At about 70% VO2max in still air, cycling time to exhaustion was longest at 10.5 °C (93.5 min) and shortest at 30.5 °C (51.6 min)
An inverted U with temperature
Key Findings
Exercise duration was longest at 10.5 °C (93.5 ± 6.2 min) and shortest at 30.5 °C (51.6 ± 3.7 min).
Eight healthy men rode to exhaustion at about 70% VO2max at 3.6, 10.5, 20.6 and 30.5 °C, humidity 70%, air velocity about 0.7 m/s.
The effect of temperature on capacity followed an inverted U.
Practical Application
Around 10 °C is where a steady effort lasts longest indoors with little airflow; both warmer and colder cost capacity.
On the road the rider's own speed adds a wind this study did not have: the same 10 °C is colder on a descent or at 35 km/h, so the trunk and hands need covering that the legs' heat production does not provide.
Limitations
N = 8, time to exhaustion rather than a time trial, clothing not stated in the abstract. Abstract only was read.