Physiological strain of stock car drivers during competitive racing

• Drivers endure increased thermal and cardiovascular stress during stock car racing.
• Competitive stock car racing in hot conditions may lead to large fluid losses.
• Drivers should consider strategies to meet the thermoregulatory challenges.

Heat strain experienced by motorsport athletes competing in National Association for Stock Car Automobile Racing (NASCAR) may be significant enough to impair performance or even result in a life-threatening accident. There is a need to carefully quantify heat strain during actual NASCAR race competitions in order to faithfully represent the magnitude of the problem and conceptualize future mitigation practices. The purpose of this investigation was to quantify the thermoregulatory and physiological strain associated with competitive stock car driving. Eight male stock car drivers (29.0±10.0 yr; 176.2±3.3 cm, 80.6±15.7 kg) participated in sanctioned stock car races. Physiological measurements included intestinal core (Tc) and skin (Tsk) temperatures, heart rate (HR), blood pressure, and body mass before and after completion of the race. Pre-race Tc was 38.1±0.1 °C which increased to 38.6±0.2 °C post-race (p=0.001). Tsk increased from 36.1±0.2 °C pre-race to 37.3±0.3 °C post-race (p=0.001) whereas the core-to-skin temperature gradient decreased from a pre-race value of 2.0±0.3 °C to 1.3±0.3 °C post-race (p=0.005). HRs post-race were 80±0.1% of the drivers' age-predicted maximum HR. Physiological Strain Index (PSI) post-race was 4.9, which indicates moderate strain. Drivers' thermal sensation based on the ASHRAE Scale increased from 1.3±0.5 to 2.8±0.4, and their perception of exertion (RPE) responses also increased from 8.4±1.6 to 13.9±1.8 after competition. Heat strain associated with competitive stock car racing is significant. These findings suggest the need for heat mitigation practices and provide evidence that motorsport should consider strategies to become heat acclimatized to better meet the thermoregulatory and cardiovascular challenges of motorsport competition.