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Fasted‐state skeletal muscle protein synthesis after resistance exercise is altered with training
Author(s) -
Kim Paul L.,
Staron Robert S.,
Phillips Stuart M.
Publication year - 2005
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2005.093708
Subject(s) - myofibril , medicine , skeletal muscle , endocrinology , resistance training , muscle hypertrophy , vastus lateralis muscle , phenylalanine , leg press , cardiology , chemistry , biochemistry , amino acid
The purpose of the present investigation was to determine how fasted‐state protein synthesis was affected, acutely, by resistance training. Eight men (24.8 ± 1.7 years, body mass index = 23.2 ± 1.0 kg m −2 ; means ± s.e.m. ) undertook an 8 week programme of unilateral resistance exercise training (3 sessions week −1 , progression from two to four sets; intensity was 80% of the subjects' single repetition maximum (1RM): knee extension and leg press). Following training, subjects underwent two primed constant infusions of l ‐[ ring ‐ 13 C 6 ]phenylalanine to determine mixed and myofibrillar muscle protein synthesis (MPS) at rest and 12 h after an acute bout of resistance exercise at the same exercise intensity – each leg 80% of 1RM. Biopsies (vastus lateralis) were taken to measure incorporation of labelled phenylalanine into mixed and myofibrillar skeletal muscle proteins and yield fractional MPS. Training resulted in significant dynamic strength gains that were greater ( P < 0.001) in the trained leg. Hypertrophy of type IIa and IIx fibres ( P < 0.05) was observed following training. After training, resting mixed MPS rate was elevated (+48%; P < 0.05). Acutely, resistance exercise stimulated mixed MPS only in the untrained leg ( P < 0.05). Myofibrillar MPS was unchanged at rest following training ( P = 0.61). Myofibrillar MPS increased after resistance exercise ( P < 0.05), but was not different between the trained and untrained legs ( P = 0.36). We observed divergent changes in resting mixed versus myofibrillar protein synthesis with training. In addition, resistance training modified the acute response of MPS to resistance exercise by dampening the increased synthesis of non‐myofibrillar proteins while maintaining the synthesis of myofibrillar proteins.