It’s getting hot! Thanks for the News Flash I hear you say...
How much effect do you think heat and humidity has on your performance? Decreases it by 5%? Maybe 10%? What about if I told you it is closer to 20%? Jeepers!!! And … The heavier you are the harder it gets.
Research is pretty clear, the hotter the air temperature is; the tougher it is to keep training at high intensities. Heart rate elevates quicker, oxygen requirements go up and your times get slower!
If you normally run 5 minutes per km in 10°C (who would run in such cold?? Eek!) it will take 5:56min to run that same km in 29°C. Your perceived effort will be the same as the temperature rises but you just won’t be running as quick. The research looked at a "hot day" of 29 degree - imagine what happens when the temperature sores to over 35 degrees?? You will be seriously affected and perhaps should think twice about completing your training.
Lesson is: Be kind to yourself in the heat, don't push too hard and accept those slower times!!