Resistance training offers promise in helping reduce or reverse spaceflight induced muscle loss. Recent studies have also shown that the timing of feedings around a session of resistance training may maximize the effect of exercise on muscle protein balance. Dr. Carmen Sceppa is testing whether the use of timed feedings given before resistance training sessions is superior to resistance training alone as a countermeasure against muscle loss induced by bed rest. Evaluation will include multiple body composition measurements and examination of muscle strength, functional performance and muscle gene expression.
Overview
Timed Feeding and Resistance Training to Prevent Muscle Atrophy
Principal Investigator:
Carmen C. Sceppa, M.D., Ph.D.
Organization:
Tufts University
Technical Summary
Muscle mass and strength, important components of health-related fitness, are significantly reduced during spaceflight due to a combination of factors, including the elimination of gravity and dietary deficits. Resistance training (RT) is an exercise modality that offers the hope of mitigating or reversing muscle loss induced by weightlessness. Recent studies suggest that the timing of an essential amino acid (AA) supplement around a session of RT may augment the affect of exercise on muscle protein balance. The present study evaluates the effect of an integrated nutrition and RT approach as a countermeasure against deleterious effects of spaceflight on muscle health using bed-rest as a model of weightlessness.
The hypotheses of this study are that:
- The combination of timed feeding (TF) of an essential AA supplement with RT (TFRT) is more effective than RT or TF alone as a countermeasure against bed-rest-induced muscle loss.
- TFRT accelerates recovery from 28 days of bed rest compared to RT or TF alone over 14 days following strict bed rest.
- TFRT works at least in part by modulating muscle levels of anabolic growth factors and cytokines (insulin-like growth factor-1, transforming growth factor-beta, and interleukin-15), and catabolic cytokines (interleukin -1beta, interleukin-6, myostatin, and tumor necrosis factor-alpha).
Earth Applications
The logistical difficulties of studying alterations in muscle during, or even after, space missions have stimulated the development of ground-based models, such as bedrest, to simulate weightlessness. In general, reductions in muscle strength and cross-sectional area (CSA) during bed rest are very similar to those seen with spaceflight. For example, thirty days of bed rest produce an 18-20% decrease in isokinetic strength of the knee extensors, a 6% decrease in the knee flexors, and an 8% reduction in mid-thigh muscle CSA. Additionally, it has been shown that knee extensor strength, whole muscle CSA, and vastus lateralis fiber CSA decreases by 25-30% (various angular velocities), 14%, and 18%, respectively, after six weeks of bed rest.
An important question relevant to spaceflight conditions, as well as to many clinical situations resulting in prolonged bed rest, is the extent of loss during immobilization in addition to the length of recovery required after a prolonged stay in space (or after post-surgery bed rest). After prolonged bed rest, significant deficits in muscle strength and muscle CSA may persist for weeks, suggesting that reambulation is not enough to recover function in a timely manner. The use of concentric and eccentric actions has resulted in strength preservation or enhancement, maintenance of muscle protein synthesis and prevention of fiber atrophy. The project is the first that we know of to propose to enhance this effect using timed feedings. An understanding of the recovery process can help us design better rehabilitation strategies since recovery in the absence of rehabilitation is incomplete and muscle function is compromised even weeks post-intervention.
The Earth-based applicability of this project is to develop an integrated nutrition and exercise countermeasure against these deleterious effects of immobilization. However, the potential of exercise and nutritional interventions to minimize the loss of muscle function and exercise capacity, and the optimal combination of these modalities, are not known. Resistance training is one modality that offers the hope of mitigating or reversing muscle loss induced by weightlessness. Recent studies suggest that the timing of feedings around a session of RT may augment the effect of exercise on muscle protein balance. This is the very question we are investigating.
This project's funding ended in 2006