NEUROMUSCULAR FATIGUE TO POWER LOADING USING A WEIGHT-STACK DEVICE FITTED WITH OR WITHOUT ADDITIONAL RUBBER BAND RESISTANCE

Peltonen, H, Walker, S, Hakkinen, K, and Avela, J. Neuromuscular fatigue to power loading using a weight-stack device fitted with or without additional rubber band resistance. J Strength Cond Res 28(7): 1802-1811, 2014-The addition of a rubber band (RB) to traditional weight-based resistance may be beneficial regarding the deceleration phase common during explosive power actions with light weights. This would lead to greater force and muscle activity during the latter part of the movement, but this may influence the distribution of neuromuscular fatigue. Fifteen men performed 2 knee extension power loadings (5 x 5 x 40% of 1 repetition maximum [1RM]) using a typical weight-stack device without (WS) and with the addition of a RB (WS + RB) in a crossover design. Concentric contractions were performed as fast as possible, and analyzed for torque, velocity, power, and vastus lateralis and medialis surface electromyography (EMG) parameters over 208 segments (range of motion, 60-180 degrees) from throughout the loading. Additionally, maximum isometric knee extension was analyzed preloading and postloading for torque and EMG parameters, and for voluntary activation level using the twitch interpolation technique. Peak concentric power occurred at 100-120 degrees on both devices but was greater during WS + RB (p <= 0.05). Electromyographic amplitude was greater in WS at 80-120 degrees, p <= 0.05-0.01. Loading-induced reductions in peak concentric power (-12 +/- 8 vs. -4 +/- 10 kW, p <= 0.05) and voluntary activation level (-5.5 +/- 7 vs. -1.1 +/- 5%, p <= 0.05) were greater when using WS + RB. However, a greater reduction in root mean square of electromyography over 0-100 milliseconds was observed after WS (-31 +/- 22 vs. 10 +/- 26%, p<0.05) accompanied by a large reduction in torque over 0-100 milliseconds. It seems that activation strategies, and consequently neuromuscular fatigue, during power loading could be modified through the addition of RB resistance.