The influence of eccentric exercise on mRNA expression of skeletal muscle regulators.

To evaluate change in myostatin, follistatin, MyoD and SGT mRNA gene expression using eccentric exercise to study mechanisms of skeletal muscle hypertrophy. Young (28+/-5 years) and older (68+/-6 years) men participated in a bout of maximal single-leg eccentric knee extension on an isokinetic dynamometer at 60 degrees /s: six sets, 12-16 maximal eccentric repetitions. Muscle biopsies of the vastus lateralis were obtained from the dominant leg before exercise and 24 h after exercise. Paired t tests were used to compare change (pre versus post-exercise) for normalized gene expression in all variables. Independent t tests were performed to test group differences (young vs. older). A probability level of P<or=0.05 was used to determine statistical significance with Bonferroni adjustments. We observed no significant change in myostatin (-0.59+/-2.1 arbitrary units (AU); P=0.42), follistatin (0.22+/-3.4; P=0.85), MyoD (0.23+/-3.1; P=0.82), or SGT (1.2+/-6.4; P=0.58) mRNA expression in young subjects 24 h after eccentric exercise. Similarly, we did not observe significant change in myostatin (-3.83+/-8.8; P=0.23), follistatin (-2.66+/-5.2; P=0.17), MyoD (-0.13+/-3.1; P=0.90), or SGT (-1.6+/-3.5; P=0.19) mRNA expression in older subjects. Furthermore, the non-significant changes in mRNA expression were not different between young and older subjects, P>0.23 for all variables. Our data suggests that a single bout of maximal eccentric exercise does not alter myostatin, follistatin, MyoD or SGT mRNA gene expression in young or older subjects.