Optimizing Recovery for Endurance Athletes

Effective endurance training is all about stress management, and the balance between stress and recovery. Individual training sessions generate physiological stress – elevations in temperature, heart rate, and stress hormones, changes in pH, depletion of fuel stores, and so on. The stress of individual training sessions is what triggers the adaptive response we look for with training, and this occurs during recovery (1). However, too much physiological stress with inadequate recovery will eventually lead to fatigue, overreaching, and maladaptation, as anyone who has dug themselves a hole with a hard training block can testify.

Therefore, when planning a training programme, and then regulating and monitoring that training programme, we are managing the balance between stress and recovery. We want to ensure there is enough stress to stimulate adaptation, but not so much that we become fatigued, overreached, and burned out. We want to make sure our recovery processes are geared up to ensure we can absorb the stress of training.

I like to depict the training process using the schematic diagram below. We start our programme with a baseline level of fitness. We undertake a training session, which stresses the body. We are fatigued when we finish the training session, and this, at least for a short period, reduces our performance capabilities. However, during recovery we respond to that stress with useful adaptations – to our heart, blood, and muscles – that not only restore our fitness, but increase it to a level slightly higher than it was prior to that training session. A successful training programme therefore sees us accumulate small adaptive gains to lots of individual training sessions, leaving us with a measurable improvement in fitness and performance.

However, if we apply too much stress in training – such as through excessive high-intensity, high-stress training with inadequate recovery – we don’t give ourselves time to generate those adaptations. We just keep adding that training stress on top of acute fatigue. That has us trending the other way, and we become maladapted and our performance gets worse. This has been shown in several recent studies (2, 3). It is also familiar to those athletes who have dug themselves into that hole I mentioned.

 Therefore, as endurance athletes, we need to carefully manage the balance between stress and recovery to ensure we get the most from the hard work we put into our training programmes. In this blog, I’ll discuss five key strategies to optimise recovery during intense training cycles.

 Training programming

The most fundamental piece of the delicate stress-recovery balance is our training programming. Like I said above, too much high-intensity training – threshold reps, V̇O₂ intervals, even sweet spot work – builds up fatigue, and generates a high recovery cost (4). That’s either going to compromise how much training you can do, or push you towards fatigue, overreaching, and maladaptation.

A general rule of thumb I like to work with is that training performed between the two thresholds – the sweet spot work we physiologists call the ‘heavy-intensity domain’ – requires at least 24 hours of recovery, whereas work above the second threshold in the ‘severe-intensity domain’ requires at least 48 hours of recovery. That doesn’t mean you don’t do any training the day after a sweet spot session, because work in the moderate-intensity domain below the first threshold – the conversational intensities some call “Zone 2” – elicits a low stress response, and fills in your training programme really nicely.

Therefore, “recovery” in this instance just refers to a focus on that easier, low-intensity work. What’s great is that this easy, low-intensity work generates useful training adaptations, particularly in slow-twitch type I fibres (5), and helps us to accumulate a bigger overall training volume without becoming fatigued and overreached. That’s the principal behind ‘polarised’ and ‘pyramidal’ training intensity distribution, where the bulk of your training week is focused on low-intensity, low-stress work (6).

So, careful training programming is a critical component of the stress-recovery balance, and we need to ensure that our high-intensity, high-stress, high-recovery cost sessions are sufficiently spaced, and that our training week is focused on low-intensity, low-stress work that has a low recovery cost and allows us to accumulate a big overall training volume.

See an example training week below:

 Heart rate variability

A useful tool to get insight into the level of stress an athlete is under is heart rate variability, or HRV. I have done a lot of research on HRV (7–10), and I use HRV with the athletes I coach. HRV refers to the variability in beat-to-beat intervals between heart beats. A less variable heart rate – or lower HRV – indicates more stress in the autonomic nervous system (11, 12).

By measuring HRV each morning upon waking, you can get insight into how effectively an athlete is absorbing their training stress (and non-training stress). Daily measurements can therefore be used to make day-to-day stress management decisions, and adjust daily training load based on the balance between stress and recovery. There are now several studies showing that adjusting pre-planned training programmes day-to-day based on morning HRV improves performance outcomes (13, 14).

A step-by-step guide on how to integrate daily HRV measures into your training is beyond the scope of this blog – or indeed any individual blog. The key point I am trying to make here is that HRV is a useful means of assessing and managing stress and recovery. There are a number of good smartphone apps that can be used to do this – my recommendation is HRV4Training, which was developed by Marco Altini – as HRV can be measured accurately using the camera on your smartphone (10). 

Sleep

Something that will almost always show up in your HRV data, impair your recovery, and reduce your ability to absorb training stress is poor sleep. Poor sleep impacts pretty much everything, and is a risk factor for coronary heart disease, high blood pressure, and type 2 diabetes (15). Poor sleep also impairs your cognitive function – how well you think and concentrate – and your endurance performance (16, 17). We all run a bit worse, or a lot worse, on bad sleep. Therefore, we ought to focus a lot of our recovery attention on making sure we get enough sleep.

On sleep, I get asked two questions, both of which are quite difficult to answer - how much sleep do I need, and what strategies can I use to improve sleep?

The most well-known recommendations are that we need ~8 hours of sleep per night; however, my suspicion is that exactly how much an individual person needs – and more specifically, an individual athlete needs – varies from person-to-person, and from athlete-to-athlete. Given the stress imposed by training, it would make sense to me that an athlete in heavy training needs a little more, but this hasn’t been properly answered in the research. What we do know is that athletes often fail to meet even the standard recommendations for sleep (18). Simple, but relatively sure signs you need more sleep are: (i) feeling sleepy and jaded during the day, (ii) feeling the need to nap, and/or (iii) relying on more-and-more caffeine to get through your day. If that sounds like you, you probably need to get more shut-eye, and I can almost guarantee that better sleep will help your recovery and give you better training outcomes.

How to do it – get more and/or better sleep – is an even harder question. Here are a few tips from a useful recent review article (19):

1. Minimise the time you spend on your phone before bed. Using devices after lights-out has a negative relationship with subsequent sleep (20, 21).
2. Get into a routine and avoid weekend ‘jetlag’, or big differences in sleep and wake times from day-to-day. Consistent sleeping patterns with non-stimulating pre-bed routines improve sleep (22, 23).
3. Take a nap if you need it. If you do struggle to get enough sleep overnight, a short daytime nap can be helpful. There is some evidence that napping improves exercise performance (24).
4. Magnesium supplementations is another method that has been shown to improve sleep quality in observational studies (25). Of course, Triple Magnesium by Pillar Performance is the best on the market with high bioavailability.

Ketones

The last intervention to optimise recovery that I’ll talk about in this blog is ketone supplementation. That’s because there’s mounting evidence that taking a ketone supplement improves recovery and boosts training outcomes (26–29).

Consuming a diet very low in carbohydrates – less than 50 grams per day or so – pushes us into ketosis, or increases the ketones in our blood. That’s why very low carbohydrate diets are called ‘ketogenic’ (30, 31). Supplements have been developed that allow us to increase our circulating ketone concentrations independently of our habitual diet, meaning we can enter ketosis regardless of the amount of carbohydrates in our diet (32). There are lots of different ketone supplements, but ketone esters are showing the greatest promise, and are what researchers are now focusing on (33).

The evidence that taking a ketone ester might help us balance the stress of training started with a study published in 2019. In that study, researchers found that a group of participants consuming a ketone supplement each day during a block of super-demanding training reduced fatigue and overreaching, as evidenced by reduced stress hormone concentrations compared to the control group, who were blasted (26).

Interestingly, ketone esters have also been found to improve sleep. High-intensity training can impair sleep, and, as discussed above, sleep is often a problem for athletes. In fact, the stress of training may even, in some cases, contribute to sleep problems. A recent study found that taking a ketone ester improved sleep duration and quality after a high-intensity training session performed in the evening, which impaired sleep in the control trial performed without ketones (29). It is possible that improved sleep may be part of the reason why the ketones improved training outcomes in the 2019 study.

So, I reckon ketone supplements are worth looking at when seeking to optimise recovery during blocks of hard training.

Summary

That’s a lot to take in on a topic that couldn’t be more important for endurance athletes. Here’s my too long, didn’t read summary:

1. Successful training programmes balance the stress needed to generate training adaptations, and the recovery required to get up and go again.
2. Training sessions need to be planned and sequenced careful to help maintain the stress-recovery balance. For endurance athletes, most training sessions should be at reasonably low intensities, and generate low stress, such that recovery requirements are low and substantial overall training volumes can be accumulated. High stress sessions, with a high recovery cost, need to be spaced appropriately throughout the training week.
3. Daily measurements of heart rate variability upon waking can be used to monitor the level of stress in your physiology, and therefore help you to make informed day-to-day decisions regarding your training.
4. Getting enough sleep is critical for the success of a training programme. We should all take steps to make sure we are getting enough sleep.
5. There is mounting evidence that ketone supplements can be used by athletes to help absorb the stress of training, improve recovery, and improve sleep.

References

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