Blood Flow Restriction (BFR) Training Summary:
Blood flow restriction (BFR) works by allowing arterial flow into the limb but restricting the venous return. During exercise, the muscles continue to fill up with blood and as it becomes fuller with blood, less oxygen becomes available.
As the exercise demand continues, the oxygen rich blood continues to deplete causing the muscle to fatigue. As this process occurs, more muscle units are recruited resulting in a higher integrity of the muscle being used.
BFR has actually been used since the 1960s-1970s for performance enhancements and in the body building industry. BFR may sound intimidating to those new to the concept but with proper education and application it can provide multiple benefits.
With traditional exercise, as load increases the muscle capability decreases. As the energy sources decrease, the muscle tissue becomes more acidic, causing the pH levels to drop.
When you exercise hard, glucose is broken down for energy which one of the byproducts is pyruvate. With continued hard exercise, hydrogen ions build up in the muscles and pyruvate helps absorb the hydrogen ions to form lactate.
Lactate is what decreases muscle acidity and can also be used to produce more energy. The accumulation of hydrogen ions is the cause for muscle soreness and fatigue during exercise.
Continuous exercise also causes stimulation in the hypothalamus, which releases growth hormone releasing hormone.
This then stimulates the pituitary gland to release growth hormone, which aids muscle growth and stimulates the liver for release of IGF-1 (Insulin Growth Factor 1)
IGF-1 is what stimulates bone growth, muscle growth, macrophages release and repair.
Blood flow restriction stimulates the release of HGH and IGF-1, which contribute to cell growth and protein synthesis.
Myostatin down regulation also occurs with BFR as myostatin inhibits muscle growth cells so BFR in turn reduces this process. So the process that already occurs in response to exercise is stimulated exponentially with the use of BFR.
So blood flow restriction basically provides an anaerobic environment where lower oxygen levels causes the body to recruit more muscle fibers normally reserved for more strenuous exercise. This process causes up regulation in muscle fibers leading to hypertrophy changes.
Common side effects are numbness, tingling, bruising, and increased pressure in the limbs being occluded.
Increased effort may also be perceived with the cuffs on causing an increase in respiratory and heart rate. Understanding what cuffs to use and how to use them is important.
The cuffs are placed on the arms and legs around the brachial and femoral artery at the axilla and the inguinal region.
Applying the cuffs in other areas provides no benefit and can actually be dangerous for localized occlusion.
Some cuffs will fully occlude and others will not as a safety mechanism. The preciseness of pressure is regulated more with pneumatic devices compared to more free attaching styles.
Free attaching styles allow for more movement freedom and accessibility during a workout. There are pros and cons to each type based on the use, demographics, financial considerations and style of rehab or training being administered.
Measuring limb occlusion pressure is part of the protocol when considering how much pressure to use.
Pressure and tightness, time on the limb, cuff width and material as well as chances of full occlusion should always be considered as well.
Some cuffs are made out of material that may be more forgiving and others may be made of more stiff material.
Some tingling and pressure in the limb is to be expected as using BFR is generally uncomfortable but excessive severity in symptoms such as increased numbness, tingling and cold sensation in the arm or leg warrants a change in the cuff pressure.
Always feel for the pulse and check capillary refill as well as level of fatigue.
If a person is having too much pain and unable to complete the task, this is an indicator that the cuffs are too tight or the resistance is too heavy.Monitoring the symptoms and response to the exercise prescription will help to ensure the proper adjustment in metrics.
It should be considered that a larger limb requires more pressure, especially if there is excessive adipose tissue on the individual. More physically fit and lean individuals will occlude faster and may require less pressure, especially at the arms due to less body fat.
Wider cuffs require less pressure to fully occlude the area. Narrower cuffs require more pressure to occlude the area and result in more discomfort.
Higher blood pressure results in higher occlusion pressure also so the level of pressure should be measured with blood pressure changes and be considered based on position changes such as sitting compared to standing when applying the cuffs and exercising.
There are two variables to consider when prescribing exercise parameters, which involve limb occlusion pressure (LOP) and resistance. The dosage of exercise is based off of percentages of a 1-rep max.
Higher levels of pressure used with percentages of a 1-rep max for an exercise, produce the best results in fatigue levels and greater cross sectional area.
Intensity of BFR training is altered by changing either LOP or resistance. Wearing a cuff at each limb will also provide a higher intensity as compared to just wearing cuffs at the legs or arms.
Research studies investigating BFR have measured many variables and currently a general guideline is as follows:
Execute an exercise for reps of 30-15-15-15 with 30 seconds rest between each set.
Research studies have demonstrated that BFR can improve multiple variables in athletics including quad and hamstring strength especially following ACL reconstruction.
In a review of over 237 studies looking at BFR in training for athletes multiple variables improved including 1 rep max numbers, sprint speed, jump power, agility metrics, strength and muscle mass.
Low to moderate intensity aerobic exercise with BFR can result in greater improvement than without but no differences have been shown with high intensity aerobic exercise with and without BFR.
Current literature demonstrates that aerobic and anaerobic training with BFR can improve performance and activity tolerance in these activities.
Improvements in V02 max, muscle strength and endurance have also been demonstrated with the use of BFR.
With aerobic training, BFR is used with low and constant pressure as where anaerobic training it is used with reduced pressure between sets to allow for perfusion.
Other findings from the research have demonstrated that BFR can help to stimulate increases in muscle size and strength effects when high loading training is not appropriate or unattainable.
It also benefits those in the rehabilitation phases of an injury when higher load training is contraindicated.
On the same note, those who cannot tolerate high loads such as the geriatric population or very de conditioned individuals will benefit from implementation of BFR.
Lifting heavy and finishing with burn out sets with BFR is one method of training with BFR.
Between heavy lifting days, BFR can be used to continue the stimulus and training of the muscle groups with the less demand from heavy lifts which can still stimulate the appropriate hormonal response.
For athletic performance and the sports population, lifting heavy with combination of BFR can also yield better results than just lifting heavy alone.
Most studies looked at high load resistance training as being >70% of 1RM and <50% of 1RM as low load. Although BFR has its benefits, studies have revealed that for pure hypertropthy and strength gains, lifting heavy is still crucial.
Heavy lifting is still important for the physiological changes to take place and cannot be completely replaced by BFR.
As stated earlier, the concept of BFR can sound scary but there are individuals who would not be appropriate.
Contraindications include impaired circulation and vascular issues, infection, tumors in the limb, open fracture, pregnancy, high blood pressure, cancer, skin grafts, lymphectomies.
Most of these contraindications are due to the alterations in blood flow that BFR causes as well as the effects the pressure will have on the limb. Open wounds, post surgical situations still healing and things like cancer can be affected negatively by the pressure changes.
The one area that BFR is really being implemented in is the high school and collegiate female athlete following ACL reconstruction surgery. It is also appropriate for males of course but females top this injury more commonly than males due to biological and neuromuscular factors.
In the early stages of ACL recovery, atrophy of the quadriceps is a major issue. Kinesiophobia or fear of movement, especially in the single leg stance position is also an issue.
Fear of putting weight through the limb can delay progress in rehab by weeks. Combining these two factors of kinesiophobia and quad weakness with the list of foundational deficits that the majority of this demographic already presents with can pose quite the challenge for rehab.
BFR can help stimulate early on healing factors and muscle function, allowing for progression to certain movement patterns earlier in the rehab.
Currently there is research looking to see if BFR can help to improve blood flow and nourishment to the graft early on. This is important as the graft lacks vascularization for months after repair and it takes time for it to transform from a graft to an actual functional ligament.
This is why the protocols restrict certain movements for such time especially return to running, plyometric movements and sports specific movements. BFR shows promising effects towards improving these parameters.
The information in this article has been derived from an educational course through Northeast Seminars taught by Dr. Trent Nessler.
As described earlier, BFR has been around since the 1960s but up until recently has not been pursued more with research and clinical implementation. It has promising benefits for the general population and athletes of all backgrounds.
About The Author:
Michael St. George PT, DPT has been practicing for 10 years primarily in the outpatient and orthopedic setting. He works for a physical therapist owned private practice based in the greater Philadelphia area and surrounding suburbs. Mike is certified through Functional Movement Systems for FMS, SFMA and FCS which consist of screens and testing used to measure movement quality and performance. Mike also has experience with working with numerous surgeons and physicians from the Rothman institute. Currently he works primarily with ACL, meniscus and post surgical recovery and sports injuries, return to sport testing and performance, running evaluation and re training and hand and upper extremity conditions.