Understanding the Negative Effects of Bed Rest and Using Exercise as Countermeasure

Physical activity appears to be an important lifestyle habit to achieve healthy aging by promoting autonomy and quality of life. Interestingly, the dramatic changes that the human body undergoes due to bedrest for illnesses and hospitalization are similar to those seen over decades of normal aging. Bedrest in otherwise healthy older individuals can lead to a reduction of muscle size and strength, changes in bone strength and function of the heart and blood vessels. Bedrest can also lead to changes in keeping proper balance as well as changes in processing and understanding information. All of these factors negatively affect activities of daily living leading to physical function impairment and development of frailty, a clinical condition associated with an increased risk for disease and death. The purpose of this study is to investigate whether exercise can counteract the negative effects of 2-week head tilt down bed rest on muscle function and metabolism, postural control, bone structure, orthostatic tolerance and cognitive function in adults. For this study the investigators will recruit 24 healthy men and women between 55 - 65 years of age. All subjects will spend a total of 26 days (5 days of adaption period, 14 days of bed rest with 6 degrees of downward inclination, and 7 days of recovery period) at the McGill University Health Centre (MUHC). During this study, 12 subjects will randomly undergo an exercise intervention as countermeasure during the 14 days of bed rest period and 12 will serve as control. Each subjects participation in this study will involve 1 telephone call (pre-screening) and 4 visits at the MUHC: 1 screening visit (Visit 1) followed by a 26-day long visit (Visit 2) and 2 follow-up visits (Visit 3 and Visit 4). During Visits 2 - 4 various measurements will be performed to assess sensorimotor control, muscle function and metabolism, bone structure, cardiovascular function, cognitive performance and function, and specimen collection (blood,