Myofibrillar Protein Synthesis and Acute Intracellular Signaling with Elastic Band Resistance Exercise in Young and Older Men.

Purpose: Resistance exercise training (RET) attenuates age-related muscle and strength loss ("sarcopenia"). However, compared with machine-based RET, the efficacy of cost-effective, accessible elastic band RET (EB-RET) for muscle adaptive remodeling lacks supporting mechanistic evidence. Methods: Eight young (YM; 24 ± 4 yr) and eight older (OM; 68 ± 6 yr) untrained males consumed an oral stable isotope tracer (D2O) combined with serial vastus lateralis muscle biopsies to measure integrated myofibrillar protein synthesis (iMyoPS) and regulatory signaling over ~48 h before (habitual) and after an acute bout of EB-RET (6 × 12 repetitions at ~70% of one-repetition maximum). iMyoPS was determined via gas chromatography–pyrolysis–isotope ratio mass spectroscopy and regulatory signaling expression by immunoblot. Results: Habitual iMyoPS did not differ between YM and OM (1.62% ± 0.21% vs 1.43% ± 0.47%·d−1, respectively, P = 0.128). There was a significant increase in iMyoPS after EB-RET in YM (2.23% ± 0.69%·d−1, P = 0.02), but not OM (1.75% ± 0.54%·d−1, P = 0.30). EB-RET increased the phosphorylation of key anabolic signaling proteins similarly in YM and OM at 1 h postexercise, including p-IRS-1Ser636/639, p-AktSer473, p-4EBP-1Thr37/46, p-P70S6KThr389, and p-RPS6Ser240/244, whereas p-TSC2Thr1462 and p-mTORSer2448 increased only in YM (all P < 0.05). There were no differences in the expression of amino acid transporters/sensors or proteolytic markers after EB-RET. Conclusions: iMyoPS was elevated after EB-RET in YM but not OM. However, the increase in acute anabolic signaling with EB-RET was largely similar between groups. In conclusion, the capacity for EB-RET to stimulate iMyoPS may be impaired in older age. Further work may be necessary to optimize prescriptive programming in YM and OM. [ABSTRACT FROM AUTHOR]