The present study investigated the relationships among metabolic risk factors, major lifestyle factors, and serum cytokines in a sample of Korean children. In a cross-sectional design, we studied a total of 275 children (130 boys and 145 girls) aged 12–13 years. Measured variables included anthropometrics, blood pressures (BP), VO2max, physical activity (PA), dietary intakes, lipids, glucose, and insulin. We explored the extent to which dietary intakes, VO2max, PA, and serum cytokines explained variance in a clustered risk score, which is a sum of Z scores for waist circumference, BP, TG, HDLC, and HOMA-IR, using a stepwise linear regression by blocks. VO2max, vigorous PA (VPA), and leptin were independent predictors for the clustered risk score while adjusting for age and Tanner stage. Our findings suggest that the clustered risk score is associated not only with low levels of VO2max and VPA, but also with elevated serum leptin in Korean children.
Hye-Ryun Hong, Jin-Kyung Cho, Ji-Young Lee, Jin-Koo Park and Hyun-Sik Kang
Kennon Francis, Scott Hopkins and Ronald Feinstein
This study was conducted to determine if VO2, of stepping in children is affected by altering the step platform height based on leg length. The effect of leg length on VO2 and heart rate (HR) during stepping was examined in 19 children, ages 8–17, who stepped onto 5 different bench heights that corresponded to hip angles of 65°, 73°, 82°, 90°, or 98°. VO2 and HR response to a work load of 8 m · min−1 assumed a U-shaped curve with 82° assuming the lowest point of the curve. Efficiency of stepping was significantly higher at 82° when compared to the other hip angles. It was concluded that VO2 and HR in children is influenced by leg length during stepping, and there is an optimum step height for stepping that can be determined from the ratio of leg length to stature.
K. Fiona Iredale and Myra A. Nimmo
Thirty-three men (age 26–55 years) who did not exercise regularly were exercised to exhaustion using an incremental treadmill protocol. Blood lactate concentration was measured to identify lactate threshold (LT, oxygen consumption at which blood lactate concentration begins to systematically increase). The correlation coefficient for LT (ml · kg−1 · min−1) with age was not significant, but when LT was expressed as a percentage of peak oxygen consumption (VO2 peak), the correlation was r = +.69 (p < .01). This was despite a lack of significant correlation between age and VO2 peak (r = −.33). The correlation between reserve capacity (the difference between VO2 peak and LT) and age was r = −.73 (p < .01 ), and reserve capacity decreased at a rate of 3.1 ml · kg−1 · min−1 per decade. It was concluded that the percentage of VO2 peak at which LT occurs increases progressively with age, with a resultant decrease in reserve capacity.
Joanne R. Williams and Neil Armstrong
A total of 100 boys and 91 girls, ages 11 to 16 years, completed a discontinuous treadmill test to voluntary exhaustion to determine the oxygen uptake/blood lactate relationship. Maturational stage was assessed in 72 boys and 47 girls using Tanner’s indices. Mean blood lactate at peak VO2 was significantly higher in the girls compared to the boys (6.1 vs. 5.8 mmol•l-1, P<0.01). Lactate at peak VO2 and percent peak VO2 at 4.0 mmol•l-1 were not significantly correlated with chronological age (p>0.05) in either sex, although a relationship was obtained between chronological age and percent peak VO2 at 2.5 mmol•l-“1 for boys (r= ‒0.226, p<.05) and girls (r= ‒0.272, p0.05). Analysis of variance revealed no significant changes (p>0.05) in any of the lactate variables examined with progression through the Tanner stages of maturity.
Colleen M. Grossner, Emily M. Johnson and Marco E. Cabrera
Differences in oxygen uptake (VO2) relative to body mass between children and adults walking or running at a given speed might be the result of body size differences. In order to determine whether body size is the main factor affecting these differences in VO2 per kg, we investigated treadmill economy in 10 female adolescents (girls) and 10 women who were matched for body size. There were no significant differences between groups in anthropometrics, stride frequency, or VO2peak. Mean mass-specific VO2 was not significantly different during walking (girls: 12.3 ± 1.7 ml·kg-1·min-1; women: 10.9 ± 1.4 ml·kg-1·min-1) or running (girls: 30.5 ± 3.5 ml·kg-1·min-1; women: 29.0 ± 2.0 ml·kg-1·min-1). Body size appears to have the largest effect on oxygen cost differences usually seen between girls and women during locomotion.
Linda Schücker, Christian Knopf, Bernd Strauss and Norbert Hagemann
The aim of this study was to examine differentiated effects of internally focused attention in endurance sports. Thirty-two active runners ran 24 min on a treadmill at a fixed speed of moderate intensity. For each 6-min block, participants had to direct their attention on different internal aspects (movement execution, breathing, or feeling of the body) or received no instructions. Oxygen consumption (VO2) was measured continuously to determine running economy. Results revealed that the different internal focus instructions had differentiated effects on VO2: A focus on breathing as well as a focus on the running movement led to higher VO2 than a focus on feeling of the body which showed similar VO2 as the control condition. We conclude that an internal focus of attention is solely detrimental to performance when directed to highly automated processes (e.g., breathing or movement). However, an internal focus on how the body feels during exercise does not disrupt movement efficiency.
Thiago Oliveira Borges, Ben Dascombe, Nicola Bullock and Aaron J. Coutts
This study aimed to profile the physiological characteristics of junior sprint kayak athletes (n = 21, VO2max 4.1 ± 0.7 L/min, training experience 2.7 ± 1.2 y) and to establish the relationship between physiological variables (VO2max, VO2 kinetics, muscle-oxygen kinetics, paddling efficiency) and sprint kayak performance. VO2max, power at VO2max, power:weight ratio, paddling efficiency, VO2 at lactate threshold, and whole-body and muscle oxygen kinetics were determined on a kayak ergometer in the laboratory. Separately, on-water time trials (TT) were completed over 200 m and 1000 m. Large to nearly perfect (−.5 to −.9) inverse relationships were found between the physiological variables and on-water TT performance across both distances. Paddling efficiency and lactate threshold shared moderate to very large correlations (−.4 to −.7) with 200- and 1000-m performance. In addition, trivial to large correlations (−.11 to −.5) were observed between muscle-oxygenation parameters, muscle and whole-body oxygen kinetics, and performance. Multiple regression showed that 88% of the unadjusted variance for the 200-m TT performance was explained by VO2max, peripheral muscle deoxygenation, and maximal aerobic power (P < .001), whereas 85% of the unadjusted variance in 1000-m TT performance was explained by VO2max and deoxyhemoglobin (P < .001). The current findings show that well-trained junior sprint kayak athletes possess a high level of relative aerobic fitness and highlight the importance of the peripheral muscle metabolism for sprint kayak performance, particularly in 200-m races, where finalists and nonfinalists are separated by very small margins. Such data highlight the relative aerobic-fitness variables that can be used as benchmarks for talent-identification programs or monitoring longitudinal athlete development. However, such approaches need further investigation.
Michal Botek, Jakub Krejčí, Andrew J. McKune and Barbora Sládečková
in a heterogenous group of athletes. Methods Participants A total of 16 male athletes (mean [SD]; age 31.6 [8.6] y, body mass 71.5 [8.8] kg, body height 177.0 [7.2] kg, body fat 13.4% [4.4%], VO 2 max 57.2 [8.9] mL·kg −1 ·min −1 ) volunteered for this study. They followed instructions to avoid using
Kenneth R. Turley and Jack H. Wilmore
This study investigated whether cardiovascular responses at a given submaximal oxygen consumption (V̇O2, L · min-1) are different between the treadmill (TM) and cycle ergometer (CE). Submaximal cardiovascular measurements were obtained at three work rates on both the TM and CE in 7- to 9-year-old children (12 males and 12 females). Using regression analysis, it was determined that there were no differences between the TM and CE in cardiac output (L · min-1), stroke volume (SV, ml · beat-1) or heart rate (beats · min-1) at a given V̇O2 (L · min-1). There were differences in the total peripheral resistance (TPR, units) and arterial-venous oxygen difference (a-vO2 diff, ml · 100 ml-1) to V̇O2 (L · min-1) relationship. While there were statistically significant differences in TPR and a-vO2 diff between the two modalities, there was substantial overlap of individual values at any given submaximal V̇O2, thus the physiological significance is questionable. Hence, we conclude that in 7- to 9-yearold children there are no differences in submaximal cardiovascular responses between the CE and TM.
Lee N. Cunningham
This study compared team performances of adolescent female cross-country runners in relation to maximal oxygen consumption (V̇O2 max), ventilatory threshold, and running economy (RE). Twenty female runners (M age = 16.0 yrs) from four high school teams that competed in the Massachusetts All-State Cross-Country Championship Meet underwent maximal treadmill testing. When physiologic parameters were grouped by team, significant differences were observed for only V̇O2 max and percent V̇O2 at a 215 m • min−1 pace. The mean VO2 max for Team 1 (the All-State Meet champions) was found to be significantly higher than that of Teams 3 and 4 (70.7 ± 4 vs. 56.5±4, and 58.6 ± 4 ml • kg−1 • min−1, respectively). When running on the treadmill at a 215 m • min−1 pace, members of Team 1 were working at a significandy lower percent of VO2 max than Team 3 (70 ± 3 vs. 84 ± 4). The estimated physiologic requirements for running the All-State Meet based upon data derived from physiologic testing were not statistically different between teams (p>0.05). In conclusion, most of the physiologic variables investigated were not sensitive enough to separate out performance differences between top high school cross-country teams. Of these variables, VO2 max is suggested to be the primary physiologic determinant for team success for this age group of female runners.