Blood Flow Restriction Training Taking The Fitness World By Storm
Overview:
They initially developed Blood Flow Restriction training in the 1960s in Japan and known as KAATSU training. It involves a pneumatic cuff, i.e., tourniquet proximally to apply to the muscle that is to train. It can apply to either the upper or lower limb. The cuff is then inflated to a specific pressure to get partial arterial and complete venous occlusion. The patient is then asked to perform resistance exercises at a low intensity of 20–30% of 1 repetition max (1RM), with high repetitions per set (15–30) and brief rest intervals between sets (30 seconds).
Understanding the Physiology of Muscle Hypertrophy:
Muscle hypertrophy is the increase in the muscle’s size and an increase in the protein content within the fibres. An increase in the cross-sectional area of the muscles directly correlates with an increase in strength. [6]
Muscle tension and metabolic stress are the two primary factors responsible for muscle hypertrophy.
Mechanical Tension & Metabolic Stress
When a muscle is under mechanical stress, the concentration of anabolic hormone levels increases. The activation of myogenic stem cells and the elevated anabolic hormones might cause the hype of proteins, metabolism, and muscle hypertrophy.
Release of hormones, hypoxia, and cell swelling occurs when a muscle is under metabolic stress. These factors are all part of the anabolism of muscle tissue.
Activation of myogenic stem cells
Myogenic stem cells are inactive and get activated in response to muscle injury or increased muscle tension. These cells take care of the damage repair of injured muscle fibres and the growth of these fibres.
Release of hormones
Any exercise, resistance, or aerobic brings about a significant increase in growth hormone. Insulin-like growth factors and growth hormones handle increased collagen synthesis after a workout and aid muscle recovery. Growth hormone itself does not directly cause muscle hypertrophy, but it aids muscle recovery and potentially facilitates the muscle strengthening process. In hypoxic training, the accumulation of lactate and hydrogen ions further increases the release of growth hormones.
High-intensity training shows down-regulation of the myostatin and provides an environment for observation of muscle hypertrophy. Myostatin controls and inhibits cell growth in muscle tissue. And it essentially needs to be shut down for muscle hypertrophy to occur.
Hypoxia
As resistance training results in the compression of blood vessels in the working muscles, it causes a hypoxic environment because of a reduction in oxygen delivery to the muscles. Because of the hypoxia, the activation of the hypoxia-inducible factor (HIF-1α) takes place. This activation leads to an increase in anaerobic lactic metabolism and the production of lactates.
Cell Swelling
When there is blood pooling and an accumulation of metabolites, cell swelling occurs. This swelling within the cells causes an anabolic reaction and results in muscle hypertrophy. The cell swelling may cause mechanical tension which then activates the myogenic stem cells, as discussed above.
Effects of Blood Flow Restriction on Muscle Strength
BFR training aims to mimic the effects of high-intensity exercise by recreating a hypoxic environment using a cuff.
Low-intensity BFR training results in greater muscle circumference when compared with low-intensity exercise.
Low-intensity BFR (LI-BFR) increases the water content of the muscle cells (cell swelling). It also speeds up the recruitment of fast-twitch muscle fibers. It also hypothesizes after the cuffs are removed, hyperemia (excess of blood in the blood vessels) will be formed that will cause further cell swelling.
Short duration, low-intensity BFR training of around 4–6 weeks has shown to cause a 10–20% increase in muscle strength. These elevations are like the gains we can achieve because of high-intensity exercise without BFR.
A study comparing high intensity, low intensity, the high and low intensity with BFR, and low intensity with BFR. While all 4 exercise regimes produced increases in torque, muscle activations, and muscle endurance over 6 weeks — the high intensity (group 1) and BFR (groups 3 and 4) produced the most effects in size and were comparable with each other.
Muscle Damage:
BFR has well established that unaccustomed exercise results in muscle damage and delayed onset muscle soreness (DOMS), especially if the exercise involves many eccentric actions. DOMS is normal after unaccustomed exercise, including after LL-BFR training, and should subside within 24–72 hours.
High-load Resistance exercise in any form can cause muscle damage. We know the excessive breakdown of striated muscle as ‘exertional rhabdomyolysis’ causes organ damage. The incidence of rhabdomyolysis from BFR-RE is very low, approximately 0.07%-0.2%, which seems like the occurrence of rhabdomyolysis during regular high load resistance training. The concern is that even with low-load BFR, the increased metabolic stress may trigger rhabdomyolysis but, the incidence levels are so low the current evidence does not suggest there is an increased risk of rhabdomyolysis during BFR-RE compared to other forms of resistance exercise.
Exercise Prescription:
Exercise prescription for BFR varies. It depends on whether it is during resistance training (BFR-RE), aerobic training (BFR-AE),, or passively without exercise (P-BFR).
BFR-RE (resistance training):
For optimal results, a person must ideally have a resistance training session 2–4 times per week. In theory, people can perform strength training with BFR daily. However, this may not be the best long-term strategy. So, training sessions of 1–2 times per day are advisable for short periods like 1–3 weeks. BFR-RE is typically a single joint exercise modality for strength training.
A person can observe muscle hypertrophy during BFR-RE within 3-weeks, but most studies advocate for longer training durations of over 3-weeks.
According to studies, a load of 20–40% 1RM produces consistent muscle adaptations for BFR-RE.
The most commonly used training volume in literature is 75 repetitions across 4-sets (30, 15, 15, 15).
Rest periods between sets are usually about 30–60 seconds.
It is inaccurate to keep the cuff inflated during the rest periods to capture the metabolites. The intermittent pressure technique can provide much better results. However, this is not as effective as continuous.
The amount of pressure needed to occlude blood flow in the limb depends on the limb size, underlying soft tissue, cuff width,, and device used. The arterial occlusion pressure applied depends on whether it is an upper or lower limb and should be between 40%-80%.
BFR-AE (aerobic training)
BFR may also improve results during aerobic exercise, and they have done researches on individuals during walking or cycling. It is much tougher to maintain cuff pressures, and the literature lacks standardization of cuff pressures during BFR-AE.
P-BFR (passively without exercise)
Passively applied BFR (i.e., BFR techniques including no exercise sessions) is less widely in research plans. However, it has shown positive results in reducing muscle atrophy post ACL surgery. The studies conducted did not use standardized pressures, and some pressures used were high enough to possibly completely occlude blood flow, which poses safety risks. P-BFR might be beneficial in postoperative patients however, more research is important in this field.
Side Effects:
Reports have shown these side effects faced by some individuals while performing Blood Flow Restriction exercises like fainting, dizziness, numbness, pain, discomfort, delayed onset muscle soreness, Nerve damage, Bruising, Subcutaneous hemorrhage, Syncope, and sometimes Rhabdomyolysis.
