Chronic exposure to high tibiofemoral joint (TFJ) contact forces can be detrimental to knee joint health. Load carriage increases TFJ contact forces, but it is unclear whether medial and lateral tibiofemoral compartments respond similarly to incremental load carriage. The purpose of our study was to compare TFJ contact forces when walking with 15% and 30% added body weight. Young healthy adults (n = 24) walked for 5 minutes with no load, 15% load, and 30% load on an instrumented treadmill. Total, medial, and lateral TFJ contact peak forces and impulses were calculated via an inverse dynamics informed musculoskeletal model. Results of 1-way repeated measures analyses of variance (α = .05) demonstrated total, medial, and lateral TFJ first peak contact forces and impulses increased significantly with increasing load. Orthogonal polynomial trends demonstrated that the 30% loading condition led to a curvilinear increase in total and lateral TFJ impulses, whereas medial first peak TFJ contact forces and impulses responded linearly to increasing load. The total and lateral compartment impulse increased disproportionally with load carriage, while the medial did not. The medial and lateral compartments responded differently to increasing load during walking, warranting further investigation because it may relate to risk of osteoarthritis.
Blake W. Jones, John D. Willson, Paul DeVita, and Ryan D. Wedge
Aude S. Lefranc, Glenn K. Klute, and Richard R. Neptune
Gait asymmetry is a predictor of fall risk and may contribute to increased falls during pregnancy. Previous work indicates that pregnant women experience asymmetric joint laxity and pelvic tilt during standing and asymmetric joint moments and angles during walking. How these changes translate to other measures of gait asymmetry remains unclear. Thus, the purpose of this case study was to determine the relationships between pregnancy progression, subsequent pregnancies, and gait asymmetry. Walking data were collected from an individual during 2 consecutive pregnancies during the second and third trimesters and 6 months postpartum of her first pregnancy and the first, second, and third trimesters and 6 months postpartum of her second pregnancy. Existing asymmetries in step length, anterior–posterior (AP) impulses, AP peak ground reaction forces, lateral impulses, and joint work systematically increased as her pregnancy progressed. These changes in asymmetry may be attributed to pelvic asymmetry, leading to asymmetric hip flexor and extensor length, or due to asymmetric plantar flexor strength, as suggested by her ankle work asymmetry. Relative to her first pregnancy, she had greater asymmetry in step length, step width, braking AP impulse, propulsive AP impulse, and peak braking AP ground reaction force during her second pregnancy, which may have resulted from increased joint laxity.
Sabrina Gomez Souffront, Angeliki M. Mavrantza, and Marcelo Bigliassi
The present study sought to investigate the effects of a self-talk intervention on free-throw performance under pressure. The experimental manipulation was designed using a video from a social media platform. Thirty male college basketball players were randomly assigned into two groups (i.e., control and experimental). The experimental protocol incorporated three trials of three free throws each. Psychophysiological stress was assessed by use of heart rate variability. The illusion of pressure was created using arena recordings of large crowds along with instructions for participants to visualize a high-pressure scenario. The results indicate that the self-talk intervention was sufficient to improve free throw shooting accuracy during the postintervention phase. Short-term heart rate variability reduced significantly for the control group and remained relatively stable for the experimental group. Self-talk appears to influence free throw accuracy during situations of psychosocial stress by inhibiting the influence of negative thoughts on peripheral physiological reactions and movement automaticity.
J.D. DeFreese, Daniel J. Madigan, and Henrik Gustafsson
Kathleen T. Mellano and Christine Pacewicz
The purpose of the current research was to examine the interaction of teammate and coach support on athlete burnout and engagement, and determine how type of teammate and coach support links with athlete burnout and engagement. Adolescent athletes (N = 176) completed measures of support, burnout, and engagement. Total teammate and coach support accounted for 14.9%–26.0% and 22.4%–36.7% explained variance across dimensions of burnout and engagement, respectively. No meaningful significant interaction was found. Teammate esteem support predicted reduced accomplishment, devaluation, confidence, and vigor (β = −0.31, −0.36, 0.28, and 0.28), while emotional and tangible support predicted dedication (β = 0.29 and 0.20) and enthusiasm (β = 0.30 and 0.22). Coach esteem support predicted reduced accomplishment (β = −0.59) and devaluation (β = −0.27). Findings suggest that support from one key agent can enhance youth athlete well-being, but types of support provided by agents differ in salience.
Tetsuya Hirono and Kohei Watanabe
Muscle fiber conduction velocity (MFCV) can be affected by muscle fiber geometry at different joint angles and during joint movements. This study aimed to investigate MFCV during electrically evoked contraction at different joint angles, during joint movements, and during voluntary contractions. Sixteen healthy young men participated. A stimulation electrode was attached on the innervation zone of the vastus lateralis, and a linear electrode array was attached on the vastus lateralis. Under a static condition, electrically evoked electromyography signals were recorded at knee joint angles set every 15° between 0° and 105°. Under a passive movement condition, signals were recorded during knee extension and flexion passively. Under a voluntary contraction condition, signals were recorded while performing 30% or 60% of maximum voluntary contraction. MFCV was calculated using cross-correlation coefficients. Under the static condition, there were no differences in MFCV among various joint angles. Under the passive movement condition, MFCV was significantly greater during high velocity or shortening. Under the voluntary contraction condition, MFCV was significantly greater during high-intensity voluntary contraction and with a shortened muscle length. Joint angles do not influence MFCV markedly during relaxation, but it is possible to overestimate MFCV during movement or voluntary contraction.
Hamed Zarei, Ali Asghar Norasteh, Lauren J. Lieberman, and Ali Brian
Purpose: The purpose of this study was to examine the balance recovery strategy in children with hearing (HI) and visual impairments (VI) compared with those without these disorders. Materials and Methods: This study featured a cross-sectional design with subjects (N = 45) placed within one of three equally stratified purposive groups (HI, VI, and comparison) within the age range of 9–13 years (mean = 11.43, SD = 1.5). Balance recovery strategy was measured in static and after-perturbation conditions by a four-camera Vicon system used to record three-dimensional lower body kinematic data. A repeated-measures analysis of variance (3 × 2, Group × Condition) was utilized to analyze data. Significance was set at p ≤ .05. Results: In the static condition, the results of the study showed that there was no significant difference between the groups in the ankle joint sway (p > .05). In hip joint sway, VI children had greater sway compared with comparison (p = .001) and HI children (p = .02). Also, HI children had greater sways than comparison (p = .02). In the after-perturbation condition, the results showed that VI children had greater sway in the hip and ankle joints than HI children (p = .001) and comparison (p = .001) to restore and maintain balance. Conclusion: It seems that comparison as well as higher proportion VI children use a hip strategy to maintain and restore balance. Also, it seems that HI children use a different strategy (ankle strategy) to maintain and restore balance compared with comparison and VI children.
Alexis D. Gidley and Joshua P. Bailey
Previous research has shown that there are differences in mechanical energy, kinematics, and muscle activation when comparing walking on level and incline surfaces, especially on inclines above 15%. Muscle activations are significantly different while walking on extreme inclines, suggesting a different coordination pattern. We utilized continuous relative phase to assess walking kinematic coordination with respect to increased incline angles. Twelve healthy, college-aged individuals walked for 7 inclines of 1 minute each on a motorized treadmill at 3 mph at 0%, 5%, 10%, 15%, 20%, 25%, and 30% inclines. Kinematic data were collected during the last 20 seconds of each stage (120 Hz). Segmental and joint angles and angular velocities in the sagittal plane were calculated, from which continuous relative phase was determined for 3 joint couples: hip–knee, hip–ankle, and knee–ankle. There were significant differences in the coordination patterns during the first part of the contact phase in the hip–knee and hip–ankle couplings between the 0% and 30% inclines, with all 3 joint couplings becoming more in-phase at inclines above 15%. Importantly, the hip–knee coupling changed significantly from more out-of-phase to more in-phase between 10% and 15% incline. Shifting lower-extremity joint coordination in response to extreme inclines identifies potential coordinative strategies to achieve steep walking.