Running will trigger a temperature increase. If the outside temperature is below 55°F, much of the body heat increase can be absorbed. But when running in temperatures of 65°F, 70°F, and above, core body temperature will continue to rise. Too much of an increase can result in a serious condition called heat disease which includes heat exhaustion and heat stroke.
Liberal walk breaks, from the beginning of a hot run, can minimize the internal heat increase. It’s always better to err on the safe side of heat issues. Frequent walk breaks can not only keep you from overheating, you’ll recover faster and finish stronger in races on warm or hot days.
On training runs, it’s always better during hot weather to run in the pre-dawn hours, before the sun gets above the horizon. Shade will also reduce some of the heat stress generated by sunshine.
Remember: It’s the length of the running segments that elevate core body temperature. By shortening the running segments and lengthening the walking segments, most runners can manage heat buildup on a hot day.
Note: If you suspect that you are in the preliminary stages of heat disease, cool off. Taking a cool shower for 5 minutes every 20-30 minutes of running, or walking gently for 10 minutes in an air-conditioned room every half hour can stop the temperature increase. If you experience extreme heat sensation, hot and cold flashes, cessation of sweating, extreme nausea, vomiting, or diarrhea, stop the workout and get help in cooling off immediately.
Here are recommended walk-break adjustments based upon temperature increase:
Starting pace/mi | < 55 ˚F | 65 ˚F | 70 ˚F | 75 ˚F | 80 ˚F | 85 ˚F |
9 min | R2min/W30sec | R1:45min/W30sec | R90sec/W30sec | R80sec/W30sec | R70sec/W30sec | R60sec/W30sec |
10 min | R90sec/W30sec | R80sec/W30sec | R70sec/W30sec | R60sec/W30sec | R45sec/W30sec | R30sec/W30sec |
11-12 min | R60sec/W30sec | R50sec/W30sec | R40sec/W30sec | R30sec/W30sec | R20sec/W20sec | R15sec/W20sec |
13-14 min | R30sec/W30sec | R25sec/W30sec | R20sec/W30sec | R15sec/W20sec | R15sec/W25sec | R15sec/W30sec |
15-16 min | R15sec/W30sec | R10sec/W30sec | R7sec/W30sec | R5sec/W30sec | Walk | Walk |
Note: It is always appropriate to walk more and run less on a hot day to prevent heat disease.
Note: Be sure to slow down 30 sec/mi for every 5°F temperature increase above 60°F.