Ok, so I’m running in the heat and humidity and my heart rate monitor says I am at 90% of my max yet my Garmin tells me I am running a good 2 min./mile slower than I normally would at that heart rate in cooler temperatures. My workout calls for intervals at 90% of my maximum HR.Even though I am shuffling along , am I still getting the same aerobic benefits as if I was running faster in cooler temperatures at the same heart rate? It’s hard to get my head around going “hard” when I am barely moving. Is 90% in cool temps. the same as 90% in hot temps?
I would guess that it is yes and no. Your heart is beating the same number of times per minute at 90% MHR in both hot and cold conditions, so in a lot of respects it is the same. However, as far as the physiological training effects, obviously you’re not running the same way in both conditions if your pace is 2 min/mile slower. I think it depends on what physiological adaptations you are trying to accomplish for a given workout. If you are doing speed work, I would say HR isn’t that important, and the 90% is a guide under normal conditions, but PE and pace are a better guideline. If you are doing a LSD, then I think HR would be more important, but still might need to be adjusted a little to get the same adaptations. In otherwords, be mindful of the high HR relative to the PE during the run, as you generally fatigue much more quickly in heat and humidity than otherwise.
Use PE in the heat. Your muscles are certainly not working as hard when your HR is elevated due to heat. You won’t be getting the same training effect to go soley by HR.
Try to run in the early morning or late night if you can.
matt
I believe that yes, your max ht. rate is what it is no matter what the evironmental conditions. The reason that your heart rate increases in the heat is that your body is working that much harder at thermoregulation. Themoregulation burns more calories in a day then all the exercise most people do in a week, and when you are training in the heat, that body system really has to work hard. I don’t know you or what kind of shape you are in, but it sounds to me as though you probably have miscalculated your max ht. rate.
No, I just suck when it gets hot. Went out today. 38 degrees with humidity (that’s celsius). Pace was only about 1 min/mile slower at same heart rate. I guess I am getting used to the heat slowly but surely. RPE was not nearly as high as it normally is with a heart rate of 90 % of max. in cooler temps.
I would like to run in morning and I usually do but in my upcoming Ironman I figure I will be starting the run right after noon.
I would like to run in morning and I usually do but in my upcoming Ironman I figure I will be starting the run right after noon.
Right after noon?!?! You’re going to do a 5 hour swim-bike? That’s awesome! 
Getting used to it takes time, but it works. I’ve been running most of the summer in the late afternoon (4-6pm), which is the hottest part of the day around here. It’s getting easier and easier. I figure the marathon at IMW will be a piece of cake, because I’ll be starting so much earlier!!
-Colin
Good idea about running later in the day to get used to that time. The fact that you get tired faster in the heat illustrates the point exactly that your heart rate is closer to your max when it is hot. I know for me, my heart rate is consistently 8-10 bpm faster over 88 degress (F) depending on the humidity. I know that if I push it too long and hard I’ll crack. Therefore I kick back and keep my rate aerobic no matter what my pace is. Sometimes it kills my weekly mileage because I typically train for time not miles, but I can still get the workouts in because my recovery is not affected too much.
Bernie
My race starts at 6 am and I said AFTER noon. That could be anywhere from 12:01 on.OK so my math sucks too.
I’m getting sick of it myself. We had only one day in the last 25 days under 100 degrees.
No, you are not getting the same training effect. your body is struggling to regulate temperature. It is not struggling to get oxygen into your system.
If you are anything like me, you are just beating yourself up with thermal stress that will hurt your recovery and not make you stronger like aerobic stress.
Long training time in the heat is just plain miserable.
Thank you for clarifying that so succinctly. I was trying to say the same thing but got hung up on maximum heart rate. I like the term “thermal stress.” That is a very descriptive term. It is kind of like when you are sick and have a fever, your heart rate is up, and you are burning calories, but it isn’t like you are getting any training benefit. The same would go for a chemical stress test I would imagine.
Bernie