Jeffrey K. Kawaguchi

Muscle Strength in the Lower Extremity Does Not Predict Postinstruction Improvements in the Landing Patterns of Female Athletes

STUDY DESIGN Preinstruction and postinstruction testing in a laboratory setting. OBJECTIVES To examine the predictive relationship between lower extremity muscle strength and the immediate postinstruction changes in landing patterns of female athletes. We hypothesized that greater strength would be associated with larger postinstruction improvements in landing patterns. BACKGROUND Female athletes in high-demand sports may be predisposed to anterior cruciate ligament injury because of poor landing patterns. Instruction has been shown to improve landing patterns. Lower extremity muscular strength may determine the potential for instruction to alter landing patterns. METHODS AND MEASURES Thirty-seven female collegiate athletes in high-demand sports participated. Strength was assessed in the following muscle groups: trunk extensors and flexors, hip abductors and extensors, knee flexors and extensors, and ankle plantar flexors. Strength testing was followed by kinetic and kinematic analysis of a drop vertical jump task. Athletes then received verbal instruction on how to improve their landing technique and were retested. Landing variables of interest were force absorption time, peak vertical ground reaction force (vGRF), peak knee flexion and abduction angle, and peak external knee abduction moment. Preinstruction and postinstruction landing variables data were compared. Linear regression models were created with strength values as independent variables and landing variables as dependent variables. RESULTS After instruction, athletes significantly increased their force absorption time and peak knee flexion angle, while decreasing their peak vGRF, peak knee abduction angle, and peak external knee abduction moment (P<.001). None of the regression models were statistically significant (P>.05). CONCLUSIONS A brief instructional session promotes short-term improvements in the landing patterns of collegiate female athletes, but muscular strength was a poor predictor of the improvements.

Acute effects of vibration-assisted stretching are more evident in the non-dominant limb

Abstract The aim of this study was to investigate the acute effects of a vibration-assisted static stretching intervention on enhancing split range of motion in gymnasts matched on initial range of motion. Twenty-two female artistic gymnasts (mean age 13.8 years, s=2.3) matched for age (±6 months) and competitive level were randomly assigned to a static stretching intervention with or without simultaneous vibration. The test consisted of adopting a forward split position with the rear leg bent to 90° and held vertically against a matted block while the pelvis remained perpendicular to the lines of the two legs. The gymnast was instructed to descend into the lowest split position of her comfortable pain tolerance. Positions were videotaped and digitized creating an angle between the split legs. The stretching intervention consisted of a forward split position with emphasis on the front leg hamstring muscle group, followed by a forward lunge position with emphasis on the rear leg quadriceps muscle group. In each position, four sets of stretches were completed each of 10 s duration with 5 s of rest between sets. The experimental group performed stretches with the vibration device turned on while the control group performed the same stretches with the vibration device turned off. A pre-test was performed to obtain baseline scores with the post-test following immediately after the vibration or control stretching intervention. Difference scores were calculated between the pre-test and post-test for each gymnast, and compared between groups using independent t-tests. Results showed significant post-test differences between the vibration and non-vibration groups (mean difference 12.2±5.2° vibration vs. 7.8±3.5° non-vibration, P=0.030) in the non-dominant limb, but no significant differences in the dominant limb (mean difference 10.2±4.3° vibration vs. 7.9±6.1° non-vibration, P=0.32). Vibration-assisted static stretching may provide a greater stimulus for range of motion improvements in limbs that have a lower initial level of flexibility.

Het effect van tapen van de patella op de kinetica van de knie bij patiënten met een patellofemoraal pijnsyndroom

Effect of patellar taping on knee kinetics of patients with patellofemoral pain syndrome [Journal of Orthopaedic and Sports Physical Therapy 1999;29(11):661-7]