Association between 90(o) push-up and cardiorespiratory fitness: cross-sectional evidence of push-up as a tractable tool for physical fitness surveillance in youth

BACKGROUND: Despite being associated with health outcomes like abdominal adiposity, depression, anxiety, and cardiovascular disease risk among youth, largely, clinicians still do not adopt physical fitness testing. A clarion call for increased surveillance was previously issued, in order to address the US population-level lack of knowledge regarding pervasive inactivity among children. Because schools often do not send home annual physical fitness testing results, many lay parents are unaware of their child’s physical fitness or the risk of associated adverse health outcomes. This study investigated associations between musculoskeletal fitness measures (including 90(o) push-up), cardiorespiratory fitness, and weight status. METHODS: Two hundred and ten students (9.7 ± 1.08 years, 138.6 ± 9.4 cm; 42.3 ± 14.4 kg) across third through fifth grades were tested for cardiorespiratory (i.e., Progressive Aerobic Cardiovascular Endurance Run (PACER)) and musculoskeletal (90(o) push-up, trunk lift, sit-and-reach and curl-up) fitness. The relationships between measures of musculoskeletal and cardiorespiratory fitness were modeled using a series of linear regression analyses. Models were adjusted for age, sex, and weight status. Significant two-tailed tests were set at p < .05. RESULTS: Of the four musculoskeletal fitness measures, only 90(o) push-up was significantly associated (β = .353; p < .001) with PACER test scores (i.e., cardiorespiratory fitness). The related model (R(2) = .324; F (4,205) = 26.061; p < .001) accounted for 32% of the variance in cardiorespiratory fitness. 90(o) push-up was associated with sit-and reach (β = .298; p < .001) and curl up (β = .413; p < = .001) test scores. When individually modeled, 90(o) push-up (β = −.461; p < .001) and PACER (β = −.436; p < .001) were inversely associated with weight status. CONCLUSIONS: The 90(o) push-up test (a measure of upper body muscle strength and endurance) was associated with cardiorespiratory fitness, anterior trunk muscle strength and endurance, and lower back and posterior thigh muscle flexibility in youth aged 8–12 years old. Although the current findings do not establish a causal relationship, it is concluded that the 90(o) push-up test is a tractable tool for physical fitness surveillance by clinicians, parents, and possibly youth themselves.