Future running partner.
Heart rate increases at high temperatures. Your heart rate is higher when running on a hot day. As the temperature increases from 60 degrees to 75 degrees, a runner?s heart rate at a given speed increases by about 2 to 4 beats per minute. When the temperature increases from 75 degrees to 90 degrees, you can expect your heart rate running at a given speed to increase by approximately 10 beats per minute. High humidity magnifies the effect of high temperatures on heart rate. To gain the same benefits as on a cool day, you should increase your heart rate zones by 2 to 4 beats per minute when the temperature is in the 70?s and the humidity is low. On a high humidity day in the 70?s or a low humidity day in the 80?s, you should increase your zones by approximately 5 to 8 beats per minute to correct for the heat factor. In more extreme conditions, such as a high humidity day over 80 degrees, you cannot accurately adjust your heart rate zones for the conditions. On the most brutal summer days, it is wise to adjust your training schedule to avoid high intensity training..
run-easy-race-hard
He's correct only in that heat affects the HR. His mistake is that he thinks a workout done at a certain pace can only be equalled if it's done at the same or faster pace. You don't need to increase the ceilings of your zones The HRM will make sure you are getting the same workout, even though it may be slower, or faster if it's cooler. Just like when you run a race all out in cool then race it all out in hot, you'll be slower in the heat. Equal workout. And the heart rate was probably the same. --Jimmy