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Effects of Different Accentuated Eccentric Load Levels in Eccentric-Concentric Actions on Acute Neuromuscular, Maximal Force, and Power Responses

Ojasto, Timo; Häkkinen, Keijo

Journal of Strength & Conditioning Research: May 2009 - Volume 23 - Issue 3 - pp 996-1004
doi: 10.1519/JSC.0b013e3181a2b28e
Original Research

Ojasto, T and Häkkinen, K. Effects of different accentuated eccentric load levels in eccentric-concentric actions on acute neuromuscular, maximal force, and power responses. J Strength Cond Res 23(3): 996-1004, 2009-This study examined the effects of different dynamic accentuated external resistance load levels during the eccentric(ECC) phase of ECC-concentric (CON) actions on acute neuromuscular, maximal force, and power responses in the bench press exercise in male subjects (age, = 32 ± 4 years; n = 11). Four maximum strength sessions consisted of 1 repetition maximum (RM) lifts with traditional isoinertial resistances and of 1RM lifts with the different dynamic accentuated external resistance (DAER) loads of 100, 105, 110, and 120% of 1 RM for the ECC phase, whereas 100% of 1RM was constantly used for the CON phase. One explosive strength session consisted of explosive repetitions with the 50, 60, 70, 80, and 90% of 1RM loads for the ECC phase, whereas 50% of 1RM was constantly used for the CON phase. Force, power, and electromyography (EMG) activation of agonist deltoid, pectoralis major, triceps brachii, and antagonist biceps brachii muscles were recorded. In all maximum strength DAER sessions (105/100%, 110/100%, and 120/100%), CON 1RM and CON force reduced (p < 0.05) compared with the control condition (100/100%). ECC muscle activity did not differ in the DAER loading conditions compared with the control loading condition. In the explosive strength session, peak power increased significantly from the 50/50% condition compared to the condition of 77.3 ± 3.2/50% (p < 0.001) that produced the highest power for each individual. ECC agonist EMG activity increased significantly from the 50% condition to that of the 77.3 ± 3.2/50% condition (p < 0.05). The present data showed that the different loads used in the DAER bench press action did not enhance maximum concentric strength production, but concentric power output during explosive actions with the individualized optimal load was larger compared with the control condition.

Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland

Address correspondence to Keijo Häkkinen, Keijo.Hakkinen@sport.jyu.fi.

© 2009 National Strength and Conditioning Association