Effects of eccentric and concentric muscle actions in resistance training

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Abstract
The adaptive responses to two different resistance training regimens were compared. Healthy males performed five sets of either 12 maximum bilateral concentric (Grp CON; n = 11) or six pairs of maximum bilateral eccentric and cocentric (Grp ECCON; n = 11) quadriceps muscle actions three times per week for 12 weeks. Uni- and bilateral eccentric and concentric peak torque at various angular velocities, vertical jump height and three-repetition maximum half-squat were measured before and after training. Muscle biopsies were obtained from m. mass vastus lateralis analysed for fibre type composition and area using histochemical techniques. In contrast to a control group (n = 7), performing no training, Grps CON and ECCON demonstrated marked increases (P < 0.05) in overall eccentric (19 and 37% respectively) and concentric (15 and 26% respectively) peak torques. Grp ECCON, however, showed greater (P < 0.05) increases in peak torque, vertical jump height and three repetition maximum than Grp CON. The 7% increase in slow-twitch fibre area in Grps CON and ECCON and in fast-twitch fibre area in Grp CON were non-significant. This study suggests that increases in peak torque and strength-related performance parameters were greater following a programme consisting of maximum concentric and eccentric muscle actions than resistance training using concentric muscle actions only. Because increases in muscle fibre areas were small it is also suggested that the increased muscle strength shown subsequent to short-term accomodated resistance training is mainly due to neural adaptation.