If you train in a gym where the oxygen concentration has been lowered to 16%, your muscles will grow 4-6 times faster than normal.
Those are the intriguing findings from a group of Japanese researchers, which I came across just the other day.
I’ll explain more about the study, how muscles grow and what the take home message is for you in just a moment.
First, here’s a quick look at how it was set up:
A group of 14 untrained male university students was assigned to either a hypoxia (low oxygen) or normoxia (normal oxygen) group. The oxygen content in the low oxygen room was set at 16% (normal oxygen levels are 21%).
The men did one exercise for the biceps and one exercise for the triceps in the low-oxygen room. The control group did the same exercises, but in a normally oxygenated room. Both groups trained only one arm.
Each training session consisted of four sets of 10 repetitions for each exercise, with one minute of rest between sets. The men trained twice a week for six weeks.
Six-fold faster gains in muscle size
The figure below shows the change in the size of the men’s biceps after six weeks of training. As you can see, the percentage change in cross-sectional area (CSA) in the hypoxia group (Hyp-Ex) was a lot bigger than it was in the normoxia (Norm-Ex) group.
In fact, the hypoxia group added muscle FOUR times faster to their triceps and SIX times faster to their biceps.
Differences between the two groups in terms of strength gains, while not statistically significant, were also greater in the hypoxia group.
Muscle strength following the triceps extension and arm curl in the hypoxia group increased by 71 and 62%, respectively, and in the normal group by 56 and 39%, respectively.
How do muscles grow?
Probably the most important trigger for muscle growth is tension overload — lifting more weight over time. But while lifting progressively heavier weights is one route to bigger muscles, it’s only half the story.
There’s a second stimulus for muscle growth, which you might see referred to as accumulating byproducts of fatigue, metabolite accumulation, metabolic fatigue (or some other variation on the theme) depending on who you listen to.
Studies that have looked at vascular occlusion suggest that the metabolic fatigue resulting from hypoxia leads to the recruitment of the larger, faster type II muscle fibers.
The muscle growth seen after exercise with hypoxia appears to come from an increased mechanical load on those muscle fibers. These are the ones with the greatest potential for growth, and are normally only recruited with heavier training.
Should you demand that your local gym install a hypoxic chamber?
I don’t think so.
For one, these are the results from just one study. As I mentioned in The Sherlock Holmes Guide to Separating Fitness Fact from Fiction, one study is not really news. It’s only when you get several studies showing the same thing, ideally from different research groups, that it’s worth sitting up and paying attention.
Researchers have actually been studying the effects of hypoxia on muscle growth for some time. But rather than use a hypoxic chamber, they’ve employed a method known as vascular occlusion, which refers to the closure or blockage of a blood vessel.
Known as KAATSU training in Japan, vascular occlusion involves applying a tourniquet to the part of the body you’re training. Wearing a tourniquet around your upper arms, for example, is going to restrict the flow of blood to and from the biceps and triceps.
Although it involves the use of very light weights (30-50% of your 1-RM), KAATSU training has been shown to trigger faster gains in muscle size compared to the same training routine done without the use of a tourniquet.
There was a lot of fuss about KAATSU training about 10 years ago, when a few studies (e.g. here and here) showed a marked increase in growth hormone levels, an elevation of electrical activity in the working muscles as well as an increase in muscle growth.
However, much of the excitement died down when follow-up studies (such as this one and this one) revealed that you could get better results with regular strength training, but simply using heavier (75% of your 1-RM) weights.
So while vascular occlusion might be useful for anyone who can’t lift heavy weights, such as people recovering from injury or the elderly, or as a way to minimize disuse atrophy, it has a limited application for everyone else.
The good news is that you don’t need to train in an oxygen room or tie a tourniquet around your arms in order to build muscle faster.
Instead, it’s possible to stimulate metabolic fatigue simply by altering a few of the variables in your training program. For example:
- You could incorporate a back-off set at the end of a series of heavy sets. To do a back-off set, all you do is crank out an additional set of 10-30 reps with a lighter weight.
- You can also use a popular bodybuilding method called drop sets (sometimes known as descending sets or stripping) to create a large amount of fatigue in a relatively short period of time. The time-saving benefits of drop sets are why they’re used a lot in Maximum Muscle Turbo.
- Extreme stretching has also been shown to reduce blood flow to certain muscles, and may have a similar effect to vascular occlusion. This might explain why it’s often promoted as a way to accelerate muscle growth. I can’t say I’ve ever been convinced by the various “fascial stretching remodels the connective tissue and gives the muscle extra space to grow” claims that seem to pop up every few years.
- Even just using a light weight (50% 1-RM), slowing down your reps (3 seconds for eccentric and concentric actions, 1-second pause, and no relaxing phase) and trying to maintain “constant tension” on the muscles has been shown to lower muscle oxygen levels, as well as building muscle just as well as heavier weights (80% 1-RM) and faster lifting speeds (1 second for concentric and eccentric actions, 1 second for relaxing).
The effect of metabolic fatigue on muscle growth is one of the reasons that Muscle Evo incorporates two distinct training protocols – a Tension Overload Protocol (TOP) and a Metabolic Fatigue Protocol (MFP). You get to attack muscle growth from both angles as well as giving your joints a break from constant heavy training.
If you want to build muscle and get strong, lifting heavy weights should still be the main focus of your training. But the addition of some kind of “fatigue stimulus” to a program that already includes some heavier training is a great way to get faster results from the time you spend in the gym.
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