Changes in surface EMG signal under the influence of peripheral fatigue

The purpose of this study was to find out if surface EMG signal enables a differentiation between high- and low-frequency peripheral fatigue that was caused with two different sports activities. Ten students (age, 24.2 ± 3.39 years; weight, 79.32 ± 12.95 kg) performed consecutive hops for 60 s (to induce high-frequency fatigue) and cycling at maximal intensity for 30 s (to induce low-frequency fatigue). Before and after both activities, the m. vastus lateralis was stimulated with 2 consecutive trains at 20 Hz and 100 Hz and, at the same time, the torque at the knee joint was measured. The torque ratio between 100 Hz and 20Hz was calculated to define the type of peripheral fatigue. Additionally, a response of m. vastus lateralis to 2 supramaximal electrical impulses delivered to the femoral nerve at 50 Hz was measured. Hopping resulted in high-frequency fatigue, the ratio between forces at 100 Hz and 20 Hz decreased for 10.7 ± 8.3% (p