Over the past few years, blood flow restriction training (BFRT) has become more popular. While it has traditionally been used in a clinical rehab setting and among power athletes, it’s gaining traction in the endurance world. Some studies have shown that it can improve specific markers of aerobic performance and strength output, both at once in some instances.
But skeptics contend that while this method can lead to improvements, these don’t exceed the gains your athletes will likely get from the regular sessions you prescribe. Let’s explore the benefits, examine the potential risks, and see whether BFRT is worth incorporating into your athletes’ programming.
Grasping the BFRT Basics
Before we explore how BFRT might positively affect your clients’ rehab and performance outcomes, we need to define what it is and how it’s utilized. The technique emerged in the 1960s and was initially used in physical therapy — sometimes called blood flow restriction therapy — to help people recover from injury.
That’s how this article came about. A friend who suffered a spinal injury in a skiing accident texted me to say his PT was combining low-intensity resistance training with BFRT in his program. It involves using a band as a tourniquet to restrict arterial inflow and limit venous outflow into the arms or legs.
Most BFRT protocols achieve this using an inflatable cuff pressurized with a pump attached to a valve that lets you dial in how much pressure is applied (some systems do this electronically). After the cuff is removed, there’s an increase in blood flow back to the area, with the thinking being that improved circulation speeds healing.
After widespread adoption in clinical settings, BFRT became popular for bodybuilders looking for a “pump” in their muscles. Studies showed that just as this technique could enable people with some kind of movement or load restriction to exercise safely with their bodyweight, it might also create physiological adaptations when combined with light weightlifting.
More research then began to indicate similar efficacy with low-intensity endurance exercise combined with BFRT. This led to more companies offering direct-to-consumer BFRT products that wouldn’t require going to a PT. However, detractors believe there are safety concerns with athletes doing BFRT outside a clinical setting. They fear too much pressure causing tissue and nerve damage and cite a lack of standardized best practices for pressure ranges and exercise prescriptions.
Enhancing Interval Training with BFRT
One of the most significant advantages BFRT can provide is an increase in strength and muscle size. Rather than focusing on trials that apply to power athletes, we’ll examine a couple of interval training studies that are more relevant to your endurance clients.
A group of Taiwanese exercise physiologists divided runners into two groups. The first just did five sets of three-minute intervals, each followed by a minute of rest. The second group did the same session but with BFRT cuffs attached. The latter increased their speed, knee flexor and extensor strength, and muscular endurance more than the former. This led to the authors writing that BFRT “may be a feasible training strategy for improving muscular fitness and endurance running performance in distance runners.”[i]
A team of Brazilian researchers wondered how BFRT might compare against other methods for potentially increasing both strength and endurance in the same type of training session. They split participants into four groups. Two did low-intensity intervals with or without BFRT devices, while the third and fourth performed high-intensity intervals with the same variable.
Only those who combined BFRT and fast intervals increased their maximum power output, VO2 max and muscle size. “This study demonstrates the advantage of short-term low-intensity interval BFR training as the single mode of training able to simultaneously improve aerobic fitness and muscular strength,” the authors concluded.[ii]
Achieving the Cardiovascular Benefits of BFRT
In a study released via the International Journal of Exercise Science, a research duo from Texas A&M University-San Antonio wrote that, while there’s a lot of research focusing on the anaerobic advantages of BFRT, there haven’t been enough investigations of how it might impact aerobic capacity. So they asked participants to walk with BFRT devices attached on a treadmill for 20 minutes three times a week, with the grade increasing from 1-5%. They then assessed their 1.5-mile time trial run performance, VO2 max and thigh muscle size.
After observing improvement in all three criteria, the authors concluded that “BFR walk training represents a singular training methodology for improving aerobic capacity, endurance and muscular size at low training volumes and intensities.”[iii] The last part of this statement is critical.
While BFRT has been shown to elevate sprint performance, it should be done slowly if the goal is to increase endurance-related output. Going at a walking pace would arguably be a gentler way to introduce your clients to the squeezing sensation that BFRT creates, and they could easily stop at any point if it became uncomfortable.
This isn’t the only walking study to explore the potential aerobic capacity-building benefits that BFRT could provide. A research team asked a group of basketball players to use BFRT cuffs as they completed five sets of walking for three minutes and resting for a minute. They repeated this session twice a day, six days a week, for two weeks. Publishing the results in the European Journal of Applied Physiology, the authors found that the players’ VO2 max went up by an average of 11.6%. They also enhanced their maximum minute ventilation (the amount of oxygen they could move in 60 seconds) by 10.6 % and increased anaerobic power by 2.6%.[iv]
Your cycling and triathlon clients might be interested in another trial in which Japanese exercise scientists asked one group to pedal for 45 minutes at 40% of their VO2 max while another to go at the same intensity for 15 minutes with a BFRT device attached. The BFRT participants elevated their VO2 max by 6.4% and saw increased knee extension strength, muscle growth in their upper legs and delayed time to exhaustion.[v] The fact that they could achieve these results in a third of the time of the control group illustrates the time-saving potential of BFRT training.
Considering the Risks of BFRT and Best Practices
While the latest literature suggests that BFRT might promise your athletes a wide range of performance benefits if they already have a good fitness foundation, the method also has some drawbacks — like any training technique. A 2019 Frontiers in Physiology review noted that as the number of coaches and PTs offering BFRT has increased, “practitioners are unclear on how to use and apply BFR in line with current research-informed standards. For example, practitioners applied a wide range of pressures that resulted in unintended consequences such as a large incidence of numbness following BFR.”[vi]
This might be the result of what’s known as total arterial occlusion — i.e., cutting off all of the blood flow through the arteries. Even if this isn’t absolute, applying too much pressure can still take an athlete beyond a safe threshold. In a blog post, Dr. Zach Long, DPT, stated that utilizing a Food and Drug Administration-approved device such as the Delfi PTS system — which needs to be used by a licensed medical professional — would alleviate the risk of applying too much pressure.
He also identified using improper cuff placement and the wrong width cuff as other common factors that increase the risks of BFRT. Long-referenced research showed that using wider cuffs reduces the amount of pressure needed. “This means that the small cuffs sold by many ‘BFR’ manufacturers increase the risk of soft tissue damage,” Long wrote. “You MUST use a wider tourniquet to minimize this.” Moving on to placement, he stated that cuffs should only be used on the upper arm or thigh, as “This will minimize the risk of nerve damage.”[vii]
Another review released via The Journal of Strength and Conditioning Research noted that the application of BFRT can impact the efficacy of an athlete’s overall training plan. Additionally, “practitioners looking to use BFR must consider the heightened physiological stress at lower workloads, which will both increase the relative exercise intensity and make it difficult to manage training loads.”
In other words, a little BFRT training goes a long way, as it’s more intense than many of your clients will be used to in traditional sessions. The authors went on to suggest that “Until best practice approaches are identified, practitioners are encouraged to apply BFR during aerobic intervals at a cuff pressure between 40% and 80% of AOP that does not cause a large reduction in sessional exercise volume and monitor the associated training load independently from non-BFR training.”[viii]
Owens Recovery Science, a leading BFRT education and research provider, has even more detailed guidelines for safe and effective protocols. “The pressure applied with BFR should be personalized to the individual’s Limb Occlusion Pressure or LOP (You’ll see us refer to this as Personalized Blood Flow Restriction or PBFR),” they wrote in an article.
“A range of pressure looks like it can be effective and different pressures may be required for the arm (40-50% of LOP) and the leg (60-80% of LOP). With BFR, resistance exercise with weight as light as 20-40% of an individual’s one repetition maximum can facilitate changes typically seen with lifting heavy weights, while endurance exercise can be prescribed for much shorter than typical durations and intensities less than 50% VO2max.”[ix]
In summary, BFRT should never be the main kind of training that your athletes do. That being said, it could be a valuable part of an injury rehab process if supervised by a PT. If they already have a solid strength training program, incorporating occasional BFRT sessions with light weights might be something to consider.
For endurance work, limit BFRT to short, low-intensity treadmill or stationary bike sessions initially so your athletes are doing it in a controlled environment. Then you could add in faster intervals later. Again, this should be a complementary training technique, not the core of your client’s programming. If you’re unsure about BFRT, seek the advice of an expert and, as with any other new kind of training, keep a close eye on your clients to ensure they’re doing it safely.
References
[i] Yun-Tsung Chen et al., “Running Interval Training Combined with Blood Flow Restriction Increases Maximal Running Performance and Muscular Fitness in Male Runners,” Scientific Reports, 2022, available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9200839.
[ii] M F M de Oliveira et al., “Short-Term Low-Intensity Blood Flow Restricted Interval Training Improves Both Aerobic Fitness and Muscle Strength,” Scandinavian Journal of Medicine & Science in Sports, September 2016, available online at https://pubmed.ncbi.nlm.nih.gov/26369387.
[iii] William Ursprung and John D Smith, “The Effects of Blood Flow Restriction Training on VO2Max and 1.5 Mile Run Performance,” International Journal of Exercise Science, February 2017, available online at https://digitalcommons.wku.edu/ijesab/vol2/iss9/108.
[iv] Saejong Park et al., “Increase in Maximal Oxygen Uptake Following 2-Week Walk Training with Blood Flow Occlusion in Athletes,” European Journal of Applied Physiology, July 2010, available online at https://pubmed.ncbi.nlm.nih.gov/20544348.
[v] Takashi Abe et al., “Effects of Low-Intensity Cycle Training with Restricted Leg Blood Flow on Thigh Muscle Volume and VO2MAX in Young Men,” Journal of Sports Science & Medicine, September 2010, available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3761718.
[vi] Stephen D Patterson et al., “Blood Flow Restriction Exercise: Considerations of Methodology, Application, and Safety,” Frontiers in Physiology, May 2019, available online at https://www.frontiersin.org/articles/10.3389/fphys.2019.00533/full.
[vii] Dr. Zach Long, “Is Blood Flow Restriction Training Safe?” The Barbell Physio, available online at https://thebarbellphysio.com/blood-flow-restriction-training-safe.
[viii] Nathan DW Smith et al., “Aerobic Training with Blood Flow Restriction for Endurance Athletes: Potential Benefits and Considerations of Implementation,” The Journal of Strength and Conditioning Research, December 2022, available online at https://journals.lww.com/nsca-jscr/Fulltext/2022/12000/Aerobic_Training_With_Blood_Flow_Restriction_for.35.aspx.
[ix] “Blood Flow Restriction” Owens Recovery Science, available online at https://owensrecoveryscience.com/blood-flow-restriction.
