EFFECTS OF DIFFERENT ACCENTUATED ECCENTRIC LOADS ON ACUTE NEUROMUSCULAR, GROWTH HORMONE, AND BLOOD LACTATE RESPONSES DURING A HYPERTROPHIC PROTOCOL

Ojasto, T and Hakkinen, K. Effects of different accentuated eccentric loads on acute neuromuscular, growth hormone, and blood lactate responses during a hypertrophic protocol. J Strength Cond Res 23(3): 946-953, 2009-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 mmol.L-1) was greater (p < 0.05) than in the control 70/70% condition (7.7 +/- 1.1 mmol.L-1). 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 mg.L-1 and 3.5 +/- 1.5 mg.L-1 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.