An essential guide to blood flow restriction training

Blood flow restriction (BFR) is commonly used in sport performance settings, and is gaining traction in rehabilitation. Blood flow restriction entails applying external mechanical pressure to the upper or lower extremities at the proximal regions of the limb, limiting blood flow to and from muscles ^[1]. This reduces venous return and creates an ischemic state in muscle tissue ^[2], which is similar to the consequences of high intensity activities like repeat sprinting and resistance training.

Coupling BFR with low load resistance training produces results comparable to high load resistance training ^[3]. This, alone, makes a powerful case for employing this combination during the rehabilitation process. The prospect of creating a large adaptive response with a lower intensity stimulus creates the opportunity to load rehabbing athletes earlier, providing them a larger period of preparation time during rehab or even accelerating their return to play ^{[4, 5]}.

BFR is beneficial across a wide range of pressures: 60-80% limb occlusion pressure (LOP, where 100% represents the pressure necessary to fully occlude blood vessels) being the most commonly used range in the lower body, and 40-60% in the upper body.

BFR also benefits recovery and ischemic pre-conditioning (IPC). This performance oriented approach to BFR gives more versatility to practitioners than they may be aware of. Modalities like passive recovery BFR involves occluding limbs that are completely at rest, whereas active recovery BFR involves coupling occluding limbs with active methods of activity, like cycling or walking.

BFR for rehabilitation

Using BFR with loads as light as 30% 1RM ^[6] can increase muscle hypertrophy and strength, which is why we see it used so frequently in rehab cases.

Loading players earlier, and doing so with safer loads, yields a smoother rehab process, especially as we can be confident that this type of work can reduce joint effusions and pain compared with higher load type rehab activities. Normally, you may need to wait several weeks before reintroducing a long term injured athlete to resistance exercise and then loading him with the necessary intensity for an adaptive response. In soft tissue injuries, you may wait three weeks before emphasizing hypertrophy type work. With BFR, the athlete can begin hypertrophy training within the first 10 days post-injury.

Passive BFR can also help athletes 3-5 days post-surgery once inflammation has settled, and even if the individual is bed bound / non-weight bearing. Using passive BFR while the athlete is immobilised and has to tolerate large periods of rest is a fantastic way to engorge the tissues with blood, help drive recovery in the injured limb, and stimulate muscle protein synthesis to offset atrophy. As an athlete progresses to loaded activities, BFR again helps intensify what is essentially bodyweight / low load to create early adaptations in the rehab process.

Using BFR can bring less fatigue with it, too. This is particularly useful when trying to rebuild muscle mass after an injury that required immobilisation.

ACL injuries or Achilles tendon ruptures, for example, can result in muscle atrophy that must be reversed prior to introducing loading and progressing towards pre-injury levels. With BFR, practitioners can load targeted muscles via high volume, high frequency training several times a week, and even numerous times a day — something that simply isn’t possible with traditional high load resistance training.

BFR for pregame or pre-training preparation

Preparation BFR has been explored for its benefits for up-regulating energy system kinetics, muscle activation, and pain modulation. The hypoalgesia effect of BFR ^[7] can offer a significant benefit when working with athletes who have to manage pain or discomfort (like joint or tendon pain).

BFR reduces pain, much like heavy load training does, but with a much lower external load and cost of fatigue. The pain reduction from BFR lasts longer, too – up to 24 hours post-exercise. This allows practitioners to do more with the time we have with our athletes.

By using BFR before a “loading” session in rehab, practitioners can transiently remove pain to give the athletes more confidence to load through more range, or use faster speeds for their rehab running activities.

Two recent clients had the same response to using BFR to manage pain that inhibited movement. One athlete had hip pain, and the other had shoulder pain associated with an impingement injury. Both reported pain in the 5/10 range before completing two 5-minute intervals of passive BFR with 3 minutes between sets. Their pain dropped to 0-1/10. This immediately opened up more training options for these athletes: we could now load them through ranges that had been limited by the presence of pain.

Preparation BFR can also include passive or active BFR prior to exercise, often known as ischemic pre-conditioning. The purpose of IPC is to impact subsequent performance outcomes, and BFR has positive effects on endurance and repeat sprint performance, as well as reducing perceptual measures of effort. For example, using BFR passively pre-exercise enhanced critical power in an all out 3 minute cycling test ^[8]; and significantly increased maximal oxygen consumption by 3% and power output by 1.6% during maximal cycling performance ^[9].

With England’s Rugby 7s, we were interested in ways we could either accelerate physical preparation for games or reduce the perceived effort of work rate in games. Passive BFR for 3 x 5 minutes pre-exercise resulted in a reduced perception of effort of subsequent workload (repeat sprint efforts) compared with a traditional warm up. Moreover, sprint times were unaffected, so we were observing a decreased perception of effort for the same level of work.

We took this knowledge into our work with individual players who used IPC as part of their “re-warm up” routine between rugby 7s matches, that were generally separated by 2.5 – 3.5 hours.

The players’ response was very positive. They reported feeling energised and more prepared for the high work rate required from kick, compared to having to get through a “second wind” during such a series of matches without BFR.

Gloucester Rugby used Hytro BFR in an IPC protocol to assess its impact on repeat resisted (prowler) sprints. There were not any immediate effects, i.e., no influence on the early reps and sets. But in the latter reps, the IPC attenuated the fatigue decrement in maximum effort sprints by about 17%.

Sprint momentum and winning collisions are obvious precursors of success in rugby, so any ability to maintain high performance in these areas in repeat efforts on the field will be advantageous.

BFR for conditioning

Combining conditioning with BFR can result in a distorted level of blood perfusion and oxygenation that gives rise to shear, hypoxic, metabolic, and oxidative stress signals ^[9]. These stressors relate to what normally occur in standard extensive training protocols (i.e., much higher volumes or intensities). As a result, BFR creates an opportunity for positive adaptation from less training input (intensity or volume).

BFR during conditioning means occluding the limbs while performing activities like cycling, using the cross-trainer, or even running. My preference is to use it during off feet activities (usually cycling), especially when trying to limit on-feet load for athletes.

Practitioners will want to know the exact pressure for BFR training options they prescribe. Although we know the positive benefits of BFR occurs across the range of 40-80% LOP, athlete tolerance to the modality likely drives adherence to any protocol. It would be far better to have an athlete perform a slightly lower LOP and complete a conditioning stimulus than put them at the upper ranges of LOP, potentially driving them to opt out of the present and future uses of the modality.

Running intervals with BFR over eight weeks (5 x 3 minutes at a set heart rate reserve, three times weekly) resulted in significant performance test improvements compared to a non-BFR training group ^[10].

Six weeks of BFR cycling with only one limb occluded resulted in an increase in time to exhaustion of the BFR trained leg. Glucose uptake significantly improved in these trained muscles ^[11]. Increased adaptations in GLUT4 availability (~30%) and nitric oxide availability also occurred, which poses an interesting option for coupling BFR with nutritional interventions. Could you create an increased rate of glycogen resynthesis acutely with BFR use after strenuous exercise? This is certainly an area that BFR research may start to investigate further, and could further proliferate BFR’s use cases.

BFR has shown strong results as a conditioning stimulus in research, but it is worth considering the limitations of existing equipment when prescribing this as training in real life sport environments. Trying to administer BFR for running on a pitch is not possible with wired devices, nor for movements like prowlers. The time to inflate and deflate is cumbersome, too, so this equipment results in time wasted.

If using BFR for conditioning, the correct device must be used to ensure safe, timely, and effective administration for athletes, as well as ensure trust in and advocacy for the method from the athletes themselves.

BFR for recovery

Potentially the most exciting and underutilised benefit to athletes lies in the space of recovery BFR solutions. The passive aspect of BFR for recovery has gained popularity at a rapid rate in recent years.

My time in Major League Baseball allowed me to witness the accelerated recovery process when BFR is used after high intensity throwing. Consistently, players reported reduced severity of delayed onset of muscles soreness (DOMS) between pitching bouts. Although anecdotally reported as ratings of muscles soreness, the evidence pushed me to take a deeper dive into using this modality more.

Table 1 shows a normal routine for pitchers, and the impact of using BFR for recovery on muscle soreness in that cycle. This practice based evidence, coupled with solid research papers showing improved neuromuscular recovery and reductions in muscle soreness ^[8,12], has made recovery BFR a staple method in the recovery toolbox for any athlete or team I now work with.

The ability to use a passive BFR recovery solution so easily affords many potential additional benefits. Anchoring BFR use in the recovery space to the ever-present fundamental rocks of recovery, like refuelling with post-exercise recovery shakes, could supercharge athletes’ recovery. Although it’s just a working hypothesis, considering what we have seen of BFR apparently upregulating GLUT4 sensitivity and the reoxygenation patterns that occur between occlusion reps, coupling passive BFR with current post-exercise refuelling strategies could level up the recovery process.

Athletes using passive recovery BFR in their homes, training environments, and during travel would be the recovery utopia. However, the dependency on electrical BFR devices has limited use not only by cost, but power supply needs (to pump up cuffs). Advancements in safe wearable BFR solutions like Hytro have overcome this barrier to access for athletes. Hytro garments have embedded strap technology that allows the athlete to very quickly and safely apply BFR. This allows practitioners to provide a safe option to empower athletes to take responsibility for recovery in multiple places without our supervision or instruction. Hytro are safe for independent use ^[13,14] and pressure validated ^[13] (See figure 5) against medical grade equipment for LOP comparisons. They have also designed products specifically for each sex, providing a more comfortable fit and effective BFR.

Safety and efficacy when using blood flow restriction

Safety is of paramount importance. With BFR partially restricting blood flow to working muscles, both proper use and risk assessment are important. Participants who have cardiovascular or neuropathy conditions are contraindicated from BFR.

Those wishing to use BFR should follow these guidelines:

1) Screen all participants for appropriate use of BFR: assess participants for a history of cardiovascular issues like thrombosis, ischemia, or rhabdomyolysis, as well as neurological conditions. Hytro have a freely available risk assessment that assesses level of risk. Always consult physicians in this screening process.
2) Apply the BFR stimulus exclusively at the most proximal point of the limb to safely restrict blood flow.
3) Use equipment that can be removed quickly and does not over inflate nor restrict vessels fully. BFR should be sub-occlusive. Using straps tied with knots is extremely dangerous.
4) Accustom users to BFR in a progressive manner. The sensation and discomfort associated with BFR is unique, and introducing the method gradually to participants is essential, as it is a novel training stimulus.
5) Do not leave limbs occluded for extreme periods of time (>20mins).

The use of BFR has moved from the clinical space to the applied setting. The original technology was developed to have cuffs that self-regulated and controlled pressure relative to LOP.

100% LOP (occlusion of the artery and veins) should be avoided unless administered by a clinician for very specific cases. A wide range of safe pressure (40-80% LOP) produces positive outcomes. Practitioners can monitor LOP via a doppler, and some technologies even have this embedded passively. However, the need for an electrical supply in these tools limits their portability. Additionally the extremely high price of such equipment creates a barrier to access for many athletes to use BFR in performance spaces (Figure 4).

Guidelines for BFR use

There are two main ways to using BFR: actively, when the limbs are occluded and are coupled with muscular activity; and passively, when BFR is the sole stimulus, there is an absence of muscular activity, and the user is occluded in a resting state.

Table 5 provides guidelines of use. It is always important to be focused on the specific outcome or adaptation you are looking to achieve.

The specific pressures for BFR change based largely on individual tolerance. As with any stimulus, progressive overload is critical to continue to reap adaptive changes from training. Athletes have positive responses across the full range of LOP’s (40-80%), so working as high as tolerable within these safe ranges is the optimal approach.

Looking into the future of BFR

Practitioners are coupling BFR with other modalities they already use in their organisations, like ice baths, contrast bathing, and pool conditioning. This is sometimes called “habit stacking,” and has as its end goal optimising recovery through the fewest number of modalities as possible, to have athletes stay engaged with the recovery process.

Blood flow restriction is an exciting modality and is highly versatile to solve numerous performance problems. The recent growth in use of BFR for recovery and preparation in professional athletes is particularly exciting, with numerous articles and summaries available online from active professionals advocating its use. The research in BFR is expanding in many directions, demonstrating BFR’s potential across areas of preparation, training, and recovery.

As with any athlete experience I have encountered, trying new methods or routines requires simplicity in order to attain buy in. Hytro users are adopting BFR during post-game travel on flights and buses, coupled with ice, heat, or hydrotherapy; wearing it in hotels as part of preparation and recovery; and carrying it in their training bags to use at any point prior, during or post training as needed. A fully manual and analogue BFR is equally safe and practical for bringing BFR to the athlete as a training solution.