Personalized Blood Flow Restriction (PBFR)
What is PBFR?
Blood Flow Restriction (BFR) is the application of tourniquets to decrease the volume of arterial blood delivered to a peripheral limb, while blocking venous return. The tourniquets may be applied around the upper thigh (most common) or around the upper arm. Commonly, left and right limbs will be blood flow restricted at the same time for a standard length of time.
PBFR is Personalized Blood Flow Restriction, and the type of BFR
that #TeamEPP prefers with our Athletes
It differs from the application of a fixed pressure (ex. a wrap around the limb) in that blood flow is constantly monitored and the pressure constantly managed to ensure a consistent blood flow rate. The percentage of normal flow is the precise parameter that optimizes the physiological effect. You cannot control the precise blood flow without a surgical grade tourniquet system.
There are 3 physiologies that are positively affected with PBFR:
Muscular Hypertrophy - 80% leg occlusion; 50% arm occlusion for increased muscle growth
Muscular Endurance - 50% leg occlusion for hypertrophy and improved V02max
Physiological Recovery - 100% occlusion to enhance the body’s adaptation response to exercise
The first 2 categories (Muscular Hypertrophy and Endurance) include exercising while having blood flow precisely diminished. For Hypertrophy, these exercises are typically done for 4 sets (30, 15, 15, 15) at your 15-30% Rep Maximum (RM). By no means are these exercises easy. Imagine doing your basic warm-up while experiencing near maximum lactic burn. Normally just doing bodyweight squats can seem impossible. Typically, 3 to 5 exercises are given in a session. #TeamEPP has been doing them at the end of a normal athlete gym routine. In a Rehab setting, they might be the only exercises an Athlete may do in a day. For Endurance, typically the leg blood flow is occluded bilaterally while on a stationary bike. Feels like you're climbing a steep hill with only minimal resistance on the bike (working at about 40% VO2max).
The last category, Recovery, is performed after sport-training or Strength & Conditioning to enhance the cellular changes that promote adaptation. 100% occlusion occurs under 5 minute on, 5 minute off cycles for 25 minutes. The legs may look mottled in colour, and feel a bit dead while the PBFR is cycling on and off, but the next day an Athlete typically feels refreshed and more ready for training.
Is PBFR Safe?
PBFR is a relatively new and novel modality, and is not common in clinical practice. Fortunately, there is a substantial volume of research literature. The technology used with PBFR is the same tourniquet technology that has been used in surgeries for many years. There are a couple topics that continually arise as the method enters more and more discussion with our medical colleagues
Thrombosis (Blood Clots) - contrary to the belief of many, tourniquets used for short periods DO NOT seem to pose an increased thrombosis risk. Studies have demonstrated there may actually be the activation of protective effects without an increase in blood clot potential.
Central Cardiac (Heart) Responses - The cardiovascular stress of exercise used in PBFR is significantly lower than the stress involved with higher intensity training. Venous return may be decreased, but heart rate increases to maintain a steady cardiac output.
Peripheral Vascular Changes - PBFR may not worsen arterial compliance (and may improve it)
An experienced clinician in the health sciences should manage the application:
Tourniquet system is classified as a Type 2 Medical Device
Must be applied ONLY to a proximal limb to avoid pressure over a joint or superficial nerve (DO NOT allow someone to apply a wrap around your knee / calf / bicep)
Medical History should be taken to identify absolute risks / contraindications:
Extremity infection
Medications and supplements known to increase clotting risk
Open fracture
Open soft-tissue injury
Elbow surgery (with excessive swelling)
Skin grafts with bleeding points
Secondary or delayed procedures after immobilization
Discontinue PBFR session:
Faint
Dizzy
Moderate to severe pain under the cuff, or begins to feel numbness or paraesthesia in the limb
No high intensity exercise (Olympic lifting, Plyometrics, Agility, Running) during or immediately after
Hypertrophy with PBFR
Hypertrophy is defined as the increase in the size of cellular components, and PBFR has primarily explored muscular hypertrophy. The American College of Sports Medicine recommends that during resistance training, the load should exceed 70% of the one-repetition maximum (RM) to achieve maximum hypertrophy.
Unfortunately, the load management demands of a competitive season or an injury inhibiting that level of loading does not allow hypertrophy as a physiological adaptation. This catabolic effect can decrease strength or minimize rehabilitation outcomes, especially when strength is needed to overcome surgery or a tendon injury.
PBFR has consistently demonstrated hypertrophy and strength improvements in these populations, and even shows an effect comparable to heavy lifting without the actual high loads on joints, bones, and soft-tissues.
Exercising at 30% RM under PBFR conditions
creates identical strength and hypertrophy outcomes as
lifting at 70% (or higher) RM.
The exact mechanisms for these adaptations are not entirely clear, there are some theories, and a likelihood that several of these mechanisms are working together:
Metabolite Accumulation - lactate accumulation creates a chemical hypoxic / acidic environment that encourages the increased activation of larger fast glycolytic fibers / motor units. It also appears this chemical state may activate satellite stem cells and growth hormone, and may explain the further benefits in tendon and bone tissue
Cellular Swelling - increased intracellular volume may activate muscular protein synthesis, and furthermore shift metabolism to a lipolysis state (break down fat instead of muscle) in order to spare protein