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Saichon Kloyiam, Sarah Breen, Philip Jakeman, Joe Conway and Yeshayahu Hutzler

The purpose of this study was to describe running economy, soccer specific endurance, and selected kinematic running criteria in soccer players with cerebral palsy (SPCP) and to compare them with values of position-matched players without CP. Fourteen international, male soccer players with cerebral palsy completed the “Yo-Yo” intermittent recovery run level 1 (IRL-1) test to assess soccer-specific endurance and a submaximal running test on a treadmill to determine running economy. The mean IRL-1 distance covered by the SPCP of the Irish CP team was found to be 43–50% below the mean distance attained by position-matched soccer players without disability, while running economy was found to be within the range of that reported for able-bodied athletes. No relationship could be found between the level of CP-ISRA classification and soccer-specific endurance or running economy in this group of elite level SPCP. Though small in number, these data support a further examination of the relationship between CP classification and sport-specific performance.

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Nicholas Tam, Ross Tucker, Jordan Santos-Concejero, Danielle Prins and Robert P. Lamberts

Running economy, defined as the oxygen or energy cost of transport, has been found to be an important and reliable predictor of running performance. 1 The value of running economy as a performance predictor arises because both metabolic and biomechanical aspects contribute to it, and by extension

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Ann F. Maliszewski and Patty S. Freedson

In this study, running economy differences between boys and men at a common speed (ABS = 9.6 kph) and at a relative speed adjusted for body size (REL = 3.71 leg lengths per second) were examined. The caloric cost relative to mass was significantly higher for the boys for ABS (men = .17, boys = .20), but not for REL (both .19). The relative heart rate (%HRmax) and ventilatory equivalent were higher for the boys at ABS, but not at REL. Boys had significantly higher stride frequencies in both conditions. Stride length/leg length was greater for boys during ABS, and for men during REL. Respiratory exchange ratios (RERs) were not different at ABS (men = .94, boys = .96), but during REL, boys had a significantly lower RER (.93 vs. .98). Running economy differences between adults and children are reduced when speeds are adjusted relative to body size. This model may be useful for identifying developmentally based differences in the physiology and biomechanics associated with exercise.

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Don W. Morgan, Wayland Tseh, Jennifer L. Caputo, Ian S. Craig, Daniel J. Keefer and Philip E. Martin

The purpose of this study was to quantify running economy (RE) during level treadmill running in 6-year-old children and to identify the potentially mediating effects of resting oxygen uptake and body fat percentage on sex differences in RE. Resting oxygen uptake (VO2), body fat, and RE at 5 mph were quantified in 15 boys and 20 girls following 30 min of treadmill accommodation. While absolute VO2 and mass-related values of gross and net VO2 were significantly higher in boys compared to girls, gross VO2 expressed relative to fat-free mass was not different between sexes. These results indicate that 6-year-old girls exhibit better RE compared to 6-year-old boys when VO2 is expressed as a function of total body mass. This sex difference in VO2 may reflect an increase in aerobic energy demands associated with the presence of a greater muscle mass in boys.

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Tracy Danner and Sharon Ann Plowman

The purpose of this study was to evaluate the influence of a preceding intense cycling bout on subsequent running economy in female duathletes and triathletes. Thirteen female duathletes and triathletes (age = 27.5 ± 3.36 yrs.) took part in three testing sessions: (a) measurement of running economy at 169, 177, 196, and 215 m·min−1 and running VO2 max; (b) remeasurement of running economy and measurement of cycling VO2 max; and (c) a 45 minute cycling bout at 70% of cycling VO2 max, immediately followed by measurement of running economy. Intraclass correlation coefficients between Day 1 and Day 2 running economy values ranged from 0.31 to 0.78. A systematic difference occurred at 169 m·min−1 only, with mean VO2 being higher on Day 1 than Day 2 (p<0.02). Based upon dependent t-tests, significantly higher running economy values (p<0.02) but not blood lactate concentrations (p>0.02) following the submaximal cycling bout compared to the control condition (mean of Day 1 and Day 2), at each of the four test velocities were found. Therefore we conclude that running economy was significantly impaired following a 45 minute intense cycling bout in female duathletes and triathletes, but lactate values remained constant.

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

This study was designed to examine the reliability and variability of running economy in 7-, 8-, and 9-year-old boys and girls. Forty-two children (21 boys and 21 girls) participated in two submaximal treadmill tests to determine running economy at two absolute work rates (5 mph and 6 mph). Reliability and variability were determined for oxygen consumption (V̇O2), heart rate (HR), respiratory exchange ratio (RER), stride frequency, and stride length. With the exception of RER and V̇O2 relative to body surface area, reliability estimates were moderate to high (.80 to .94). Mean variability of all responses were similar to those reported for adults, however, the range of intraindividual variability was slightly greater. These results indicate that two submaximal measurements result in higher reliability estimates than a single test and may therefore provide a more appropriate description of a child’s running economy.

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Jordan Santos-Concejero, Jesús Oliván, José L. Maté-Muñoz, Carlos Muniesa, Marta Montil, Ross Tucker and Alejandro Lucia

Purpose:

This study aimed to determine whether biomechanical characteristics such as ground-contact time, swing time, and stride length and frequency contribute to the exceptional running economy of East African runners.

Methods:

Seventeen elite long-distance runners (9 Eritrean, 8 European) performed an incremental maximal running test and 3 submaximal running bouts at 17, 19, and 21 km/h. During the tests, gas-exchange parameters were measured to determine maximal oxygen uptake (VO2max) and running economy (RE). In addition, ground-contact time, swing time, stride length, and stride frequency were measured.

Results:

The European runners had higher VO2max values than the Eritrean runners (77.2 ± 5.2 vs 73.5 ± 6.0 mL · kg−1 · min−1, P = .011, effect sizes [ES] = 0.65), although Eritrean runners were more economical at 19 km/h (191.4 ± 10.4 vs 205.9 ± 13.3 mL · kg−1 · min−1, P = .026, ES = 1.21). There were no differences between groups for ground-contact time, swing time, stride length, or stride frequency at any speed. Swing time was associated with running economy at 21 km/h in the Eritrean runners (r = .71, P = .033), but no other significant association was found between RE and biomechanical variables. Finally, best 10-km performance was significantly correlated with RE (r = –.57; P = .013).

Conclusions:

Eritrean runners have superior RE compared with elite European runners. This appears to offset their inferior VO2max. However, the current data suggest that their better RE does not have a biomechanical basis. Other factors, not measured in the current study, may contribute to this RE advantage.

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Viswanath B. Unnithan and Roger G. Eston

Previous studies have consistently shown that the body mass/relative oxygen cost of submaximal treadmill running is greater in children than in young adults. It has been suggested that the obligatory increased stride frequency in children might be at least partly responsible. This hypothesis was investigated by examining the association between stride frequency and oxygen demand characteristics in 10 aerobically fit prepubescent boys (ages 9-10 yrs) and 10 fit young men (ages 18-25 yrs) while running at fixed submaximal speeds on an electronically driven treadmill. The oxygen demand was higher at all running speeds in the boys’ group. To compensate for a shorter stride length, the boys demonstrated higher stride frequency at all speeds. To determine if the inferior running economy in the boys was partly due to the greater stride frequency, the relative oxygen demand per stride was compared between groups at all speeds. This value was similar in both groups. It is concluded that the apparently greater oxygen demand of running in boys may be due in part to the greater stride frequency required to maintain similar running speeds.

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Charles L. Dumke, Christopher M. Pfaffenroth, Jeffrey M. McBride and Grant O. McCauley

Purpose:

In this study, a comparison was made between muscle strength, power and muscle and tendon (km and kt respectively) stiffness of the triceps surae muscle group and running economy (RE) in trained male runners.

Methods:

Twelve well-trained male runners (age = 21 + 2.7 y, height = 178.1 ± 7.1 cm, body mass = 66.7 + 3.2 kg, VO2 max = 68.3 + 4.3 mLkg–1min–1, 5000-m time = 15:04 min:s) underwent passive stiffness testing using a free oscillation method. Muscle strength was determined via a maximal isometric squat test and power determined via a maximal countermovement jump (CMJ). On a separate day, subjects performed an incremental treadmill test and their RE, lactate threshold, and VO2 max were determined. Fingertip blood lactate was determined at the end of each 3-min stage. Lactate threshold was defined as a nonlinear increase in lactate accumulation.

Results:

A statistically significant correlation was found between k m and VO at stage 6 (r = -0.69, P = .01). In addition, statistically significant correlations were observed between CMJ peak force production and VO2 at stage 2 (r = .66, P = .02), stage 3 (r = .70, P = .01), and stage 4 (r = .58, P = .04). No other statistically significant correlations were observed.

Conclusion:

These data suggest that greater muscle stiffness and less power are associated with greater RE. Future study in this area should focus on determining the mechanisms behind this relationship and how to best apply them to a running population through training techniques.

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Kyle R. Barnes, Will G. Hopkins, Michael R. McGuigan and Andrew E. Kilding

Purpose:

Runners use uphill running as a movement-specific form of resistance training to enhance performance. However, the optimal parameters for prescribing intervals are unknown. The authors adopted a dose-response design to investigate the effects of various uphill interval-training programs on physiological and performance measures.

Methods:

Twenty well-trained runners performed an incremental treadmill test to determine aerobic and biomechanical measures, a series of jumps on a force plate to determine neuromuscular measures, and a 5-km time trial. Runners were then randomly assigned to 1 of 5 uphill interval-training programs. After 6 wk all tests were repeated. To identify the optimal training program for each measure, each runner’s percentage change was modeled as a quadratic function of the rank order of the intensity of training. Uncertainty in the optimal training and in the corresponding effect on the given measure was estimated as 90% confidence limits using bootstrapping.

Results:

There was no clear optimum for time-trial performance, and the mean improvement over all intensities was 2.0% (confidence limits ±0.6%). The highest intensity was clearly optimal for running economy (improvement of 2.4% ± 1.4%) and for all neuromuscular measures, whereas other aerobic measures were optimal near the middle intensity. There were no consistent optima for biomechanical measures.

Conclusions:

These findings support anecdotal reports for incorporating uphill interval training in the training programs of distance runners to improve physiological parameters relevant to running performance. Until more data are obtained, runners can assume that any form of high-intensity uphill interval training will benefit 5-km time-trial performance.