Yes, it’s hot outside. And yes, we should be grateful that we can run (outside). But when the temps dip into the high 80s or low 90s — or higher — and include some (or a lot) of humidity, running outside can become, well, hard.
It’s important to note that it feels hard because you are probably trying to hit your more normal temperature paces, which is neither wise or good for you. There are actually heat index calculators that scientists, aka people much smarter than me, have developed that demonstrate the real time effect of heat and humidity on performance and real effort.
The research shows that the ideal racing/running temps hover somewhere in the low 50s. For every 5 degree increase in temperature, you can and should expect your paces to slow somewhere around 5-10 sec per mile. So if “ideal” is say 55 degrees and you’re running/training in 85 degrees, that equates to 30-60 sec slower per mile.
The next question comes, how can I train at 30-60 sec slower per mile and reach my pace goals for a fall race? The good news is your body only knows perceived exertion, not pace. This is where heart rate training can be a real asset. Your speed and long run days are based on the appropriate max heart rate percentage (best taken from a mile TT or VO2 Max test) for any given run. As a general rule, short speed (100s to 400s) are done at about 85-90% if doing intervals; and longer speed, 600s to mile+ at about 80% max heart rate. Long runs should be in the 70% range — remember, the key to long runs is to be on your feet for a long period of time — it’s not about how fast you go.
The rule of thumb during the summer is run based on equivalent “effort” or heart rate and adjust your pace goals by the formula above. You’re still doing speed work and as temperatures drop so should your pacing. That’s why when you travel to cooler places in the summer, you feel like a rock star. Because you are.
Remember, feeling good is the ultimate goal in running and in life. Part of this is making sure you are well hydrated, running as early in the day as possible, and taking in sports drink before and during your run (the salt and electrolytes really help). If you set yourself up (and adjust pacing )to feel good, you’re much more likely to have a good run. Just like a good day. So, head out (early) and appreciate the early morning cooler temps, peace, and quiet, and be thankful you get to run.