Acta Physiol Scund 1990, 140, 31-39
Effects of eccentric and concentric muscle actions in resistance training E. B. C O L L I A N D E R and P . A. T E S C H Department of Environmental Medicine, Karolinska Institute, and Department of Clinical Neurophysiology, Karolinska Hospital, Stockholm, Sweden
P. A. 1990. Effects of eccentric and concentric muscle COLLIANDER, E. B. & TESCH, actions in resistance training. Actu Physiol Scund 140, 31-39. Received 16 January 1990, accepted 18 April 1990. ISSN 0001-6772. Department of Environmental Medicine, Karolinska Institute, and Department of Clinical Neurophysiology, Karolinska Hospital, Stockholm, Sweden. 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 concentric (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. vastus lateralis and 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% increases in slow-twitch fibre area in Grps CON and ECCON and in fast-twitch fibre area in Grp CON were nonsignificant. 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 accommodated resistance training is mainly due to neural adaptation.
Key words: bilateral muscular strength, fibre type composition and area, hypertrophy, strength training. Increases in muscular strength are induced by the performance of low-repetition high-force muscle actions (DeLorme 1945). Although heavy-resistance training may produce muscle hypertrophy (MacDougall et al. 1980, Hakkinen et al. 1985, Sale et al. 1987), the increased strength observed subsequent to short-term programmes is mainly due to neural adaptations (Moritani & deVries 1979). This is manifested in increases in strength that are not paralleled by Correspondence : E.B.' Colliander, Department of Environmental Medicine, Karolinska Institutet, S104 01 Stockholm, Sweden.
corresponding increases in muscle fibre size (Thorstensson et al. 1976, MacDougall et al. 1980) or muscle cross-sectional area (Ikai & Fukunaga 1970, Moritani & deVries 1979, Jones & Rutherford 1987). Accordingly, strengthtrained athletes show greater strength relative to muscle cross-sectional area than non-athletes (Sale & MacDougall 1984, Ryushi et al. 1988), albeit this is not a consistent finding (Schantz et al. 1983, Sale et al. 1987). Maximal voluntary force is greater during eccentric than concentric muscle actions (Asmussen et al. 1965, Komi & Viitasalo 1977). If high
E. B. Colliander nnd P. A. Tesch
force production p u se is a decisive stimulus for strength increases, thcn it appears conceivable that training optimizing the eccentric load would be more effectiw than training consisting of concentric muscle actions only. T h i s h!-pothesis is supported b!. greater strength increases denionstrated subsequent to maximurn training employing voluntary eccentric muscle actions (Komi & Ruskirk 1977) or combined overload eccentric and concentric muscle actions, using free weights (Hikkinen & Komi 1981), than training using concentric muscle actions only. However, eccentric training regimens not necessarily providing optimal load have produced strength gains cornparable to those of concentric training (Seliger t-t al. 1968, Johnson et a / . 1976, Joncs & Rutherford 1987). The aim ofthis study was to further imestigate 15 het her eccentric muscle actions are essential to induce optimal increases in muscular strength. To studj- this, one experimental group carried out combined eccentric and concentric muscle actions. For comparison, in a second subject group eccentric actions were substituted by concentric muscle actions. Hence, each individual performed an identical number of bilateral maximum voluntary muscle actions. For the purposes of training and testing, a dynamometer providing accommodated resistance at constant angular velocity \+as used. More specifically, this study examined the responses to these two regimens with regard to uni- and bilateral Concentric and eccentric muscle strength at various angular velocities, functional strength performance and skeletal muscle morpholog!,.
11A T E R I A L S A N D I I E T H O D S Sltbjii.ts
Physically active males (n = 31) with asymptomatic knee function and nithout preyious experience of regular strength-training programmes volunteered. The protocol was approved by the Karolinska Institute Ethics Committee. After giving their informed consent the subjects were randomly assigned to Grp concentric (