MUSCLE MORPHOLOGICAL AND STRENGTH ADAPTATIONS TO ENDURANCE VS. RESISTANCE TRAINING

Farup, J, Kjolhede, T, Sorensen, H, Dalgas, U, Moller, AB, Vestergaard, PF, Ringgaard, S, Bojsen-Moller, J, and Vissing, K. Muscle morphological and strength adaptations to endurance vs. resistance training. J Strength Cond Res 26(2): 398-407, 2012-Fascicle angle (FA) is suggested to increase as a result of fiber hypertrophy and furthermore to serve as the explanatory link in the discrepancy in the relative adaptations in the anatomical cross-sectional area (CSA) and fiber CSA after resistance training (RT). In contrast to RT, the effects of endurance training on FA are unclear. The purpose of this study was therefore to investigate and compare the longitudinal effects of either progressive endurance training (END, n =7) or RT (n = 7) in young untrained men on FA, anatomical GSA, and fiber GSA. Muscle morphological measures included the assessment of vastus lateralis FA obtained by ultrasonography and anatomical GSA by magnetic resonance imaging of the thigh and fiber GSA deduced from histochemical analyses of biopsy samples from m. vastus lateralis. Functional performance measures included (V) over dotO(2)max and maximal voluntary contraction (MVC). The RT produced increases in FA by 23 +/- 8% (p < 0.01), anatomical GSA of the knee extensor muscles by 9 +/- 3% (p = 0.001), and fiber GSA by 19 +/- 7% (p < 0.05). RT increased knee extensor MVC by 20 +/- 5% (p < 0.001). END increased (V) over dotO(2)max by 10 +/- 2% but did not evoke changes in FA, anatomical GSA, or in fiber GSA. In conclusion, the morphological changes induced by 10 weeks of RT support that FA does indeed serve as the explanatory link in the observed discrepancy between the changes in anatomical and fiber GSA. Contrarily, 10 weeks of endurance training did not induce changes in FA, but the lack of morphological changes from END indirectly support the fact that fiber hypertrophy and FA are interrelated.