There is increasing evidence of the importance of musculoskeletal fitness as a determinant of health outcomes both in healthy young, middle-aged, and elderly adults and in adults with disability or chronic disease. A review of the relationship of early test batteries to health outcomes revealed that the evidence was limited, even though there was sound anatomical logical validity for a link between abdominal and back health and musculoskeletal fitness (Plowman, 1992). More recent evidence lends additional support to the idea that tests of abdominal and back extensor muscle endurance relate to back health status, as assessed by history of low-back pain, in adults (Payne et al., 2000).
In recent years, the link between musculoskeletal fitness and health in adults has extended beyond the initial focus on low-back health. Recent reviews have established positive associations between muscle strength and personal independence and quality of life, and inverse associations with cardiometabolic risk factors, frequency of cardiovascular disease events, risk of general morbidity for nonfatal diseases (e.g., fracture risk and cognitive decline), and all-cause mortality in middle-aged and elderly adults (Bohannon, 2008; Cooper et al., 2011; Garber et al., 2011; Warburton et al., 2001; Williams et al., 2007). Likewise, muscle endurance has been positively associated with overall quality of life and negatively associated with likelihood of falling and associated skeletal and soft tissue injuries (Warburton et al., 2001). Muscle power appears to decline more rapidly than muscle strength with aging, and loss of muscle power is strongly associated with decreases in functional ability (e.g., reduced ability to stand from sitting in a chair), and it may be predictive of decreased mobility and premature mortality in adults (Reid and Fielding, 2012; Warburton et al., 2001).
Skeletal muscle and its functional capacities may also be related to more health-related outcomes than has previously been appreciated. Reductions in skeletal muscle mass associated with acute or chronic illness may negatively impact musculoskeletal fitness as assessed by muscle strength, endurance, and power tests. Reduced muscle strength and function with accompanying loss of muscle mass in acute or chronic illness are related to increased recovery times, impaired patient quality of life, and likelihood of institutionalization (Wolfe, 2006). Further, skeletal muscle is a major regulator of glucose and fat metabolism and may play an important role in the development of the metabolic syndrome and perhaps even obesity (Jurca et al., 2005). The degree to which musculoskeletal fitness tests are predictive of the development of these conditions and their responsiveness to clinical management in adults remains an interesting yet untested question. Lastly, skeletal muscle may be an important determinant of bone and joint health in middle-aged and older adults as a result of direct muscle