The Effects Of Exercise Induced Muscle Injury On Knee Joint Position Sense

Abstract

The effect of fatigue and injury on joint position sense is reported throughout the literature. However, there are few studies that have looked at the effects of exercise induced muscle injury on joint position sense. PURPOSE To evaluate the effects of exercise induced muscle injury in the quadriceps on weight bearing knee joint position sense. METHODS Twenty healthy college age students (21.7 ± 2.0 yrs, 169.85 ± 11.49 cm, 68.89 ± 15.82 kg) volunteered to participate in the study. Measurement of knee position sense was done with the subject in a standing weight-bearing position with both knees fully extended, and feet approximately shoulder width apart and in a position of slight external rotation. The subjects were instructed to perform a twolegged squat to specific knee flexion angles (20, 30, 40, 50, and 60°) in a randomized order. The test angle was held for 5 seconds, after which the subjects actively returned to the starting position. After a 7 second interval, they returned to what was perceived as the test angle. Each angle represented one trial for a total of five trials. The absolute angle error (AAE) was measured for each test angle using an electrogoniometer attached to the lateral aspect of the dominant leg. The output was recorded on a differential amplifier and displayed on the Biopac Electromyography system. AAE was the absolute difference between the test angle and the perceived angle. The average absolute angle error was calculated for each test angle and then averaged for each baseline and test session. Following baseline testing, eccentric knee flexion exercises on a Hammer Strength Leg Extension machine was performed. The protocol involved continuous eccentric knee flexion repetitions on a four second count. Once the participants could no longer lower the weight on a four second count, the weight was decreased and the exercise was continued. The exercise was terminated when the subjects could no longer support a 7 kg weight. Following the exercise-induced muscle injury subjects returned 24, 48, and 72 hours for retesting on knee joint position sense. A one-way repeated measures ANOVA was used. RESULTS The average AAE means for each condition were: baseline (3.43±1.30), 24 h (3.44±1.43), 48 h (4.03±1.89) and 72 h (3.74±1.39). There was no significant effect of time on average absolute angle error (F1,3= .917, P= .439). CONCLUSIONS In this study there were no significant differences between baseline 24, 48, and 72 hour average absolute angle error. This is opposite of what was observed in previous studies that evaluated the effects of exercise induced muscle injury on elbow joint position sense. Therefore, further research should be conducted on this topic.