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Neil Armstrong

In Volume 1 of Pediatric Exercise Science (PES), a paper by Fenster et al. (25) investigated the relationship between peak oxygen uptake (peak V̇O2) and physical activity (PA) in 6- to 8-year-old children. They used both questionnaires and large-scale integrated activity monitors (LSIs) to estimate daily PA and determined peak V̇O2 using an incremental treadmill test to volitional exhaustion. They concluded that peak V̇O2 correlated well with PA as measured by LSIs but commented that questionnaire data were only weakly and nonsignificantly associated with LSI and peak V̇O2 data. Peak V̇O2 and PA are the most researched and reported variables in the 25-year history of PES. Yet, the assessment and interpretation of young people’s aerobic fitness and PA remain problematic and any meaningful relationship between them during childhood and adolescence is shrouded with controversy. The present paper uses Fenster et al.’s (25) report as an indicator of where we were 25 years ago, outlines how far we have advanced since then, and suggests future directions of research in the study of aerobic fitness and PA.

In the first volume of PES, Fenster et al. (25) investigated the relationship between 6- to 8-year-old children’s peak oxygen uptake (peak V̇O2) and physical activity (PA). Five boys and 13 girls participated in the study and their data were pooled for analysis. Peak V̇O2 was determined during an incremental treadmill test to voluntary exhaustion and PA was estimated using both questionnaires and large-scale integrated activity monitors (LSIs). On the basis of a significant interclass correlation coefficient of r = .59 between peak V̇O2 and the log of LSI average counts per hour Fenster et al. (25) concluded that “aerobic capacity, as measured by peak V̇O2 correlated well with physical activity as measured by LSI” (p.134).

They also commented that questionnaire data were only weakly and nonsignificantly associated with LSI and peak V̇O2 data. Young people’s peak V̇O2 and PA are the most researched and reported variables in the 25-year history of PES and yet the assessment and interpretation of peak V̇O2 and PA and any meaningful relationship between them during growth and maturation are still shrouded with controversy. The present paper uses Fenster et al.’s (25) work as an indicator of our understanding of young people’s peak V̇O2 and PA in 1989, briefly reviews what we know in 2013, and suggests future directions of research.

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Andrew M. Jones and Mark Burnley

The rate at which VO2 adjusts to the new energy demand following the onset of exercise strongly influences the magnitude of the “O2 defcit” incurred and thus the extent to which muscle and systemic homeostasis is perturbed. Moreover, during continuous high-intensity exercise, there is a progressive loss of muscle contractile efficiency, which is reflected in a “slow component” increase in VO2. The factors that dictate the characteristics of these fast and slow phases of the dynamic response of VO2 following a step change in energy turnover remain obscure. However, it is clear that these features of the VO2 kinetics have the potential to influence the rate of muscle fatigue development and, therefore, to affect sports performance. This commentary outlines the present state of knowledge on the characteristics of, and mechanistic bases to, the VO2 response to exercise of different intensities. Several interventions have been reported to speed the early VO2 kinetics and/or reduce the magnitude of the subsequent VO2 slow component, and the possibility that these might enhance exercise performance is discussed.

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M. Kathleen Ellis and Lynn A. Darby

This study compared balance and peak oxygen consumption (peak VO2) among hearing, congenital nonhearing, and acquired nonhearing female intercollegiate athletes. Twenty-seven subjects completed two measures of peak VO2 and two measures of balance (static and dynamic). Two pieces of exercise equipment requiring different levels of balance were used: the bicycle ergometer (minimal balance) and the bench-step (maximal balance). Significant differences were found for dynamic balance and for peak VO2 for all subject groups. The significant difference remained among the groups for peak VO2 using the bicycle ergometer when dynamic balance was used as a covariate. There was no significant difference for peak VO2 dependent on type of test when dynamic balance was controlled. The results indicated that dynamic balance affected peak VO2 performance on the bench-step, but not on the bicycle ergometer. These findings suggest that if dynamic balance is required for an assessment of peak VO2, balance should be tested in nonhearing populations.

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Benoit Capostagno and Andrew Bosch

This study examined the differences in fat and carbohydrate oxidation during running and cycling at the same relative exercise intensities, with intensity determined in a number of ways. Specifically, exercise intensity was expressed as a percentage of maximum workload (WLmax), maximum oxygen uptake (%VO2max), and maximum heart rate (%HRmax) and as rating of perceived exertion (RPE). Ten male triathletes performed maximal running and cycling trials and subsequently exercised at 60%, 65%, 70%, 75%, and 80% of their WLmax. VO2, HR, RPE, and plasma lactate concentrations were measured during all submaximal trials. Fat and carbohydrate oxidation were calculated from VO2 and VCO2 data. A 2-way ANOVA for repeated measures was used to determine any statistically significant differences between exercise modes. Fat oxidation was shown to be significantly higher in running than in cycling at the same relative intensities expressed as either %WLmax or %VO2max. Neither were there any significant differences in VO2max and HRmax between the 2 exercise modes, nor in submaximal VO2 or RPE between the exercise modes at the same %WLmax. However, heart rate and plasma lactate concentrations were significantly higher when cycling at 60% and 65% and 65–80%WLmax, respectively. In conclusion, fat oxidation is significantly higher during running than during cycling at the same relative intensity expressed as either %WLmax or %VO2max.

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Candace D. Perkins, James M. Pivarnik and Matthew R. Green

Background:

The reliability and validity of the SensorMedics VmaxST was tested.

Methods:

Thirty subjects (age = 24.5 ± 4.0 years, height = 174.8 ± 9.8 cm, weight = 70.3 ± 12.6 kg) performed treadmill exercise on three occasions, twice using the VmaxST and once using the SensorMedics 2900 system. Oxygen consumption (VO2; L/min) and heart rate (HR; beats/min) were measured continuously during three, 6- minute stages: 80 m/min, 0% grade; 94 m/min, 5% grade; and 160 m/min, 0% grade, and VO2max.

Results:

Reliability was high, and measurement error was low for VO2 (Rxx range = 0.97 - 0.99, CI = 0.94 - 1.00, SEM = 0.03 - 0.08 L/min) and HR (Rxx = 0.94 - 0.99, CI = 0.88 - 1.00, SEM = 1.8 - 3.2 beats/min). Validity was high for VO2 (Rxy range = 0.92 - 0.98, CI = 0.84 - 0.99, SEE = 0.08 - 0.21 L/min) and HR (Rxy = 0.97 - 0.99, CI = 0.94 - 1.00, SEE = 0.9 - 1.8 beats/min). Mean differences in VO2 between VmaxST and 2900 were small yet significant (P < 0.001).

Conclusions:

The VmaxST demonstrated excellent reliability and validity for measuring VO2 and HR over several exercise intensities. Small overestimates in VO2 by the VmaxST are countered by low measurement error.

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Neil Armstrong and Melitta McNarry

Peak oxygen uptake (V̇O2) is widely recognized as the criterion measure of young people’s aerobic fitness. Peak V̇O2 in youth has been assessed and documented for over 75 years but the interpretation of peak V̇O2 and its trainability are still shrouded in controversy. Causal mechanisms and their modulation by chronological age, biological maturation and sex remain to be resolved. Furthermore, exercise of the intensity and duration required to determine peak V̇O2 is rarely experienced by most children and adolescents. In sport and in everyday life young people are characterized by intermittent bouts of exercise and rapid changes in exercise intensity. In this context it is the transient kinetics of pulmonary V̇O2 (pV̇O2), not peak V̇O2, which best describe aerobic fitness. There are few rigorously determined and appropriately analyzed data from young people’s pV̇O2 kinetics responses to step changes in exercise intensity. Understanding of the trainability of pV̇O2 kinetics is principally founded on comparative studies of trained and untrained youth and much remains to be elucidated. This paper reviews peak V̇O2, pV̇O2 kinetics, and their trainability in youth. It summarizes “what we know,” identifies significant gaps in our knowledge, raises relevant questions, and indicates avenues for future research.

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Han C.G. Kemper, Jos W.R. Twisk and Willem van Mechelen

In the Amsterdam Growth And Health Longitudinal Study (AGAHLS), a group of approximately 650 12- to 14-year-old boys and girls was followed in their growth, and development of their health their lifestyle including diet, physical activity and smoking. One of the main interests was the change in their aerobic fitness. From 12 to 36 years of age in total, eight repeated measurements were performed to measure peak oxygen uptake (peak VO2). In this study the data of peak VO2 are revisited and extended: We made use of all collected data as a mixed longitudinal design including cross-sectionally measured subjects as well as longitudinally measured subjects. This led to the availability of 1,194 boys and 1356 girls. With generalized estimating equations (GEE) the longitudinal changes with chronological age and differences between boys and girls were analyzed. Teenage boys and girls increased their peak VO2 (ml/min) significantly (p < .001) until age 14 in girls and until age 17 in boys. However peak VO2 relative to bodyweight (peak VO2/BW) had significantly (p < .001) decreased over the whole age range from 12 to 36 in both sexes. Vigorous physical activity (VPA) also showed a decrease and was significantly (p < .001) related with lower peak VO2/BW (Beta = 0.001). This relation was stronger in boys than in girls. Because at the start of AGAHLS no fast responding metabolic instruments were available, future longitudinal studies about aerobic fitness should include also measurement of VO2 kinetics.

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Lee N. Cunningham

To compare the physiologic differences between adolescent male and female cross-country runners, 12 male and 12 female high school nonelite distance runners who had competed successfully at the All State 5-km championship cross-country meet were tested in the laboratory. Data were analyzed in relation to maximal oxygen consumption (VO2max), ventilatory threshold (VT), and running economy (RE). Male runners were taller, heavier, had less body fat, and ran faster by 2 minutes and 18 seconds than female runners. Running economy was similar between gender. VO2 at a 215 m•min−1 pace was 46.7 ml•kg−1•min−1 for male runners and 47.8 ml•kg−1•min−1 for female runners. At the VT, males demonstrated a higher VO2 and treadmill velocity than females. Heart rate, percent HR max, and percent VO2 max at the VT were not different between gender. Males demonstrated a higher VO2 max of 74.6 versus 66.1 ml•kg−1•min−1 than female runners. The fractional utilization of VO2 at race pace was not different between males (90%) and females (91%). In conclusion, the primary physiologic determinant for performance differences between nonelite, competitive male and female adolescent distance runners is associated with VO2 max.

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Juliane R. Fenster, Patty S. Freedson, Richard A. Washburn and R. Curtis Ellison

The relationship between physical activity measured using the LSI (Large Scale Integrated Activity Monitor), and questionnaire, with physical work capacity 170 (PWC 170) and aerobic capacity (peak V̇O2) was evaluated in 6- to 8-year-old children (n = 18). The mean (± SD) peak V̇O2 was 44.1 ± 5.6 ml • kg−1 • min−1. Peak V̇O2 was not significantly different for children (n = 8) who had completed two treadmill trials (45.4 vs. 43.5 ml • kg−1 • min−1; R = 0.67, p<0.05). The log LSI expressed as counts per hour (M ± SD = 2.1 ±.22 cts/hr) was the only activity method significantly related to peak V̇O2 (r = 0.59, p<0.05). The correlation between peak V̇O2 with the questionnaire was positive but nonsignificant (r = 0.20). PWC 170 was not related to peak V̇O2 (r = 0.21) or the activity variables (r = 0.12 questionnaire; r = 0.18 log LSI). When the group was divided into high and low peak V̇O2 groups (high: M = 48.8 ml • kg−1 • min−1; low: M = 39.5 ml • kg−1 • min−1), the log LSI was able to distinguish significant differences in activity levels (high: 2.23 ±. 19 cts/hr; low: 1.99±.19 cts/hr). This study suggests that activity measured with the LSI and aerobic capacity are related in this sample of 6- to 8-year-old children.

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Hervé Assadi and Romuald Lepers

Purposes:

To compare the physiological responses and maximal aerobic running velocity (MAV) during an incremental intermittent (45-s run/15-s rest) field test (45-15FIT) vs an incremental continuous treadmill test (TR) and to demonstrate that the MAV obtained during 45-15FIT (MAV45-15) was relevant to elicit a high percentage of maximal oxygen uptake (VO2max) during a 30-s/30-s intermittent training session.

Methods:

Oxygen uptake (VO2), heart rate (HR), and lactate concentration ([La]) were measured in 20 subjects during 2 maximal incremental tests and four 15-min intermittent tests. The time spent above 90% and 95% VO2max (t90% and t95% VO2max, respectively) was determined.

Results:

Maximal physiological parameters were similar during the 45-15FIT and TR tests (VO2max 58.6 ± 5.9 mL · kg−1 · min−1 for TR vs 58.5 ± 7.0 mL · kg−1 · min−1 for 45-15FIT; HRmax 200 ± 8 beats/min for TR vs 201 ± 7 beats/min for 45-15FIT). MAV45-15 was significantly (P < .001) greater than MAVTR (17.7 ± 1.1 vs 15.6 ± 1.4 km/h). t90% and t95% VO2max during the 30-s/30-s performed at MAVTR were significantly (P < .01) lower than during the 30-s/30-s performed at MAV45-15. Similar VO2 during intermittent tests performed at MAV45-15 and at MAVTR can be obtained by reducing the recovery time or using active recovery.

Conclusions:

The results suggested that the 45-15FIT is an accurate field test to determine VO2max and that MAV45-15 can be used during high-intensity intermittent training such as 30-s runs interspersed with 30-s rests (30-s/30-s) to elicit a high percentage of VO2max.