The objectives of this study were to assess the sex-specific relationships between motor and sensory adaptations to repetitive arm motion–induced neck/shoulder fatigue, and to measure how additional sensory stimulation affects these adaptations. Twenty-three participants performed two sessions of a repetitive pointing task until scoring 8 on the Borg CR10 scale for neck/shoulder exertion or for a maximum of 45 min, with and without sensory stimulation (i.e., light touch) applied on the fatiguing shoulder. Just before reaching the task termination criteria, all participants showed changes in mean and variability of arm joint angles and experienced a fivefold increase in anterior deltoid sensory threshold in the stimulus-present condition. Women with the greatest increases in anterior deltoid sensory thresholds demonstrated the greatest increases in shoulder variability (r = .66), whereas men with the greatest increases in upper-trapezius sensory thresholds demonstrated the greatest changes in shoulder angle (r = −.60) and coordination (r = .65) variability. Thus, sensory stimulation had no influence on time to termination but affected how men and women differently adapted, suggesting sex differences in sensorimotor fatigue response mechanisms.
Zachary R. Weber, Divya Srinivasan, and Julie N. Côté
Karin Lobenius-Palmér, Birgitta Sjöqvist, Anita Hurtig-Wennlöf, and Lars-Olov Lundqvist
This study compared accelerometer-assessed habitual physical activity (PA), sedentary time, and meeting PA recommendations among 102 youth with disabilities (7–20 years) in four subgroups—physical/visual impairments, intellectual disability, autism spectrum disorders, and hearing impairment—and 800 youth with typical development (8–16 years). Low proportions of youth with disabilities met PA recommendations, and they generally were less physically active and more sedentary than youth with typical development. The hearing impairment and autism spectrum disorder groups were the most and least physically active, respectively. Older age and to some extent female sex were related to less PA and more sedentary time. Considering the suboptimal levels of PA in youth with disabilities, effective interventions directed at factors associated with PA among them are needed.
Kelly P. Arbour-Nicitopoulos, Viviane Grassmann, Krystn Orr, Amy C. McPherson, Guy E. Faulkner, and F. Virginia Wright
The objective of this study was to comprehensively evaluate inclusive out-of-school time physical activity programs for children/youth with physical disabilities. A search of the published literature was conducted and augmented by international expertise. A quality appraisal was conducted; only studies with quality ratings ≥60% informed our best practice recommendations. Seventeen studies were included using qualitative (n = 9), quantitative (n = 5), or mixed (n = 3) designs. Programs had a diversity of age groups, group sizes, and durations. Most programs were recreational level, involving both genders. Rehabilitation staff were the most common leaders. Outcomes focused on social skills/relationships, physical skill development, and psychological well-being, with overall positive effects shown in these areas. The best practice recommendations are consistent with an abilities-based approach emphasizing common group goals and interests; cooperative activities; mastery-oriented, individualized instruction; and developmentally appropriate, challenging activities. Results indicate that inclusive out-of-school time physical activity programs are important for positive psychosocial and physical skill development of children/youth with physical disabilities.
Tomomasa Nakamura, Yuriko Yoshida, Hiroshi Churei, Junya Aizawa, Kenji Hirohata, Takehiro Ohmi, Shunsuke Ohji, Toshiyuki Takahashi, Mitsuhiro Enomoto, Toshiaki Ueno, and Kazuyoshi Yagishita
The aim of this study was to analyze the effect of teeth clenching on dynamic balance at jump landing. Twenty-five healthy subjects performed jump-landing tasks with or without teeth clenching. The first 3 trials were performed with no instruction; subsequently, subjects were ordered to clench at the time of landing in the following 3 trials. We collected the data of masseter muscle activity by electromyogram, the maximum vertical ground reaction force (vGRFmax) and center of pressure (CoP) parameters by force plate during jump-landing. According to the clenching status of control jump-landing, all participants were categorized into a spontaneous clenching group and no clenching group, and the CoP data were compared. The masseter muscle activity was correlated with vGRFmax during anterior jump-landing, while it was not correlated with CoP. In comparisons between the spontaneous clenching and the no clenching group during anterior jump-landing, the spontaneous clenching group showed harder landing and the CoP area became larger than the no clenching group. There were no significant differences between pre- and postintervention in both spontaneous clenching and no clenching groups. The effect of teeth clenching on dynamic balance during jump-landing was limited.
Bente R. Jensen, Line Hovgaard-Hansen, and Katrine L. Cappelen
Running on a lower-body positive-pressure (LBPP) treadmill allows effects of weight support on leg muscle activation to be assessed systematically, and has the potential to facilitate rehabilitation and prevent overloading. The aim was to study the effect of running with weight support on leg muscle activation and to estimate relative knee and ankle joint forces. Runners performed 6-min running sessions at 2.22 m/s and 3.33 m/s, at 100%, 80%, 60%, 40%, and 20% body weight (BW). Surface electromyography, ground reaction force, and running characteristics were measured. Relative knee and ankle joint forces were estimated. Leg muscles responded differently to unweighting during running, reflecting different relative contribution to propulsion and antigravity forces. At 20% BW, knee extensor EMGpeak decreased to 22% at 2.22 m/s and 28% at 3.33 m/s of 100% BW values. Plantar flexors decreased to 52% and 58% at 20% BW, while activity of biceps femoris muscle remained unchanged. Unweighting with LBPP reduced estimated joint force significantly although less than proportional to the degree of weight support (ankle).It was concluded that leg muscle activation adapted to the new biomechanical environment, and the effect of unweighting on estimated knee force was more pronounced than on ankle force.
Samantha L. Winter, Sarah M. Forrest, Joanne Wallace, and John H. Challis
The purpose of this study was to validate a new geometric solids model, developed to address the lack of female-specific models for body segment inertial parameter estimation. A second aim was to determine the effect of reducing the number of geometric solids used to model the limb segments on model accuracy. The full model comprised 56 geometric solids, the reduced model comprised 31, and the basic model comprised 16. Predicted whole-body inertial parameters were compared with direct measurements (reaction board, scales), and predicted segmental parameters with those estimated from whole-body dual x-ray absorptiometry scans for 28 females. The percentage root mean square error (%RMSE) for whole-body volume was <2.5% for all models and 1.9% for the full model. The %RMSE for whole-body center of mass location was <3.2% for all models. The %RMSE whole-body mass was <3.3% for the full model. The RMSE for segment masses was <0.5 kg (<0.5%) for all segments; Bland-Altman analysis showed the full and reduced models could adequately model thigh, forearm, foot, and hand segments, but the full model was required for the trunk segment. The proposed model was able to accurately predict body segment inertial parameters for females; more geometric solids are required to more accurately model the trunk.
John D. McCamley, Eric L. Cutler, Kendra K. Schmid, Shane R. Wurdeman, Jason M. Johanning, Iraklis I. Pipinos, and Sara A. Myers
Patients with peripheral artery disease (PAD) experience significant leg dysfunction. The effects of PAD on gait include shortened steps, slower walking velocity, and altered gait kinematics and kinetics, which may confound joint torques and power measurements. Spatiotemporal parameters and joint torques and powers were calculated and compared between 20 patients with PAD and 20 healthy controls using independent t tests. Separate analysis of covariance models were used to evaluate group differences after independently adjusting for gait velocity, stride length, and step width. Compared with healthy controls, patients with PAD exhibited reduced peak extensor and flexor torques at the knee and hip. After adjusting for all covariates combined, differences between groups remained for ankle power generation in late stance and knee flexor torque. Reduced walking velocity observed in subjects affected by PAD was closely connected with reductions in joint torques and powers during gait. Gait differences remained at the knee and ankle after adjusting for the combined effect of spatiotemporal parameters. Improving muscle function through exercise or with the use of assistive devices needs to be a key tool in the development of interventions that aim to enhance the ability of PAD patients to restore spatiotemporal gait parameters.