http://orcid.org/0000-0002-9823-3915
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ABSTRACT
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 (V̇O2max), running economy (RE), velocity at V̇O2max (vV̇O2max), 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 (R2 = 0.72) nor GXTCOOL (R2 = 0.86) predicted performance in the heat as strongly has previously been reported in cool conditions. vV̇O2max was the strongest individual predictor of performance, both when assessed in GXTHOT (r = −0.83) and GXTCOOL (r = −0.90). The GXTs revealed the following correlations for individual predictors in GXTHOT; V̇O2max r = −0.7, RE r = 0.36, LT r = −0.77, LTP r = −0.78 and in GXTCOOL; V̇O2max r = −0.67, RE r = 0.62, LT r = −0.79, LTP r = −0.8. These data indicate (i) GXTHOT does not predict 5 km running performance in the heat as strongly as a GXTCOOL, (ii) as in cool conditions, vV̇O2max may best predict running performance in the heat.
Abbreviations
| GXT | = | Graded exercise tesp |
| GXTCOOL | = | Graded exercise test conducted in cool environment |
| GXTHOT | = | Graded exercise test conducted in hot environment |
| HR | = | Heart rate |
| LT | = | Lactate threshold |
| LTP | = | Lactate turnpoint |
| RE | = | Running economy |
| RER | = | Respiratory exchange ratio |
| RH | = | Relative humidity |
| RPE | = | Rating of perceived exertion |
| TCORE | = | Core temperature |
| TS | = | Thermal sensation |
| TSKIN | = | Skin temperature |
| TT | = | Time trial exercise protocol |
| V̇O2 | = | Oxygen consumption |
| V̇O2max | = | Maximal oxygen consumption |
| V̇O2peak | = | Peak oxygen uptake |
| vV̇O2max | = | Estimated velocity at maximal oxygen consumption |
| WBGT | = | Wet bulb globe index |
Disclosure of potential conflicts of interest
No potential conflicts of interest were disclosed.
