Musculoskeletal and physiological responses to vortex wave stimulation in older adults

Reductions in musculoskeletal mass and function can occur with ageing and disuse. While resistance exercise training is known to minimise these detriments, it is not always feasible. Vortex wave stimulation (VWS) may mitigate skeletal muscle decline in such scenarios. The aim of the present study was to explore the acute physiological and metabolic effects of VWS in healthy older adults. Fourteen participants consumed deuterium oxide (D₂O) stable oral isotope tracer for 7 days. Serial skeletal muscle biopsies were obtained to measure integrated rates of myofibrillar (iMyoPS) and sarcoplasmic (iSarcPS) muscle protein synthesis and regulatory signalling over ∼48 h before (habitual) and after two consecutive-day bouts of VWS. Myoelectrical activity and muscle oxygenation during VWS, and pre-post changes in peripheral blood flow and concentrations of inflammatory and bone turnover markers were also measured. There was an increase in iMyoPS (0.23% day^-1, P = 0.025), but not iSarcPS (0.07% day^-1, P = 0.582) above habitual rates following VWS. There was no difference in the expression of anabolic signalling proteins, nor peripheral blood flow following VWS. Myoelectrical activity increased during VWS (9.47 µV, P = 0.010), while muscle oxygenation decreased at the gastrocnemius (P = 0.001) and quadriceps (P = 0.017). There was a reduction in P1NP (8.27 µg L^-1) and lactate (0.84 mmol L^-1) concentration post-VWS (both P < 0.001), while there was no difference in other biomarkers. This is the first study to demonstrate that VWS elicits acute physiological responses congruent with musculoskeletal adaptive remodelling, which warrants further exploration. KEY POINTS: Resistance exercise is known to mitigate skeletal muscle atrophy associated with ageing and/or disuse but is not always feasible. We investigated, for the first time, the effects of a novel mechanical stimulus - vortex wave stimulation (VWS) - on integrated rates of myofibrillar and sarcoplasmic muscle protein synthesis, alongside other musculoskeletal and physiological outcomes, in healthy older adults. We demonstrated that VWS elevated myofibrillar, but not sarcoplasmic muscle protein synthesis compared to baseline, while increasing myoelectrical activity and reducing muscle oxygen saturation, lactate and bone turnover markers. These findings suggest VWS elicits acute physiological responses congruent with musculoskeletal adaptive remodelling.