Oxygen Consumption at 30 W of Exercise Is Surrogate for Peak Oxygen Consumption in Evaluation of Cardiorespiratory Fitness in Young-Adult African-American Females

Body mass index (BMI) is negatively correlated with cardiorespiratory fitness, measured by maximal or peak oxygen consumption (VO2peak). VO2peak measurements require heavy aerobic exercise to near exhaustion which increases the potential for adverse cardiovascular events. This study tests the hypothesis that VO2 measured at a fixed submaximal workload of 30 W is a surrogate for VO2peak. We studied 42 normotensive African-American female university students, 18–25 years of age. We measured VO2peak, blood pressure, and VO2 at a 30 W exercise workload and computed BMI. We found significant negative correlations between BMI and VO2peak (r=−0.41, P<0.01) and between BMI and VO2 at 30 W (r=−0.53, P<0.001). Compared to VO2peak, VO2 at 30 W increased the significance of the negative correlation with BMI. The heart rate-systolic pressure product at 30 W was positively correlated with BMI (r=0.36, P<0.01) and negatively correlated with VO2peak (r=−0.38, P<0.001). The positive correlation between BMI and the heart rate-systolic pressure product and the greater negative correlation between VO2 and BMI at 30 W of exercise than that at exercise to fatigue suggest that normalized measurements of VO2 at the fixed exercise workload of 30 W could be useful surrogates for measurements of VO2peak.

Maximal Lactate Steady State in Children

Maximal lactate steady state (MLSS) corresponds to the prolonged constant workload whereby the kinetics of blood lactate concentration clearly increases from steady state. Different results of MLSS in children may reflect specific test protocols or definitions. Three methods corresponding to lactate time courses during 20 min (MLSS I), 16 min (MLSS II), and 8 min (MLSS III) of constant submaximal workload were intraindividually compared in 10 boys. At MLSS I, lactate, V̇O2peak, heart rate, and workload were higher (p < .05) than at MLSS II and at MLSS III. The differences between MLSS I, MLSS II, and MLSS III reflect insufficient contribution to lactate kinetics by testing procedures, strongly depending on the lactate time courses during the initial 10 min of constant workload. Previously published divergent results of MLSS in children seem to reflect a methodological effect more than a metabolic change.

Comparative Efficiencies of Conventional and Super-Swimfin Designs

One female and six male subjects were used to evaluate the effectiveness of four modern “super-swimfin” designs when compared to a set of conventional fins. Oxygen consumption and heart rates were measured at a predetermined submaximal workload using a swimming ergometer. Times for kicking 22.9 m were also compared. The results demonstrated that significantly less oxygen was consumed during the trials in which the vented super-fins of large surface area were used than when the conventional fins were used. Significant V̇O2differences were also noted between super-fins, with large surface area, inflexible, or venturi designs resulting in the consumption of more oxygen than the others. A statistically significant linear correlation (r = −.90) was computed when comparing oxygen consumption to fin surface area. Flexibility of the fins was noted to be directly related to the speed that could be attained (r = .90). It was concluded that only the super-fin designs that were vented and had a large surface area are more efficient than the conventional fins tested.