Does short-duration heat exposure at a matched cardiovascular intensity improve intermittent running performance in a cool environment?


Calvin P. Philp, Martin Buchheit, Cecilia M. Kitic, Christopher T. Minson, James W. Fell. Does short-duration heat exposure at a matched cardiovascular intensity improve intermittent running performance in a cool environment? IJSPP, In press.

Full text here


Purpose: To investigate whether a five-day cycling training block in the heat (35°C) in Australian rules footballers was superior to exercising at the same relative intensity in cool conditions (15°C) for improving intermittent running performance in a cool environment (<18°C).

Methods: Using a parallel-group design, 12 semi-professional football players performed five days of cycling exercise [70% heart rate reserve (HRR) for 45 min (5 x 50 min sessions in total)] in a hot (HEAT, 35±1°C, 56±9% RH) or cool environment (COOL, 15±3°C, 81±10% RH). A 30-15 Intermittent Fitness Test to assess intermittent running performance (VIFT) was conducted in a cool environment (17±2°C, 58±5% RH) prior to, one and three days after the intervention.

Results: There was a likely small increase in VIFT within each group [HEAT: 0.5±0.3 km.h-1, 1.5±0.8 x smallest worthwhile change (SWC); COOL 0.4±0.4 km.h-1, 1.6±1.2 x SWC] three days post the intervention, with no difference in change between the groups (0.5±1.9%, 0.4±1.4 x SWC). Cycle power output during the intervention was almost certainly lower in the HEAT group (HEAT 1.8±0.2 vs. COOL 2.5±0.3, -21.7±3.2 x SWC, 100/0/0).

Conclusions: This study indicates that when cardiovascular exercise intensity is matched (i.e. 70% HRR) between environmental conditions, there is no additional performance benefit from short-duration moderate-intensity heat exposure (5 x 50 min) for semi-professional footballers exercising in cool conditions. However, the similar positive adaptations may occur in the HEAT with 30% lower mechanical load, which may be of interest for load management during intense training or rehabilitation phases.

Key Words: heat acclimation; football; plasma volume; relative-intensity exercise, VIFT




Psychometric and physiological responses to a pre-season competitive camp in the heat with a 6-hr time difference in elite soccer players

Buchheit, M., Cholley Y. and Lambert P. Psychometric and physiological responses to a pre-season competitive camp in the heat with a 6-hr time difference in elite soccer players. IJSPP, In press.


Purpose. The aim of the present study was to examine in elite soccer players some psychometric and physiological responses to a competitive camp in the heat, after travelling across 6 time-zones. Methods. Data from 12 elite professional players (24.6±5.3 yr) were analyzed. They participated in an 8-day pre-season summer training camp in Asia (heat index 34.9±2.4 ⁰C). Players’ activity was collected during all training sessions and the friendly game using 15-Hz GPS. Perceived training/playing load was estimated using session rate of perceived exertion (RPE) and training/match duration. Psychometric measures of wellness were collected upon awakening before, during and after the camp using simple questionnaires. HR response to a submaximal 4-min run (12 km/h) and the ratio between velocity and force load (accelerometer-derived measure, a marker of neuromuscular efficiency) response to 4 ~60-m runs (22-24 km/h) were collected before, at the end and after the camp. Results. After a large increase, the RPE/m.min-1 ratio decreased substantially throughout the camp. There were possible small increases in perceived fatigue and small decreases in subjective sleep quality on the 6th day. There were also likely moderate (~3%) decreases in HR response to the submaximal run, both at the end and after the camp, which were contemporary to possible small (~8%) and most-likely moderate (~19%) improvements in neuromuscular efficiency, respectively. Conclusions. Despite transient increases in fatigue and reduced subjective sleep quality by the end of the camp, these elite players showed clear signs of heat acclimatization, which were associated with improved cardiovascular fitness and neuromuscular running efficiency.

Fig 1 final color2

Figure 1. Upper panel: change in locomotor load (measured via GPS) and heat index before, during and after the Asian camp. The flights represent the different flying trips, with their specific duration indicated into brackets. As wearing GPS was not allowed during the official match, the total distance covered was extrapolated from historical club data (Team A) against Team B for illustration. The timing of the monitoring sessions is also indicated, with Run standing for the submaximal run and the 4 60-m runs, and Wellness for the psychometric questionnaires. Lower panel: changes in perceived training load (rate of perceived exertion, RPE, method) and the RPE/distance per min ratio. The gray area represents the Hong Kong (HK) camp, while the grey and shaded area represents the time spent in Beijing. ****: very likely different vs. pre camp.

Keywords: heart rate monitoring, wellness, neuromuscular efficiency, association football, heat training.

Effect of sauna-based heat acclimation on plasma volume and heart rate variability

Stanley, J., Halliday, A., D’Auria, S., Buchheit, M. and Leicht, AS. Effect of sauna-based heat acclimation on plasma volume and heart rate variability. Eur J App Physiol, In press.

PV EAJP Full text here / Video of the talk here

Purpose: We investigated the effect of post-exercise sauna bathing on plasma volume (PV) expansion and whether such responses can be tracked by changes in heart rate (HR) based measures.
Methods: Seven, well-trained, male cyclists were monitored for 35 consecutive days (17 d baseline training, 10d training plus sauna, 8d training). Sauna exposure consisted of 30 min (87°C, 11% relative humidity) immediately following normal training. Capillary blood samples were collected to assess PV changes while resting seated. HR (HRwake) and vagal-related HR variability (natural logarithm of square-root mean squared differences of successive R−R intervals, ln rMSSDwake) were assessed daily upon waking. A sub-maximal cycle test (5 min at 125 W) was performed on days 1, 8, 15, 22, 25, 29, and 35 and HR recovery (HRR60s) and ln rMSSDpostex were assessed post-exercise. Effects were examined using magnitude-based inferences.
Results: Compared with baseline, sauna resulted in: 1) peak PV expansion after 4 exposures with a likely large increase [+17.8% (90% confidence limits, 7.4;29.2)]; 2) reduction of HRwake by a trivial-to-moderate amount [−10.2% (−15.9;−4.0)]; 3) trivial-to-small changes for ln rMSSDwake [4.3% (1.9;6.8)] and ln rMSSDpostex [−2.4% (−9.1;4.9)]; and 4) a likely moderate decrease in HRR60s [−15.6% (−30.9;3.0)]. Correlations between individual changes in PV and HR measures were all unclear.
Conclusions: Sauna-bathing following normal training largely expanded PV in well-trained cyclists after just 4 exposures. The utility of HR and HRV indices for tracking changes in PV was however uncertain. Future studies will clarify mechanisms and performance benefits of post-training sauna bathing.
Keywords: heat exposure; blood volume; cardiac parasympathetic activity; post-exercise; cyclists.


Adding heat to the live-high train-low altitude model: a practical insight from professional football

aus-rule-football-2Finally! After 7 rejections, ‘one of the most rejected paper’ was accepted this morning in the Altitude for team sports BrJSM issue (following Aspetar conference in March 2013). I already see some readers saying “hum… a special issue? Aspetar is actually paying for it? This is why the paper was accepted!  – can’t be a good one with its rejection history!” Fair enough. But to be honest, I really don’t care why or where this paper is published today. The study ran with the Carlton FC (AFL) boys in November 2011 in Doha is probably one the very best study I ever had the chance to be involved in (competing with the 2012 Football project in La Paz for the first place). Results have to be published, because they matter to us (physiologists, sport scientists or strength & conditioning coaches). I would like to see someone working in elite team sports not interested in the results… any one?

The scientific publication process is a game; Sometimes you lose, Sometimes you win. The story of this study is worth taking a few minutes of your time, since it perfectly illustrates the problem that we have to face at each submission.

1. We are interested in practical studies, with practical results in elite players. I can’t be bothered conducting an altitude training study in recreational players, since these latter might definitively not be lucky enough to be given the opportunity (time and money) to do so. The problem is that with elite players in a real life scenario (i.e., pre-season camp), you have to do some concessions, which might partly affect the study design (e.g., group allocation, nature of the performance/physiological measures). However, the practical outcomes undoubtedly balance some of the possible methodological flaws/limitations. In the present study, our aim was ONLY to compare the MAGNITUDE of the effect on performance and some physiological variables of 2 different training approaches (heat only, or heat + altitude), that could be practically implemented in elite players. We definitively missed a control group (no heat, no simulated altitude) to assess the exact effect of heat per se. Fair enough. But from a practical point of view, this is not that of a problem. We just wanted to know whether adding the hypoxic stimuli is worthwhile, compared with heat only. Results show that the additional altitude training effect is very limited, which clearly answer our question – and again, I am sure that most practitioners would be happy with this. When compared with historical data from the previous years, we also documented a greater and faster improvement in performance, suggesting that the present intervention(s) were pretty awesome (likely because of the heat, but we can’t say it with absolute confidence…:)). Again, from a practical point of view, this is a cool result and this should be enough to deserve publication!?

–> Problem: Reviewers and editors want perfectly controlled study designs, and don’t care about the practical applications. They want you to answer physiological questions first. They don’t understand how load can be controlled outside the lab. They have never heard about session RPE, or GPS technology (actually this is the lady voice that asks you to do a u-turn when you missed the exit in your car). In short, the ignorance of reviewers and editors lead them to miss the fact that our field studies are actually much more controlled that they though. This attitude lead some editors to reject the paper at their level (didn’t want to waste reviewers’ time – MSS, EJAP – and even better, in Scan JMSS, S. Harridge, the editor in chief managed to disregard a quite positive review from a well-known AIS physiologist – pretending he didn’t get the review to justify his rejection. Yes, this is the reality!! This same editor had already rejected another paper because cold water immersion was not blinded in this study… !?). Just to show you how treated our papers are sometimes.

2. We have to use appropriate statistics, i.e., which highlight the magnitude of the training effects.

–> Problem: Reviewers in the altitude business spent too much time behind their desk, and simply want P values. With the 7 rejections and sometimes 3 reviews per submission, I had the chance to gather a few nuggets, as the legendary: “The study has some potential, but could you please run some stats?” What can we do? Will Hopkins wrote on another occasion: “I can’t be bothered addressing this kind of criticism. If you believe in God, no amount of evidence against His existence will disabuse you of your belief. Similarly, if you believe in null-hypothesis testing, the evidence for a better method of making inferences about true effects means nothing to you. In any case, has this person read the evidence? I doubt it.”

If I (we) had to do it again, I (we) would do exactly the same.

2011-10-20 14.45.16 2011-10-19 17.13.58

Buchheit, M., Racinais, S., Bilsborough, J., Hocking, J., Mendez-Villanueva, A., Bourdon, P.C., Voss, S., Livingston, S., Christian R.,  Périard J., Cordy, J., and Coutts, A.J. Adding heat to the live-high train-low altitude model: a practical insight from professional football. BJSM In press.

What is known on this subject
•    Hypoxic exposure (live-high, train-low model) can increase hemoglobin mass, especially in athletes with low baseline levels such as team sport players.
•    Short term heat acclimatization can increase plasma volume team sport players.
•    Combined, increased hemoglobin mass and plasma volume improve total blood volume and convective O2 delivery, which can, under some circumstances, improve high-intensity exercise performance.

What is this study adds
•    Pre-season outdoor football training in hot ambient conditions induces (at least) partial heat acclimatization in professional Australian Rules Football players, and is associated with very large improvements in high-intensity running performance.
•    The substantial increases in hemoglobin mass and blood volume observed immediately after a ‘live high-train low in the heat’ camp can last at least one month.
•    Compared with training in the heat only, an additional hypoxic stimulus during sleep and some training sessions has no high-intensity running performance benefits immediately after the camp. The possible greater delayed effects of the hypoxic exposure, if any, are only small in magnitude.


Objectives. To examine with a parallel group study design the performance and physiological responses to a 14-day off-season ‘live high-train low in the heat’ training camp in elite Football players.
Methods. Seventeen professional Australian Rules Football players participated in outdoor football-specific skills (32±1˚C, 11.5h) and indoor strength (23±1˚C, 9.3h) sessions, and slept (12 nights) and cycled indoors (4.3h) in either normal air (NORM, n=8) or normobaric hypoxia (14±1 h/day, FiO2 15.2-14.3%, corresponding to a simulated altitude of 2500-3000 m, HYP, n=9). They completed the Yo-Yo Intermittent Recovery level 2 (Yo-YoIR2) in temperate conditions (23±1˚C, normal air) Pre and Post. Plasma volume (PV) and hemoglobin mass (Hbmass) were measured at similar times and 4 weeks post camp (4WPost). Sweat sodium concentration ([Na+]sweat) was measured Pre and Post camp during a heat-response test (44ºC).
Results. Both groups showed very large improvements in Yo-YoIR2 at Post (+44%; 90%CL 38,50), with no between-group differences in the changes (-1%; -9,9). Post camp, large changes in PV (+5.6%; -1.8,5.6) and [Na+]sweat (-29%; -37,-19) were observed in both groups, while Hbmass only moderately increased in HYP (+2.6%; 0.5,4.5). At 4WPost, there was a likely slightly greater increase in Hbmass (+4.6%; 0.0,9.3) and PV (+6%; -5,18, unclear) in HYP than in NORM. Conclusions. The combination of heat and hypoxic exposure during sleep/training might offer a promising ‘conditioning cocktail’ in team sports.

Physiological and Performance Responses to a Training-Camp in the Heat in Professional Australian Football Players

2011-10-21 11.49.17

Sebastien Racinais, Martin Buchheit, Johann Bilsborough, Pitre C. Bourdon, Justin Cordy and Aaron J Coutts. International Journal of Sports Physiology and Performance, In press.


Purpose: To examine the physiological and performance responses to a heat-acclimatization camp in highly-trained professional team sport athletes. Methods: Eighteen male Australian Rules Football players trained for two weeks in hot ambient conditions (31-33ºC, humidity 34-50%). Players performed a laboratory-based heat-response test (24 min walk + 24 min seated; 44ºC), a YoYo Intermittent Recovery Level 2 Test (YoYoIR2; indoor, temperate environment, 23ºC) and standardized training drills (STD; outdoor, hot environment, 32ºC) at the beginning and end of the camp. Results: The heat-response test showed partial heat acclimatization (e.g., a decrease in skin temperature, heart rate and sweat sodium concentration, p<0.05). In addition, plasma volume (PV, CO-rebreathing, +2.68, 95%CI[0.83;4.53] ml·kg-1]) and distance covered during both the YoYoIR2 (+311[260;361]m) and the STD (+45.6[13.9;77.4]m) increased post camp (p<0.01). None of the performance changes showed clear correlations with PV changes (r<0.24), but the improvements in running STD distance in hot environment was correlated with changes in haematocrit during the heat-response test (r=-0.52,90%CI[-0.77;-0.12]). There was no clear correlation between the performance improvements in temperate and hot ambient conditions (r<0.26). Conclusion: Running performance in both hot and temperate environments was improved following a Football training-camp in hot ambient conditions that stimulated heat-acclimatization. However, physiological and performance responses were highly individual and the absence of correlations between physical performance improvements in hot and temperate environments suggests that their physiological basis might differ.

Keywords: acclimation; acclimatization; exercise; hot environment; temperature; football