Author(s): WADDELL, A., KORZEPA, M., BELFIELD, A., FRY, B., ELHASSAN, Y., MESQUITA, R., SMITH, D., QUINLAN, J., BREEN, L., Institution: UNIVERSITY OF LEICESTER, Country: UNITED KINGDOM, Abstract-ID: 2459

INTRODUCTION:
Reductions in skeletal muscle mass, strength and function can occur with ageing and disuse events triggered by illness and/or injury. While resistance exercise training is known to minimise some of these detriments, it is not always feasible. Vortex wave stimulation (VWS) may be a potential tool to mitigate skeletal muscle decline in such physiological scenarios, with efficacy shown in equine models. The aim of the present study was to explore the acute musculoskeletal and physiological effects of VWS in healthy older adults.
METHODS:
Fourteen healthy older adults (70.86 ± 5.70 years, BMI: 25.17 ± 2.75kg·m²) consumed deuterium oxide (D2O) stable oral isotope tracer, and underwent serial skeletal muscle biopsies to measure integrated rates of myofibrillar (iMyoPS) and sarcoplasmic (iSarcPS) protein synthesis and regulatory signalling over ~48 hours before (habitual) and after two consecutive day bouts of VWS. Myoelectrical activity during VWS was measured via surface electromyography as a surrogate for neuromuscular activation. Quadricep and gastrocnemius muscle oxygenation during VWS was measured via frequency-domain diffuse optical spectroscopy. Pre- to post-VWS changes in peripheral blood flow were assessed via duplex ultrasound to the superficial femoral artery, and circulating concentrations of inflammatory and bone turnover markers were also measured before, immediately following and 24 hours post-VWS. Data are expressed as mean difference (MD), and statistical significance was set as P < 0.05.
RESULTS:
There was an increase in iMyoPS (MD = 0.226%·day-1, P = 0.025), but not iSarcPS (MD = 0.074%·day-1, P = 0.582) above habitual rates following VWS. There was no difference in the expression of anabolic signalling proteins (all P > 0.05), nor peripheral blood flow (P = 0.118) following VWS. Myoelectrical activity increased during VWS (MD = 9.471 μV, P = 0.010), while muscle oxygenation decreased at both the quadricep (P = 0.017) and gastrocnemius (P = 0.001). There was a reduction in the concentration of P1NP post-VWS (P < 0.001), while there was no difference in other bone-turnover or inflammatory biomarkers.
CONCLUSION:
This is the first study to explore the musculoskeletal and physiological effects of VWS in humans. We demonstrated that two bouts of VWS significantly elevated integrated rates of myofibrillar protein synthesis, while also elevating myoelectrical activity, potentially indicating heightened neuromuscular activation. We also observed a decrease in lower limb muscle oxygenation, suggesting an increase in tissue oxygen extraction. These findings provide novel insights into VWS as a potential tool to offset some of the detrimental musculoskeletal effects of ageing, disuse and critical illness.