Table 1. Incidence (% occurrence in all trials) of lower abdominals (LA) EMG burst during the flexion-relaxation response. Each subject performed four trials under stable and unstable base conditions. Stable Unstable 4 / 4 trials 44.4% 0% 2-3 / 4 trials 27.7% 16.6% 0-1 / 4 trials 27.7% 83.3%