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John A. Mercer, Janet S. Dufek and Barry T. Bates

Objective:

To compare peak oxygen consumption (VO2) and heart rate (HR) during treadmill (TM) running and exercise on an elliptical trainer (ET).

Design:

A graded exercise test (GXT) during TM running and ET exercise.

Participants:

Physically active college students (N = 14; 25 ± 4.6 years). Each completed a TM GXT and ET GXT on separate days.

Results:

There were no differences in either VO2peak or peak HR between TM (53.0 ± 7.7 ml · kg–1 · min–1, 193.4 ± 9.4 bpm) and ET (51.6 ± 10.7 ml · kg–1 · min–1, 191.2 ± 11.5 bpm; P > .05). Correlations between HR and VO2 data for all stages of exercise for all subjects were similar between machines (ET: r = .88; TM: r = .95; P > .05).

Conclusion:

No adjustments to the target HR used during TM running are necessary when using the ET.

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Thomas W. Rowland

In adults, maximum oxygen uptake (VO2max) serves as a useful indicator of cardiopulmonary reserve as well as performance in endurance exercise events. Whether VO2max can be interpreted in the same manner in children is less certain, since maximal oxygen uptake per kg body weight remains essentially stable during the growing years while endurance performance improves dramatically. Gains in ability in endurance events may be achieved through improved submaximal exercise economy, qualitative changes in oxygen delivery not indicated by VO2max, or the development of nonaerobic factors (speed, strength). Maximal oxygen uptake in children may therefore be a less valid indicator of cardiopulmonary function, endurance capacity, and response to training than in adult subjects.

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Kenneth R. Turley, Danette M. Rogers, Kevin M. Harper, Kathleen I. Kujawa and Jack H. Wilmore

This study was designed to determine the differing cardiorespiratory responses between maximal treadmill (TM) and cycle (CY) ergometry, and the reliability and variability of these responses in 46 children 7 to 9 years old (23 boys and 23 girls). Two maximal TM and two maximal CY tests were administered, as well as a body composition assessment. The TM resulted in a 9.4%, 11,1%, and 10.2% higher maximal oxygen consumption values (V̇O2, ml·kg−1·min−1) than the CY in boys, girls, and the total population, respectively. Both the TM and the CY proved to be reliable measures of maximal V̇O2 (ml·kg−1·min−1) in both boys and girls, with intraclass correlations ranging from R = .63 to .90. Variability was significantly less (p ≤ .05) on the CY (V̇O2 in L·min−1) than the TM, 4.4% versus 6.2%, respectively.

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Darlene A. Sedlock

This study is a comparison of both the magnitude and duration of excess postexercise oxygen consumption (EPOC) between women and men. Eighteen (9 women, 9 men) physically active, young adult volunteers performed a moderate exercise in the early morning after having refrained from any strenuous activity for the previous 36-48 hr. Baseline oxygen uptake (VO2) and heart rate (HR) were measured for the last 15 min of a 45 min seated rest. The 30 min cycle ergometer exercise was performed at 60% of each subject’s previously determined peak VO2. Subjects sat quietly in a chair during recovery until VO2 returned to baseline. The women had a significantly lower (t=4.22, p<0.01) resting VO2(0.22±0.03 L min−1) than the men (0.31±0.06 L min−1), however no significant difference was observed when resting VO2 was expressed relative to body weight. VO2 values during exercise were also significantly lower in the women compared to the men (t=4.85, p<0.01). Duration of EPOC was similar between the two groups (women=27.6±15.6, men=28.2±15.9 min). The 38% difference in magnitude of EPOC between the women (9.4±4.7 kcal) and men (13.0±4.6 kcal) was not statistically significant and approximated 5% of the exercise energy expenditure in each group. It was concluded that there was no sex difference in EPOC duration following moderate exercise conditions. Magnitude of EPOC was small for both groups, with women having a slightly lower value.

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Eadric Bressel, Gerald Smith, Andrew Miller and Dennis Dolny

Context: Quantification of the magnitudes of fluid resistance provided by water jets (currents) and their effect on energy expenditure during aquatic-treadmill walking is lacking in the scientific literature. Objective: To quantify the effect of water-jet intensity on jet velocity, drag force, and oxygen uptake (VO2) during aquatic-treadmill walking. Design: Descriptive and repeated measures. Setting: Athletic training facility. Participants, Interventions, and Measures: Water-jet velocities were measured using an electromagnetic flow meter at 9 different jet intensities (0-80% maximum). Drag forces on 3 healthy subjects with a range of frontal areas (600, 880, and 1250 cm2) were measured at each jet intensity with a force transducer and line attached to the subject, who was suspended in water. Five healthy participants (age 37.2 ± 11.3 y, weight 611 ± 96 N) subsequently walked (~1.03 m/s or 2.3 miles/h) on an aquatic treadmill at the 9 different jet intensities while expired gases were collected to estimate VO2. Results: For the range of jet intensities, water-jet velocities and drag forces were 0-1.2 m/s and 0-47 N, respectively. VO2 increased nonlinearly, with values ranging from 11.4 ± 1.0 to 22.2 ± 3.8 mL × kg-1 × min-1 for 0-80% of jet maximum, respectively. Conclusions: This study presented methodology for quantifying water-jet flow velocities and drag forces in an aquatic-treadmill environment and examined how different jet intensities influenced VO2 during walking. Quantification of these variables provides a fundamental understanding of aquatic-jet use and its effect on VO2. In practice, these results indicate that VO2 may be substantially increased on an aquatic treadmill while maintaining a relatively slow walking speed.

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Dietmar Wallner, Helmut Simi, Gerhard Tschakert and Peter Hofmann

Purpose:

To analyze the acute physiological response to aerobic short-interval training (AESIT) at various high-intensity running speeds. A minor anaerobic glycolytic energy supply was aimed to mimic the characteristics of slow continuous runs.

Methods:

Eight trained male runners (maximal oxygen uptake [VO2max] 55.5 ± 3.3 mL · kg−1 · min−1) performed an incremental treadmill exercise test (increments: 0.75 km · h−1 · min−1). Two lactate turn points (LTP1, LTP2) were determined. Subsequently, 3 randomly assigned AESIT sessions with high-intensity running-speed intervals were performed at speeds close to the speed (v) at VO2max (vVO2max) to create mean intensities of 50%, 55%, and 60% of vLTP1. AESIT sessions lasted 30 min and consisted of 10-s work phases, alternated by 20-s passive recovery phases.

Results:

To produce mean velocities of 50%, 55%, and 60% of vLTP1, running speeds were calculated as 18.6 ± 0.7 km/h (93.4% vVO2max), 20.2 ± 0.6 km/h (101.9% vVO2max), and 22.3 ± 0.7 km/h (111.0% vVO2max), which gave a mean blood lactate concentration (La) of 1.09 ± 0.31 mmol/L, 1.57 ± 0.52 mmol/L, and 2.09 ± 0.99 mmol/L, respectively. La at 50% of vLTP1 was not significantly different from La at vLTP1 (P = .8894). Mean VO2 was found at 54.0%, 58.5%, and 64.0% of VO2max, while at the end of the sessions VO2 rose to 71.1%, 80.4%, and 85.6% of VO2max, respectively.

Conclusion:

The results showed that AESIT with 10-s work phases alternating with 20 s of passive rest and a running speed close to vVO2max gave a systemic aerobic metabolic profile similar to slow continuous runs.

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Oliver Faude, Tim Meyer and Wilfried Kindermann

Purpose:

The work rate (WR) corresponding to ventilatory threshold (VT) is an appropriate intensity for regenerative and low-intensity training sessions. During incremental ramp exercise, VO2 increase lags behind WR increase. Traditionally, a VO2 time delay (t d) of 45 seconds is used to calculate the WR at VT from such tests. Considerable inaccuracies were observed when using this constant t d. Therefore, this study aimed at reinvestigating the temporal relationship between VO2 and WR at VT.

Methods:

20 subjects (VO2peak 49.9 to 72.6 mL · min–1 · kg–1) performed a ramp test in order to determine VT and a subsequent steady-state test during which WR was adjusted to elicit the VO2 corresponding to VT. The difference in WR and heart rate at VT was calculated between the ramp and the steady-state test (WRdiff, HRdiff) as well as the time delay corresponding to WRdiff during ramp exercise.

Results:

Mean values were t d = 85 ± 26 seconds (range 38 to 144), WRdiff = 45 ± 12 W (range 23 to 67), HRdiff = 1 ± 9 beats/min (range –21 to +15). The limits of agreement for the difference between WR at VT during ramp and steady-state exercise were ± 24 W. No signifi cant influence on t d, WRdiff, or HRdiff from differences in endurance capacity (VO2peak and VT; P > .10 for all correlations) or ramp increment (P = .26, .49, and .85, respectively) were observed.

Conclusion:

The wide ranges of t d, WRdiff, and HRdiff prevent the derivation of exact training guidelines from single-ramp tests. It is advisable to perform a steady-state test to exactly determine the WR corresponding to VT.

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Giovani Dos Santos Cunha, Marco Aurélio Vaz, Jeam Marcel Geremia, Gabriela T. Leites, Rafael Reimann Baptista, André Luiz Lopes and Álvaro Reischak-Oliveira

The present study investigated the effects of pubertal status on peak oxygen uptake (VO2peak), respiratory compensation point (RCP), and ventilatory threshold (VT) in young soccer players using different body size descriptors. Seventy-nine soccer players (14 prepubescent, 38 pubescent and 27 postpubescent) participated in this study. A maximal exercise test was performed to determine the VO2peak, RCP, and VT. Ultrasonography was used to measure lower limb muscle volume (LLMV). LLMV (mL-b) was rated as the most effective body size descriptor to normalize VO2peak (mLO2•mL-0.43•min-1), RCP (mLO2•mL-0.48•min-1), and VT (mLO2•mL-0.40•min-1). The values of VO2peak, RCP, and VT relative to allometric exponents derived by LLMV were similar among groups (p > .05; 0.025 < η2 < 0.059) when the effect of chronological age was controlled. Allometric VO2peak, RCP, and VT values were: 100.1 ± 7.9, 107.5 ± 9.6, and 108.0 ± 10.3 mLO2.mL-0.43•min-1; 51.8 ± 5.3, 54.8 ± 4.7, and 57.3 ± 5.8 mLO2•mL-0.48•min-1; and 75.7 ± 7.1, 79.4 ± 7.0, and 80.9 ± 8.3 mLO2•mL-0.40•min-1 for prepubertal, pubertal, and postpubertal groups, respectively. Maturity status showed no positive effect on VO2peak, RCP, and VT when the data were properly normalized by LLMV in young soccer players. Allometric normalization using muscle volume as a body size descriptor should be used to compare aerobic fitness between soccer players heterogeneous in chronological age, maturity status, and body size.

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Denis M. Pelletier, Guillaume Lacerte and Eric D.B. Goulet

Lately, the effect of quercetin supplementation (QS) on endurance performance (EP) and maximal oxygen consumption (VO2max) has been receiving much scientific and media attention. Therefore, a meta-analysis was performed to determine QS’s ergogenic value on these variables. Studies were located with database searches (PubMed and SPORTDiscus) and cross-referencing. Outcomes represent mean percentage changes in EP (measured via power output) and VO2max between QS and placebo. Random-effects model meta-regression, mixed-effects model analog to the ANOVA, random-effects weighted mean effect summary, and magnitudebased inferences analyses were used to delineate the effects of QS. Seven research articles (representing 288 subjects) were included, producing 4 VO2max and 10 EP effect estimates. Mean QS daily intake and duration were, respectively, 960 ± 127 mg and 26 ± 24 d for the EP outcome and 1,000 ± 0 mg and 8 ± 23 d for the VO2max outcome. EP was assessed during exercise with a mean duration of 79 ± 82 min. Overall, QS improved EP by 0.74% (95% CI: 0.10–1.39, p = .02) compared with placebo. However, only in untrained individuals (0.83% ± 0.78%, p = .02) did QS significantly improve EP (trained individuals: 0.09% ± 2.15%, p = .92). There was no relationship between QS duration and EP (p = .69). Overall, QS increased VO2max by 1.94% (95% CI: 0.30–3.59, p = .02). Magnitude-based inferences suggest that the effect of QS on EP and VO2max is likely to be trivial for both trained and untrained individuals. In conclusion, this meta-analysis indicates that QS is unlikely to prove ergogenic for aerobic-oriented exercises in trained and untrained individuals.

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Dennis-Peter Born, Thomas Stöggl, Mikael Swarén and Glenn Björklund

Purpose:

To investigate the cardiorespiratory and metabolic response of trail running and evaluate whether heart rate (HR) adequately reflects the exercise intensity or if the tissue-saturation index (TSI) could provide a more accurate measure during running in hilly terrain.

Methods:

Seventeen competitive runners (4 women, V̇O2max, 55 ± 6 mL · kg–1 · min–1; 13 men, V̇O2max, 68 ± 6 mL · kg–1 · min–1) performed a time trial on an off-road trail course. The course was made up of 2 laps covering a total distance of 7 km and included 6 steep uphill and downhill sections with an elevation gain of 486 m. All runners were equipped with a portable breath-by-breath gas analyzer, HR belt, global positioning system receiver, and near-infrared spectroscopy (NIRS) device to measure the TSI.

Results:

During the trail run, the exercise intensity in the uphill and downhill sections was 94% ± 2% and 91% ± 3% of maximal heart rate, respectively, and 84% ± 8% and 68% ± 7% of V̇O2max, respectively. The oxygen uptake (V̇O2) increased in the uphill sections and decreased in the downhill sections (P < .01). Although HR was unaffected by the altering slope conditions, the TSI was inversely correlated to the changes in V̇O2 (r = –.70, P < .05).

Conclusions:

HR was unaffected by the continuously changing exercise intensity; however, TSI reflected the alternations in V̇O2. Recently used exclusively for scientific purposes, this NIRS-based variable may offer a more accurate alternative than HR to monitor running intensity in the future, especially for training and competition in hilly terrain.