Comparison of muscle activity and tissue oxygenation during strength training protocols that differ by their organisation, rest interval between sets, and volume

Abstract

Purpose: The acute effects of a single training session on muscle activity and oxygenation were compared between a new strength training method (3/7 protocol) and a more classical method (4 × 6 and 8 × 6 protocols).

Method: All protocols consisted of lifting and lowering a load (70 % 1RM) with the elbow-flexor muscles. The 3/7 protocol involved 5 sets of increasing number of repetitions during successive sets (from 3 to 7 repetitions), and brief rest interval between sets (15 s). The other two protocols consisted of either 4 or 8 sets of 6 repetitions with a rest interval between sets of 2.5 min. Surface electromyogram (EMG) of biceps brachii, brachioradialis, and triceps brachii, and tissue oxygenation index (TOI) of the two elbow flexors were recorded.

Result: For all muscles, EMG increased similarly (50-60 %) during each set in the 4 × 6 and 8 × 6 protocols but gradually during the successive sets in the 3/7 protocol. At protocol completion, EMG reached greater value (p < 0.003) in the 3/7 protocol. TOI decreased during each set in all protocols but contrary to 4 × 6 and 8 × 6 protocols, it did not return to resting values between sets in the 3/7 protocol. The deficit in TOI per repetition was greater (p < 0.001) in the 3/7 (-142.5 ± 48.8 %) than 4 × 6 (-113.1 ± 48.8 %) and 8 × 6 (-105.9 ± 59.2 %) protocols for biceps brachii but not brachioradialis.

Conclusion: The results indicate that brief rest interval between sets and incremental number of repetitions in successive sets induced greater muscle activity and metabolic changes compared with method of constant repetitions per set and longer rest interval.

Keywords: Dynamic contractions; Electromyography; Metabolic stress; Near-infrared spectroscopy; Training methods.