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

Abstract 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 90o pushup), 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 (90o push-up, trunk lift, sit-and-reach and curlup) 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 90o push-up was significantly associated (β = .353; p < .001) with PACER test scores (i.e., cardiorespiratory fitness). The related model (R2 = .324; F(4,205) = 26.061; p < .001) accounted for 32% of the variance in cardiorespiratory fitness. 90o push-up was associated with sit-and reach (β = .298; p < .001) and curl up (β = .413; p<= .001) test scores. When individually modeled, 90o push-up (β = -.461; p < .001) and PACER (β = -.436; p < .001) were inversely associated with weight status. Conclusions The 90o 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 90o push-up test is a tractable tool for physical fitness surveillance by clinicians, parents, and possibly youth themselves.