King Grub
2008-11-13, 11:13
We investigated how myofibrillar protein synthesis and muscle anabolic signalling were affected by resistance exercise at 20-90% of 1 repetition maximum (1 RM) in two groups of 25 each, postabsorptive, healthy, young (24+/-6 y) and old (70+/-5 y) men with identical body mass indices (24+/-2 kg.m(-2)). We hypothesized that, in response to exercise, anabolic signalling molecule phosphorylation and MPS would be modified in a dose-dependant fashion, but to a lesser extent in older men. Vastus lateralis muscle was sampled before, immediately after, and 1, 2 and 4 h post-exercise. MPS was measured by incorporation of [1,2-(13)C]leucine (gas chromatography-combustion-mass spectrometry using plasma [1,2-(13)C]alpha-ketoisocaparoate as surrogate precursor); the phosphorylation of p70 ribosomal S6 kinase (p70s6K) and eukaryotic initiation factor 4E binding protein 1(4EBP1) was measured using Western analysis with anti-phosphoantibodies. In each group, there was a sigmoidal dose-response relationship between MPS at 1-2 h post-exercise and exercise intensity, which was blunted (P<0.05) in the older men. At all intensities, MPS fell in both groups to near basal values by 2-4 h post-exercise. The phosphorylation of p70s6K and 4EBP1 at 60-90% 1 RM was blunted in older men. At 1 h post-exercise at 60-90% 1 RM, p70s6K phosphorylation predicted the rate of MPS at 1-2 h post-exercise in the young but not in the old. The results suggest that in the postabsorptive state (i) MPS is dose-dependant on intensity rising to a plateau at 60-90% 1 RM; (ii) older men show anabolic resistance of signalling and MPS to resistance exercise.
J Physiol. 2008 Nov 10. Age-related differences in dose response of muscle protein synthesis to resistance exercise in young and old men.
http://jp.physoc.org/cgi/rapidpdf/jphysiol.2008.164483v1
J Physiol. 2008 Nov 10. Age-related differences in dose response of muscle protein synthesis to resistance exercise in young and old men.
http://jp.physoc.org/cgi/rapidpdf/jphysiol.2008.164483v1