P. Hespel, Exercise Physiology Research Group, KU Leuven
In the recent Amgen Tour of California, cyclists during stages were exposed to temperatures exceeding 40°C. This extreme heat stress made several riders to abandon the race, of course. Nonetheless, Tom Boonen, one of the top riders in the peloton stated that ‘competition in the heat improves his performance upon return to competitions is colder environments’.
Is this statement true or false?
In this regard, in 2010 Lorenzo and his co-workers published an interesting study entitled; “Heat Acclimation Improves Exercise Performance”. Trained cyclists performed 10 days of training in either a cool (13°C) or hot environment. Before and after the training period they participated in a typical incremental VO2max test as well as a simulated 60-min time-trial, in both a cold (13°C) and a hot environment (38°C).
What did the study show?
Training in the heat improved VO2max in the cold by +5%, versus + 8% in the heat. Accordingly, heat acclimation enhanced time-trial performance by + 8% in hot conditions, versus +6% in cold conditions. Furthermore, following heat acclimation blood volume was increased by ~6.6%, which resulted in a 9% higher cardiac output during maximal exercise in the cold, versus only +4.5% higher cardiac output during exercise in the heat.
Take home message:
The statement by Tom Boonen is true and compatible with available scientific evidence. Training in the heat, by increasing blood volume and maximal cardiac output, can enhance cycling performance in the cold. Thus, there is a logic rationale for using training and/or competition in the heat to augment later cycling performance in temperate-cool conditions.
Lorenzo S, Halliwill JR, Sawka MN, Minson CT. Heat acclimation improves exercise performance. J Appl Physiol 2010;109:1140–47.