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.
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.
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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.
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 part of 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.
The fatigue resulting from hypoxia leads to the recruitment of the larger, faster type II muscle fibers . These are the ones with the greatest potential for growth and are normally only recruited with heavier training. The muscle growth seen after exercise with hypoxia appears to come from an increased mechanical load on those muscle fibers .
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.
Vascular occlusion refers to the closure or blockage of a blood vessel. You might see it called KAATSU training, blood flow restriction training (BFR), tourniquet training or some other variation on the theme.
The idea is that you wrap a tourniquet (knee wraps seem to do the job just fine) around the top of your arms when you’re training biceps or triceps, or the top of the legs when you’re working quads or hamstrings.
Blood flows into the muscle, but can’t get out. This leads to the build-up of metabolites in the working muscle.
As a result, muscle fibers normally recruited later in the set are called into action sooner, which ultimately leads to those fibers (and your muscles) getting bigger.
Although it involves the use of very light weights, KAATSU training has been shown to trigger faster gains in muscle size compared to the same training routine done using heavier weights and without the use of a tourniquet .
This means you can train your arms and legs using very light weights, giving your joints a break from heavy lifting. Some people like to use BFR training to work around knee or elbow pain. I’ve also seen it used during post-surgical knee rehabilitation to maintain muscle size and knee function.
There was a lot of fuss about KAATSU training about 10 years ago, when a few studies 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 [2, 4].
However, much of the excitement died down when follow-up studies revealed that you could get better results with regular resistance training .
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.
If you do want to try BFR training, there are a few things to keep in mind.
From Dr Brad Schoenfeld:
“The goal should be to secure the wraps so that they’re snug on the limb but not to the point where there’s excessive discomfort at rest. On a scale from 1-10, pressure should be about a 7 or so.
“Position the wraps as high as possible on the limbs being trained. For the upper arms, they should be wrapped as high on the biceps as you can get. For the thighs, they should be wrapped just beneath the gluteal fold.
“You don’t want a tourniquet that’s too thick either. A couple of inches or so is about right, which is approximately the size of most knee wraps. From a practical standpoint, this means you should bind the wraps as closely over one another as possible so there’s maximum overlap.”
I should also point out that BFR training isn’t the only way to stimulate metabolic stress, and 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.
- 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) .
- Myo-Reps, a form of rest pause training developed by Norwegian trainer Borge Fagerli, is also a highly effective to create metabolic stress. If you Google “myo reps” you’ll find a bunch of articles on the subject explaining exactly how to do them.
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.
1. Nishimura A, Sugita M, Kato K, Fukuda A, Sudo A, Uchida A. (2010). Hypoxia increases muscle hypertrophy induced by resistance training. International Journal of Sports Physiology and Performance, 5, 497-508
2. Takarada Y, Nakamura Y, Aruga S, Onda T, Miyazaki S, Ishii N. (2000). Rapid increase in plasma growth hormone after low-intensity resistance exercise with vascular occlusion. Journal of Applied Physiology, 88, 61-65
3. Meyer RA. (2006). Does blood flow restriction enhance hypertrophic signaling in skeletal muscle? Journal of Applied Physiology, 100, 1443-1444
4. Takarada Y, Takazawa H, Sato Y, Takebayashi S, Tanaka Y, Ishii N. (2000). Effects of resistance exercise combined with moderate vascular occlusion on muscular function in humans. Journal of Applied Physiology, 88, 2097-2106
5. Yasuda T, Ogasawara R, Sakamaki M, Ozaki H, Sato Y, Abe T. (2011). Combined effects of low-intensity blood flow restriction training and high-intensity resistance training on muscle strength and size. European Journal of Applied Physiology, 111, 2525-2533
6. Takarada Y, Takazawa H, Ishii N. (2000). Applications of vascular occlusion diminish disuse atrophy of knee extensor muscles. Medicine and Science in Sports and Exercise, 32, 2035-2039
7. Tanimoto M, Ishii N. (2006). Effects of low-intensity resistance exercise with slow movement and tonic force generation on muscular function in young men. Journal of Applied Physiology, 100, 1150-1157
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