Purpose. The purpose of the present study was to analyze the influence of static stretching duration on quadriceps muscle isometric force and electromyographic (EMG) activity of the rectus femoris and vastus lateralis. Basic procedures. Twenty recreationally-active healthy men were selected for the study. On two separate days, participants took part in two stretching protocols of different durations. Following a specific warmup, participants performed isometric strength assessments of the dominant leg before and after a bout of quadriceps stretching. The stretching protocol consisted of two stretches for the quadriceps muscle for three repetitions of 30 seconds on one visit, and 60 seconds on the other. Main findings. The results revealed a significant reduction in quadriceps muscle mean and peak forces and EMG activity for the rectus femoris with both 30- and 60-second stretching protocols (p ≤ 05). However, EMG activity of the vastus lateralis decreased significantly only in the 60-second protocol (p ≤ 05). Conclusions. Both stretching protocols induced significant decreases in strength and EMG activity, although the stretching duration (60 × 30) did not appear to be a major influencing factor for the current strength reductions. In this perspective, coaches and athletes should avoid flexibility training which consists in stretching repetitions of 30 seconds or longer prior to competitions.