The Impact of Bed Rest, Aging and NMES on Skeletal Muscle

Loss of muscle mass is common phenotypic trait of muscular disuse and ageing. The loss of muscle mass affects, among others, the ability to maintain homeostasis of glucose metabolism and the energy reservoir in catabolic conditions, while also affecting mechanical muscle function which can cause detrimental impairments in general functional status and hence quality of life.However, a limited amount of research has attempted to elucidate molecular regulators of muscle mass loss following bed rest in older individuals and across genders. Consequently, the mechanistic drivers are unresolved and there are currently no effective therapeutic strategies to counteract muscle wasting and loss of function in individuals submitted to bed rest e.g. during hospitalization.Purpose The purpose is to examine the effects of 5 days of bed rest on muscle mass, including myofibrillar protein synthesis and breakdown, and muscle function, and elucidate molecular regulators of muscle mass loss and metabolic pathways, while also investigating if potential negative effects can be counteracted by daily NeuroMuscular Electrical Stimulation (NMES) across different age and genders.Methods The study is designed as a randomized controlled cross-over 5-day bed rest study including a group of healthy young (18-30 years) and healthy old (65-80 years) men and women.Participants will receive daily electrical stimulation (NMES) of the thigh muscles (30 min x 3/day) on one leg (ES), while the other leg serves as a control (CON).Participants will be tested at baseline (pre) and after (post) intervention for muscle strength, muscle power, balance, and muscle activation. Blood samples are collected at several time points and muscle biopsies are sampled pre- and post-intervention along with assessment of whole-body muscle mass and thigh muscle mass.Scientific exposition The results from the study can potentially provide insight into the adaptive mechanisms associated with NMES training and muscular disuse on both cellular- and whole-body level. The understanding of the underlying mechanisms is crucial for the application of NMES in a therapeutic context and will furthermore help us understand the basic mechanism regulating the skeletal muscle mass during both training and muscular disuse.Overall, the results can potentially help establishing treatments to counteract loss of muscle mass, muscle function and muscle health during periods of muscular disuse.

Inclusion Criteria:HealthyAge between 18-30 or 65-80 yearsInjury free in the lower extremities (No previous or current knee injuries or knee pain)Normal weightConsumes normal dietExclusion Criteria:Cognitive impairment affecting the ability to participate in the study.Health related contraindications to participating in the intervention (i.e., bed rest and/or NMES), such as eczema and rash on the lower extremitiesSmokerObesityNot able to speak or understand Danish.Acute or chronic diseases such as diabetes, cancer, embolism, infection, cardio-vascular diseasesUse of medication which affects myofibrillar protein synthesis or the skeletal muscle tissueUse of other medication (e.g. anticoagulants, adrenal cortex hormone [within the last 3 months] etc.)Previous or current use of anabolic steroidsPrevious participation in research trials involving deuterium oxide or another stable isotope tracer