Influence of eccentric actions on skeletal muscle adaptations to resistance training

Abstract

Three different training regimens were performed to study the influence of eccentric muscle actions on skeletal muscle adaptive responses to heavy resistance exercise. Middle-aged males performed the leg press and leg extension exercises two days each week. The resistance was selected to induce failure within six to twelve repetitions of each set. Group CON/ECC (n = 8) performed coupled concentric and eccentric actions while group CON (n = 8) used concentric actions only. They did four or five sets of each exercise. Group CON/CON (n = 10) performed twice as many sets with only concentric actions. Eight subjects did not train and served as controls. Tissue samples were obtained from m. vastus lateralis using the biopsy technique before and after 19 weeks of training, and after four weeks of detraining. Histochemical analyses were performed to assess fibre type composition, fibre area and capillarization. Training increased (P less than 0.05) Type IIA and decreased (P less than 0.05) Type IIB fibre percentage. Only group CON/ECC increased Type I area (14%, P less than 0.05). Type II area increased (P less than 0.05) 32 and 27%, respectively, in groups CON/ECC and CON/CON, but not in group CON. Mean fibre area increased (P less than 0.05) 25 and 20% in groups CON/ECC and CON/CON, respectively. Capillaries per fibre increased (P less than 0.05) equally for Type I and Type II fibres. Capillaries per fibre area for both fibre types, however, increased (P less than 0.05) only in groups CON and CON/CON. The changes in fibre type composition and capillary frequency were manifest after detraining.(ABSTRACT TRUNCATED AT 250 WORDS)

A mechanism for increased contractile strength of human pennate muscle in response to strength training: changes in muscle architecture

“…5B), indicating a more readily evoked hypertrophy response for the type II fibres. These relative changes are in agreement with those previously observed with heavy-resistance strength training regimes (Hather et al 1991;Staron et al 1994;Volek et al 1999). Comparable evidence of a preferential or more pronounced type II fibre hypertrophy in response to heavy resistance training has been reported previously (e.g.…”

“…Comparable evidence of a preferential or more pronounced type II fibre hypertrophy in response to heavy resistance training has been reported previously (e.g. Hather et al 1991;Roman et al 1993;Volek et al 1999;Kadi et al 1999;Andersen & Aagaard, 2000;Hortobagyi et al 2000). Apparently, type II muscle fibres seem to possess a greater adaptive responsiveness to the intense muscle-loading regimes associated with heavy-resistance training.…”

“…The apparent discrepancy between these results (~10 %) likely resides from inter-study differences in subject age, size and training status, which obviously will have a strong influence on muscle CSA and volume. It is interesting to note that the above discrepancy also was apparent at the muscle fibre level, as pre-training muscle fibre areas were ~10 % lower than those frequently observed for physically active young males (Hather et al 1991;Staron et al 1994).…”

Electrically stimulated resistance training in SCI individuals increases muscle fatigue resistance but not femoral artery size or blood flow

“…6 Short-term high-load resistance training has been shown to evoke increases in not only muscle mass, but also in capillarity, albeit in AB subjects. [7][8][9] The significance of these adaptations is that development of cardiovascular disease and Type II diabetes with SCI may be diminished or delayed by improving the muscles and arteries of individuals with SCI. 10 One potential limitation to NMES training for individuals with SCI is excessive muscle fatigue.…”

Resistance Training Supplements and their Potential Benefit

“…The mTOR signal serves to increase protein synthesis by increasing the number of messenger RNA translated per ribosome. Insulin concentrations parallel changes in blood glucose, and the response is enhanced when protein and carbohydrates are ingestion prior to, during, or after a workout [26].…”