Anna Brachman

Most falls in older adults occur during walking, and more than 30% of these result from a trip that causes sudden balance loss in the forward direction. This study aimed to investigate the potential effect of lower-limb dominance on reactive balance control in healthy young and older adults.17 healthy older and 16 healthy young adults participated in the study. Following a 10-minute acclimatization session on the treadmill and the custom-made tripping device, each participant underwent seven trip perturbations, with the first perturbation applied to the dominant leg. The remaining six perturbations were administered randomly to both legs, with a 2min washout phase in between. To measure gait stability, margin of stability (MoS) in the anteroposterior direction was used.Older adults walked more slowly than young adults and also had significantly higher Timed Up and Go scores. The results demonstrated a significant effect of age on gait stability: older adults required more steps to regain balance than their younger counterparts, and the perturbed step was significantly less stable in the older group. However, no significant effect of lower-limb dominance on reactive balance control was observed in either group..These findings suggest that lower-limb dominance does not play a significant role in reactive balance control. Therefore, in a clinical context (e.g., gait rehabilitation and fall prevention programs), these results indicate that balance training may not need to preferentially target either the dominant or non-dominant limb.

Background: Motor adaptation is a process where movements need to be modified in response to changes in the task, environment, or organism itself. Even a very short-term process of adaptation to different movement execution conditions leads to improvements in task performance. There is no information in the literature on whether such a gain would be present in older adults with different fear of falling levels (FoF). Methods: Thirty older adults with various FoF underwent short-term adaptive gait training on a treadmill. Participants’ spatiotemporal and foot loading characteristics were assessed directly before and after stimulation in two walking conditions: with preferred speed, and in challenging conditions (maximum speed). Results: Correlation analysis revealed moderate-to-strong associations with fear (0.66–0.74) in a majority of spatiotemporal parameters, as well as in rear and forefoot loading (0.48–0.82). In more challenging conditions, observed associations were more pronounced; however, comparative analysis revealed that the correlation was significantly stronger only in stride length (p = 0.03), walking speed (p = 0.03), forefoot (p = 0.01), and rearfoot loading (p = 0.02). There was a marginal effect of adaptive training during walking with preferred speed, but in demanding conditions, results showed significant improvements in each fear level group. Conclusions: The correlation between fear and plantar loading during walking in older adults implies a more cautious foot roll-over pattern with increasing FoF. Results also suggest that the relationship between fear and detrimental gait changes scales to some extent with motor task difficulty. The data suggest preserved but possibly attenuated gait adaptability in highly fearful older adults.

The stabilizing influence of a light touch (LT) on a postural sway has been consistently shown in the literature, however there is still no consensus in what way attentional resources are used when adopting LT during standing. To better elucidate the underlying mechanisms we introduced additional feedback (LT), which seems to distracts from postural control, and verified it by center of pressure (COP) regularity level and simple reaction time task. 25 healthy students randomly performed eight postural tasks, four without (NoRT)/ four with simple reaction task (RT). COP displacements were measured on a force plate in two visual conditions: eyes open/closed and two sensory conditions: without (NoLT)/with light touch (LT). Participants were asked to consider the postural task as the primary task. Although simple reaction time did not differ between postural conditions (p > 0.05), LT decreased postural sway velocity in anteroposterior direction (p < 0.001, η2 = 0.86) and decreased standard deviation (p < 0.001, η2 = 0.91) in both, reaction and visual conditions. Interestingly, RT task modified subjects behavior in NoLT conditions and caused slower COP velocity (p < 0.001, η2 = 0.53) without changes in signal regularity. Results also showed a significant increase in irregularity during standing with LT (p < 0.001, η2 = 0.86) in both vision and reaction conditions, suggesting that the signal was more random. Current results suggests that providing LT enhance postural steadiness and also seem to redirect attention externally, as shown by increased signal irregularity. Hence, LT possibly reduce the attention invested in the postural task itself. A RT task can be not sensitive enough to detect such subtle changes.

The stabilizing influence of a light touch on a postural sway has been consistently shown in the literature, however there is still no consensus in what way attentional resources are used when adopting additional tactile information during controlling an upright posture. To better elucidate the underlying mechanisms we introduced conditions of both sensory deprivation (closing the eyes), additional feedback (light touch), which seems to distracts from postural control and verified it by introducing dual task paradigm (i.e. measuring simple reaction time to an unpredictable auditory stimulus). Twenty five healthy students randomly performed eight postural tasks, four with (RT) and four without simple reaction task (NoRT). Center of pressure displacements were measured on a force plate in two visual conditions: eyes open (EO), eyes closed (EC) and two sensory conditions: with light touch (LT), without light touch (NoLT). Before each measurement participants were asked to consider the postural task as the primary task. Although simple reaction time did not differ between postural conditions (p>0.05), additional tactile information in anteroposterior direction caused decreased postural sway velocity (p<0.001, η2=0.86) and decreased standard deviation (p<0.001, η2=0.91) in both, reaction and visual conditions relative to NoLT conditions. Interestingly, simple reaction task modified subjects behavior in NoLT conditions and caused slower COP velocity (p<0.001, η2=0.53) without changes in signal regularity. Results also showed a significant increase in irregularity during standing with LT (p<0.001, η2=0.86) in both vision and reaction conditions, suggesting that the signal was more random. Although there were no significant changes between length of the reaction time between postural conditions but there was strong effect of light touch on COP regularity, we can conclude that light touch is attention demanding but changes of flow of attention are very subtle in this simple postural tasks. Furthermore COP regularity analysis is sensitive to even such subtle changes.

We examined the influence of perceived cognitive fatigue on static balance control in healthy young adults to gain greater clarity about this issue than provided in previous research. Based on the prevailing assumption in pertinent literature, we hypothesized that the influence of cognitive fatigue on balance control depends on the attentional effort required by the balance tasks being performed. To test this hypothesis, 44 young adults (24 women and 20 men) were alternately assigned to either the experimental group that was cognitively fatigued (using the 16-min TloadDback-task with individualized settings) or the control group (who watched a documentary). Before and after the intervention, the participants performed six balance tasks that differed in (attentional) control requirements, while recording the center of pressure (COP). From these time series, sway variability, mean speed, and sample entropy were calculated and analyzed statistically. Additionally, perceived cognitive fatigue was assessed using VAS scales. Statistical analyses confirmed that the balance tasks differed in control characteristics and that cognitive fatigue was elevated in the experimental group, but not in the control group. Nevertheless, no significant main effects of cognitive fatigue were found on any of the COP measures of interest, except for some non-robust interaction effects related primarily to sample entropy. These results suggest that, in young adults, postural control in static balance tasks is largely automatic and unaffected by task-induced state fatigue.

We examined the influence of mental fatigue on static balance control in healthy young adults to gain greater clarity about this issue than provided in previous research. Based on the prevailing assumption in pertinent literature, we hypothesized that mental fatigue leads to a reduced cognitive regulation of quiet upright standing, as reflected in center of pressure (COP) excursions. More specifically, we hypothesized that the influence of mental fatigue on balance control depends on the attentional effort required by the balance tasks being performed. To test these hypotheses, 44 young adults (24 women and 20 men) were quasi-randomly assigned to either an experimental group that was mentally fatigued (using the TloadDback-task with individualized settings) or a control group (who watched a documentary). Before and after the intervention the participants performed six balance tasks that differed in (attentional) control requirements, while their COP was being recorded. From these time-series sway variability, mean speed, and sample entropy were calculated and analyzed statistically. Additionally, mental fatigue was assessed using VAS scales. Statistical analyses confirmed that the balance tasks differed in control characteristics and that mental fatigue was elevated in the experimental group, but not in the control group. Nevertheless, no significant main effects of mental fatigue were found on any of the COP measures of interest, except for some non-robust and difficult to interpret interaction effects involving the factor group. These results suggest that, in young adults, postural control in static balance tasks is largely automatic and unaffected by mental fatigue.

The aim of this study was to examine whether target width and target distance influence the planning phase of a fencing lunge (early and anticipatory postural adjustments) as well as the execution phase of a fencing lunge. Eight elite female fencers participated in the study. The displacement of the center of foot pressure, muscle activity of the tibialis anterior, and kinematics of center of mass were recorded using force plates. The results show that target width and distance have no effect on early and anticipatory postural adjustments as well as the acceleration and velocity of the center of mass at the moment of foot-off. However, a greater target distance was associated with a greater max center of mass acceleration and velocity, and larger target width resulted in a greater max center of mass acceleration during lunging (p < 0.05). We suppose that the effect of task parameters on preparing a fencing lunge may be mitigated due to the specific technique adopted by expert fencers and the ballistic nature of a fencing lunge.

The aim of the study was to determine whether Whole Body Vibration Training (WBVT) affects intrinsic risk factors for falls in women aged 60+ at fall risk. Design: Randomized controlled clinical trial. Blinding was applied to the persons in charge of evaluating the intervention’s clinical results and statistical analysis. Methods: Forty-two women over 60 years old were randomly assigned to an experimental group (EG—12-week WBVT; n = 22) and a control group (CG—no additional physical activities; n = 20). Fear of falling was measured by the FES-I questionnaire, gait and dynamic balance using the Time-Up and Go test (TUG), aerobic endurance with the 6-Minute Walk Test (6MWT), and the functional strength of the lower body muscles with the 30-s Chair Stand Test (30SCST) at baseline and post-intervention. Additionally assayed were participants’ blood concentrations of interleukin-6 (IL-6). Results: The 12-week WBVT improves gait and balance (TUG, p = 0.009), exercise tolerance (6MWT, p = 0.001), and functional strength (30SCST; p = 0.027) but does not reduce the intensity of fear of falling (FES-I, p = 0.655) and the IL-6 serum concentration (p = 0.377). Conclusions: WBVT affects selected fall risk factors in women aged 60+ at fall risk.

In recent years the use of sample entropy (SampEn) to evaluate the complexity of the locomotor system in human gait data has gained in popularity. However, it has been suggested that SampEn is sensitive to various input parameters and signal preprocessing methods. This study quantified the effects of different temporal and spatial normalization approaches and various lengths of the template vector (m) on SampEn calculations. The discriminatory ability of SampEn was studied by comparing two walking conditions. Twenty-three participants (seven males, 55.7 ± 8.5 years, 165.7 ± 7.9 cm, 80.5 ± 16.7 kg) walked on a treadmill with preferred (Vpref) and maximum (Vmax) speed. Data were segmented and resampled (SEGM), resampled and spatially normalized (NORM), resampled and detrended (ZERO). For vertical ground reaction force (vGRF) and center of pressure in anterio-posterior direction (COPap), in both walking conditions, SampEn was generally sensitive to the vector length and not to the data processing, except for COPap in ZERO, m = 2, 4. For the COPml SampEn behaved oppositely, it was sensitive to preprocessing method and not to the m length. The regularity of COPap and vGRF in all processed signals increased in Vmax condition. For the COPml only two signals, WHOLE and ZERO, revealed increased complexity caused by more demanding walking conditions. SampEn was able to discriminate between different walking conditions in all analyzed variables, but not in all signals. Depending on evaluated variable, SampEn was susceptible in different way for the m level and processing method. Hence, these should be checked and selected for each variable independently. For future studies evaluating influence of walking velocity on COP and vGRF regularity during treadmill walking it is advised to use raw time series. Furthermore, to maintain template vector which represents biological relevance it is advised to detect highest frequencies present in analyzed signals and evaluate minimal time interval which can reflect change caused by response of a neuromuscular system. During evaluating treadmill walking measured with 100 Hz sampling frequency it is recommended to adopt m from 6 to 10, when average stride time is up to about 1 s.