Volume, intensity and physiological adaptations with prof. David Bishop | EP#215
Professor David Bishop is a world leader in muscle exercise physiology with more than 250 publications to date. He explains how high training volume and high-intensity training each leads to particular endurance adaptations on a cellular and mitochondrial level. Knowing about these adaptation pathways and effects of different training methodologies is essential for triathletes and coaches when planning out their training.
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In this Episode you'll learn about:
- The difference between mitochondrial content and mitochondrial function.
- How high-volume training skews towards increased mitochondrial content, and high-intensity training towards improved mitochondrial function.
- Mitochondrial content may the more important adaptation of the two when it comes down to performance.
- Different intensity levels and their benefits and drawbacks.
- Guidelines on appropriate Training Intensity Distributions.
- "Training Low" - adaptations to training with love glycogen stores.
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About David Bishop
- I initially started out as a physical education teacher and then did a Masters and a PhD.
After this my first job was working at the Western Australia Institute of Sport, directly with elite athletes.
I worked with kayak athletes who went to the Sydney Olympics in 2000, and also hockey, water polo and a few other team sports.
- From there I moved to a University position - which was nearly 20 years ago.
- Since then I've been doing research broadly trying to understand and optimise adaptations to training.
This has mostly been around team sports (intermittent performance), but also endurance performance.
Mitochondria and their importance
- As a researcher, you need to try and focus in a little as there's so much going on.
Thus most of my research has been on skeletal muscle adaptations - looking at how the muscle adapts to training and different types of training prescriptions.
- Previously a lot of my work was on pH regulation and preventing lactate build up in the muscles.
In the last 10 years the focus has switched to mitochondria - the energy power houses of the muscle.
- Mitochondria is what generates most of the ATP or energy that we're using.
Even while sitting talking, there's a baseline energy expenditure and mitochondria will be working hard to supply this.
- As you do endurance exercise and your energy demands increase, the mitochondria work hard to provide the extra energy you need to perform this task.
- There's a lot of different mitochondrial adaptations that can occur:
We can look at the content, which refers to the amount of mitochondria you have in the muscles, which is important for health and endurance performance.
Having more mitochondria seems to be linked to a greater ability to utilise fat when you're exercises.
- We can also improve the function of the mitochondria, which refers to the amount of energy they can produce.
- You can get improvement in mitochondrial function without improvements in mitochondrial content.
- Most people find when they start exercising they have oxygen debt.
Your muscles aren't like a car where you get all the fuel immediately - it takes a few minutes for the aerobic metabolism to ramp up.
This is related to the mitochondria and with training we hope to see the mitochondria reacting more rapidly and increase their production of energy when you start to exercise.
Research on mitochondria adaptations
- There's some debate amongst different scientists working in this area.
- With our research we've seen that high intensity exercise that is close to VO2max or above seems to increase mitochondrial function.
- Conversely, increasing mitochondrial content seems to be more related to the volume of training.
- We recently had a cross talk debate where different researchers with different views on a topic debate the different sides.
We were arguing that the mitochondrial content is more important.
- Our research suggests that the greatest increases in mitochondrial content are typically seen at the greatest volumes of training.
- This aligns with what elites athletes do - there are not too many elites that don't do high volumes of training at certain points during the week.
Why is content of mitochondria more important?
- We don't know entirely why content is more important.
- They are producing energy so the assumption is that having more and better mitochondria is likely to improve endurance performance.
However, it's difficult to find a lot of research backing this up, which may be because most of the best athletes don't give muscle biopsies so we don't know exactly what their mitochondrial content or function is like.
- Having more mitochondria closer to where the energy needs to go in terms of muscle contraction, having more can be a benefit to get the energy where it needs to go.
Relationship between training volume and training intensity with mitochondrial content
- Looking at all the research currently available we haven't seen anything like a mitochondrial plateau.
- Therefore my thoughts are that greater volumes of training will lead to greater increases in mitochondrial content.
- There's some really great studies by Hixon back in the 1980's and they looked at changes in VO2max over a 10-12 week training period with quite high volumes of training.
They also didn't see any plateau in VO2max after that time.
Obviously VO2max will plateau at some stage.
- Similarly with mitochondria there will eventually be a point at which it plateaus but with most of the research I've seen there does generally seem to be a linear relationship between training volume and increases in mitochondrial.
- Studies with high intensity training have definitely seen improvements in mitochondrial content.
E.g. studies have shown if you do all out sprints at 150-200% VO2max you can get mitochondrial content increases as shown in the muscle.
You would also see a similar increase if you do some sort of high intensity interval training.
- However we don't see any relationship between the intensity and the changes in mitochondrial content - it's not a linear relationship.
Going from 80% - 150% VO2max we don't see greater increases in mitochondrial content.
So if you do high intensity training there's no evidence that it'll lead to greater increases in mitochondrial content.
- With high volumes of training we can see upwards of 50% increase in mitochondrial content, but with high intensity training it's usually closer to 15%.
- My view is there's not one magic intensity - our research supports a polarised training concept as Stephen Seiler has researched.
There's a definite role for high volume, low-moderate intensity training when it comes to mitochondria.
- There's also a place for high intensity interval training - intervals of 1-6 minutes.
I would agree with Paul Laursen that close to VO2max is where you want to be.
- We've also seen different adaptations with sprint interval training - close to all out for 20-30 seconds with recovery up to 4 minutes.
- This is likely consistent with how most athletes are training.
Similar to the diet pyramid which suggests different types of nutrition are important, it's the same with training.
Different types of training all have their role, the challenge is getting the balance right with how to put the components together.
Polarised training on a physiological level
- Most research on this has been at a performance level.
There was a paper a couple of years ago backing up Stephen's ideas where one group did mixed training distributed evenly across LT1, 2 & 3.
Another group then did more polarised training, which had the greater improvement in performance.
- From a cellular level, I've got a PhD student who is about to start looking at this but I'm not aware of any previous research looking at the cellular adaptations of polarised training.
- The closest you can get is if we look across the literature and at least for the mitochondria our research suggests there are different roles for those different types of training.
- Our work aligns with the idea that you need a high volume of training - 80% of high volume training to get the large increase in mitochondrial volume.
- But also to get that high intensity training is (100% of VO2max and above) as this is important in increasing mitochondrial function.
Moderate intensity training
- The challenges with tempo training is that it's different for different people, particularly if it's being based on the lactate threshold.
- We published a paper towards the end of last year showing that depending on how the lactate threshold is calculated you can get a very different power output.
- You need to be careful that you're comparing apples with apples in terms of threshold training when looking at different studies.
- Stephen Seiler's work suggests that athletes don't do too much tempo/threshold training.
We haven't done a lot of research on the cellular adaptations but the research does support this too.
- One caveat would be that we're only talking about the physiological adaptations here, and tempo work can be quite hard so a sports psychologist may advocate for it's use.
Talking to coaches and athletes there is a role for that tough psychological training to improve psychological aspects.
- It's good to look at elite athletes and you can find examples of people doing contrasting training.
E.g. you'll find successful athletes who follow the polarised model, and some who do high intensity interval training for more than the 20% and there will also be some who do a lot of tempo training.
- One of the difficulties is making sure we're talking about the same thing.
What people call the different thresholds can be different across researchers or training groups.
- We've seen that by exercising below the lactate threshold, which would include tempo training, you can still get quite high volume training here.
- For elite Ironman runners, even the first lactate threshold work can be quite hard!
- There are different threshold models for example the German rowing models or the Australian cycling or rowing models.
They typically have three levels:
Level 1 which is below the first active threshold and is recovery.
level 2 and 3 are both below the lactate threshold too.
- There's more work to try and have a more universal model so people are more on the same page.
- I do think some of this 'moderate' training can still fit into the polarised model.
- You need to try and avoid doing too much training really close to the lactate threshold, but 5-10% below I would still include as high volume work.
- We used fairly well trained runners in our research and there was still 150 watts difference from the highest calculated lactate value and the lowest.
We made recommendations in our paper with lead author Nick Jamnick about calculating lactate threshold.
We used around 30 different methods - showing it can vary quite a lot depending on how it's been calculated.
- There's a little bit of art to the science!
Practical takeaways for training adaptations
- There's lots of different ways to get to the same point - there is no magical training intensity.
- It's important to get a little bit across the different training intensities.
- I still believe the volume is critical.
- Stephen's polarised model is pretty close in terms of approximately getting polarised 80/20, but I agree that L1 is possibly too low in some of the research.
I think some of the training such as tempo can be included in the 80%.
- I wouldn't be doing too many training sessions at the lactate threshold.
Trying to spread the training across the volume and intensities is important.
- I've also noticed with the good athletes I've worked with that they're good at monitoring, recording and reviewing the type of training.
The big benefit of whatever approach an athlete takes is then reviewing it at the end of each year and seeing how it's distributed and how it helped.
You can then go and modify the training in the future based on this review.
- Personally I tend to split the 80/20 in terms of training volume, as I think duration can be misleading.
- E.g. in strength training you do the number of reps multiplied by the weight to get a volume of weight lifted.
We tend to apply the same approach to endurance training, we take the intensity and multiply that by the exercise duration in the actual training session.
In this way a 20 minute high intensity interval session isn't the same as a 20 minute L1 low intensity training session.
- In the lab we typically multiply the percent of VO2max by the duration.
E.g. if someone does intervals they might get 30 minutes at 100% VO2max then you could get 300 units/points for this particular session.
Whereas if you did 60% of VO2max, 50 minutes would also give you 300 points/units.
- Scoring from percent of VO2max might be more accurate as the bottom and top of the zones can be very different intensities.
We calculate a combination of duration and intensity to give a points score.
Thoughts on Training Stress Score (TSS) model
- It's really hard to get an accurate measure of training stress.
Different types of training activate different pathways in the muscles so it's difficult to compare them.
- I think it is useful when people are comparing their training.
People can get an idea about their accumulation of training stress and whether a certain level gives them good adaptations or over-reaching/fatigued.
- It's not going to be possible to get a perfect measure of training stress, but as long as people are using the same method they can accumulate historical knowledge of what works for them.
They can then use this as a base to manipulate and modify their training going forward.
- From our work in the lab we know that different types of training stress will simulate different adaptations.
We looked at some of the cellular pathways that are activated when you do an exercise session either below or above the lactate threshold.
We found there's not that much in common between the two, showing there are specific adaptations for different types of work.
- This shows it shouldn't just be about getting as high a training stress as possible, but more about getting the right amount of stress in the different training zones.
Cellular pathways for different intensity levels
- The fuel use changes - when you're in level 1 you'll be predominantly using fatty acids.
Around the first lactate threshold you'll get a peak in fat oxidation and as you start to increase lactate in the muscle it'll feedback and decrease the fatty acid contribution, increasing the glycolic contribution and getting further increases in lactate.
- We know that fatty acids and lactate and some of the other changes in metabolism stimulate different stimulus pathways.
By exercising in the different training zones you'll get different signals in the metabolic muscle and that will act downstream to simulate different training adaptations.
- Low intensity training where you're predominantly using fatty acids seems to drive increases in mitochondrial content and drives increases in fat metabolism.
Those two seem to be related - people with a greater mitochondrial content seem to use fat as an energy source.
- As you increase the intensity you start to get different signalling pathways activated and different stimulus adaptation in the muscle as well.
Twice a day exercise
- We did a study looking at the response to one day of training with two exercise sessions.
We saw that when one training session was closely followed by another session there was a much greater activation of some of these signalling pathways.
- We're still trying to work out exactly why, but part of it is that when you're exercising you're decreasing the fuel sources within the muscle (e.g. muscle glycogen, fatty acids).
We know that this nutrient deprivation is a powerful signal to activate some of these signalling pathways.
- When you're exercising twice a day you exercise your muscles when they're nutrient deprived which augments the training stimulus.
- One of the challenges is that it's really hard!
- If people want to study overtraining they often do twice a day training so it is clearly a powerful stimulus that needs to be used carefully to avoid overtraining.
- Beyond the single response, there are studies that show greater improvements in fat metabolism when twice a day training is applied a few times a week for a few weeks.
- There's some evidence that it does work, but you have to be especially careful with what you do the day after this type of training.
We're just doing another study at the moment and we're seeing that participants are less able to do a high intensity interval training session the day after a double day.
- The first study we did looked specifically at signally and we saw a powerful increase in this with twice a day training.
- Our signalling doesn't always match up with what happens with performance.
When we then looked at performance after three weeks of this type of training we didn't see any differences. John Hawley's work hasn't seen any differences in performance either.
- We do see greater differences in fat metabolism with those sort of adaptations and John has seen great increases in a marker of mitochondrial content.
- The important caveat is that all training studies have been short and limited to 3-4 weeks so it may be that a longer time is required to see any performance benefits with this type of training.
- In these studies we always try and control the volume of training.
When some participants are doing twice a day training, this group isn't able to train at as high intensity as they'd normally be able to do.
This may be part of the compromise - you're getting greater signalling but they may end up doing less intervals or lower intensity during their second session.
Nutrition considerations with twice a day workouts
- John Hawley and Louise Burke had a good paper last year talking about how to periodise nutrition.
- Because of the previous training session you can end up having low muscle glycogen stores for the second HI interval training which may limit some of the performance there.
- We've been seeing that if you delay the carbohydrate intake after the high intensity training sessions, performance the next day is impaired.
- Consistent with the current guidelines, if you're doing twice a day training it's important to get carbohydrate in quickly post training so you can rapidly replenish muscle glycogen stores.
Impact of nutrition on signalling and performance adaptations
- The training low idea (training with low muscle glycogen stores) is really powerful to increase the signalling.
- What we don't seem to see is that translated into performance.
This may be because if the participants are training with low muscle glycogen it's probably impacting the quality of their training session.
- The recommendations keep evolving but the current idea is to use the low muscle glycogen type training for when there's low intensity training.
It may feel harder but the athlete should still be able to complete the session.
- If there's going to be a hard training session the next day, replacing muscle glycogen stores quite quickly by taking carbohydrate within the first 1-2 hours post-exercise, will be important to ensure the quality of the next day.
- There is a limit to how often you should do the 'train low' type sessions.
There's not any specific research that has looked at what the optimal number of these sessions would be.
My guiding principle would be to ensure you're getting good training quality so 2-4 will probably be the most you can do without interfering with the high intensity quality.
- Most of my lab work is trying to optimise endurance adaptations to training.
- We look at different training prescriptions, nutritional strategies, cold water immersion post-exercise and also training in the heat to see if we can augment the training adaptations.
- We're increasingly seeing that the training is the most important aspect.
We haven't seen things like using cold-water or heat or other augmentations are taking over the importance of training.
- We want to look at some of the research gaps - e.g. how do you put these different types of training together to get the best molecular and performance adaptations.
A lot of research might be comparing low intensity training to high intensity training, but that's not how athletes train as there's a mixture of training zones that go into a week.
Rapid fire questions
- What is your favourite book, blog or resource related to endurance sports or physiology?
- Factfulness by Hans Rosling - it's about interpreting data.
- What is a personal habit that has helped you achieve success?
- You need to block out your time - I try and have a few hours each day where I don't look at any emails or messages. Avoiding distractions is key to getting quality work.
- Who is somebody in sports or academia that you look up to?
- Good scientists who can communicate scientific findings simply and clearly such as Professor Keith Baar and Trent Sellingworth.
Links, resources and contact
Links and resources mentioned
- CrossTalk opposing view: Exercise training volume is more important than training intensity to promote increases in mitochondrial content
- Polarised training with Stephen Seiler, PhD | EP#177
- Endurance sports nutrition: state of the art in 2019 with prof. John Hawley | EP#181
- Interval Training – Science and Application part 1 with Paul Laursen | EP#128
- Interval Training – Science and Application part 2 with Paul Laursen | EP#129
- Interval Training – Science and Application part 3 with Paul Laursen | EP#163
Connect with David Bishop
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Hi! I'm your host Mikael,
I am a full-time triathlon coach and an ambitious age-group triathlete. My goal is podium at the Finnish national championships within the next few years.
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