What if I told you you can now exercise with a cuff wrapped around your arm or leg to cut off circulation, and increase those gains? Excuse me?
It's called Blood Flow Restriction Training (BFRT) and it's taking the fitness industry by storm. It consists of an application of external pressure around the extremities, enhancing greater strength gains lifting lighter loads, while reducing stress placed on the joints. It creates a "mild tourniquet" approach creating enough pressure to SLIGHTLY restrict blood flow, not completely.
The claim is that while restricted blood flow to the working muscle, it will increase the tissue's metabolic demand. It is geared to muscle specific training, rather than the whole body. The theory is that less muscle breakdown is noted, due to less levels of creatine kinase, lipid proxies, torque output and delayed onset muscle soreness.
Limited oxygen to the muscle means that Type I muscle fibers (slow twitch, aerobic) aren't as active since they require oxygen. Therefore, Type II muscle fibers (fast twitch, anaerobic) are recruited instead. So instead of having to recruit more Type II fibers at high intensity, adding BFRT at lower loads can have the same effect.
BFRT is more geared toward hypertrophy, and not so much focusing on maximizing strength or power, although is some cases, such as rehabilitation, some gains can be seen. It will not help with peak performance changes due to low load and low intensity training.
Most of what I have found has been leaning toward great options for post injury and surgical interventions. Below you can read a brief breakdown of many different articles I have found useful in this research.
In a rehabilitation setting, BFRT is starting to take off with athletes. It creates low-loading training with rapid movements without risking the injury site. The idea it to unload the body when compromised while making gains. Due to higher reps, this also creates a lactate response.
BFRT is not for everyone. Those with concussions, deep vein thrombosis, or circulatory problems should avoid. For safety purposes, you should not cut off blood circulation of extended periods of time. Also avoid heavy loads and high intensity should be avoided until safe parameters are more explored.
Again, since this is such a new concept, much more research is needed to form a strong opinion on gaining muscle size and functional outcomes.
A 2017 study in the Journal of Strength and Conditioning Research suggested that there was no added benefit to football athletes in performing sprinting and jumping tasks.
Another 2017 study in the Journal of Strength and Conditioning Research tested low intensity sprint training in the 100 meter dash. It suggested there was decreased muscle damage, increased rectus femoris muscle thickness and higher rate of force development in the BFRT training group. However, there was no increase in the biceps femoris or biceps brachii. Also, hormone responses (GH, cortisol and testosterone) did not change.
A 2018 Journal of Sports Rehabilitation suggested that when combining neuromuscular electrical stimulation and BFRT on leg strength, it lease to increased muscular strength on the knee extensors but no change in muscle mass.
A 2018 Journal of Foot and Ankle Surgery studied 2 different athletes with Achilles tendon rupture. Both experienced plantar flexion peak torque improvement, power gains, and strength benefits during rehabilitation and were able to return to sports/running after 6 weeks.