Table 2.

Summary of studies that explored the effects of caffeine on exercise performance in the heat

Author	Participants	Protocol	Outcome
Cohen et al. 1996 [362]	Endurance trained competitive road racers (male = 5; female = 2)	• Placebo • 5 mg/kg caffeine • 9 mg/kg caffeine	⬌ Running performance
Del Coso et al. 2008 [363]	Endurance trained male cyclists (n = 7)	• No fluid • Water • 6%CHO Solution • No fluid + 6 mg/kg caffeine capsule • Water + 6 mg/kg caffeine capsule • 6%CHO solution + 6 mg/kg caffeine capsule	⬌ Maximal voluntary contraction in heat *↑ Maximal cycling power in heat *↑ Maximal leg force via voluntary activation ONLY in water + caffeine and 6%CHO + caffeine
Cheuvront et al. 2009 [364]	Healthy males (n = 10)	• 9.0 mg/kg caffeine • Placebo	⬌ TT performance ⬌ RPE
Ganio et al. 2011 [365]	Male cyclists (n = 11)	• Participants consumed either 3 mg/kg caffeine or placebo 60 min prior to and after 45 min of the following trials (4 trials total; total 6 mg/kg): • Warm environment (33 °C): 90 min cycling followed by 15 min performance trial • Cool environment (12 °C): 90 min cycling followed by 15 min performance trial	Caffeine *↑ increased performance versus placebo independent of temperature
Roelands et al. 2011 [265]	Trained male cyclists or triathletes (n = 8)	• 6 mg/kg caffeine • Placebo	⬌ Acute cycling TT performance
Pitchford et al. 2014 [366]	Well-trained males (n = 9)	• 3 mg/kg caffeine • Placebo	⬌cycling TT performance in heat
Suvi et al. 2017 [359]	Healthy males (n = 13) and females (n = 10)	• 6 mg/kg caffeine • Placebo	⬌ Time to walking exhaustion
Beaumont et al. 2017 [310, 367]	Recreationally active males (n = 8)	• 6 mg/kg caffeine • Placebo	*↑ Endurance cycle performance in heat *↓ RPE during initial 60 min of exercise

Outcomes are bold caffeine group specific; * = significant difference, ⬌ = no change, ↑ = improved performance, TT = time trial, mg/kg = milligram per kilogram, CHO = carbohydrate, min = minutes, RPE = rating of perceived exertion