Author(s): BOGDANIS, G., TSOUKOS, A., Institution: NATIONAL & KAPODISTRIAN UNIVERSITY OF ATHENS, Country: GREECE, Abstract-ID: 875

INTRODUCTION:
Previous studies have shown that exercise at long muscle length may have a significant effect on force and power output and may also induce a greater degree of fatigue [1]. Also, it has been suggested that training at long muscle lengths using a relatively long time under tension (TUT) may maximize muscle hypertrophy [2]. However, little is known regarding the reduction in muscle performance during repeated sets of resistance exercise at different muscle lengths. Therefore, the aim of this study was to examine the impact of muscle length on inter- and intra-set decrease in power output during repeated sets of bench press exercise.
METHODS:
Following familiarization and maximum strength testing (1RM), ten resistance trained men performed three sets to failure with two min of recovery at two different ranges of motion (ROM) in the bench press exercise on a Smith machine: (a) one condition in which the barbell was moved at the upper half of the full ROM (SHORT) and (b) another condition in which the barbell was moved at the lower half of the full ROM (LONG). Repetitions were executed as fast as possible, against a load of 65% of the ROM-specific 1RM. Force was measured using two force plates on which the bench was placed, and barbell velocity was monitored by a linear transducer.
RESULTS:
Barbell vertical displacement was similar in SHORT and LONG (25.1 ± 27.0 vs. 26.4 ± 28.0 cm, respectively, p>0.5). 1RM was higher in SHORT than LONG (120 ± 14 vs. 94 ± 17 kg, p<0.001). Mean power output at the start of each set was higher at SHORT compared with LONG (set 1: 511 ± 27 vs. 426 ± 63 W, p<0.001), but it dropped to similar values at the end of each set, irrespective condition . The percent drop of mean power within each set was similar across both sets conditions (SHORT: 45 ± 17, LONG: 43 ± 13%), as was the drop of mean power at the initial repetitions (6 ± 16% vs. 2 ± 12% from set 1 to set 2, respectively, p>0.5 and 12 ± 10% vs. 15 ± 8% from set 2 to set 3, respectively, p>0.5). TUT was 25 % higher (57.1 ± 9.6 vs. 46.0± 10.1 s, p=0.012) and total impulse was 60% higher in SHORT than long (49.0 ± 10.2 vs. 30.6 ± 9.1 kN.s, p<0.001).
CONCLUSION:
Exercising at the upper part of the full ROM in the bench press exercise results in considerably higher applied forces over a longer period of time (TUT), compared with exercise at the lower part of ROM. These differences may be due to the different muscle length and the mechanical advantage at the upper part of ROM and the findings may have implications for training.