Search Results

You are looking at 141 - 150 of 1,150 items for :

Clear All
Restricted access

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.

Restricted access

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.

Restricted access

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.

Restricted access

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.

Restricted access

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.

Open access

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

Restricted access

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.

Restricted access

Christopher D. Black and Patrick J. O’Connor

Ginger has known hypoalgesic and anti-inflammatory properties. The effects of an oral dose of ginger on quadriceps muscle pain, rating of perceived exertion (RPE), and recovery of oxygen consumption were examined during and after moderateintensity cycling exercise. Twenty-five college-age participants ingested a 2-g dose of ginger or placebo in a double-blind, crossover design and 30 min later completed 30 min of cycling at 60% of VO2peak. Quadriceps muscle pain, RPE, work rate, heart rate (HR), and oxygen uptake (VO2) were recorded every 5 min during exercise, and HR and VO2 were recorded for 20 min after exercise. Compared with placebo, ginger had no clinically meaningful or statistically significant effect on perceptions of muscle pain, RPE, work rate, HR, or VO2 during exercise. Recovery of VO2 and HR after the 30-min exercise bout followed a similar time course in the ginger and placebo conditions. The results were consistent with related findings showing that ingesting a large dose of aspirin does not acutely alter quadriceps muscle pain during cycling, and this suggests that prostaglandins do not play a large role in this type of exercise-induced skeletal-muscle pain. Ginger consumption has also been shown to improve VO2 recovery in an equine exercise model, but these results show that this is not the case in humans.

Restricted access

Yagesh N. Bhambhani, Robert S. Burnham, Gary D. Wheeler, Peter Eriksson, Leona J. Holland and Robert D. Steadward

In this study we compared the ventilatory threshold (VT) between 8 untrained and 8 endurance-trained males with quadriplegia during simulated wheelchair exercise. Each subject completed an incremental velocity test in his personal wheelchair mounted on a customized roller system designed to provide velocity and distance feedback. VT was identified by two trained evaluators using established respiratory gas exchange criteria. A significant interevaluator reliability coefficient of .90 (p < .01) was observed for the detection of VT. Relative oxygen uptake (V̇O2, ml · kg-1 · min-1) at VT and peak V̇O2 were significantly (p < .05) higher in the endurance-trained compared to untrained subjects. However, no significant difference (p > .05) was observed between the two groups when VT was expressed as a percentage of peak V̇O2. Significant correlations of .86 and .81 (p < .01) were observed between VT and peak V̇O2 in the untrained and trained groups, respectively. It was concluded that endurance training improves both VT and peak V̇O2 during wheelchair exercise in male subjects with quadriplegia but does not improve VT when it is expressed relative to peak V̇O2.

Restricted access

Sigurbjörn Árni Arngrímsson, Torarinn Sveinsson and Erlingur Jóhannsson

The purpose of this study was to validate an equation that has been used to predict peak oxygen uptake (VO2peak) and, if invalid, to develop a new equation predicting VO2peak from performance on a cycle ergometer test. Forty-five 9- and 15-year-old children underwent a VO2peak test and were randomized into developmental (DEV) and cross-validation (C-V) groups. The equation under validation, which requires knowledge of resting energy expenditure (REE), underestimated VO2peak (p < .05), but once adjusted with a new parameter calculated in DEV, it cross-validated well (r YY′ = .98, SE = .18 L · min−1). The accuracy of a new prediction equation built in DEV, not using REE, was confirmed in C-V (r YY′ = .98, SE = .17 L · min−1) and the slope and intercept were not different from the line of identity (p < .05). VO2peak in schoolchildren can be predicted with good accuracy from an equation based on the whole sample [VO2peak′ = −1.5986 + 0.0115 · (maximal power output) + 0.0109 · (mass) + 0.1313 · (gender) + 0.0085 · (maximal heart rate)].