Proceedings of The Physiological Society
University College Dublin (2009) Proc Physiol Soc 15, C38
Effect of doubling the volume of resistance exercise on myofibrillar protein synthesis (MPS) and anabolic signaling in muscle of postabsorptive young and old men
V. Kumar1, A. Selby1, D. Rankin1, K. Smith1, P. Atherton1, W. Hildebrandt1, N. Hiscock2, M. J. Rennie1
1. Clinical Physiology, The University of Nottingham, Derby, United Kingdom. 2. Unilever Discover R & D, Sharnbrook, United Kingdom.
Figure 1. Time course of responses of MPS (%/h) to exercise at 75% 1RM of 3 or 6 sets of leg extension exercise in post absorptive young and older subjects. Mean ± SEM. * = P<0.05 vs. basal (ANOVA with Bonferroni post hoc adjustment). NB protein synthesis is measured over 2.5 h in the basal pre-exercise state and then over the periods shown post-exercise.
We have previously reported that older men show a blunted dose response relationship between increases in MPS and intensity of resistance exercise in the post absorptive state (Kumar et al 2009). We have now tested the hypothesis that doubling the volume of exercise would increase the MPS response in overnight fasted men, both young (n=5, 24±6 y, body mass index (BMI) 23±2 kg.m-2) and elderly (n=6, 70±5 y, BMI 24±2 kg.m-2). The subjects performed, at a 3 months interval, first 3 and then 6 sets of 8 repetitions of isotonic unilateral leg extension at 75% of their one repetition maximum (1 RM). Muscle biopsies were taken from the vastus lateralis of the exercised leg under local anaesthesia (1% lignocaine sc) before, immediately after and 1, 2 and 4 h after exercise. After separation of myofibrillar protein, incorporation of [1,2-13C]leucine was measured (by gas chromatography-combustion-mass spectrometry) and MPS calculated using plasma labeling of α-ketoisocaproate as surrogate precursor. Figure 1. In young men doubling the volume of exercise at 75% 1RM had no additional effect on the response of MPS in the post absorptive state; however, in older men, it resulted in a more rapid and greater response. The results suggest that there is increased latency of response to exercise in muscle of older men.
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