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Hytro Coaches Newsletter – Issue 1

Every month, Hytro founder and BFR innovator, Dr Warren Bradley shares with the Coaches Community key news and insights from within the world of Blood Flow Restriction Training and the exciting development of the wider Hytro business.

Welcome to the brand new Hytro Coaches Newsletter, I hope to share some of my thoughts and insights on what’s happening in the world of sport in relation to Blood Flow Restriction. 

To begin, I am sure you’re all aware of the growing discussion around the prevalence of ACL injuries in female athletes. The Women’s Football World Cup is bringing this to the forefront as Lionesses captain Leah Williamson is missing from the line-up and Kiera Walsh was temporarily out with what was initially a suspected ACL injury. Sadly, there appears to be a growing trend with this particular injury in recent years across most female sports which raises the question – why is this happening more commonly in female athletes? 

While there are ideas around why females are more susceptible to this injury, there is a distinct lack of research in this area.  I believe that currently, only a small percentage of research on athletes has been conducted with females, leading to a huge lack of scientific knowledge specific to this gender. This leads to practitioners only being able to draw insight from predominantly male-based research, which with such physiological differences between the genders, means this just doesn’t work. This is disappointing especially as we are seeing an explosion in female sports, with professionalism increasing alongside the interest of the public.  This does however present a great opportunity for a drive to focus on this gap of research so that with a better understanding we can work to remedy and manage this injury risk. 




Anecdotally, through my own reading and network, I am aware of two key schools of thought on what is potentially contributing to the increase in these injuries, and it would be amazing to substantiate these ideas with evidence-based research.  

The menstrual cycle is thought to affect collagen production in the body, and there is an argument to say that female athletes could be more vulnerable to connective tissue injuries, like an ACL rupture, at certain points in their menstrual cycle when collagen synthesis is reduced, and collagen breakdown increased. That said, emerging evidence has suggested that any increase in estrogen during the menstrual cycle is not great enough to result in a meaningful change in collagen synthesis. A more likely candidate for the increase in injury incidence in female athletes is suggested to be related to joint laxity. Females inherently have greater joint laxity than their male counterparts, and furthermore, fluctuations in hormone levels throughout the cycle can cause increasing changes in anterior knee laxity (AKL), stiffness, and general joint laxity (GJL). Whether these changes are of any tangible significance to exercise performance and ultimately an increase in risk of injury must be further explored, and it’s certainly an important area in need of research.  

With more knowledge of how the menstrual cycle affects the physiological body of an athlete, we can adapt training programmes to ensure for example that female athletes are not undertaking a high-intensity week of training during the most high-risk stage of their cycle. 



The second school of thought, particularly from my own perception, is that female athletes tend to start their training and participation in sports much later than their male counterparts who regularly join academies from a very young age. This means they haven’t necessarily had the same exposure to the rigorous training and demands of professional sports and are having to level up their performance in a shorter space of time. In addition to this, due to the lack of specific female-focused research, training programmes within female sports are often designed based on male-specific research, though it would be remiss of me not to highlight the many incredible coaches who provide very targeted and specific training programs for their female athlete cohorts. In general, though, the foundations of female-specific training may not always be in place to support a high level of intense training meaning it could be having a detrimental impact and the potential of increasing the risk of injury.  


At Hytro, we have a number of female athletes currently utilising the Hytro BFR wearables to recover from ACL injury with reports that BFR training has supported them as they prepare, train and recover during the rehabilitation.  

Charlie Willett, Ealing Trailfinders Rugby Union and Ireland Rugby League Player, used the Hytro BFR Performance Shorts to address the usual quad muscle loss seen with this injury, leading to her legs being of equal size 13 weeks post-surgery. Also, Charlotte Potts, Newcastle United player, has used the shorts to train smarter during certain phases of her menstrual cycle to lower the risk of injury when she believes her joints are less stable and muscles less flexible, to still ensure an effective training session. 

With this feedback, and the knowledge we have about what BFR can achieve, I see a future for BFR being used within women’s sports around the menstrual cycle to mediate the risks posed at various points. This means females can still train effectively throughout the month but without the potential increase in vulnerability to this injury.  



Evidence-based research has always been a priority for me, and the Hytro team, so I want to take this opportunity to address the gender imbalance in the research done within professional sports to support all athletes and to progress the field of performance, recovery, and health in sport. Going forward, a number of our studies will prioritise females to enable us to plug that gap. 

Check out the recent announcement on the our research partnership with the Bristol City FC Womens’s team, just one example many many more projects we have coming down the line.


If you are interested in collaborating to advance the research on this topic or know someone who would, then I would love to hear from you.  Either get in contact via the button below or email me direct at warren@hytro.com. 

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