The use of occlusion during exercise has become a hot topic in recent literature. Occlusion is just a fancy way of saying that a hollow organ – in this case, veins – is closed or blocked. The occlusion of airways and other organs ought to be avoided during exercise, but venous occlusion may have value as an ergogenic aid.
There are a fair number of studies out there regarding the topic of restricted blood flow and its effects on hypertrophy and strength, but they investigate a far-reaching set of circumstances and hypothesize in many ways. This is all a good thing, and a part of a long-term scientific process, but sometimes with so much varied information we need a good review to put it all together for us. That’s exactly what researchers did in a study published recently in the Journal of Strength and Conditioning Research.
The process of occluding a vein is simpler than it might seem. In the studies reviewed the occlusion was created by simple tourniquets or pressurized cuffs. A tourniquet is a tight bandage that squeezes your veins, and a pressurized cuff is the same thing that is controllable by adding air pressure, like the cuff a doctor uses to check your blood pressure.
The amount of pressure used in venous occlusion is important. The blood flow restriction shouldn’t be so great as to cause arterial occlusion, which would be detrimental to the results. Arteries, which are pressurized by the heart, bring oxygenated blood to your muscles, whereas veins bring deoxygenated blood back from your muscles. It takes less pressure to block your veins than it does to block your arteries.
The result of blocking veins and not arteries is that blood pools in the muscles. This has an interesting effect. According to the researchers, there is universal agreement that when we add blood flow restriction to our weight training it yields improved strength and size. Of course, regular strength training does that too. The interesting thing here is that the results we usually get working with 60-100% of our one rep max actually happen with only 20-50% when we add venous occlusion.
The extent of the pressure to be used depends on the size of the person, but when using occlusion, stimuli as little as walking can yield size and strength gains. Pretty crazy. Not only that, but it seems to be effective on muscles on both sides of the occluding device. In other words, if you put a tourniquet around your arm near your armpit and do a bench press, your tricep and your pec may both benefit.
The reason occlusion works is unclear. From hormonal or neurological signaling, to increased muscle damage, it probably works on several levels, but we don’t know all the important details yet. In addition to being effective, the method also seems to be fairly safe. There are some possible deleterious side effects, but they do not seem substantial or common based on the research out there now.
So there you have it. Mild occlusion is safe and effective, and may be a useful adjunct to our progress.
1. Zachary Pope, et. al., “Exercise and Blood Flow Restriction,” Journal of Strength and Conditioning Research, 27(10), 2013.
Photo courtesy of Melody Schoenfeld.