Skeletal muscle is very adaptable and has a fast response to various developmental effects
(growth, exercise, lifestyle, injury, illness, etc.). Influences from the environment (altitude, temperature,
gravity, etc.) also affect skeletal muscle characteristics. In addition, skeletal muscle loses the flexibility and
weight as well as its function with age, as long as it is not used enough. If the muscle is not exposed to regular
or high physical stress (such as: inactive life or sedentary lifestyle, hospitalization – bed rest, immobilization,
flight to space, etc.) can occur loss of muscle tone and volume - muscle atrophy. This area is now rapidly
gaining in importance, because of the aging of the population, sedentary lifestyle and ultimately travelling
to space (microgravity). To confront and understand the adjustments in this kind of environment we have
to simulate these environments with horizontal bed rest. Many older individuals decline functionally during
hospitalization, and the deleterious consequences of bed rest may be one cause. This study reports on the effect
of 14-days of bed rest on muscle parameters in healthy young and older adults. Healthy young (N=7) and
older adults (N=12) remained on bed rest for 14 days continuously followed by recovery. Measures of muscle
caracteristics were measured before and after bed rest and also after recovery. In healthy older adults, 14 days
of bed rest results in loss of muscle fibre and whole muscle characteristics. Identification of interventions to
maintain muscle function during hospitalization or periods of bed rest in older adults should be a high priority.
