A single bout of prior resistance exercise attenuates muscle atrophy and declines in myofibrillar protein synthesis during bed‐rest in older men

Abstract

Impairments in myofibrillar protein synthesis (MyoPS) during bed rest accelerate skeletal muscle loss in older adults, increasing the risk of adverse secondary health outcomes. We investigated the effect of prior resistance exercise (RE) on MyoPS and muscle morphology during a disuse event in 10 healthy older men (65–80 years). Participants completed a single bout of unilateral leg RE the evening prior to 5 days of in‐patient bed‐rest. Quadriceps cross‐sectional area (CSA) was determined prior to and following bed‐rest. Serial muscle biopsies and dual stable isotope tracers were used to determine rates of integrated MyoPS (iMyoPS) over a 7 day habitual ‘free‐living’ phase and the bed‐rest phase, and rates of acute postabsorptive and postprandial MyoPS (aMyoPS) at the end of bed rest. Quadriceps CSA at 40%, 60% and 80% of muscle length significantly decreased in exercised (EX) and non‐exercised control (CTL) legs with bed‐rest. The decline in quadriceps CSA at 40% and 60% of muscle length was attenuated in EX compared with CTL. During bed‐rest, iMyoPS rates decreased from habitual values in CTL, but not EX, and were significantly different between legs. Postprandial aMyoPS rates increased above postabsorptive values in EX only. The change in iMyoPS over bed‐rest correlated with the change in quadriceps CSA in CTL, but not EX. A single bout of RE attenuated the decline in iMyoPS rates and quadriceps atrophy with 5 days of bed‐rest in older men. Further work is required to understand the functional and clinical implications of prior RE in older patient populations. imageKey points Age‐related skeletal muscle deterioration, linked to numerous adverse health outcomes, is driven by impairments in muscle protein synthesis that are accelerated during periods of disuse. Resistance exercise can stimulate muscle protein synthesis over several days of recovery and therefore could counteract impairments in this process that occur in the early phase of disuse. In the present study, we demonstrate that the decline in myofibrillar protein synthesis and muscle atrophy over 5 days of bed‐rest in older men was attenuated by a single bout of unilateral resistance exercise performed the evening prior to bed‐rest. These findings suggest that concise resistance exercise intervention holds the potential to support muscle mass retention in older individuals during short‐term disuse, with implications for delaying sarcopenia progression in ageing populations.

Scheduled for surgery? Prescription: exercise!

“…All in all, the study by Smeuninx et al. (2024) is well conducted, of high scientific impact and much needed in the field, and our critical discussion of the applicability of the chosen exercise model in a clinical setting does not detract from this. There remains an abundance of scientific advances to pursue.…”

“…In a recent study published in The Journal of Physiology , Smeuninx et al. (2024) investigated the impact of a single bout of lower‐limb resistance exercise performed the evening before commencing a 5 day bed rest period in healthy elderly individuals. In line with the expectation of the authors, the exercise bout reduced the decline in muscle protein synthesis rate by ∼0.1% per day relative to the control leg.…”

“…At the convergence of exercise physiology, geriatrics and skeletal muscle biology, the study by Smeuninx et al. (2024), has sparked several new questions for future research. Below, we will discuss, firstly, the acute changes in muscle protein synthesis after exercise and how these should be disentangled from those observed with muscle injury, and secondly, how prehabilitative exercise initiatives in the future can take on a bigger role in clinical practice.…”

“…At the cellular level, neither prehabilitative exercise nor bed rest led to changes in muscle fibre cross-sectional area, which, as the authors rightly suggest, might be attributable to larger intra-individual variation for that measure. At the convergence of exercise physiology, geriatrics and skeletal muscle biology, the study by Smeuninx et al (2024), has sparked several new questions for future research. Below, we will discuss, firstly, the acute changes in muscle protein synthesis after exercise and how these should be disentangled from those observed with muscle injury, and secondly, how prehabilitative exercise initiatives in the future can take on a bigger role in clinical practice.…”

“…As depicted in Fig. 1A, some studies, such as the one by Smeuninx et al (2024), use an acute intervention that alters the immediate trajectory during the period of disuse. With this model, the protein synthesis is maintained, initially overriding any declines that would occur during bedrest.…”