Defining the determinants of endurance running performance in the heat

• Published in: Temperature (Austin) 2017, Vol.4 (3), p.314-329
• Main Authors: James, Carl A., Hayes, Mark, Willmott, Ashley G. B., Gibson, Oliver R., Flouris, Andreas D., Schlader, Zachary J., Maxwell, Neil S.
• Format: Article
• Language: English
• Subjects: 2max; endurance; heat stress; lactate threshold; Research Paper; running; thermoregulation; V̇O
• ISSN: 2332-8940; 2332-8959
• DOI: 10.1080/23328940.2017.1333189

In cool conditions, physiologic markers accurately predict endurance performance, but it is unclear whether thermal strain and perceived thermal strain modify the strength of these relationships. This study examined the relationships between traditional determinants of endurance performance and time to complete a 5-km time trial in the heat. Seventeen club runners completed graded exercise tests (GXT) in hot (GXTHOT; 32°C, 60% RH, 27.2°C WBGT) and cool conditions (GXTCOOL; 13°C, 50% RH, 9.3°C WBGT) to determine maximal oxygen uptake (V̇O 2max ), running economy (RE), velocity at V̇O 2max (vV̇O 2max ), and running speeds corresponding to the lactate threshold (LT, 2 mmol.l −1 ) and lactate turnpoint (LTP, 4 mmol.l −1 ). Simultaneous multiple linear regression was used to predict 5 km time, using these determinants, indicating neither GXTHOT (R 2 = 0.72) nor GXTCOOL (R 2 = 0.86) predicted performance in the heat as strongly has previously been reported in cool conditions. vV̇O 2max was the strongest individual predictor of performance, both when assessed in GXT HOT (r = −0.83) and GXT COOL (r = −0.90). The GXTs revealed the following correlations for individual predictors in GXT HOT ; V̇O 2max r = −0.7, RE r = 0.36, LT r = −0.77, LTP r = −0.78 and in GXT COOL ; V̇O 2max r = −0.67, RE r = 0.62, LT r = −0.79, LTP r = −0.8. These data indicate (i) GXT HOT does not predict 5 km running performance in the heat as strongly as a GXT COOL , (ii) as in cool conditions, vV̇O 2max may best predict running performance in the heat.