Blood Flow Restriction Training: Is it Safe?

In last week’s blog post, I provided a brief overview of BFR, pointing out a few of its potential uses as a rehab/training tool. In this, post I will discuss some of the safety concerns with BFR and the research that has been done to assess these risks.

The risk that raises the most concern is typically the possibility of cardiovascular incidents such as blood clots. Blood clots are a concern due to the pooling of blood that occurs during BFR (similar to why clotting is a concern during long distance airplane travel). Given this risk, Nakajima et al. (2006) surveyed Japanese facilities implementing BFR to determine whether BFR training was associated with an increased rate of dangerous blood clots. They found that over the course of about 300, 000 training sessions, 0.06% resulted in a clotting event. This is a lower rate of clot formation than the general Japanese population (0.2-0.26%). The most commonly reported side-effects of the training were bruises from the cuff and a feeling of numbness in the exercising limb. These side-effects can both be mitigated as we will see later.

In 2016, Yasuda et al. (2017) re-did the survey to determine whether there had been any changes in the data that Nakajima’s group collected. In this, more recent study, 232 facilities in Japan (representing ~12,827 individuals) were surveyed. The results were consistent with those of the 2006 study--the most common side effects were numbness and bruising from the cuff. However, in this study there were zero reports of more serious side effects such as blood clots. It is important to note that in both the 2006 and the 2016 studies, the individuals surveyed ranged widely in age (under 20 to over 80) and included both healthy athletes and individuals with a variety of pre-existing illnesses.

Adding further support for the safety of BFR with regards to blood clotting, Brandner et al (2018) performed a thorough review of the literature and repeatedly found the risk of clotting events to be minimal in both young and elderly populations acutely after BFR exercise and weeks to months later. Furthermore, analysis of bloodwork from participants in these experiments shows no significant activation of clotting pathways. Rather, BFR exercise actually appears to activate the fibrinolytic (clot busting) system, effectively lowering the risk of clots.

As the research around BFR has developed, interest in applying the technology to people with a variety of medical conditions has also mounted given the potential benefits. This, of course raises additional questions of safety, which has lead to studies of BFR in populations with a series of different conditions. For instance, Wong et al. (2018) reviewed and analyzed the results of 6 randomized controlled trials that looked specifically at the safety of BFR training in individuals with high blood pressure. The 6 studies included a total of 86 participants. The author’s were able to perform a meta-analysis (a statistical comparison of the results of different studies) of 3 of the 6 trials. They found that BFR training does not significantly raise or lower blood pressure immediately after the exercise or in the following hours/days. When the authors looked at the results of all 6 studies, while also considering the results of the meta-analysis just described, they observed that no adverse events occurred in any of the 86 participants. Thus Wong et al concluded that, in light of the current evidence, BFR exercise appears safe in patients with high blood pressure if applied safely by a trained practitioner.

In Bradner et al.’s summary of the current BFR literature (2018), it was found, as in the studies already discussed, that serious complications are exceedingly rare and may not necessarily be due to BFR itself. However, reports of less serious side-effects such as mild bruising, transient numbness, discomfort and delayed onset muscle soreness (DOMS) are more common. The good news is that these side-effects can be effectively mitigated if the BFR is applied by a trained and knowledgeable professional using appropriate equipment. In the earlier days (~1998-2012) of BFR research, the equipment used to restrict blood flow was much less sophisticated--simple blood pressure cuffs or thin bands. Furthermore, the method of deciding how much pressure should be used to restrict blood flow was somewhat arbitrary and did not account for individual differences.

Our clinic uses a BFR system called the Delphi Personal Tourniquet System (PTS). This equipment is the only BFR system approved by and registered with Health Canada, largely because it has a variety of safety features to reduce the risk of unpleasant side-effects. Let’s discuss how the PTS safety features reduce risks associated with BFR:

1. Wide cuffs--The Delphi PTS system uses wide cuffs (11 cm), whereas many of the early studies used thinner (3-5 cm) cuffs. Wider cuffs dissipate force over a larger area of the skin and require relatively less pressure to exert the same level of blood flow restriction. This reduces the risk of bruises and decreases the amount of pressure placed on nerves, which protects against numbness (like when you sleep on your arm funny and wake up with it completely numb). Wider cuffs also mitigate discomfort associated with blood flow restriction during an exercise session (Hughes et al., 2018).

1. Personalized pressure--Rather than arbitrarily assigning a restriction pressure, the PTS begins every session by calculating the individual’s Limb Occlusion Pressure (LOP), the pressure required to totally restrict blood flow to the limb. Then a percentage of this value is taken to provide partial restriction (typically 80% for the legs and 60% for the arms). Then, once exercise is started, the machine constantly monitors the cuff pressure and adjusts to stay at the calculated percentage throughout the exercise session. Additionally, your physio or other practitioner can choose to have you work at lower levels of restriction. For example, if you are new to BFR and 80% restriction seems a bit scary, the restriction level could be set to 60% for the first few sessions while you get accustomed to the sensation (plus even at lower levels of BFR you can still get gains! (Counts et al., 2016)).

As you can see, these two important features are important in reducing, as much as possible, risks like bruising, discomfort or having your leg fall asleep during the exercise session. Aside from the features of the equipment, the competency of your physio is also pretty important. For example, your physio can help you reduce delayed onset muscle soreness (that feeling you get after you workout for the first time in a while) by introducing BFR at a reasonable pace relative to your current level of fitness/exercise experience. That being said, it is reasonable to expect some mild soreness after that first few sessions of a new exercise program, but your physio should at least warn you of this!

On a more serious note, your physio should be aware of your medical history in order to screen for potential risk factors that may pose more of a threat to your health. Although the incidence of any dangerous side effects from BFR are extremely rare, it is still crucial for your physio to discuss any serious risk factors with you and your Doctor to determine whether the benefits of BFR outweigh any potential risks. To make this process easier, a few groups of researchers have created assessment tools to help practitioners determine each individual’s potential risk (Nakajima et al., 2011; Kacin et al., 2015; Brandner et al., 2018).

A large volume of research involving huge numbers of people ranging from young and healthy to the elderly has revealed a miniscule number of serious side-effects. Furthermore, studies carried out in high-risk populations such as cardiovascular disease, pregnancy, diabetes, high blood pressure and obesity have shown no reported adverse effects (Brandner et al., 2018). The take home message is really that low-load BFR exercise is no more dangerous than traditional high load exercise and may actually be safer in some circumstances. Therefore, if you believe BFR could be of benefit to you, I encourage you not to be fearful of the new technology, but to speak to your physio about it and, if necessary, get clearance from your Doctor to be ultra-safe.

References

Brandner, CR, May, AK, Clarkson, MJ., Warmington, SA. (2018). Reported Side-Effects and Safety Considerations for the Use of Blood Flow Restriction During Exercise in Practice and Research. Techniques in Orthopaedics, ahead of print.

Counts, BR, Scott, Dankel, SJ, Barnett, BE, Kim, D, Mouser, JG, Allen, KM, Thiebaud, RS, Abe, T, Bemben, MG & Loenneke, JP. (2015). Muscle and Nerve, 53: 438-445.

Hughes, L, Rosenblatt, B, Gissane, C, Paton, B & Patterson SD. (2018). Interface pressure, perceptual and mean arterial pressure responses to different blood flow restriction systems. Scand J Med Sci Sports, DOI:10.1111/sms.13092.

Kacin, A, Rosenblatt, B, Grapar Zargi, T & Biswas, Anita. (2015). Safety consideration with blood flow restricted resistance training.. Annales Kinesiologiae, 6(1): 3-26.

Nakajima, T., Kurano, M., Iida, H., Oonuma, H., Morita, T., Meguro, K., Sato., Y., Nagata, T. & KAATSU Training Group. (2006). Use and safety of KAATSU training: Results of a national survey. Int J KAATSU Training Res, 2:5-13.

Nakajima, T., Morita, T. & Sato, Y. (2011). Key considerations when conducting KAATSU training. Int J KAATSU Training Res, 7:1-6.

Wong, ML, Formiga, MF, Owens, J, Asken, T & Cahalin, LP. (2018). Safety of Blood Flow Restricted Exercise in Hypertension: A Meta-Analysis and Systematic Review With Potential Applications in Orthopedic Care. Techniques in Orthopaedics, ahead of print.

Yasuda, T., Meguro, M., Sato, Y. & Nakajima, T. (2017). Use and safety of KAATSU training: Results of a national survey in 2016. Int J KAATSU Training Res, 13:1-9.