Fatigue, Electomyographic, And Metabolic Responses To Repeated Bench Press Sets At Different Ranges Of Motion

PURPOSE: To examine the effects of performing full or partial repetitions on fatigue, surface electromyographic activity (sEMG) and blood lactate concentration (BL) during repeated sets to failure in the bench press exercise. METHODS: Eight resistance trained men performed three bench press sets as fast as possible until failure against a load of 65% of 1-RM with 2 min rest on three occasions one week apart. On one occasion, the full movement was performed (FULL), while on the other two occasions movement was restricted either to the top half (HIGH, 24.9 ± 3.0 cm) or the bottom half (LOW, 25.8 ± 2.7 cm) of the full barbell vertical displacement. Fatigue was quantified by the number of repetitions in each set, and by the rate of decrease in mean barbell velocity. sEMG activity of the pectoralis major and triceps brachii were expressed as a percentage of sEMG attained during maximal isometric contraction. BL was measured at rest and twice after set 3 (30 s and 3 min). RESULTS: The load was heavier in HIGH (p < 0.001) compared to FULL and LOW (118 ± 13 vs. 96 ± 12 vs. 92 ± 13 kg, respectively). The number of repetitions in set 1 was higher in HIGH compared to LOW and FULL (29 ± 5 vs. 23 ± 6 vs. 16 ± 3 repetitions, all p < 0.001) but percent drop in the number of repetitions in sets 2 and 3 was similar in all conditions (44 and 67% compared to set 1, respectively). Mean barbell velocity was higher in FULL (p < 0.001), but similar in HIGH and LOW (0.71 ± 0.05 vs. 0.63 ± 0.07 vs. 0.67 ± 0.11 m/s). The rate of decline in mean velocity was doubled in set 3 compared to set 1 (0.02 ± 0.01 to 0.05 ± 0.02 m/s per repetition, p < 0.01), and was 50% higher in FULL than HIGH and LOW, which were identical. sEMG of pectoralis major increased from the start to the end of each set (88 ± 17 vs. 128 ± 28%, p < 0.001) with no differences between conditions and sets. sEMG of the triceps brachii also increased from the start to the end of each set but was lower in LOW compared to FULL and HIGH (88 ± 30 vs. 110 ± 40 vs. 101 ± 28%, p < 0.05). Peak BL was lower in LOW than FULL and HIGH (5.6 ± 1.3 vs. 6.5 ± 1.6 vs. 6.3 ± 1.5 mmol/L, p < 0.05). CONCLUSIONS: Fatigue is less in partial than full repetitions, and partial repetitions at the top half of the bench press exercise allow for more repetitions with heavier loads. The lower sEMG, BL and number of repetitions in LOW compared with HIGH may be explained by the longer length of the muscles involved.