Energy expenditure and influence of physiologic factors during marathon running.

This study examined energy expenditure and physiologic determinants for marathon performance in recreational runners. Twenty recreational marathon runners participated (10 males aged 41 +/- 11.3 years, 10 females aged 42.7 +/- 11.7 years). Each subject completed a V(.-)O2max and a 1-hour treadmill run at recent marathon pace, and body composition was indirectly determined via dual energy X-ray absorptiometry. The male runners exhibited higher V(.-)O2max (ml x kg(-1) x min(-1)) values (52.6 +/- 5.5) than their female counterparts (41.9 +/- 6.6), although ventilatory threshold (T-vent) values were similar between groups (males: 76.2 +/- 6.1 % of V(.-)O2max, females: 75.1 +/- 5.1%). The male runners expended more energy (2,792 +/- 235 kcal) for their most recent marathon as calculated from the 1-hour treadmill run at marathon pace than the female runners (2,436 +/- 297 kcal). Body composition parameters correlated moderately to highly (r ranging from 0.50 to 0.87) with marathon run time. Also, V(.-)O2max (r = -0.73) and ventilatory threshold (r = -0.73) moderately correlated with marathon run time. As a group, the participants ran near their ventilatory threshold for their most recent marathon (r = 0.74). These results indicate the influence of body size on marathon run performance. In general, the larger male and female runners ran slower and expended more kilocalories than smaller runners. Regardless of marathon finishing time, the runners maintained a pace near their T-vent, and as T-vent or V(.-)O2max increased, marathon performance time decreased.

Effect of obesity status on heart rate peak in female youth.

The purpose of this study was to compare heart rate peak in obese (n = 43) and normal weight (n = 45) female youth. Heart rate (HR) peak was significantly lower (p < or = 0.05) in the obese group as compared to the normal weight group (192.3 +/- 9.3, 203.4 +/- 7.6), and VO2 (L x min(-1)) peak similar between groups (1.77 +/- 0.53, 1.97 +/- 0.60). Bivariate correlations for heart rate peak with body weight, percent fat, and body mass index yielded the following: -0.53, -0.54, and -0.57. These findings agree with the adult data indicating low HR peak in obese individuals. Further research is needed to explore physiologic factors that may lead to reduced HR peak in obese female youth.