TWO STRENGTH-TRAINING SESSIONS PRODUCE CHANGES IN MUSCLE FUNCTION
Patikas, D., Paraschos, I., Bassa, E., Galazoulas, C., Skooufas, D., & Kotzamanidis, C. (2009). The effects of a short-term isometric training program on the neuromuscular function of elite Greek jumpers and long-distance runners. A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.
This study assessed the effect of a two-day strength training protocol on the neuromuscular function and especially on the rate of force development of the plantar flexor muscles in elite jumpers (N = 9) and long-distance runners (N = 9). Ss were tested 48 hours before and after an isometric, ballistic type, strength training protocol consisting of two sessions separated by 48 hours. Testing and training were conducted on the plantar flexor muscles of the ankle. Torque and EMG amplitude as well as frequency component using spike analysis for the gastrocnemius, soleus, and tibialis anterior muscles were measured during maximal voluntary contraction. Additionally, the maximal M-wave and the twitch torque properties were measured after a supramaximal electrical stimulation over the tibial nerve.
Maximal voluntary isometric torque remained unchanged, while, the voluntary maximal rate of force development recorded 100 ms after the onset of contraction improved only in the long-distance runners. This was accompanied by an increase in the gastrocnemius EMG frequency. The peak twitch torque, contraction time, half-relaxation time, and maximal M-wave remained unchanged in both groups. Before training, jumpers exhibited higher twitch torque, shorter contraction time, and shorter half-relaxation time, compared to the values of the long-distance runners.
Implication. Rate of force development is enhanced after two sessions of a strength training program, with no parallel increase in maximal strength, in persons with a relatively low level of strength. Such quick adaptations are evident in muscles with a larger proportion of fast motor units, such as gastrocnemius. Since the adaptations occur so quickly, it is likely the changes occur through neural adaptations, which supports the notion that spinal and supraspinal centers contribute to the adaptations observed after a short-term, ballistic, isometric training.
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