The current physical activity recommendations to improve bone mineral density (BMD) and physical fitness are not suitable for all populations. For instance, many older adults cannot perform high load, low repetition resistance training to increase BMD and individuals with orthopedic limitations cannot complete weight bearing, high intensity interval training (HIIT) to increase physical fitness.

STUDY 1:​ To evaluate an alternative to improve BMD, 20 untrained adults were randomly assigned to 27 weeks of either full body, low load, high repetition strength training (S-WEIGHT) or core focused strength training (S-CORE). BMD increased significantly for S-WEIGHT in the arms (+4%), legs (+8%), pelvis (+6%) and lumbar spine (+4%), but not for S-CORE. Therefore, a low load, high repetition resistance training program may be an effective method to improve BMD in older or untrained adults.

STUDY 2:​ To evaluate an alternative to improve cardiovascular and musculoskeletal fitness with HIIT, 36 trained adults were assigned to either a 6-week experimental group, in which they replaced one of their current 60-minute cardiovascular exercise sessions with 2, 30-minute HIIT indoor cycling sessions (G-HIIT) or a control group, in which they maintained their current physical activity regimen (G-FIT). Peak oxygen consumption increased significantly for only GHIIT (+9.7%), while mean leg strength increased (+12.0%) and body fat mass decreased (-5.8%). There were no significant changes with G-FIT. Thus, HIIT cycling may be an efficacious method to enhance physical fitness in trained adults. In summary, low load, high repetition resistance training and non-weight bearing high intensity cycling training could be effective alternatives to improve health and fitness in greater segments of the population.