Low-load resistance training during step-reduction attenuates declines in muscle mass and strength and enhances anabolic sensitivity in older men.
Level 2 - randomized trial
Randomized trial using a within-subject unilateral exercise model and parallel nutritional groups
PubMed 26265753 · doi:10.14814/phy2.12493
What was done
Thirty older men (mean age 70 ± 1 years) underwent 14 days of step-reduction (<1500 steps/day) combined with supplementation of either 5 g/day citrulline or glycine placebo alongside different whey protein formulations (n = 10 per group). Using a within-subject unilateral leg model, one leg was subjected to step-reduction alone (SR) while the contralateral leg performed low-load resistance training three times weekly (SR + RT). Postabsorptive and postprandial myofibrillar fractional synthetic rate (FSR) and leg fat-free mass were measured.
What was found
Citrulline supplementation did not affect muscle protein synthesis, so dietary groups were collapsed. Daily steps fell by 80 ± 2% during step-reduction (P < 0.001). Leg fat-free mass declined by 124 ± 61 g in the SR leg and increased by 126 ± 68 g in the SR + RT leg (P = 0.003). Postabsorptive myofibrillar FSR was lower in the SR leg compared to the SR + RT leg (0.026 ± 0.001%/h vs. 0.045 ± 0.001%/h; P < 0.0001), as was postprandial FSR (0.055 ± 0.002%/h vs. 0.115 ± 0.003%/h; P < 0.0001).
Why it matters
Short periods of disuse cause rapid muscle loss and anabolic resistance in older adults; this study shows that low-load resistance exercise effectively preserves muscle mass and anabolic sensitivity during inactivity, whereas citrulline supplementation does not.
Limits
The study included only healthy older men, limiting generalizability to women and clinical populations. The sample size was small (n = 30), the duration was short (14 days), and numerical data for strength outcomes were omitted from the abstract despite being referenced in the title.
Cited by
- supports Abrupt step reduction induces anabolic resistance in older individuals.