Effect of 14-days of reduced physical activity on muscle function and size, inflammatory profile, and exercise-induced activation of stress responses in skeletal muscle in healthy older males
Background
We know that after the age of 50 our muscles start to get smaller by about 1% per year. We also know that with age we lose strength, but much faster than we would expect based on the rate at which muscle size is lost. Keeping physically active as we age is likely to be the key factor in slowing down this loss of muscle size and strength. We know that when people don’t use their muscles for a long period of time, such as during bed rest, then muscle size and strength are lost very quickly. Compared to younger people, older people are much more vulnerable to muscle loss as a result of bed rest, often losing over twice as much muscle over the same length of time as younger people.
There is, however, new evidence to suggest that limiting the amount of walking a person does (in this example, by limiting their steps to less than 1,500 per day for two weeks) can have a dramatic effect on muscle size. 1,500 steps per day is roughly the equivalent to being housebound. Data from previous studies show that younger people who reduce their daily steps to 1,500 per day for two weeks, lost 2.5% of leg muscle size, whilst an older group lost 4% over the same period.
What the research hopes to achieve
The aim of this research project is to understand changes in the body that lead to dramatic muscle loss when older people’s activity is reduced for two weeks. We also aim to understand what happens to muscle strength during this two week period of step-reduction. We want to discover ways in which older people can prevent losses in muscle size and strength if, for example, they had no option but to reduce their physical activity for a period of two weeks. In particular, we are interested in using exercise to protect against this muscle loss; either in the weeks leading up to the step-reduction period, or in small, regular bouts during the step-reduction period. Thereafter, we aim to explore the best ways to restore lost muscle size and strength using exercise and diet.