Improving Muscle for Functional Independence Trial

Overview

Aging is associated with declines in muscle strength, power, and overall functional ability that lead to disability and loss of independence. Furthermore, the existing high prevalence of obesity in the elderly is greatly exacerbating these aging-related declines in function. To date, regular exercise, especially resistance exercise, is the only known treatment to consistently improve muscle function and perhaps delay the onset of disability. However, not all individuals experience the same magnitude of benefit from a given exercise stimulus, and accumulating data show that obesity limits muscle adaptations to chronic exercise.Therefore, the proposed study is designed to determine the effects of caloric restriction on improvements in skeletal muscle function in response to RT.

Design Overview: This is a 5-month randomized trial in 130 older, overweight or obese, sedentary men and women. Phase 1 involves recruitment and screening followed by baseline research testing (Phase 2). Next, subjects will be randomly assigned to one of two 5-month treatments (Phase 3): RT intervention alone (RT) or to an RT with caloric restriction (RT+CR) intervention. Subjects will return for visits the completion of their 5 month intervention. A subset of participants (n=30) will return for an 18 month follow up. Interventions: Resistance training+ Caloric Restriction:Participants assigned to RT+CR group will be instructed to follow a hypocaloric diet (-600 kcal/d) for 20 weeks, as well as the resistance training program noted below.In addition, all participants will be provided with a daily calcium (1200 mg/d) and vitamin D (800 IU/d) supplement.The intervention will incorporate meal replacements, nutrition education, and lifestyle behavior modifications. Resistance training: The maximal weight that can be lifted with correct form in a single repetition (1RM) will be used to prescribe intensity. Strength testing will be repeated every 4 wks and the training loads adjusted so that they are consistent with the 70% 1RM goal. Participants will exercise 3 d/wk on Nautilus resistance machines, under the supervision of two exercise leaders who are trained in basic life support and in emergency management procedures. All exercise will take place at Wake Forest University's Department of Health and Exercise Science Clinical Research Center (CRC). Participants will exercise in small groups which will allow a rotation/rest between machines and enhance the social environment. Heart rate and blood pressure will be measured before and after each session. Subjects will warm-up by walking or cycling for 5 minutes at a slow pace followed by large muscle flexibility exercises. The interventionists will ensure that participants adjust the equipment appropriate to their body size and complete the exercises with correct form. Training sessions will end with a cool-down by walking or cycling for 5 minutes at a slow pace followed by light stretching.