J.J. de Koning

Optimal pacing strategy: from theoretical modelling to reality in 1500-m speed skating

Purpose Athletes are trained to choose the pace which is perceived to be correct during a specific effort, such as the 1500-m speed skating competition. The purpose of the present study was to “override” self-paced (SP) performance by instructing athletes to execute a theoretically optimal pacing profile. Methods Seven national-level speed-skaters performed a SP 1500-m which was analysed by obtaining velocity (every 100 m) and body position (every 200 m) with video to calculate total mechanical power output. Together with gross efficiency and aerobic kinetics, obtained in separate trials, data were used to calculate aerobic and anaerobic power output profiles. An energy flow model was applied to SP, simulating a range of pacing strategies, and a theoretically optimal pacing profile was imposed in a second race (IM). Results Final time for IM was ∼2 s slower than SP. Total power distribution per lap differed, with a higher power over the first 300 m for IM (637.0 (49.4) vs 612.5 (50.0) W). Anaerobic parameters did not differ. The faster first lap resulted in a higher aerodynamic drag coefficient and perhaps a less effective push-off. Conclusion Experienced athletes have a well-developed performance template, and changing pacing strategy towards a theoretically optimal fast start protocol had negative consequences on speed-skating technique and did not result in better performance.

Relative importance of pacing strategy and mean power output in 1500-m self-paced cycling

Introduction Both mean power output (MPO) and the distribution of the available energy over the race, that is, pacing strategy, are critical factors in performance. The purpose of this study was to determine the relative importance of both pacing strategy and MPO to performance. Methods Six well-trained, regionally competitive cyclists performed four 1500-m ergometer time trials (∼2 min). For each subject, the fastest (Fast) and slowest (Slow) time trials were compared and the relative importance of differences in power output and pacing strategy were determined with an energy flow model. Results The difference in final time between Fast and Slow was 4.0 (2.5) s. Fast was performed with a higher MPO (437.8 (32.3) W vs 411.3 (39.0) W), a higher aerobic peak power (295.3 (36.8) vs 287.5 (34.7) W) and a higher anaerobic peak power (828.8 (145.4) W vs 649.5 (112.2) W) combined with a relatively higher, but not statistically different anaerobic rate constant (0.051 (0.016) vs 0.041 (0.009) W). The changes in MPO (63% anaerobic, 37% aerobic) largely explained the differences in final times. Athletes chose a different pacing strategy that was close to optimal for their physiological condition in both Fast and Slow. Conclusion Differences in intraindividual performance were mainly caused by differences in MPO. Athletes seemed to be able to effectively adjust their pacing profile based on their “status of the day”. Keywords modelling performance, energy expenditure, aerobic, anaerobic, sports.

Factors Affecting Gross Efficiency in Cycling

There is little standardization of how to measure cycling gross efficiency (GE). Therefore, the purposes of these studies were to evaluate the effect of: i) stage duration, ii) relative exercise intensity, iii) work capacity and iv) a prior maximal incremental test on GE. Trained subjects (n=28) performed incremental tests with stage durations of 1-, 3-, and 6-min to establish the effect of stage duration and relative exercise intensity on GE. The effect of work capacity was evaluated by correlating GE with peak power output (PPO). In different subjects (n=9), GE was measured at 50% PPO with and without a prior maximal incremental test. GE was similar in 3- and 6-min stages (19.7 ± 2.8% and 19.3 ± 2.0%), but significantly higher during 1-min stages (21.1 ± 2.7%), GE increased with relative exercise intensity, up to 50% PPO or the power output corresponding to the ventilatory threshold and then remained stable. No relationship between work capacity and GE was found. Prior maximal exercise had a small effect on GE measures; GE was lower after maximal exercise. In conclusion, GE can be determined robustly so long as steady state exercise is performed and RER ≤ 1.0.

Effects of wind application on thermal perception and self-paced performance

Physiological and perceptual effects of wind cooling are often intertwined and have scarcely been studied in self-paced exercise. Therefore, we aimed to investigate (1) the independent perceptual effect of wind cooling and its impact on performance and (2) the responses to temporary wind cooling during self-paced exercise. Ten male subjects completed four trials involving 15xa0min standardized incremental intensity cycling, followed by a 15-km self-paced cycling time trial. Three trials were performed in different climates inducing equivalent thermal strain: hot humid with wind (WIND) and warm humid (HUMID) and hot dry (DRY) without wind. The fourth trial (W3-12) was equal to HUMID, except that wind cooling was unexpectedly provided during kilometers 3–12. Physiological, perceptual and performance parameters were measured. Subjects felt generally cooler during the WIND than the HUMID and DRY trials, despite similar heart rate, rectal and skin temperatures and a WBGT of ~4xa0°C higher. The cooler thermal sensation was not reflected in differences in thermal comfort or performance. Comparing W3-12 to HUMID, skin temperature was 1.47xa0±xa00.43xa0°C lower during the wind interval, leading to more favorable ratings of perceived exertion, thermal sensation and thermal comfort. Overall, power output was higher in the W3-12 than the HUMID-trial (256xa0±xa029 vs. 246xa0±xa022xa0W), leading to a 67xa0±xa048xa0s faster finish time. In conclusion, during self-paced exercise in the heat, wind provides immediate and constant benefits in physiological strain, thermal perception and performance. Independent of physiological changes, wind still provides a greater sensation of coolness, but does not impact thermal comfort or performance.

Effects of radiant heat exposure on pacing pattern during a 15-km cycling time trial

Abstract The goal of this study was to investigate the effects of different durations of skin temperature manipulation on pacing patterns and performance during a 15-km cycling time trial. Nineteen well-trained men completed three 15-km cycling time trials in 18°C and 50% relative humidity with 4.5-km (short-heat), 9.0-km (long-heat) or without (control) radiant heat exposure applied by infrared heaters after 1.5 km in the time trial. During the time trials, power output, mean skin temperature, rectal temperature, heart rate and rating of perceived exertion were assessed. The radiant heat exposure resulted in higher mean skin temperature during the time trial for short-heat (35.0 ± 0.6°C) and long-heat (35.3 ± 0.5°C) than for control (32.5 ± 1.0°C; P < 0.001), whereas rectal temperature was similar (P = 0.55). The mean power output was less for short-heat (273 ± 8 W; P = 0.001) and long-heat (271 ± 9 W; P = 0.02) than for control (287 ± 7 W), but pacing patterns did not differ (P = 0.55). Heart rate was greatest in control (177 ± 9 beats · min−1; P < 0.001), whereas the rating of perceived exertion remained similar. We concluded that a radiant heat exposure and associated higher skin temperature reduced overall performance, but did not modify pacing pattern during a 15-km cycling time trial, regardless of the duration of the exposure.

The effect of pre-warming on performance during simulated firefighting exercise

This study examined the effect of active pre-warming on speed and quality of performance during simulated firefighting exercise. Twelve male firefighters performed two trials in counterbalanced order. They were either pre-warmed by 20-min cycling at 1.5xa0Wattxa0kg(-)(1) body mass (WARM) or remained thermoneutral (CON) prior to a simulated firefighting activity. After the pre-warming, gastrointestinal temperature (Pxa0<xa00.001), skin temperature (Pxa0=xa00.002), and heart rate (Pxa0<xa00.001) were higher in WARM than in CON. During the firefighting activity, rating of perceived exertion, thermal sensation and discomfort were higher for WARM than for CON. Finish time of the firefighting activity was similar, but the last task of the activity was completed slower in WARM than in CON (Pxa0=xa00.04). In WARM, self-reported performance quality was lower than in CON (Pxa0=xa00.04). It is concluded that pre-warming reduces the speed during the last part of simulated firefighting activity and reduces self-reported quality of performance.

Authors' reply to périard: "cardiovascular determinants involved in pacing under heat stress" : the complex skill of pacing: is there an interplay between central and peripheral determinants?

By posing the question we already give the answer: the time has passed when exercise physiologists divided the human body into a heart and muscles and the ‘‘mysterious’’ brain. Exercise physiology integrates both and pacing is a very nice example of the interplay between peripheral factors including cardiovascular regulation, metabolism, muscle physiology, and central factors such as neurotransmission, perception of effort, control of thermoregulation, and others [1, 2]. We therefore thank Dr Périard for his feedback [3] on our article and for pointing out the importance of cardiovascular limitations during prolonged exercise [4]. Indeed, cardiovascular limitations induced by adjustments in thermoregulation can significantly influence the maintenance of a given absolute intensity or pace, as was stated by Périard. Evidence from studies in our laboratory [5–7] showed that fixed-intensity exercise (60 min at 55 % of the maximal power output) resulted in significantly higher heart rates in hot conditions (30 C) when compared with normal (18 C) ambient temperature. Unfortunately, we did not measure stroke volume, cardiac output, or blood flow as was done in the study by Périard et al. [4] and that would have provided interesting information. During the 30-min time trial that followed the 60-min fixed-intensity exercise, the observed difference in heart rate disappeared. This could be explained by the attainment of higher power outputs in normal conditions compared with hot ambient conditions. Furthermore, from 10 min to the termination of exercise, heart rates followed a similar pattern in both conditions. This outcome is not identical to the findings of Périard et al. [4] but again emphasizes the interplay between peripheral and central aspects in pacing. Generally, these data demonstrate that the cardiovascular system is a coinfluencer of exercise performance (and thus pacing strategy) that cannot be overlooked. The data also encourage scientists to further unravel the mechanisms behind changes in pace and the onset of fatigue, certainly during prolonged exercise bouts in the heat. In our review, we acknowledged the complexity of the concept of pacing, and consequently the interplay between peripheral and central factors. However, our main area of expertise lies in the central aspects of fatigue and the manipulation of brain neurotransmission in different ambient settings [8]. Our review was therefore focused on the ‘‘central aspects’’ of exercise in the heat, an area that has gained more importance in the recent years. Furthermore, in our article we directed interested readers to the excellent review by Abbiss and Laursen [2], who described nine different models of fatigue, including the cardiovascular model. This reply refers to the comment available at doi:10.1007/s40279-013-0050-0.

Authors’ Reply to Périard: “Cardiovascular Determinants Involved in Pacing Under Heat Stress”

By posing the question we already give the answer: the time has passed when exercise physiologists divided the human body into a heart and muscles and the ‘‘mysterious’’ brain. Exercise physiology integrates both and pacing is a very nice example of the interplay between peripheral factors including cardiovascular regulation, metabolism, muscle physiology, and central factors such as neurotransmission, perception of effort, control of thermoregulation, and others [1, 2]. We therefore thank Dr Périard for his feedback [3] on our article and for pointing out the importance of cardiovascular limitations during prolonged exercise [4]. Indeed, cardiovascular limitations induced by adjustments in thermoregulation can significantly influence the maintenance of a given absolute intensity or pace, as was stated by Périard. Evidence from studies in our laboratory [5–7] showed that fixed-intensity exercise (60 min at 55 % of the maximal power output) resulted in significantly higher heart rates in hot conditions (30 C) when compared with normal (18 C) ambient temperature. Unfortunately, we did not measure stroke volume, cardiac output, or blood flow as was done in the study by Périard et al. [4] and that would have provided interesting information. During the 30-min time trial that followed the 60-min fixed-intensity exercise, the observed difference in heart rate disappeared. This could be explained by the attainment of higher power outputs in normal conditions compared with hot ambient conditions. Furthermore, from 10 min to the termination of exercise, heart rates followed a similar pattern in both conditions. This outcome is not identical to the findings of Périard et al. [4] but again emphasizes the interplay between peripheral and central aspects in pacing. Generally, these data demonstrate that the cardiovascular system is a coinfluencer of exercise performance (and thus pacing strategy) that cannot be overlooked. The data also encourage scientists to further unravel the mechanisms behind changes in pace and the onset of fatigue, certainly during prolonged exercise bouts in the heat. In our review, we acknowledged the complexity of the concept of pacing, and consequently the interplay between peripheral and central factors. However, our main area of expertise lies in the central aspects of fatigue and the manipulation of brain neurotransmission in different ambient settings [8]. Our review was therefore focused on the ‘‘central aspects’’ of exercise in the heat, an area that has gained more importance in the recent years. Furthermore, in our article we directed interested readers to the excellent review by Abbiss and Laursen [2], who described nine different models of fatigue, including the cardiovascular model. This reply refers to the comment available at doi:10.1007/s40279-013-0050-0.