Running In the Heat - Detailed Data Analysis

How can heat affect your training session, a deep dive on some data!

For those of us currently in the Southern Hemisphere and sweating through the Australian summer. How can heat influence our running training and ability to perform in a session?

The images below show the data from two hill repeat sessions, separated by only a week. These sessions were run under very different weather conditions. Workout 1 was completed under shade, and in temperatures around 25C. Workout 2 was completed under full sun, and in temperatures around 35C, yep it was hot.

They key part, with some smart science and data analytics tool, we can see a big difference and the actual impact of the heat on the 2 sessions. Using a metric called dFRC (Dynamic Functional Reserve Capacity), which in simple terms is how much our battery is drained and restored during a training session or race and represents the energy we used in the session.

On workout 1, you can see the purple line representing dFRC, gets down to near zero, and was the aim in both these harder hill repeat sessions. The battery was well drained. Workout goal achieved!

On workout 2, you can see the purple line representing dFRC, goes down, and then starts rising again for the last 2 repetitions. In this case the final reps of the session were not completed as planned. Looking at the data, there was still enough energy in the battery to complete the session (dFRC above zero). The last part of these final reps was spent walking, due to the impact of the heat and overheating, not due to a drained battery.

Applying this practically, ideally for these harder sessions should be completed in cooler (morning/evening) temperatures. If you don’t have that option, very simply you will have to slow down. Accept that trying to complete a session in much hotter temperatures, you will not be able to execute it to the same level as a cooler day, and that’s OK!

Interested in applying this to your own training, give me a shout!