Resistance exercise volume affects myofibrillar protein synthesis and anabolic signalling molecule phosphorylation in young men

• Published in: The Journal of physiology 2010-08, Vol.588 (16), p.3119-3130
• Main Authors: Burd, Nicholas A., Holwerda, Andrew M., Selby, Keegan C., West, Daniel W. D., Staples, Aaron W., Cain, Nathan E., Cashaback, Joshua G. A., Potvin, James R., Baker, Steven K., Phillips, Stuart M.
• Format: Article
• Language: English
• Subjects: Adult; Biopsy; Blood Glucose - metabolism; Blotting, Western; Electromyography; Eukaryotic Initiation Factor-2B - metabolism; Fasting; Humans; Infusions, Intravenous; Insulin - blood; Intracellular Signaling Peptides and Proteins - metabolism; Male; Muscle Fatigue; Muscle Proteins - biosynthesis; Myofibrils - metabolism; Phenylalanine - administration & dosage; Phenylalanine - blood; Phosphorylation; Postprandial Period; Quadriceps Muscle - metabolism; Resistance Training; Ribosomal Protein S6 - metabolism; Ribosomal Protein S6 Kinases, 70-kDa - metabolism; Ribosomal Protein S6 Kinases, 90-kDa - metabolism; Signal Transduction; Skeletal Muscle and Exercise; Time Factors; Young Adult
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.2010.192856

We aimed to determine if any mechanistic differences exist between a single set (1SET) and multiple sets (i.e. 3 sets; 3SET) of resistance exercise by utilizing a primed constant infusion of [ring‐13C6]phenylalanine to determine myofibrillar protein synthesis (MPS) and Western blot analysis to examine anabolic signalling molecule phosphorylation following an acute bout of resistance exercise. Eight resistance‐trained men (24 ± 5 years, BMI = 25 ± 4 kg m−2) were randomly assigned to perform unilateral leg extension exercise at 70% concentric one repetition maximum (1RM) until volitional fatigue for 1SET or 3SET. Biopsies from the vastus lateralis were taken in the fasted state (Fast) and fed state (Fed; 20 g of whey protein isolate) at rest, 5 h Fed, 24 h Fast and 29 h Fed post‐exercise. Fed‐state MPS was transiently elevated above rest at 5 h for 1SET (2.3‐fold) and returned to resting levels by 29 h post‐exercise. However, the exercise induced increase in MPS following 3SET was superior in amplitude and duration as compared to 1SET at both 5 h (3.1‐fold above rest) and 29 h post‐exercise (2.3‐fold above rest). Phosphorylation of 70 kDa S6 protein kinase (p70S6K) demonstrated a coordinated increase with MPS at 5 h and 29 h post‐exercise such that the extent of p70S6K phosphorylation was related to the MPS response (r= 0.338, P= 0.033). Phosphorylation of 90 kDa ribosomal S6 protein kinase (p90RSK) and ribosomal protein S6 (rps6) was similar for 1SET and 3SET at 24 h Fast and 29 h Fed, respectively. However, 3SET induced a greater activation of eukaryotic translation initiation factor 2Bɛ (eIF2Bɛ) and rpS6 at 5 h Fed. These data suggest that 3SET of resistance exercise is more anabolic than 1SET and may lead to greater increases in myofibrillar protein accretion over time. An acute bout of weight lifting or resistance exercise stimulates the muscles to make more protein, and the accumulation of protein within them leads to their enlargement. It is unknown if increasing the amount of exercise from one set to three will lead to a greater increase in the rates at which the muscles make more protein. We report that in young men performing leg extension exercise for either one set or three sets to fatigue at 70% of their best effort, muscle protein synthesis was stimulated at 5 hours post‐exercise. However, the response was greater for three sets, and the elevation in protein synthesis was sustained a day later only after the performance of three sets. These res