Resistance Training at Simulated Altitude – Part 2

In Part One of our blog on this topic, we reviewed the science behind resistance training with a hypoxic (low oxygen) stimulus – one that simulates altitude through a hypoxic chamber or mask system. While there had been some initial focus on blood flow restriction by occlusion, recent studies have presented a strong case for the potential benefits of doing resistance training in a full hypoxic environment. The aim of this follow-up blog is to outline a more practical-based approach to implementing a hypoxic resistance training program with the needs of athletes, players and coaches in mind. 

Benefits of hypoxic resistance training

We now know, based on the science to date (albeit limited),that resistance training with a hypoxic stimulus, where oxygen delivery to the muscle is reduced; results in selective recruitment of fast twitch glycolytic muscle fibres. The increased mechanical loading on these fast twitch muscle fibres under hypoxic conditions results in increased metabolic stress, resulting in:

 
· Increased muscle hypertrophy

· Increased muscle strength and strength endurance

· Greater anabolic response including growth hormone secretion

· Modified behaviour of fast twitch muscle fibres increasing their maximal power output and reducing their fatigability.

So what does this mean for an athlete or coach who may look to implement a hypoxic resistance training program?

Greater training stimulus

The most obvious benefit for any sportsperson to combine their resistance training program with a hypoxic stimulus is that it enhances the training stimulus and potentially maximises training adaptations. With enhanced fast twitch muscle fibre recruitment, one could theorize that greater motor unit activation occurs. Greater increases in muscle hypertrophy, strength and anabolic growth hormone response are reported to occur when doing resistance training in a hypoxic environment, than when carrying out the same work in normoxic (normal room oxygen) conditions (Kon et al 2010, Nishimura et al 2010). 

For a well-trained athlete or a weightlifter in an advanced stage of training, there would be potential benefits associated with implementing a phase of hypoxic resistance training. We would recommend a period of 4 weeks exercising at over 3000m altitude to achieve an optimum stimulus and sufficient time for training adaptations to occur. The ‘hypoxic dose’ can be monitored by wearing a pulse-oximeter where we recommend exercising at close to 80% SpO2. That would mean you are exercising with 20% less oxygen circulating in the arterial blood, which would undoubtedly make that work load more challenging, causing a host of adaptive responses. 

Most studies on hypertrophic, strength and growth hormone response achieved with hypoxic stimulus have been based on single joint movements or ones where a single muscle has been targetted by using blood flow resistance or occlusion training. One would presume, based on strength and conditioning principles, that greater overall gains would be achieved during multi-joint compound lifts such as squat or deadlift with the hypoxic stimulus, where more muscles and a greater number of motor units are recruited. A hypoxic chamber or using a hypoxic mask system allows multi-joint compound lifts to be done more efficiently than blood flow restriction or occlusion. 

Less load is required to achieve increase in muscle size and strength

It has been shown that loads as low as 20% 1 Rep Max with a hypoxic stimulus can achieve muscle hypertrophy and strength gains. This would be of major benefit to an injured athlete, an athlete who’s had injury reoccurrence or compromised in other ways and cannot lift heavier loads.

Take for example a field sport player who’s in the advanced rehabilitation phase after knee surgery and cannot squat with heavy loads. By exposing the player to a hypoxic environment in a chamber or using a hypoxic exercise mask system, he or she can lift lighter loads and achieve hypertrophic or strength gains. It has been suggested that similar hypertrophic gains appear to be achieved at 20-30% of 1 Rep max with hypoxic stimulus, as would be achieved normally with 60-70% of 1 Rep max. By avoiding muscle atrophy and de-conditioning during their rehabilitation phase, the hypoxic stimulus may help accelerate their return to play.

There may be a strong case for a highly trained athlete during an overload or indeed over-reaching phase that may be experiencing fatigue and may be advised to pull back from lifting high loads. The same would apply to an athlete or field sport player during in-season who may wish do maintenance loading to maintain strength and muscle function. A hypoxic resistance training phase may be implemented as a means to managing fatigue by allowing the same gains to be achieved with less resistance load and stress on the body. 

Change the behavior of fast twitch muscle fibres

Resistance training with a hypoxic stimulus appears to result in an early fatiguing of type I and premature recruitment of high threshold fast twitch type IIa muscle fibres. Improvements shown in both maximal power output and muscular endurance can be attributed theoretically due to the modified behaviour of those type IIa fibres improving their anaerobic potential making them operate more metabolically efficient. Through regular activation, type IIa muscle fibre become more readily accessible. Potentially, following a period of hypoxic training, an athlete could have have access to a broader population of fast twitch type IIa fibres through two mechanisms: (i) a decrease in type IIx fibres and (ii) increased habitual activation of type IIa fibres.  

Similar mechanisms to the improved repeated sprint ability performance in hypoxia by Faiss et al (2013) appear to be working in the case of resistance training. For endurance sports (marathon running), combat sports (boxing) and intermittent type field sports (rugby or GAA) these type IIa fibres become more fatigue resistant and behave with the same efficiency as their type I slow twitch counterparts. Hypoxic training also results in faster re-oxygenation of muscles resulting in faster re-synthesis of creatine phosphate stores and ATP repletion. This results in accelerated recovery between high intensity bouts of speed or power resulting in delayed onset of fatigue. Hypoxic training has developed into a very effective training modality for field sports and combat sports and one adopted by many teams and athletes. 

A period of 4 weeks, before which maximal speed and power has been developed, would be a suggested optimal period to maximise the potential to develop muscular endurance and repetitive power capacity during pre-season. The physiological demands of field sports where intermittent high intensity efforts are required for 70 minutes in a championship GAA match to 4 hours in a tennis match, would present a strong argument for such a training programme. The altered behaviour of fast twitch muscle fibres making them more efficient and fatigue resistant, coupled with the ability to refuel muscle ATP stores at a faster rate; would certainly increase work capacity and enhance field sport performance. 

As it now appears that hypoxic resistance training can improve maximal strength, it is also worth examining the potential effect hypoxic resistance training may play in the faster glycolytic type IIx fibres. These fibres have a high degree of fatigability resulting in a switch back to type IIa slower glycolytic fibres at high loads. We know that weightlifters (or other athletes in short power sports or events) have a greater ratio of type IIa fibres to type IIx. When a period of rest or tapering occurs (10-14 days) an ‘overshoot’ of type IIx fibres occur. This supercompensation shift would seem an ideal scenario going into competition where the potential for increased maximal strength or power could be achieved with a greater pool of type IIx available.

It has not been properly investigated but it could be suggested that hypoxic resistance training where increased mechanical and metabolic stress occurs on the type IIa fibres perhaps as a compensatory switch-back from type IIx fibre fatigue, could perhaps build greater reserve pool of type IIa for type IIx potential in short speed or power performance. If this were to be the case, it would provide a very effective training modality for sprinters or weightlifters. 

Conclusion

Despite the fact that this has been an under-researched topic, from what has been shown so far, it would seem that the hypoxic stimulus added to a resistance training program offers a new variable to achieve the specific training stimulus that is being targeted. Some athletes and players are already using hypoxic resistance training such as British Cycling and England Rugby League. Who will be next?

 

 

 

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