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Effects of different accentuated eccentric loads on acute neuromuscular, growth hormone, and blood lactate responses during a hypertrophic protocol

Timo Ojasto, Keijo Häkkinen
Journal of Strength and Conditioning Research 2009, 23 (3): 946-53
19387381
This study monitored acute neuromuscular responses and growth hormone (GH) and blood lactate (La) concentrations in the eccentric-concentric (ECC-CON) hypertrophic protocol by using various dynamic accentuated external resistance (DAER) loads in the bench press exercise. Male subjects (age = 32 +/- 4 years; n = 11) performed 4 sets of 10 repetitions with 2 minutes of recovery between the sets. The loads were 70, 80, 90, and 100% of 1 repetition maximum (RM) for the ECC phase, whereas 70% RM was constantly used for the CON phase. Electromyographic activity (EMG), ECC, CON, and isometric (ISOM) forces, serum GH and blood La, were measured at pre- and postloading. Significant reductions occurred in ISOM and CON pre- to postforces in all loading conditions (p < 0.01 - 0.001). Pre- to postchange in blood La in the 90/70% condition (9.5 +/- 2.3 mmolxL) was greater (p < 0.05) than in the control 70/70% condition (7.7 +/- 1.1 mmolxL). The highest individual pre- to postchange in blood La was larger after the 90/70% (p < 0.001) condition compared with the 70/70% condition. The post-GH concentration in the 90/70% loading was 8.7 +/- 1.9 microgxL and in the abstract. --> 3.5 +/- 1.5 microgxL in the control condition, but the difference did not reach statistical significance. ECC EMG of the agonists increased with the increase in load but significantly only in the deltoid anterior (p < 0.01). A significant relationship was observed between the "optimal" ECC load and 1RM per body mass (BM)-ratio (r = 0.85; p < 0.05). The findings suggest that the acute metabolic and GH responses in the 90/70% condition were more favourable compared with the 70/70% condition, and a significant correlation between the optimal ECC load and 1RM per BM-ratio was observed. The findings can be applied into practice in designing exercise protocols in training for muscle hypertrophy and suggest the importance of individualized load selection for DAER exercises.

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