Abstract
Objective: Design and Setting: All data were collected in the Jowers Center Biomechanics Supplemental Research Lab, Texas State University-San Marcos. Subjects: Sixteen healthy, physically active males and ten healthy, physically active females (age= 26.9 ± 6.5 yrs, height= 177.2 ± 10.6 cm, and weight= 79.1 ± 15.1 kg) with no reports of current lower limb or low back injuries. Measurements: All subjects performed three short step countermovement jumps each on a sand surface and a rigid surface. A 4-channel electromyography (EMO) system recorded output from the rectus femoris, vastus lateralis, biceps femoris, and gastrocnemius muscles of the right leg. A wireless waist belt accelerometer obtained subject jump height. Mean and mean peak EMO data from the lower extremity muscles was compared between the two surfaces along with jump height. Results: Analysis using an ANOVA was conducted between the two surfaces. There was a significant difference between jumping surfaces for the normalized mean and mean peak percentage EMG output measures. The rectus femoris
and vastus lateralis muscles of the quadriceps registered significantly higher normalized mean and mean peak percentage EMG output measures on a sand surface. The biceps femoris and gastrocnemius muscles were significantly higher on a rigid surface for both the normalized mean and mean peak percentage EMG output measures. Conclusion: Jumping from a sand surface requires more output from the quadriceps muscles than jumping from a rigid surface.
