BACKGROUND: Low levels of physical activity and high levels of sedentary behavior are generally associated with decreased overall muscular fitness (MF) and cardiorespiratory fitness (CRF) in young adults. However, it is unclear whether reduced lower body MF is associated with lower peak performance on a VO2Peak test. This study assessed whether MF, as well as the relative reason (muscular fatigue and cardiorespiratory factors) for terminating a VO2Peak test are associated with CRF, controlling for sociodemographic and anthropometric characteristics. METHODS: Data were collected from 30 young adults 18-20 years of age (37% female, 47% Non-Hispanic White, body mass index (BMI) =24.3 kg/m2). MF was assessed as standing broad jump (SBJ) distance (cm). CRF was assessed as the highest value of milliliters of oxygen used in one minute per kilogram of body weight [mL/kg/min] during a graded VO2Peak treadmill test. After completing their VO2Peak test, participants rated the relative extent (0-100 scale) to which muscular fatigue or cardiorespiratory factors affected their decision to terminate the test. A score of 0 meant that participants stopped primarily because their legs were tired, and a score of 100 meant that participants stopped primarily because they were out of breath or their heart was beating hard/fast. Linear regression analysis assessed the relationship between VO2Peak (response), SBJ (explanatory variable), and self-reported reasons using the relative scale for terminating the VO2Peak test (explanatory variable). All analyses controlled for sociodemographic (sex, race/ethnicity) factors and BMI as additional covariates. RESULTS: Results showed a significant positive association between SBJ and VO2Peak (​​β = 0.18, p = 0.001). No other covariates were found to be significant. There was no significant association between the relative extent to which muscular fatigue or cardiorespiratory factors attributed to the decision to terminate the VO2Peak test and VO2Peak (​​β = 0.09, p = 0.16). CONCLUSIONS: The ability to jump 1 cm further was significantly associated with 0.18 mL/kg/min increased VO2Peakcontrolling for all other covariates. Self-reported reasons for terminating the VO2Peak test did not significantly explain VO2Peak. Future assessments should consider alternative tests of MF and muscular fatigue including tests of maximal strength performance and/or muscular endurance.

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