My Heat Training Intervention
My heat training experience as someone who suffers with heat.
Disclaimer
Heat training can be extremely dangerous. This post is purely to share my experiences around heat training and to provide some potential inspiration. This is in no way a how to guide on heat training. More information about safety around heat training can be found here.
Heat Training Intervention
Using heat as a training stimulus has really taken off over the past few years. Both in research and practice, people are finding more advantages for using it as a training intervention. For me personally heat and how to combat its effects on performance has always been a keen interest for me. This is simply because I suffer with the heat more so than others. I would say my heat tolerance is generally well below average. After bad experiences at Powerman Zofingen in 2022 and 2023 with the heat, I decided to take a more serious approach to my heat training for this year’s race. As I do tend to have poor heat tolerance, I thought it would be good to share my approach and data for others. Another reason for sharing the data is that I am much larger serious endurance athlete compared to others. Data on related to anything to do with endurance performance is limited to nonexistence for this group. Sharing what data I have is a very small steep to help grow resources for larger athletes and their coaches.
2023 Heat Prep
I first used a dedicated heat block last year preparing for Powerman Zofingen. This was a relatively short block more in line with what you see being used throughout the scientific literature. The block was also something planned a little more last minute. For this block the aim was to use a heat/paint suit for 6-8 sessions over a 2 week period starting 3 weeks out from the race. I then would use my race week sessions to help keep the heat adaption topped up. In the end I only did 5 sessions (4 in paint suits, 1 outside) as the sessions were taking too much out of me, especially the paint suit sessions. I pushed too hard with the heat in these sessions and learnt a valuable lesson. Heat training loads for the paint suit sessions was between 4.3 and 5.7. Then when I had got to Switzerland, they experienced a cold snap for the first half of race week which made maintaining adaptions more challenging. Race day comes around and it is warm, sunny and humid. I end up being taken to Hospital from the race course in the back of an ambulance suffering from dehydration and heat related issues. Looking back at this, I think my approach to the heat training may have contributed to what ended up happening. Physiologically speaking, I had made some of the adaptions that you would expect from undertaking a heat training protocol but wasn’t fully adapted. I also had not made critical non-physiological adaptions which are also critically required to perform in the heat, like adapting to the higher fluid requirements thanks to an increased sweat rate.
This Year’s Approach
I formulated a new approach to heat training this year, taking what I had learnt from last years’ experience and combine it with all the extra knowledge that has been produced by others in the past 12 months. The approach needed to fit in better around training and needed to address 3 key elements. It needs to work on the physiological adaption response to heat, the psychological effects of heat and then the effect that heat has on fuelling and the GI system. I concluded that I needed to treat heat as another discipline, just like I treat running or cycling. This would help dictate how I would structure and implement the intervention. With this information I created this loose framework for how I would build and implement the protocol. The key points of the framework were:
⁃ Use every session as a learning opportunity. Where appropriate, use these learnings in the remaining sessions.
⁃ Due to life constraints and the 3 key elements, active heat training would be the main method used.
⁃ Do baseline testing using both core sensor data and RPE to establish a starting point.
⁃ Progressively build the heat load over the block. Use a longer block of heat training to facilitate this.
⁃ Early in the block focus on learning to cope better with high core temps (around 38.5) and then look to increase skin temps to increase heat load further.
⁃ Vary heat training load day to day like training to help prevent too much stress build up.
⁃ Use a variety of different training Intensities while doing heat session to help the learning process and monitor adoptions.
⁃ Use varying combinations on internally generated (workload) and externally generated (clothing, environment) to create the heat stress.
⁃ Reduce amount of externally generated heat load for higher intensity sessions to keep heat stress within appropriate levels and have performance impaired less.
⁃ Add passive sessions where possible on non-training days to provide an additional “maintenance” stimulus, especially towards end of block.
⁃ Do not restrict hydrating during sessions and aim to drink a little more than what was comfortable to train the GI system. Look to increase how much liquid I can tolerate in these sessions. Off past experience, sweat rates will be well above what you can consume so over drinking less of a concern.
⁃ Most training session would be completed indoors on the bike and be around 60min long. This is to allow for adaption while still fitting in with my regular training routine.
As mentioned above, before starting my block I did a few different sessions with the core sensor on and made notes about how I was perceiving body temperature as well as how performance changed. I was starting to really notice the effects at low level of heat strain, around a heat strain index of 2 which is right in the middle of heat zone 2. This is a zone lower than what most people would expect to see. Confirmation that at least for now, I had what Core refer to as a ‘low thermostat’. I also reached out to core at various stages for any additional advice or specific knowledge they might have had on my situation.
This Years’ Experience
This years’ experience could not have been more different to last year. While the sessions themselves were still not pleasant, the recovery from the sessions was greatly improved. This is where starting off with lower-than-normal heat training loads and building them up progressively over the weeks made a big difference. Importantly I felt this more gradual approach allowed for physiologically and psychologically changes to happen in sync with each other.
Towards the end of the heat training block, the adaptions started to become very clear. 12 days out I was able to complete my hardest heat training session, hitting new highs and managed it a lot better than previous years. After this session it suddenly become much harder to achieve higher Heat Strain Scores, requiring more and more clothing to be worn. This became most apparent in the last 2 heat training sessions I completed before heading across to Switzerland. This first was an indoor bike session where I found myself putting on more and more clothes and running the heater just to reach a max heat strain of 2.48. The next day I did a run outside. Pre heat training I would be starting runs in 5-10 degree weather in shorts and a long sleeve top. Within a single kilometre, my sleeves would normally be rolled up because of the heat. For this run I layered up on top, with a warmer base layer, long sleeve top, rain jacket and hat. Despite being overdressed and it being 15 degrees and sunny, I was completely comfortable the whole run.
Doing some more intense sessions with slightly less externally generated heat load worked great as well. The heat training load for these sessions did still end up higher than intended in some cases, but importantly output wasn’t significantly affected nor was recovery post session. It also gave me some vital data and experience on how my body reacted to going hard at higher core temps and heat strains.
The Heat Training Data
I have made a copy of the spreadsheet I used to help track heat training public which can be found here. I tracked heat training via a number of different ways. This was to allow me to see if there were any particular correlations I could find which could further improve the process. Compared to 2023, I completed close to 3 times as many heat training sessions (9 V 26). The WKO HSS is a metric I modified from an old Core WKO chart. I modified it so lower intensity heat training sessions would generate a score. The number itself doesn’t really mean anything in particular but does allow me to compare session to session heat stress. Blow is some graphs displaying different information from the data.
Learnings And Ideas For Future Blocks
I would say the block workout about as good as it could have. The heat adaption process took less of an overall toll on my body. Unfortunately for several reasons (see my race report) I didn’t get to really evaluate if there was any improvement in race day performance. Even with this in mind, I’ve seen enough evidence to continue to use this as a training intervention moving forward. I will look to change how its implemented and look to test a multiphase. I would do a specific heat block earlier on in the block where I’m a lot less worried about training implementations. This would be followed by a maintenance phase before once again introducing a second focused block of heat where unlike the first heat block we are also concerned more about performance.
These two build have highlighted to me the importance of having the ability to measure core temperature and quantify objectively heat stress. The data became invaluable through this build. Its so easy to overcook yourself doing heat training and having some kind of objective measure helps you make better choices.
Undertaking this particular heat training protocol did seem to bring my baseline tolerance for heat from a well below average to an average level. From here there’s two future tests that I will be doing. The first one will be after a wash out period, has my baseline tolerance for heat been altered to a more average level or does it return to pre heat training baselines.
The second test involve extending out the heat training protocol to see whether there’s a leveling off in heat tolerance or if it can keep improving further. The longer heat training protocol would also look to evaluate further potential performance gains which is starting to be seen in the research.
I had developed a detailed pre and in race cooling strategy. Unfortunately, I couldn’t implement and test it out fully so that one stays in the pile of things still to test out. I’m not going to go into detail about what that strategy involved here as it is completely untested.
One unusual trend I did start to notice as the heat training loads increased was that there would be a point in these sessions, approx. 45min in, where the heat strain score would start to decrease. This was simply because I had sweated so much that skin temps would start to decrease, even in a paint suit as shown from the Core sensor data below. In future blocks, as I became more heat adapted, I would look to add additional layers external of the “water proof” layer to provide further insulation. Training in an environment with a higher ambient temperature would also help reduce this.