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Richard Ferguson, PhD, has his main research interests in the areas of blood flow restricted (BFR) exercise on skeletal muscle and peripheral vascular adaptations. In this interview, we discuss his research findings on these topics and how they may relate to endurance athletes.
In this Episode you'll learn about:
- A primer on adaptations to endurance training and limiters to endurance performance
- Blood Flow Restricted (BFR) exercise: what is it, how may it be beneficial, and what are the mechanisms behind it
- BFR combined with Sprint Interval Training: Theory and application in endurance sports.
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- My name is Richard Ferguson and I am currently a senior lecturer at Loughborough University within the field of exercise physiology.
During my career I have been conducted research within a broad range of topics within exercise physiology (mainly on endurance performance) but recently I have focused quite a bit on how to further improve adaptation processes to training.
One such method is ”blood flow restricted training”, which seems to be able to enhance the body’s adaptive response to training.
- To be able to understand the principles behind blood flow restricted training, one needs to comprehend some basic mechanistic of aerobic performance and aerobic energy production.
To start with, one can divide aerobic performance into a central component and one peripheral component, where the central component basically is determined by cardiac output and the peripheral component is highly dependent on mitochondrial density and function as well as capillary supply to the muscles.
The capillary supply to the muscles is highly correlated to critical power, which in turn is extremely well correlated to endurance performance.
- The capillarisation process (enhanced capillary supply) is stimulated by something called sheer stress, which one can view as the pressure on the small blood vessels.
There are sensors of the cells of the inner layer of the blood vessels that recognize this sheer stress (pressure) on the small blood vessels/capillaries, which in turn kick starts a cascade of signaling molecules promoting the capillarisation process.
- It appears that for highly trained individual, it is quite difficult to stimulate the capillarisation process much further by ”only” increasing the volume of training.
However, it also appears that high intensity training (despite that it exposes the blood vessels for a relatively high degree of sheer stress) does not promote a strong capillarisation respons, instead, long duration of moderate sheer stress (i.e. for instance long aerobic endurance rides) seems to stimulate this process.
The same also applies for mitochondria density (number of mitochondria), which also seems to be most dependent on training volume, whereas mitochondria function mostly seems to be driven by intense training and not so much the overall training volume.
Blood flow restricted training
- To start with, I would like to point out that blood flow restricted training has been around for quite a long time, mainly, however, within the strength training domain of exercise research.
- The principle of the method is that one reduces the blood flow to one limb (so it is only possible to conduct this type of training on limbs), most often using a strap or cuff.
What we typically see as we implement this training method is that the molecular signals that are associated with adaptation are elevated (both signals correlated to capillarisation as well as metabolic and mitochondrial adaptation), even when the exercise is conducted at a very low intensity.
- Unfortunately, the protocol is still very much laboratory based, and it is still quite difficult to find a good way to implement these protocols in the field.
However, in the research study that we have conducted, the subjects have typically performed 2mins intervals with 2mins recovery (repeated 4-6 times), where they have had the cuff inflated (blood flow restricted) during the intervals and had it released during the recovery.
We have not yet been able to show any major improvements on actual performance indicators such as VO2max and/or critical power following these protocols, even though we have seen quite a large spikes in adaption signals that are associated with physical adaptations.
- To start with I would like to state that we did see some pretty major improvements here, around 5 % increases in VO2max in two separate study groups (on reasonably well trained athletes).
The protocol used here was 4 bouts of 30s all out sprints on the bike with 4.5mins recovery between efforts, the subjects performed the sprints without any restricted blood flow (it wasn’t practically viable to place a cuff on as they executed the sprints), however, immediately following the sprint interval, the subjects jumped off the bike and cuffs was placed around the legs (inflated to 120ml Hg, so not very high), which remained on during the remaining of the recovery.
We did see some major spikes in adaptive signals, which we believe are what are responsible for the increase in VO2max.
However, we did not see any improvement in time trial performance (15mins), which awakes plenty of interesting questions.
Moreover, we followed up this study by looking at actual capillarisation on the blood flow restricted group, and here we couldn’t either see any improvements.
- In summary, one can say that there are numerous factors that indicate that this could be an effective training method, but there is still much that we do not understand and we also are yet to discover if it can actually be translated into performance in some way.
We also need to figure out a way to make this practically applicable, and until then I would actually advice against trying anything related to this from a safety point of view.
Rapid fire questions
- What is your favorite book, blog or resource related to endurance sports?
I am myself a cyclist, and hence my favorite books are all cycling related, I really enjoyed the ”A Rough Ride” by Paul Kimmage, ”We Were Young and Carefree”, which is the autobiography of Laurent Fignon but my favorite book is probably ”The Secret Race” by Tyler Hamilton.
- What is a personal habit that have helped you achieve success? I have a good solid work-life balance and I always allow time to exercise.
- How is someone you look up to or have inspired you? I would say an adventurer by the name of Ranulph Fiennes, who has written a lot of books about his voyages.