CIPN remains a risk factor for imbalance in this population, CRF warrants consideration in clinical practice and research as a mechanism of postural instability.

Application of Interactive Video Games as Rehabilitation Tools to Improve Postural Control and Risk of Falls in Prefrail Older Adults

The purpose of this study was to examine whether interactive video game (IVG) training is an effective way to improve postural control outcomes and decrease the risk of falls. A convenience sample of 12 prefrail older adults were recruited and divided into two groups: intervention group performed IVG training for 40 minutes, twice per week, for a total of 16 sessions. The control group received no intervention and continued their usual activity. Outcome measures were centre of pressure (COP), mean velocity, sway area, and sway path. Secondary outcomes were Berg Balance Scale, Timed Up and Go (TUG), Falls Efficacy Scale International (FES-I), and Activities-Specific Balance Confidence (ABC). Assessment was conducted with preintervention (week zero) and postintervention (week eight). The intervention group showed significant improvement in mean velocity, sway area, Berg Balance Scale, and TUG (p < 0.01) compared to the control group. However, no significant improvement was observed for sway path (p = 0.35), FES-I (p = 0.383), and ABC (p = 0.283). This study showed that IVG training led to significant improvements in postural control but not for risk of falls.

Differences in sensory reweighting due to loss of visual and proprioceptive cues in postural stability support among sleep-deprived cadet pilots

BACKGROUND

Sleep deprivation is known to diminish postural control.

RESEARCH QUESTION

We investigated whether sleep deprivation affects sensory reweighting for postural control due to loss of visual and proprioceptive cues.

METHODS

Two cohorts of cadet pilots were deprived of sleep for 40 h. Variabilty in force-platform center of pressure was analyzed based on the whole path length (WPL); circumference area (CA); mean of displacement along x and y axes and corresponding standard deviations (SDx, SDy); and frequency of body-sway intensity, all of which were recorded while the cadets stood with eyes open (NEO), eyes closed (NEC), and eyes closed on a foam platform base (FEC) A sleepiness index (SUBI) based on principal component analysis of selected Cohort 1 data (n = 37) was used to compare Cohort 2 data (n = 29) with scores for the Stanford Sleepiness Scale (SSS) and Pittsburg Sleep Quality Index (PSQI).

RESULTS

Balance began to deteriorate at 16 h for NEO and at 28 h for NEC and FEC (p < 0.05). At 40 h, WPL, CA, and SDy of COP for NEO indicated balance deteriorated further while WPL and SDy for NEC and WPL, CA, SDx, and SDy for FEC indicated balance incrementally improved. Frequency bias of body-sway differed between NEO, NEC, and FEC. In Cohort 2, the SUBI correlated significantly with SSS (p < 0.05), but not with PSQI.

SIGNIFICANCE

Effects of sleep deprivation were mitigated over time, suggesting that compensatory mechanisms influenced sensory reweighting for NEC and FEC between 28 and 40 h of sleep deprivation, but not for NEO. Frequency bias of body-sway suggested that sensory reweighting in the absence of visual cues differed from that in the absence of both visual and proprioceptive cues.

Postural Control of Elderly Adults on Inclined Surfaces

This study analyzed the postural control of older adults on inclined surfaces, and was conducted in 17 elderly adults and 18 young adults of both genders. Ground reaction forces and moments were collected using two AMTI force platforms, one of which was in a horizontal position (HOR), while the other was inclined 14° in relation to the horizontal plane. Each participant executed three 70 s-trials of bipedal standing with their eyes open and eyes closed in three inclination conditions: the HOR, the inclined position at ankle dorsi-flexion (UP), and the inclined position at ankle plantar-flexion (DOWN). Spectral analysis, global (mean velocity-Velm, ellipse area-Area and F80), and structural stabilometric descriptors (sway density curve-SDC, detrended fluctuation analysis-DFA, sample entropy-SEn) were employed to assess the center of pressure sway. Velm and F80 were greater for the elderly, whereas SDC, DFA, and SEn were smaller for this group. Global, SDC and DFA variables were sensitive to visual deprivation, however the relative difference from the EO to EC condition was higher in young than in elderly. The DOWN condition was more stable than the UP condition for both young and older adults. With regard to the UP condition, the challenge observed is essentially associated with the corresponding biomechanical constraints. In conclusion, the elderly showed significant differences compared to the young, but age per se may not necessarily result in compromised postural control.