Muscle activation during resistance training with no external load - effects of training status, movement velocity, dominance, and visual feedback

To explore the acute effects of training status, movement velocity, dominance, and visual feedback on muscle activation and rating of perceived exertion (RPE) during resistance training with no external load (no-load resistance training; NLRT). Thirty-three men (17 untrained and 16 trained), performed elbow flexions in four NLRT sessions: 1) slow velocity with EMG visual feedback, 2) slow velocity without EMG visual feedback, 3) fast velocity with EMG feedback, and 4) fast velocity without EMG feedback. RPE was measured using the Borg Discomfort scale. EMG for the biceps and triceps were recorded for both arms. EMG feedback had no influence on RPE. The peak and mean EMG values were not different for the biceps (93.8 ± 11.5% and 50 ± 13.1%) and triceps (93.7 ± 23.9% and 49.6 ± 16.2%). The results revealed a difference in the training status, with higher peak EMG for untrained than for trained participants (96.9 ± 20% vs. 90.2 ± 15.6%). However the values for mean EMG were not different between the untrained and trained (50.3 ± 15.7% vs. 49.2 ± 13.7%) participants. There was no difference in the peak (92.8 ± 19% vs. 94.7 ± 20.4%) and mean (49.8 ± 15.0% vs. 49.7 ± 14.5%) EMG values for the dominant and non-dominant sides. Peak EMG values were not different between faster and slower velocities (93.6 ± 19.6% and 93.9 ± 17.8%). However, mean EMG was higher for slower (50.5 ± 14.4%) than for faster (48.5 ± 15.4%) velocities. The peak and mean EMG during contractions with (93.3 ± 17.5% and 49.5 ± 14.1%) and without visual feedback (94.2 ± 19.9% and 50 ± 15.4%) were not significantly different. NLRT produces high levels of muscle activation independent of training, status, dominance, movement velocity, and visual feedback.