I am exploring the idea of heat training and I was wondering how a specific heat training session will be reported in intervals.icu, mainly from a training load perspective. As this is new to me, I am afraid of over-extending myself and having accurate training load readings in the fitness page would help on top of the pure RPE values.
Let’s assume a 45 minutes heat training workout done at 38.5°C, with an average power of 50% of FTP. Will this be reported as a light recovery ride based solely on Power, or could it reflect the more taxing effort of spending that much time with such an elevated body temperature?
I ain’t an expert but I don’t think there is a good relationship between HR and Body Temperature (otherwise, no one would buy such sensor), so changing the logic from Power back to HR probably doesn’t solve it either.
When conducting your heat training at 50% of Functional Threshold Power (FTP), your training load will correspond precisely to 50% of FTP for a duration of 45 minutes. This is due to the fact that the training load is calculated based on the mechanical load expended on the pedals, rather than the overall metabolic energy expenditure required by your body.
If your FTP is set at 260W and you are exerting 130W while your core body temperature is at 37°C, and your gross efficiency is 20% (assuming you performed some heat training before, if not you will be somewhere below 19%), the total metabolic load you experience is 650W. This total is divided into a mechanical load of 130W at the pedals and a thermal load of 520W that your body needs to manage to alleviate heat stress.
When your core body temperature reaches 38.5°C and you maintain the same wattage on the pedals, your thermal load will go up. This results in your body working harder, which can lead to the sensation of increased workload. However, it is essential to understand that this change is attributed to the body’s thermal management efforts to convert energy into heat, rather than an increase in the stress associated with training.
When heat training is conducted effectively, both the core temperature and skin temperature recorded by your Core device will continue to decrease as your thermal tolerance will increase. Consequently, it will be necessary to slightly increase the power applied to the pedals in order to stimulate further adaptation in subsequent sessions.