Light-load resistance exercise increases muscle protein synthesis and hypertrophy signaling in elderly men

• Published in: American journal of physiology: endocrinology and metabolism Vol. 312; no. 4; pp. E326 - E338
• Main Authors: Agergaard, Jakob, Bülow, Jacob, Jensen, Jacob K., Reitelseder, Søren, Drummond, Micah J., Schjerling, Peter, Scheike, Thomas, Serena, Anja, Holm, Lars
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.04.2017
• Subjects: Age; Aged; AKT protein; Elongation; Exercise; Exercise - physiology; Geriatrics; Humans; Hypertrophy; Intracellular signalling; Leg; Load distribution; Load resistance; Male; Maltodextrin; Men; Muscle Proteins - biosynthesis; Muscle, Skeletal - drug effects; Muscle, Skeletal - metabolism; Muscles; Muscular system; Older people; Phosphorylation - drug effects; Protein Biosynthesis; Protein synthesis; Proteins; Proto-Oncogene Proteins c-akt - metabolism; Quadriceps muscle; Rapamycin; Resistance Training; Signal Transduction - drug effects; Signaling; Skeletal muscle; Strength training; TOR protein; Translation; Translation elongation; Treatment Outcome; Whey; Whey protein; Whey Proteins - administration & dosage; muscle protein synthesis; mTORC1 signaling; resistance exercise; hypertrophy; light load; sarcopenia
• ISSN: 0193-1849; 1522-1555; 1522-1555
• DOI: 10.1152/ajpendo.00164.2016

The present study investigated whether well-tolerated light-load resistance exercise (LL-RE) affects skeletal muscle fractional synthetic rate (FSR) and anabolic intracellular signaling as a way to counteract age-related loss of muscle mass. Untrained healthy elderly (>65-yr-old) men were subjected to 13 h of supine rest. After 2.5 h of rest, unilateral LL-RE, consisting of leg extensions (10 sets, 36 repetitions) at 16% of 1 repetition maximum (RM), was conducted. Subsequently, the subjects were randomized to oral intake of 4 g of whey protein per hour (PULSE, n = 10), 28 g of whey protein at 0 h and 12 g of whey protein at 7 h postexercise (BOLUS, n = 10), or 4 g of maltodextrin per hour (placebo, n = 10). Quadriceps muscle biopsies were taken at 0, 3, 7, and 10 h postexercise from the resting and the exercised leg of each subject. Myofibrillar FSR and activity of select targets from the mechanistic target of rapamycin complex 1-signaling cascade were analyzed from the biopsies. LL-RE increased myofibrillar FSR compared with the resting leg throughout the 10-h postexercise period. Phosphorylated (T308) AKT expression increased in the exercised leg immediately after exercise. This increase persisted in the placebo group only. Levels of phosphorylated (T37/46) eukaryotic translation initiation factor 4E-binding protein 1 increased throughout the postexercise period in the exercised leg in the placebo and BOLUS groups and peaked at 7 h. In all three groups, phosphorylated (T56) eukaryotic elongation factor 2 decreased in response to LL-RE. We conclude that resistance exercise at only 16% of 1 RM increased myofibrillar FSR, irrespective of nutrient type and feeding pattern, which indicates an anabolic effect of LL-RE in elderly individuals. This finding was supported by increased signaling for translation initiation and translation elongation in response to LL-RE.