Differences in motor response to stability perturbations limit fall-resisting skill transfer

This study investigated transfer of improvements in stability recovery performance to novel perturbations. Thirty adults (20-53 yr) were assigned equally to three treadmill walking groups: groups exposed to eight trip perturbations of either low or high magnitude and a third control group that walked unperturbed. Following treadmill walking, participants were exposed to stability loss from a forward-inclined position (lean-and-release) and an overground trip. Lower limb joint kinematics for the swing phase of recovery steps was compared for the three tasks using statistical parametric mapping and recovery performance was analysed by margin of stability and base of support. The perturbation groups improved stability (greater margin of stability) over the eight gait perturbations. There was no group effect for stability recovery in lean-and-release. For the overground trip, both perturbation groups showed similar enhanced stability recovery (margin of stability and base of support) compared to controls. Differences in joint angle kinematics between treadmill-perturbation and lean-and-release were more prolonged and greater than between the two gait perturbation tasks. This study indicates that: (i) practising stability control enhances human resilience to novel perturbations; (ii) enhancement is not necessarily dependent on perturbation magnitude; (iii) differences in motor response patterns between tasks may limit transfer

Comparison of physical fitness between healthy and mild‐to‐moderate asthmatic children with exercise symptoms: A cross‐sectional study

.Objective Asthma is a chronic disease that may affect physical fitness, although its primary effects on exercise capacity, muscle strength, functionality and lifestyle, in children and adolescents, are still poorly understood. This study aimed to evaluate the differences in cardiorespiratory fitness, muscle strength, lifestyle, lung function, and functionality between asthmatics with exercise symptoms and healthy children. In addition, we have analyzed the association between clinical history and the presence of asthma. Study Design Cross-sectional study including 71 patients with a diagnosis of asthma and 71 healthy children and adolescents (7–17 years of age). Anthropometric data, clinical history, disease control, lifestyle (KIDMED and physical activity questionnaires), lung function (spirometry), exercise-induced bronchoconstriction test, aerobic fitness (cardiopulmonary exercise test), muscle strength and functionality (timed up and go; timed up and down stairs) were evaluated. Results Seventy-one patients with asthma (mean age 11.5 ± 2.7) and 71 healthy subjects (mean age 10.7 ± 2.5) were included. All asthmatic children had mild to moderate and stable asthma. EIB occurred in 56.3% of asthmatic children. Lung function was significantly (p < .05) lower in the asthmatic group when compared to healthy peers, as well as the cardiorespiratory fitness, muscle strength, lifestyle and functionality. Moreover, asthmatic children were more likely to have atopic dermatitis, allergic reactions, food allergies, and a family history of asthma when compared to healthy children. Conclusions Children with mild-to-moderate asthma presenting exercise symptoms show a reduction in cardiorespiratory fitness, muscle strength, lung function, functionality, and lifestyle when compared to healthy peers. The study provides data for pediatricians to support exercise practice aiming to improve prognosis and quality of life in asthmatic children.S

Differences in muscle synergies among recovery responses limit inter-task generalisation of stability performance

Generalisation of adaptations is key to effective stability control facing variety of postural threats during daily life activity. However, in a previous study we could demonstrate that adaptations to stability control do not necessarily transfer to an untrained motor task. Here, we examined the dynamic stability and modular organisation of motor responses to different perturbations (i.e. unpredictable gait-trip perturbations and subsequent loss of anterior stability in a lean-and-release protocol) in a group of young and middle-aged adults (n = 57; age range 19–53 years) to detect potential neuromotor factors limiting transfer of adaptations within the stability control system. We hypothesized that the motor system uses different modular organisation in recovery responses to tripping and lean-and-release, which may explain lack in positive transfer of adaptations in stability control. After eight trip-perturbations participants increased their dynamic stability during the first recovery step (p < 0.001), yet they showed no significant improvement to the untrained lean-and-release transfer task compared to controls who did not undergo the perturbation exposure (p = 0.44). Regarding the neuromuscular control of responses, lower number of synergies (3 vs. 4) was found for the lean-and-release compared to the gait-trip perturbation task, revealing profound differences in both the timing and function of the recruited muscles to match the biomechanical specificity of different perturbations. Our results provide indirect evidence that the motor system uses different modular organisation in diverse perturbation responses, what possibly inhibits inter-task generalisation of adaptations in stability control