Low‐load resistance training during step‐reduction attenuates declines in muscle mass and strength and enhances anabolic sensitivity in older men

• Published in: Physiological reports Vol. 3; no. 8; pp. e12493 - n/a
• Main Authors: Devries, Michaela C., Breen, Leigh, Von Allmen, Mark, MacDonald, Maureen J., Moore, Daniel R., Offord, Elizabeth A., Horcajada, Marie‐Noëlle, Breuillé, Denis, Phillips, Stuart M.
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01.08.2015; John Wiley & Sons, Ltd
• Subjects: Aging; Anabolic resistance; Arginine; Atrophy; Citrulline; Dietary supplements; Glycine; Human subjects; Leg; Metabolism; Musculoskeletal system; Nitric oxide; Older people; Original Research; Physical training; Protein biosynthesis; Proteins; resistance training; Sarcopenia; step‐reduction; Strength training; Vasodilation; Whey; step‐reduction; resistance training; Anabolic resistance; sarcopenia
• ISSN: 2051-817X; 2051-817X
• DOI: 10.14814/phy2.12493

Step‐reduction (SR) in older adults results in muscle atrophy and an attenuated rise in postprandial muscle protein synthesis (MPS): anabolic resistance. Knowing that resistance exercise (RT) can enhance MPS, we examined whether RT could enhance MPS following 2 weeks of SR. In addition, as we postulated that SR may impair feeding‐induced vasodilation limiting nutrient delivery to muscle, we also examined whether citrulline (CIT), as an arginine and nitric oxide precursor, could attenuate muscle anabolic resistance accompanying SR. We used a unilateral leg model to compare older subjects’ who had undergone SR to a loaded condition of SR plus RT (SR + RT). Thirty older men (70 ± 1 years) underwent 14 days of SR (<1500 steps/day) with supplementation of either 5 g/day CIT or glycine placebo. Throughout SR, subjects performed unilateral low‐load RT thrice weekly. We assessed muscle protein synthesis in the postabsorptive and postprandial state (20 g whey isolate plus 15 g glycine or as micellar‐whey with 5 g CIT or 15 g glycine, n = 10/group). As MPS was similar after ingestion of either whey isolate, micellar‐whey, or micellar‐whey + CIT data related to different dietary groups were collapsed to compare SR and SR + RT legs. Subjects’ daily steps were reduced by 80 ± 2% during SR (P < 0.001) compared with baseline. Leg fat‐free mass decreased with SR (−124 ± 61 g) and increased in the SR + RT (+126 ± 68 g; P = 0.003). Myofibrillar FSR was lower (P < 0.0001) in the SR as compared with the SR + RT leg in the postabsorptive (0.026 ± 0.001%/h vs. 0.045 ± 0.001%/h) and postprandial states (0.055 ± 0.002%/h vs. 0.115 ± 0.003%/h). We conclude that low‐load RT, but not supplementation with CIT, can attenuate the deleterious effects of SR in aging muscle. Older adults who take less daily steps lose muscle because their muscle becomes resistant to the usual effect of protein feeding and the synthesis of new proteins is suppressed. We think these data have massive ramifications for understanding how sarcopenia progresses in older persons. The good news is that even a small amount of low‐load contraction can offset the loss of muscle, in fact it even stimulated a small amount of muscle growth.