By Colin Griffin
This is a topic that has interested me for some time. Having experienced resistance training on altitude training camps in places such as Font Romeu (1800m), Sierra Nevada (2350m) and Mexico (2200m) with some perceived benefits, I have been always curious as to what physiological adaptations actually occur when doing resistance training at altitude. With my background as an athlete, altitude training and in more recent years as a strength and conditioning student, it has led me to explore this whole area further.
Recently published papers and discussions around blood flow restriction using 'vascular occlusion' combined with resistance training, and the local hypoxic environment created increasing muscle hypertrophy and strength, as well as growth hormone response due to the increased metabolic stress; has raised a legitimate argument for the same benefits experienced in systemic hypoxic conditions such as a chamber or hypoxic mask system. I've had some constructive discussions too with Dr Andy Franklyn-Miller, Sports Medicine Physician at the Santry Sports Surgery Clinic. Andy reviewed two papers on this topic recently in his weekly research review - one on muscle hypertrophy by Shoenfeld (2013) and another on the growth hormone response by Kon et al (2010), with the latter paper suggesting an increased anabolic hormone response due to increased metabolic stress from doing resistance training in hypoxic conditions.
In a study by Nishimura et al (2010), it was suggested that resistance training under hypoxic conditions improves muscle strength and induces muscle hypertrophy faster than under normoxic conditions. Vascular occlusion was used here, with a resistance load of 70% 1RM for 4 sets of 10 reps. It postulated that "muscle hypertrophy can be more efficiently induced by placing the entire body in a hypoxic environment to induce muscle hypoxia followed by resistance training".
A study by Manimmanakorn et al (2013) looked at the effects of both vascular occlusion and systemic hypoxia on well-trained female athletes and found that a 5 week program of low load resistance exercise (20% 1 Rep Max) in either vascular occlusion or hypoxia (using hypoxic mask system) improved 3 second and 30 second maximal voluntary contraction, dynamic muscle endurance, as well as muscle hypertrophy. The results showed similarities between the vascular occlusion and systemic hypoxia groups over the control group. What was also interesting to note was that the hypoxic group worked at a blood oxygen saturation (SpO2) of 80%, a level we recommend our clients work at when doing hypoxic high intensity exercise. It is now suggested that the positive adaptations from vascular occlusion training are as a result of reduced oxygen availability as opposed to restricted blood flow (Katayama et al. 2010).
Resistance training under hypoxic conditions appear to result in an early fatiguing of slow-twitch oxygen-dependent muscle fibres, requiring premature recruitment of larger fast twitch type II fibres to maintain a given force, which would increase the mechanical loading on these type II fibres (Manini et al. 2009). The increased mechanical loading of these glycolytic fibres results in greater accumulation of lactic acid, inorganic phosphate as well as reduced muscle PH. This increased metabolic stress induces adaptations that include increased hypertrophic response and strength gains as well as an increase in growth hormone response. We know that training under hypoxic conditions increases capillarization and number of mitochondria thus improving muscle buffering (Gore et al 2001). It is suggested that when exercising in normoxic (sea-level) conditions the adaptations that occur during hypoxic training results in less motor units recruited in order to perform the same workload resulting in enhanced glycogen storage - an obvious benefit for endurance athletes, or field sport players where repeated intermittent bouts of short speed or power are required. That along with increased muscle strength and size would surely result in performance gains if implemented cleverly into a training program in a periodized manner?
It has been shown that low load resistance training 20-30% 1 Rep Max with the muscles under hypoxic conditions with vascular occlusion induces muscle hypertrophy and strength gains on par with heavy load resistance training (Shoenfeld et al 2013). Some would question whether low load resistance training, even with hypertrophy gains, is functional for elite athletes; although in an article on T-Nation Shoenfeld argues the case for 'mixing the intensity' and not to neglect slow twitch type 1 fibres. One obvious case for implementing low load resistance training with a hypoxic stimulus would be for individuals who may not be able to lift higher loads in various circumstances. These would included injured athletes during their rehabilitation phase, elderly people or those suffering from chronic pain syndromes or obesity and not able to tolerate high loads or joint stress. By adopting this method, the hypoxic stimulus with low load resistance may prevent muscle wastage, maintain or improve muscle tone and metabolic conditioning. In the case of the injured athlete or player it may provide a effective means of progressing them back up to higher resistance loads sooner. In the case of middle-aged or elderly population, one study by Akasaki et al. (2013) that emerged this week suggests that restoration of type II muscle fibre and muscle mass may offset metabolic dysfunction with aging!
High load resistance training with a hypoxic stimulus appears to induce a greater hypertrophic response and strength gains and neuromuscular function in well trained elite athletes. It also appears to trigger a greater anabolic response including increased growth hormone levels. These hypoxic resistance training adaptations may drive performance gains for athletes or players if implemented during key training phases in the training and pre-competition season. In general, if an athlete or indeed a weightlifter or bodybuilder feel that they are plateauing in the gym, an added hypoxic stimulus for a period of time may help break through that plateau. Vascular occlusion, while cheap and easy to use, has its limitations where a person is restricted to single joint movements as opposed to being able to do multi-joint movements freely in a hypoxic chamber or mask system. There is perhaps less risk of rupturing a blood vessel too!
Like any altitude training program, in order to achieve some meaningful adaptations and performance gains, a period of 4 weeks would be recommended with a minimum 2-3 hypoxic sessions per week. This can be done using a mask system with air supplied from a hypoxic generator, or in a simulated altitude chamber.
It must be acknowledged that research into resistance training combined with a hypoxic stimulus is in its infancy and we may be pushing the boundaries of what research to date permits, but there appears to be sufficient evidence to suggest that this method may improve muscular performance in the gym, and in the case of athletes; transfer into performance gains on the track, road or playing field. It may also have other beneficial uses to non-sporting population too.
For more information visit www.altiudecentre.ie