Written by Michael J. Rudolph, PH.D
05 September 2015

15NN115-DENVER

Will Denver be the New MECCA?

The Phil Heath Advantage: Research Shows Training at High Altitude Boosts Muscle Gains

 

 

When I first heard about lifting weights in a low-oxygen environment, a technique also known as “hypoxic training,” I thought it sounded risky and was probably just another trendy fad that would quickly go by the wayside. Of course, I had heard about the effectiveness of training at high altitude under low oxygen or hypoxic conditions to facilitate training for endurance athletes— but not for athletes that wanted to build significant muscle mass. It just didn’t make sense that hypoxic training would stimulate muscle growth. Well, wouldn't you know it, a cluster of recent scientific studies have clearly demonstrated that hypoxic training does, in fact, stimulate muscle growth. This exciting new research may usher in a completely novel approach toward resistance training, producing superior gains in muscle and strength.

 Does current Mr. Olympia champion Phil Heath have a competitive advantage living and training 1 mile high (5,000 feet above sea level) in Denver, Colorado?

  

Transient Hypoxia Creates an Anaerobic Environment, Leading to Greater Muscle Growth

 In order for a muscle cell to contract, it needs energy. Glucose is a primary source for cellular energy and when combined with oxygen during aerobic respiration, produces energy for the muscle cell. During hypoxic conditions, there is a low amount of oxygen and that inhibits aerobic respiration— leading the muscle cell to convert glucose into energy without oxygen by anaerobic respiration. Anaerobic respiration leads to an increase in lactic acid, which decreases the ability of the muscle cell to contract. Consequently, additional muscle cells must be activated in order to maintain muscular contraction. This additional muscle cell recruitment leads to larger muscles. In addition, the lack of oxygen during hypoxic training causes a preference for type II muscle fiber contraction due to that fiber’s greater ability for anaerobic respiration compared to oxidative, type I muscle fibers— which prefer aerobic respiration. Because the type II muscle fiber is the larger fiber type, its preferential stimulation over type I muscle fibers also generates greater muscle size and strength.

 

Hypoxia Dramatically Increases Growth Hormone and Testosterone Production

 Heavy weight training has been shown to stimulate growth hormone secretion, thus increasing muscle growth. For example, previous studies by Kraemer et al.1,2 showed that high-intensity resistance exercise triggers more than a 100-fold increase in the plasma concentration of growth hormone. However, a recent study by Takarada et al.3 revealed that low-intensity training under hypoxic conditions increased growth hormone secretion tremendously. In this study, six young male subjects performed 5 sets of leg extensions at 20 percent of their 1 repetition max (1RM) until failure with a short rest period of 30 seconds, under hypoxic conditions. The concentration of growth hormone increased up to 290 times higher than before exercise under hypoxic conditions. Interestingly, this level of growth hormone increase was almost twice as high as reported by Kraemer et al. in their high-intensity resistance exercise study under normal oxygen levels.

 In another study, Hwang et al.4 examined the effects hypoxia had on the production of testosterone. Male rats were treated with or without intermittent hypoxia for eight hours per day for four days, and had their testosterone levels measured. The level of testosterone in hypoxic rats was significantly higher than in normal rats. Furthermore, researchers also showed that rats under hypoxic conditions fed the testosterone precursor androstenedione had significantly higher testosterone production than normal mice. These findings indicate that exercise combined with hypoxia can provoke strong endocrine responses— stimulating the production of growth hormone and testosterone, facilitating muscle growth.

 

Hypoxia Stimulates mTOR Activity, Leading to Muscle Growth

 Activation of the important enzyme mTOR stimulates muscle protein synthesis and inhibits muscle protein breakdown, therefore increasing muscle mass and strength. A study by Fujita et al.5 established a link between hypoxia and mTOR activation leading to muscle protein synthesis and muscle cell growth. In this study, six male subjects performed 4 sets of 15 repetitions of leg extensions at 20 percent of their 1RM with 30-second rest intervals, with and without hypoxic conditions. Remarkably, the hypoxic group showed an increase in mTOR activity that was three times larger than the group exercising under normal oxygen levels. This study also showed that resistance training under hypoxic conditions led to an increase in IGF-1 levels that were comparable to those seen in other studies where the subjects performed high-intensity resistance exercise. This substantial increase in IGF-1 levels may directly activate mTOR and muscle protein synthesis.

 

Low-intensity Resistance Training Combined With Hypoxia Mimics High-intensity Resistance Training

 Under normal conditions, type I muscle fibers are recruited first and as the exercise intensity increases, the larger type II muscle fibers are activated as needed. This effect is one of the main reasons why high-intensity training promotes muscle growth. However, a recent study by Takarada et al. supports the extraordinarily unexpected feature of hypoxic training— that type II muscle fibers are recruited, even though the training intensity is low. In this study, 24 women performed low-intensity (30 percent of 1RM) triceps extensions until failure. Some of the subjects performed the exercise with their arms in a blood pressure cuff, occluding oxygen from the muscle and creating hypoxia in the arm. In addition, another group performed high-intensity resistance exercise (triceps extensions at 80 percent of their 1RM), again until failure. The group performing low-intensity exercise with hypoxia had similar increases in strength and muscle size to the high-intensity group. The results suggest that resistance exercise at low intensity is effective in inducing muscular growth and strength when combined with a hypoxic environment.

 Perhaps low-intensity training combined with hypoxia could be used by the bodybuilder or athlete as an additional technique for maximizing muscle growth, while reducing injury potential. However, hypoxic training via muscle occlusion seems like a crude and risky way to induce hypoxia. Moreover, this type of hypoxic training would only be possible with the extremities. Another group, Nishimura et al.,6 addressed this issue by investigating the effect of hypoxic training on muscle growth in a room with lower than normal oxygen levels, thus imposing hypoxia upon the entire body. Interestingly, they found a similarly positive influence on muscle growth and strength. This finding suggests that hypoxic environments created by controlling the concentration of oxygen in the air, instead of the more crude technique of muscle occlusion, is equally effective in producing muscle growth— perhaps making hypoxic training more appetizing for the bodybuilder and athlete as an innovative tactic augmenting muscle size.

 

CONCLUSION

In conclusion, hypoxia in conjunction with resistance exercise, even at low intensity, evidently stimulates muscle growth and strength through a variety of mechanisms such as the preferred contraction of type II muscle fibers and the increasing of anabolic hormone levels as well as protein synthesis. Yet more insight is necessary in order to convert this rudimentary scientific information into specific workout protocols that are safe and effective for the bodybuilder and athlete.

 

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