Variable power output during cycling improves subsequent treadmill run time to exhaustion.

The aim of this study was to investigate the effect of constant versus variable power output cycling exercise on subsequent high-intensity, running performance. Eight triathletes completed two testing sessions (in a random order), which required the subjects to perform 30 min of cycling at either, a constant power output (90% of the lactate threshold), or a variable power output with power output alternating every 5 min (+/-20% of the constant workload). Each cycling bout was immediately followed by a high-intensity treadmill run (16.7+/-0.7 km h(-1)) to exhaustion. No significant differences were found for mean metabolic values or power output between cycling conditions. However, a significant (P<0.05) improvement in run time to exhaustion was reported after 30 min of variable cycling (15:09+/-4:43 min) compared to constant cycling (10:51+/-3:32 min). The results of this study demonstrate that, despite similar average physiological responses during 30 min of cycling, variable-intensity cycling results in an improved running performance compared to constant-intensity cycling. It is hypothesised that the reduced power output in the final 5 min of variable cycling protocol may allow recovery before transition, however the mechanisms involved cannot be determined from the current study.     

Energy cost of running during a specific transition in duathlon]

The aim of the present study was to investigate the variability of the energy cost of running (Cr) during a simulated duathlon performed in outdoor conditions by elite duathletes. This duathlon consisted of 5 km of running, 30 km of cycling, and 5 km of running. The main result was the lack of significant difference in Cr between the two running bouts (210 +/- 10 mL d'O2.km-1.kg-1 vs. 217 +/- 10 mL d'O2.km-1.kg-1). This result is different from those observed during a triathlon, where an increase of energy cost of running bout has been reported. Furthermore, during a short-distance duathlon performed by well-trained subjects, none of the physiological (ventilation alteration, metabolic changes, or dehydration) or biomechanical factors that are classically evoked in triathlon research to explain Cr variability seem to be affected by the run-cycle-run transition. These results seem to minimize the negative effect of the cycle-to-run transition during a short-duration event in well-trained subjects.     

Effects of swimming with a wet suit on energy expenditure during subsequent cycling.]

The aim of this study was to investigate the effects of swimming with a wetsuit on energy expenditure during subsequent cycling. Nine well-trained triathletes underwent three submaximal trials. The first trial (SC) consisted of a 750-m swim realised at a competition pace, followed by a 10-min cycling exercise at a power output corresponding to the ventilatory threshold . The two other trials were composed of the same cycling exercise, preceded either by a 750-m swim with a wetsuit (WSC) or by a cycling warm-up (Ctrl). The main results are that the WSC trial was characterised by significantly lower swimming cadence (-14%), heart rate (-11%), and lactate values (-47%) compared to the SC trial, p < 0.05. Moreover, cycling efficiency was significantly higher in the WSC trial compared to the SC trial (12.1% difference, p < 0.05). The lower relative intensity observed during swimming with a wetsuit suggest the relative importance of swimming condition on the total performance in a sprint triathlon.     

Evolution of electromyographic signal, running economy, and perceived exertion during different prolonged exercises

The purpose of this study was to compare the electromyographic (EMG) signal of the vastus lateralis muscle obtained during a run section of a triathlon and at the end of a prolonged run performed at the same running velocity. Seven subjects were studied on three occasions: a 2 h 15 min triathlon (30 min swimming, 60 min cycling, and 45 min treadmill running at 75% of the maximal aerobic speed), a 2 h 15 min run, where the last 45 min (Prolonged Run, PR) were run at the same speed as the Triathlon Run (TR) on a motorized treadmill, and a 45 min Isolated Run (IR) performed at the same TR and PR velocity. The three experimental trials were randomised. Oxygen uptake (VO2), heart rate (HR), and EMG data were recorded during the three run sections. The results confirm a greater VO2 and HR during PR compared with IR (P<0.01) and TR (P<0.05). Also the VO2 values obtained during TR were significantly greater compared to IR (P < 0.05). EMG signal, obtained from the vastus lateralis muscle during 4 sec of isometric contraction at 35 % of maximal voluntary contraction (MVC), showed that after PR the mean power frequency (MPF) shifted significantly to lower frequencies (P<0.01) compared with MPF recorded before the prolonged run. Moreover, the signal amplitude (RMS) was increased significantly after PR in comparison to pre-trial (P < 0.01). Similar results were obtained for the TR at P < 0.05. The integrated EMG flow, QIEMG (iEMG/burst duration), recorded during all run sections, was significantly increased near the end of PR (i.e. 2 h 10 min of running) compared with QiEMG recorded after 1 h 30 min of running. No significant increase in QiEMG was observed with TR and IR situations. The results suggest that a long exercise bout of running led to a greater increase in muscle fatigue compared with a triathlon or an isolated run performed at the same running speed. In addition it is suggested that the rating of perceived exertion recorded during isometric contractions is a good indice to approach the level of fatigue during prolonged exercises.     

Single and choice reaction time during prolonged exercise in trained subjects: influence of carbohydrate availability

The aim of the present study was to examine the effects of prolonged exercise at the ventilatory threshold and carbohydrate ingestion on single (SRT) and choice (CRT) reaction time. Eight well-trained triathletes completed three testing sessions within a 3-week period. Maximal oxygen uptake was determined in the first test, whereas the second and the third sessions were composed of a 100-min run (treadmill 15 min, overground 70 min, treadmill 15 min) performed at the velocity associated with the ventilatory threshold. During these submaximal tests, the subjects ingested (in random order) 8 ml·kg^–1 body weight of either a placebo (Pl) or 5.5% carbohydrate (CHO) solution prior to the first submaximal run and 2 ml·kg^–1 body weight every 15 min after that. The cognitive tasks were performed before and after exercise for CRT, and before, during each submaximal run and after exercise for SRT. Furthermore, at the end of each submaximal test subjects were asked to report their rating of perceived exertion (RPE). Results showed a significant positive effect of CHO ingestion on RPE and CRT performance at the end of exercise, while no effect of exercise duration was found in the Pl condition. After a 100-min run, during the CHO condition, CRT mean (SD) group values decreased from 688.5 (51) ms to 654 (63) ms, while during the Pl condition, RPE mean group values increased from 11 (2) to 16 (1.02) and CRT mean values remained stable [688 (104) ms vs 676 (73.4) ms, P>0.05]. No similar effect was observed for SRT. These results suggest that CHO-electrolyte ingestion during a100-min run results in an improvement in the complex cognitive performance measured at the end of that run. Electronic Publication     

Effect of two drafting modalities in cycling on running performance

PURPOSE: The purposes of this study were first to compare the physiological responses during a triathlon where cycling was performed alternatively with another cyclist (alternate draft triathlon, ADT) or continuously behind him (continuous draft triathlon, CDT), and second to study the incidence of these two drafting modalities in cycling on the subsequent running performance done during a simulated triathlon. METHODS: Ten male triathletes of national level performed a sprint distance triathlon (0.75-km swim, 20-km bike, 5-km run) on two different sessions, one where the triathlete alternatively rode in front or at the back of another cyclist and rotating every 500 m, the other where the triathlete drafted continuously a professional cyclist whose task was to reproduce all split times recorded during the alternate situation. Oxygen uptake (VO2), expiratory flow (VE), heart rate (HR) were recorded during the entire bike and run sections and blood lactate concentrations ([La-]b) were analyzed at the end of each event composing the triathlon. RESULTS:The results showed that expiratory flow, oxygen uptake, heart rate and blood lactate concentrations were significantly lower in CDT on the bike compared with drafting in alternation (148.1 vs. 167.2 L.min-1, 49.9 vs. 59.8 mL.min-1.kg-1, 154.7 vs. 173.1 beats.min-1, 3.5 vs. 6.3 mmol.L-1, respectively). The results also revealed that running after biking in CDT (for similar cycling speeds) significantly improved the subsequent running speed compared to ADT (17.87 vs. 17.15 km.h-1). Furthermore, VE, VO2, HR, and [La-]b were significantly higher during CDT run compared with ADT run (175.6 vs. 170.4 L.min-1, 69.7 vs. 66.8 mL.min-1.kg-1, 182.6 vs. 177.3 beats.min-1, 9.6 vs. 7.5 mmol.L-1, respectively). CONCLUSIONS: These results showed that drafting continuously behind a lead cyclist allows triathletes to save a significant amount of energy during the bike leg of a sprint triathlon and creates the conditions for an improved running performance compared with a situation where cycling is performed alternating the lead with another cyclist.     

Analyse de la sollicitation physiologique lors de la navigation en Laser

Objectifs. – Évaluer le niveau de sollicitation physiologique imposée au sportif dans des conditions proches de celles de la régate et vérifier si l'utilisation de la fréquence cardiaque de réserve (ΔFC) est un témoin valide de la consommation d'oxygène lors de la navigation en Laser^®.Protocole expérimental. – Neuf sujets de sexe masculin, et de niveau international, ont effectué deux parcours successifs de 30 minutes de navigation (avec virement de bord toutes les 2 minutes) séparés de 15 minutes de repos. Les mesures de et FC étaient réalisées en continu. Une mesure de lactatémie était effectuée avant le départ de chaque parcours puis à l'arrêt des 30 minutes de navigation.Résultats. – Les valeurs moyennes de , de ΔFC et de lactatémie sont respectivement pour les parcours 1 et 2 de : 58,7 et 54,5 % , 59,1 et 55,3 % ΔFC, 2,57 et 2,77 mmol/l^–1 observés, quels que soient l'intensité du vent et le parcours réalisé. Dans ce cadre, une relation significative est objectivée pour chaque sujet entre les valeurs moyennes de la réserve de fréquence cardiaque et de la consommation d'oxygène.Conclusion. – Lors d'un parcours d'une durée proche de celle de la régate, la consommation d'oxygène lors de la navigation en Laser^® est significativement plus élevée que celle communément relevée dans la littérature scientifique. Dans ce cadre, nos résultats montrent que la dépense énergétique moyenne d'un effort en Laser^® peut être estimée grâce à la fréquence cardiaque de réserve.Purpose. – The first aim of this study was to evaluate the physiological demand during Laser^®sailing in a situation closed to competition. The second one is to analyse the validity of relative heart rate (ΔHR) to assess energy expenditure during Laser^®sailing.Protocol. – Nine male international dinghy sailors performed two successive 30-min sailing tests tacking every 2 min with a 15 min rest in between each test. Measurements of , HR were performed during the whole test. [La]_b levels were measured just prior to the test and immediately after each 30 min of sailing.Results. – Mean values of , ΔHR and [La]_b were, respectively, 58.7% and 54.5% , 59.1% and 55.3% ΔHR, 2.57 and 2.77 mmol l^–1 for test 1 and 2 whatever the speed of the wind. Furthermore a significant relationship was observed between mean relative heart rate value and oxygen consumption in each subject.Conclusions. – In our study closed to regatta condition in Laser^®sailing, energy expenditure values recorded is higher than those classically reported in scientific literature during simulated conditions. Furthermore in this study, our results indicate that relative heart rate can be used as an useful tool to assess energy spending during Laser^® sailing.     

Physiological demands of different sailing techniques of the new Olympic windsurfing class

The introduction of the new Olympic class windsurf-board has prompted sailors to develop a new technique of sail “pumping” (rhythmically pulling the sail so that it acts as a wing). Contrary to the old technique that mainly involved upper body activity, the new one requires both upper and lower body muscle activity. Accordingly, the aim of the present study was to compare the performance characteristics of the board (speed and pointing angle ability relative to the direction of the wind) as well as the sailors’ physiological demands during sail pumping with the old and new pumping techniques. Nineteen male, highly-trained (O_2max: 65.1 ± 5.9 ml min⁻¹ kg⁻¹), international level windsurfers from six different countries underwent two testing sessions on-water in a balanced order. Compared to the old pumping technique the mean distance sailed with the new technique (1,872 ± 15 and 1,764 ± 13 m, respectively) and the board speed (3.42 ± 0.49 and 3.81 ± 0.28 m s⁻¹, respectively) were significantly (P < 0.05) shorter and greater, respectively. Consequently, the time taken to sail the testing course was significantly shorter with the new compared to the old technique (390 ± 8 vs. 420 ± 16 s). Despite the finding that the new technique was sustained at a significantly higher fraction of O_2max (80.5 ± 5.2 and 72.7 ± 4.5%, respectively) compared to the old technique, total energy expenditure (130.7 ± 11.3 and 128.1 ± 9.2 Kcal, respectively) and blood lactate concentration 3 min into recovery (9.4 ± 2.2 and 8.5 ± 1.7 mmol l⁻¹, respectively) were not different. It is concluded that application of the new sail pumping technique improves the performance characteristics of the board without increasing the sailors’ total metabolic requirement.