Mitigation of effects of heat and humidity at Tokyo 2020 Olympic Summer Games equestrian events

Abstract

The physiological challenge of Tokyo 2020, the XXXII Olympic Summer Games held in July-August 2021, was adaptation to training and competing in the subtropical summer weather conditions. Dressage, Eventing, and Jumping horses (n = 248) arrived at 05:00-06:30 h on six European and two Australian overnight chartered flights 8-to-10 days prior to beginning competition. All horses were housed at Japan Racing Association Equestrian Park in Bagi Koen. Eventing Cross Country was held an hour’s drive away at Sea Forest. All stables and conveyances were air-conditioned. Cooling stations were available at both venues and consisted of tall arched tents with large containers of water chilled to ≤15 °C, cooling/misting fans, and rubberised flooring for traction safety. Training hours began at 06:00 h daily with a mandatory mid-day break between 11:00 and 15:00-16:00 h when arenas were re-opened until 22:00. Daytime temperatures ranged 28.8-36.8 °C and peak humidity remained high throughout the Games (58-97%). There were no heat-related illnesses in horses observed by clinic veterinarians who were present at all training and competition rings whenever horses were exercising. Individual horses received elective intravenous fluids (10 litre minimum) on arrival in Japan, after cross country, and/or before departure. Reported ailments included post-transport pneumonia, exercise-induced pulmonary haemorrhage, orthopaedic injury, laceration, impaction colic, acute piroplasmosis, and laminitis. A persistent brisk westerly wind began nightly around 17:00 h, making evening competition sessions cooler than daytime training sessions. It was concluded that safe competitions were held despite persistently elevated subtropical ambient heat and humidity conditions.