Cardiorespiratory Fitness, Lower Body Muscular Fitness, And VO2Peak test Termination In 18-20-Year-Olds

BACKGROUND: It is unclear whether lower body muscular fitness (LBMF) is linked to cardiorespiratory fitness (CRF). It is assumed that the termination of a VO2Peak test, which measures CRF, is due solely to cardiorespiratory factors. The relative contribution of LBMF to CRF has not been explored. This study assessed the relative extent to which 18-20 year olds reported lower body muscular fatigue vs. cardiorespiratory factors as the reason for terminating a VO2Peak test and how their response and a measure of LBMF explained CRF, controlling for biodemographic characteristics. METHODS: Data were collected from 44 young adults (age M = 18.86, SD = 0.77, 43% female, 47% Non-Hispanic White, body mass index (BMI) = 23.9 kg/m2). The standing broad jump (SBJ) was used to assess LBMF, with results operationalized as the longest distance jumped in centimeters. A graded VO2Peak treadmill test was used to assess CRF, and results were operationalized as the highest value of milliliters of oxygen used in one minute per kilogram of body weight [mL/kg/min]. Participants also rated the relative extent (0-100 scale) to which muscular fatigue or cardiorespiratory factors affected their decision to terminate their VO2Peak test (RR; 0 = stopped primarily because of muscular fatigue; 100 = stopped primarily due to being out of breath or heart beating hard/fast). To control for the potential nonlinearity of RR, which combines two metrics of interest, we performed a gamma additive regression model to assess VO2Peak performance using a thin plate spline for RR while controlling for SBJ, sex, race/ethnicity, and BMI. RESULTS: SBJ was significantly associated with VO2Peak (??β = 0.009, p = 0.002). No other covariates were statistically significant in this model. The spline curve was not statistically significant (p = 0.196), though initial graphical and numerical evidence of a potential nonlinear association was present, with a positive slope at lower values of RR curving toward a flatter slope for higher values. CONCLUSIONS: Controlling for all other covariates, an individual would see a 0.9% increase in their VO2Peak with every 1 cm increase in their SBJ. Future research should assess whether participants who indicate lower body muscular fatigue as the primary reason for terminating their VO2Peak test have lower CRF and LBMF. NIH NICHD - R01HD105768