Fatiguing exercise intensity influences the relationship between parameters reflecting neuromuscular function and postural control variables.

The purpose of this study was to investigate the influence of fatiguing exercise intensity on the nature and extent of fatigue-induced changes in neuromuscular function and postural stability in quiet standing. We also explored the contribution of selected neuromuscular mechanisms involved in force production to postural stability impairment observed following fatigue using an approach based on multivariate regressions. Eighteen young subjects performed 30-s postural trials on one leg with their eyes closed. Postural trials were performed before and after fatiguing exercises of different intensities: 25, 50 and 75% of maximal isometric plantarflexor torque. Fatiguing exercises consisted of sustaining a plantarflexor isometric contraction at the target intensity until task failure. Maximal isometric plantarflexor torque, electromyographic activity of plantarflexor and dorsiflexor muscles, activation level (twitch interpolation technique) and twitch contractile properties of plantarflexors were used to characterize neuromuscular function. The 25% exercise was associated with greater central fatigue whereas the 50 and 75% exercises involved mostly peripheral fatigue. However, all fatiguing exercises induced similar alterations in postural stability, which was unexpected considering previous literature. Stepwise multiple regression analyses showed that fatigue-related changes in selected parameters related to neuromuscular function could explain more than half (0.51≤R(2)≤0.82) of the changes in postural variables for the 25% exercise. On the other hand, regression models were less predictive (0.17≤R(2)≤0.73) for the 50 and 75% exercises. This study suggests that fatiguing exercise intensity does not influence the extent of postural stability impairment, but does influence the type of fatigue induced and the neuromuscular function predictors explaining changes in postural variables

Influence of an Adapted Physical Activity Program on Self-Esteem and Quality of Life of Breast Cancer Patients after Mastectomy

International audienc

Effects of fatiguing isometric and isokinetic ankle exercises on postural control while standing on firm and compliant surfaces

Abstract Background Fatiguing exercises used across studies to induce alterations in postural control are diverse and may explain the different findings reported. This study aimed to compare the effects of two types of fatiguing plantarflexion exercises on postural control on a firm and a compliant surface. Ten healthy young men (29 ± 4 years) were asked to stand as steadily as possible for 30 s, blindfolded with feet together, on a firm and a compliant surface before and immediately after an isometric and an isokinetic fatiguing exercise. Results Maximal force reduction due to fatigue was found significant but similar between exercises. No significant difference was found between the fatiguing exercises on all Center of Pressure (CoP) parameters. Both fatiguing exercises induced increases in CoP excursion area, CoP variability and CoP velocity in both planes (antero-posterior, mediolateral) on the compliant surface. On the firm surface, both fatiguing exercises only induced increases in CoP variability and CoP velocity in the fatigued plane (antero-posterior). Conclusions Isometric and isokinetic fatiguing exercises, when producing a similar level of force reduction, induce similar decreases in postural control. The effects of fatigue on postural control in healthy young men are more pronounced when standing on a compliant surface, i.e. when proprioceptive information at the ankle is altered.</p

Changes in postural variables over time.

<p>A: changes in sway area; B: changes in AP velocity; C: changes in ML velocity. Significantly different from pre-fatigue values: ***: p<0.001, **: p<0.01, *: p<0.05. Values are means ± SD.</p

Changes in gastrocnemii muscles activity (RMS) over time for the 25, 50, and 75% MVIT fatiguing exercises.

<p>Significantly different from pre-fatigue values: ***: p<0.001; **: p<0.01; *: p<0.05. Values are means ± SD.</p

Effects of Physical Activity Program on Body Composition, Physical Performance, and Neuromuscular Strategies during Walking in Older Adults with Sarcopenic Obesity: Randomized Controlled Trial

The potential impact of a specific physical activity program on biomechanical gait parameters and neuromuscular strategies around the ankle joint in older adults with sarcopenic obesity (SO) remains largely unexplored. The objective of this study was to investigate the effectiveness of a 24-week posture, strengthening, and motricity (PSM) program on improving neuromuscular strategies and biomechanical gait parameters in older adults with SO. 40 participants were randomly assigned to either the trained group (TG) and the control group (CG). Only the TG received the PSM program. Standardized evaluations were performed before and after the intervention, including walking tests on an instrumented gait analysis treadmill to evaluate biomechanical gait parameters and EMG activity of ankle muscles. After the PSM program, TG exhibited an increase in comfortable walking speed (+80%, p p p p < 0.05). The PSM program effectively improved gait and neuromuscular capacities in older adults with SO. Notably, these results shed light on the remarkable trainability of neuromuscular capacities in older adults with SO, despite the adverse effects of aging and obesity

Multiple linear regressions results explaining the fatigue-induced changes in postural variables from the fatigue-induced changes in neuromuscular parameters (predictors).

***<p>p<0.001;</p>**<p>p<0.01;</p>*<p>p<0.05.</p><p>Δ: fatigue-induced changes; MVIT: maximal voluntary isometric torque; PT: peak torque; CT: contraction time; HRT: half-relaxation time; VA: voluntary activation; GAS: gastrocnemii muscle activity; SOL: soleus muscle activity; TA: tibialis anterior muscle activity.</p

Experimental design.

<p>EC: postural trial performed with eyes closed. : electrical stimulation. MVC: maximal voluntary contraction of DFs (black bars) and PFs (red bars). MVIT: maximal voluntary isometric torque. R: 30-second rest period.</p

Values of neuromuscular function parameters before and after fatigue according to the intensity of the fatiguing exercise.

<p>Values are means ± SD. MVIT: maximal voluntary isometric torque.</p>***<p>significantly different from pre-fatigue values (p<0.001).</p>†<p>% change significantly different from the two other intensities (p<0.05).</p>‡<p>% change significantly different from 75% (p<0.05).</p