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.
Tomomasa Nakamura, Yuriko Yoshida, Hiroshi Churei, Junya Aizawa, Kenji Hirohata, Takehiro Ohmi, Shunsuke Ohji, Toshiyuki Takahashi, Mitsuhiro Enomoto, Toshiaki Ueno and Kazuyoshi Yagishita
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.
Matthew S. Tenan, Andrew J. Tweedell and Courtney A. Haynes
Justine J. Reel and Emily Crouch
Terese Wilhelmsen, Marit Sørensen and Ørnulf N. Seippel
This article is focused on how combinations of motivational attributes and motivational climates support social and pedagogical inclusion in physical education among children with disabilities. Theoretically, the authors integrate tenets from achievement-goal theory and self-determination theory. To capture the motivational complexity underlying children’s experiences of inclusion in physical education, they use a 2-step fuzzy qualitative comparative analysis. The analyses of contextual conditions yielded 2 sufficient inclusion-supportive climates, namely a physically inclusive and mastery-oriented climate or a physical inclusive, autonomy-supportive, and low performance-oriented climate. The configurations of motivational attributes in the inclusion-supportive climates indicated 4 sufficient pathways to social and pedagogical inclusion. The path with the largest coverage of children was in the physically inclusive and mastery-oriented climate and represented children who were task and ego oriented and low on amotivation and experienced satisfaction of the need for autonomy, competence, and relatedness.