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 remodelling lacks supporting mechanistic evidence.

METHODS: 8 young (YM; 24 ± 4 yrs) and 8 older (OM; 68 ± 6 yrs) 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 signalling over ~48 hrs prior to (habitual) and following an acute bout of EB-RET (6x12 repetitions at ~70% of one-repetition maximum). iMyoPS was determined via gas chromatography-pyrolysis-isotope ratio mass spectroscopy and regulatory signalling expression by immunoblot.

RESULTS: Habitual iMyoPS did not differ between YM and OM (1.62 ± 0.21 vs 1.43 ± 0.47%·day ^-1, respectively; P = 0.128). There was a significant increase in iMyoPS after EB-RET in YM (2.23 ± 0.69%day ^-1; P = 0.02), but not OM (1.75 ± 0.54%day ^-1; P = 0.30). EB-RET increased the phosphorylation of key anabolic signalling proteins similarly in YM and OM at 1 h post-exercise, including p-IRS-1^Ser636/639, p-Akt^Ser473, p-4EBP-1^Thr37/46, p-P70S6K^Thr389 and p-RPS6^Ser240/244, whereas p-TSC2^Thr1462 and p-mTOR^Ser2448 increased only in YM (all P < 0.05). There were no differences in the expression of amino acid transporters/sensors or proteolytic markers following EB-RET.

CONCLUSIONS: iMyoPS was elevated following EB-RET in YM but not OM. However, the increase in acute anabolic signalling 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 optimise prescriptive programming in YM and OM.