Heat and Fatigue
Why hot sessions feel harder and end earlier.
In the heat, your body sends more blood to the skin to shed heat while your muscles still demand blood flow for work. Heart rate rises for the same pace, and the same effort feels harder. Across repeated efforts, output usually drops sooner than it would in cool conditions.
Heat is only one contributor to fatigue. The task itself, sleep, fueling and prior training all matter, and feeling exhausted is not a reliable gauge of body temperature. Treat how you feel as one signal among several, not a measurement.
The practical response is to manage what you can: conditions, session length, intensity, breaks and cooling. If you feel dizzy, nauseous, unusually unwell or confused, stop and cool down. Symptoms always outrank any plan or score.
Heat raises the cost of the same work; manage the session, not just the effort.
Source modules
Adapted from 0th Law course modules 2, 4. These short lessons do not award CEUs or certificates.