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Yongming Li, Margot Niessen, Xiaoping Chen and Ulrich Hartmann

The knowledge of relative energy contributions (W AER %) is of theoretical and practical interest for a given sport. 1 A description of this knowledge seems to be imperative for most textbooks on exercise physiology and training science. 2 , 3 Regarding women’s Olympic kayaking (200- and 500-m

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Philippe Hellard, Robin Pla, Ferran A. Rodríguez, David Simbana and David B. Pyne

high anaerobic power. 7 , 13 No swimming study to date has compared the metabolic contributions during a 100-m trial at a real race pace as a function of age and expertise level. The aim of this study was, therefore, to measure the relative metabolic energy contributions in elite junior and senior

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Daniel A. Keir, Raphaël Zory, Céline Boudreau-Larivière and Olivier Serresse

Objectives:

Mechanical efficiency (ME) describes the ratio between mechanical (P MECH) and metabolic (P MET) power. The purpose of the study was to include an estimation of anaerobic energy expenditure (AnE) into the quantification of P MET using the accumulated oxygen deficit (AOD) and to examine its effect on the value of ME in treadmill running at submaximal, maximal, and supramaximal running speeds.

Methods:

Participants (N = 11) underwent a graded maximal exercise test to determine velocity at peak oxygen uptake (vVO2peak). On 4 separate occasions, subjects ran for 6 min at speeds corresponding to 50%, 70%, 90%, and 110% of vVO2peak. During each testing session, P MET was measured from pulmonary oxygen uptake (VO2p) using opencircuit spirometry and was quantified in 2 ways: from VO2p and an estimate of AnE (from the AOD method) and from VO2p only. P MECH was determined from kinematic analyses.

Results:

ME at 50%, 70%, 90%, and 110% of vVO2peak was 59.9% ± 11.9%, 55.4% ± 12.2%, 51.5% ± 6.8%, and 52.9% ± 7.5%, respectively, when AnE was included in the calculation of P MET. The exclusion of AnE yielded significantly greater values of ME at all speeds: 62.9% ± 11.4%, 62.4% ± 12.6%, 55.1% ± 6.2%, and 64.2% ± 8.4%; P = .001 (for 50%, 70%, 90%, and 110% of vVO2peak, respectively).

Conclusions:

The data suggest that an estimate of AnE should be considered in the computation of P MET when determining ME of treadmill running, as its exclusion leads to overestimations of ME values.

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Geraldine A. Naughton and John S. Carlson

A definitive measure for assessing the energy contribution of anaerobic pathways during exhaustive exercise remains inconclusive. The accumulated oxygen deficit (AOD) has been used in several studies to estimate energy contribution. The underlying assumptions of the AOD measure have been criticized for underestimating the true contribution of anaerobic metabolism in high intensity exercise. Indeed, the AOD measure has been the subject of much controversy. Several of the physiological exercise responses of children may lead to an even greater underestimation of the anaerobic energy contribution to high intensity exercise in children than adults when AOD measures are calculated.

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Nathan G. Lawler, Chris R. Abbiss, Aaron Raman, Timothy J. Fairchild, Garth L. Maker, Robert D. Trengove and Jeremiah J. Peiffer

Purpose:

To examine the influence of manipulating aerobic contribution after whole-blood removal on pacing patterns, performance, and energy contribution during self-paced middle-distance cycling.

Methods:

Seven male cyclists (33 ± 8 y) completed an incremental cycling test followed 20 min later by a 4-min self-paced cycling time trial (4MMP) on 6 separate occasions over 42 d. The initial 2 sessions acted as familiarization and baseline testing, after which 470 mL of blood was removed, with the remaining sessions performed 24 h, 7 d, 21 d, and 42 d after blood removal. During all 4MMP trials, power output, oxygen uptake, and aerobic and anaerobic contribution to power were determined.

Results:

4MMP average power output significantly decreased by 7% ± 6%, 6% ± 8%, and 4% ± 6% at 24 h, 7 d, and 21 d after blood removal, respectively. Compared with baseline, aerobic contribution during the 4MMP was significantly reduced by 5% ± 4%, 4% ± 5%, and 4% ± 10% at 24 h, 7 d, and 21 d, respectively. The rate of decline in power output on commencement of the 4MMP was significantly attenuated and was 76% ± 20%, 72% ± 24%, and 75% ± 35% lower than baseline at 24 h, 21 d, and 42 d, respectively.

Conclusion:

Removal of 470 mL of blood reduces aerobic energy contribution, alters pacing patterns, and decreases performance during self-paced cycling. These findings indicate the importance of aerobic energy distribution during self-paced middle-distance events.

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Roy C.M. Mulder, Dionne A. Noordhof, Katherine R. Malterer, Carl Foster and Jos J. de Koning

Previous research showed that gross efficiency (GE) declines during exercise and therefore influences the expenditure of anaerobic and aerobic resources.

Purpose:

To calculate the anaerobic work produced during cycling time trials of different length, with and without a GE correction.

Methods:

Anaerobic work was calculated in 18 trained competitive cyclists during 4 time trials (500, 1000, 2000, and 4000-m). Two additional time trials (1000 and 4000 m) that were stopped at 50% of the corresponding “full” time trial were performed to study the rate of the decline in GE.

Results:

Correcting for a declining GE during time-trial exercise resulted in a significant (P < .001) increase in anaerobically attributable work of 30%, with a 95% confidence interval of [25%, 36%]. A significant interaction effect between calculation method (constant GE, declining GE) and distance (500, 1000, 2000, 4000 m) was found (P < .001). Further analysis revealed that the constant-GE calculation method was different from the declining method for all distances and that anaerobic work calculated assuming a constant GE did not result in equal values for anaerobic work calculated over different time-trial distances (P < .001). However, correcting for a declining GE resulted in a constant value for anaerobically attributable work (P = .18).

Conclusions:

Anaerobic work calculated during short time trials (<4000 m) with a correction for a declining GE is increased by 30% [25%, 36%] and may represent anaerobic energy contributions during high-intensity exercise better than calculating anaerobic work assuming a constant GE.

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Simon A. Rogers, Chris S. Whatman, Simon N. Pearson and Andrew E. Kilding

Purpose: To examine relationships between methods of lower-limb stiffness and their associations with running economy (RE) and maximal velocity (v max) in middle-distance (MD) runners. Methods: Eleven highly trained male MD runners performed a series of mechanical and physiological tests to determine maximal overground sprint speed, RE, and V˙O2peak. Achilles tendon stiffness (k T) was estimated using ultrasonography during maximal isometric ankle plantar flexion. Global stiffness qualities were evaluated using a spring-mass model, providing measures of leg (k leg) and vertical stiffness (k vert) during running and jumping, respectively. Results: Very large (r = −.70) and large (r = −.60) negative relationships existed between RE and k T and k vert, during plantar flexion and unilateral jumps, respectively. There were large (r = .63) and extremely large (r = −.92) associations between k vert and k T and k leg during sprinting, respectively. Runners’ v max had large positive associations between k T (r = .52) and k leg (r = .59) during sprinting. Conclusions: In well-trained MD athletes, greater stiffness appears linked to faster and more economical running. Although k T had the strongest relationship with RE, k leg while sprinting and k vert in maximal unilateral jumps may be more practical measures of stiffness. Agreement between global stiffness assessments and k T highlights the energy contribution of the Achilles tendon to running efficiency and velocity. Further research incorporating these assessment tools could help establish more comprehensive mechanical and metabolic athlete profiles and further our understanding of training adaptations, especially stiffness modification, longitudinally.

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Micah Gross, Kathrin Bieri, Hans Hoppeler, Barbara Norman and Michael Vogt

Introduction:

Supplementation with beta-alanine may have positive effects on severe-intensity, intermittent, and isometric strength-endurance performance. These could be advantageous for competitive alpine skiers, whose races last 45 to 150 s, require metabolic power above the aerobic maximum, and involve isometric muscle work. Further, beta-alanine supplementation affects the muscle force-frequency relationship, which could influence explosiveness. We explored the effects of beta-alanine on explosive jump performance, severe exercise energy metabolism, and severe-intensity ski-like performance.

Methods:

Nine male elite alpine skiers consumed 4.8 g/d beta-alanine or placebo for 5 weeks in a double-blind fashion. Before and after, they performed countermovement jumps (CMJ), a 90-s cycling bout at 110% VO2max (CLT), and a maximal 90-s box jump test (BJ90).

Results:

Beta-alanine improved maximal (+7 ± 3%, d = 0.9) and mean CMJ power (+7 ± 2%, d = 0.7), tended to reduce oxygen deficit (-3 ± 8%, p = .06) and lactate accumulation (-12 ± 31%) and enhance aerobic energy contribution (+1.3 ± 2.9%, p = .07) in the CLT, and improved performance in the last third of BJ90 (+7 ± 4%, p = .02). These effects were not observed with placebo.

Conclusions:

Beta-alanine supplementation improved explosive and repeated jump performance in elite alpine skiers. Enhanced muscle contractility could possibly explain improved explosive and repeated jump performance. Increased aerobic energy production could possibly help explain repeated jump performance as well.

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Ursula F. Julio, Valéria L.G. Panissa, João V. Esteves, Rubiana L. Cury, Marcus F. Agostinho and Emerson Franchini

Purpose:

To estimate the contribution of the 3 energy systems to simulated judo matches.

Methods:

Twelve judo athletes (18 ± 1 y, 175.1 ± 5.3 cm, 74.3 ± 10.5 kg, 11.7% ± 1.5% body fat, 8 ± 2 y of practice) performed 5 combats with different durations (1, 2, 3, 4, and 5 min), against the same opponent, on different days and blinded to the duration. The estimated energy contributions for the oxidative, glycolytic, and ATP-PCr systems were calculated based on oxygen uptake (V̇O2) during activity, Delta of lactate, and the fast phase of excess V ̇ O2, respectively. Analysis of mixed models for repeated measures was used to compare the contribution of the 3 energy systems and different durations of judo matches, followed by a post hoc Bonferroni test.

Results:

The oxidative system’s contribution (70%) was higher than those of the glycolytic (8%; P < .001) and ATP-PCr (21%; P < .001) energy systems (in all durations), and the ATP-PCr contribution was higher than that of the glycolytic energy system (up to 3 min). In addition, during the match there was an increase in the oxidative (from 50% to 81%; P < .001), a decrease in the ATP-PCr (from 40% to 12%; P < .001), and maintenance of the glycolytic contributions (between 6% and 10%).

Conclusions:

There is a predominance of the oxidative system to supply the energy cost of judo matches from the first minute of combat up to the end, compared with the anaerobic systems.

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Mark H. Roltsch, Judith A. Flohr and Patricia B. Brevard

The purpose of this study was to examine the metabolic consequences of a moderate variation in dietary fat content of male endurance athletes during submaximal exercise. Six males (age, 29.8 ± 11 years; weight, 72.3 ± 10 kg) · with an average maximum oxygen uptake (V̇O2max) of 66 ± 10 ml/kg/min were tested on their normal diet and 3 experimental diets. The energy contributions from protein, carbohydrates, and fats were 16/59/22 (3% alcohol), 14/53/33, 13/72/15, and 16/61/23% for the normal diet (N), fat supplemented diet (F), high carbohydrate diet (C), and adjusted normal diet (AN), respectively. The F diet was designed to significantly increase fat content compared to the normal diet and be easily maintained by the athletes. Caloric content of the F, C, and AN diets were adjusted to meet estimated total daily energy expenditure. The difference between the N and AN diets is that the AN has been adjusted to meet estimated total daily energy expenditure. The diets were randomly assigned after substrate utilization testing on the N diet and were consumed for 7 days prior to testing. Substrate utilization was recorded at steady state (73 ± 1.4% of V̇O2max) while running on a treadmill for 40 min. There were no significant differences in respiratory exchange ratio between any of the dietary manipulations. No significant differences were observed for lactate, V̇O2, or HR during submaximal testing on the N, F, C, and AN diets. These data indicate that a fat supplemented diet did not affect substrate utilization during 40 min of steady-state submaximal exercise when compared to a high carbohydrate diet or the participant’s normal and adjusted normal diets.