Objective: To evaluate the health-related content validity of nine fitness tests by studying how low, mid, and high levels of fitness are associated with perceived health and musculoskeletal functioning.
Design: Cross-sectional methodological study.
Setting: A research institute for health promotion.
Participants: Middle-aged (37 to 57 years) men (n = 245) and women (n = 253), evenly selected from five age cohorts of a random population sample.
Main outcome measures: The odds ratios (ORs) of selected health outcomes for low (least fit 20%), mid (next 40%), and high (most fit 40%) fitness categories in the different tests adjusted for several possible confounders.
Results: Cardiorespiratory fitness, as measured by 2-km walk test, was strongly and consistently associated with perceived health and mobility (stair climbing) in both genders (range of ORs, 2.4 to 17.6), and a somewhat weaker relationship was found with leg power and with leg strength (ORs, 2.5 to 7.2). Low fitness in back muscular endurance and upper-body strength were associated with mobility disability (ORs, 2.8 to 8.5) and with back dysfunction and pain (ORs, 2.9 to 6.1). High fitness in back endurance in men and in balance in women were related to positive back health (ORs, 2.5 to 3.7). Body mass index was associated with musculoskeletal disability in women (ORs, 2.4 to 5.3). Balance, leg strength, and leg flexibility in men; and leg power, trunk and leg flexibility in women were not associated with health outcomes.
Conclusions: Among a middle-aged population, the majority of the evaluated fitness tests demonstrated health-related validity by strong associations with perceived health and musculoskeletal functioning, and by weaker associations with back symptoms.