The effect of protective knee braces on agility and muscle performance

Thirty-two Virginia Tech varsity football players served as subjects to examine the effect of protective knee braces on agility and selected isokinetic strength, power, and endurance measures. Each subject performed the Semo agility test in each of three experimental conditions: braced with the Anderson knee stabler (B,An); braced with the Arco knee guard (Bâ Ar); and unbraced (Un). The order of agility tests was randomized. The subjects were than administered a Cybex knee extension/flexion test at 60 deg/sec and 300 deg/sec. Each subject performed the Cybex tests in each of the three experimental conditions (B-An, B-Ar, and Un). The order of Cybex tests was randomized. The test protocol consisted of three maximal repetitions at 60 deg/sec and 40 maximal repetitions at 300 deg/sec. The following isokinetic variables were recorded: (1) peak torque/body weight ratio of the quadriceps and hamstrings at 60 deg/sec and 300 deg/sec; (2) average range of motion for knee extension/flexion at 60 deg/sec and 300 deg/sec; (3) average power, torque acceleration energy, and endurance ratio of the quadriceps and hamstrings at 300 deg/sec. Repeated measures analysis of variance revealed no significant difference (p > .05) in agility test scores between the three experimental conditions. Repeated measures analysis of variance also revealed no significant difference (p > .05) in the isokinetic responses of subjects as they were tested within the three experimental conditions. The investigator concluded that protective knee braces had no effect on agility, isokinetic strength, power, and endurance.