Sport and Exercise Medicine: The UK trainee perspective (A twice-monthly series on the BJSM blog)
By Dr Stefan Kluzek and Rachel Turner
Normobaric hypoxic training environments allow controlled decrements in the amount of oxygen available whilst an athlete exercises or rests. Many of our elite athletes use hypoxic tents or masks as standard. As a result, researchers continue to research new mechanisms to explain the potential multi-systemic effects of hypoxic exposure.
From a practical point of view how much do we know or should we know about the implementation of hypoxic training?
I asked Rachel Turner a few questions about new hypoxic training models and practical aspects of implementation from a medical perspective. A postgraduate researcher from Limerick University, she was previously a member of the specialist team at the Altitude Centre UK. Her current work is predominantly focused on the optimization of hypoxic training practices in elite sport. Rachel is based at the newly established National Altitude Training Centre (NATC), a residential normobaric hypoxic facility.
Q: Rachel, what do you recommend “Live High-Train Low” or “Live High-Train High”? Does it really make a significant difference and if so in what respect?
A: I would argue that LH-TH is actually considered the ‘old’ altitude training paradigm- subsequently considered suboptimal due to the reduction in work intensity capable at certain terrestrial altitudes, potential immunological suppression and reduction in muscle mass reported with longitudinal high altitude exposure. As a consequence LH-TL was introduced in order to maximize altitude exposure in order to target any potential hematological benefit, whilst allowing training to progress as normal at sea level (or low level altitude), where the required high intensity can be maintained.
A ‘new’ training paradigm that is currently under scrutiny is entitled: Living High-Training Low and High, interspersed (LHTLHi). LHTLHi is a form of amalgamation of the two aforementioned hypoxic training paradigms- thought to be a method that may maximize both hematological and any further potential intramuscular adaptation through the addition of intermittent hypoxic training (IHT). Future research will aim to develop this new concept and specifically validate the incorporation of IHT, both for endurance and team sport athletes.
Q: Can one get an altitude sickness by spending too much time in artificial hypoxic environment?
A: Acute Mountain Sickness (AMS) can be evident in simulated altitude environments (both in normobaric hypoxia and normoxic hypobaria. Similarly to incidence at high terrestrial altitude, AMS symptomatology is usually expressed when the altitude ascent profiles utilized are too rapid and the incremental progression in altitude is either missing or the steps are too severe. The hypobaric nature of a high altitude environment (> 4000m) has also been reported to result in more severe AMS, which presents far sooner than when a similar PiO2 created in a normobaric hypoxic environment. The issue that we face more regularly within athlete populations is a false view that ‘the higher the altitude the better’- each individual program should be considered separately and athletes educated to the fact that optimisation rather than maximisation of a hypoxic stimulus is the way forward.
Q: A lot of our athletes have started to sleep in hypoxic tents. Can this be done safely without supervision?
A: In my opinion in order to achieve successful incorporation of an altitude sleep program, daily feedback and monitoring of both relevant physiological and training parameters is highly recommended. Gone are the days where a ‘suck it and see’ approach is viable. Support and guidance as to how and when to progress the altitude ascent profile, plus altitude training incorporation throughout a season/macro-cycle is just as crucial when incorporating hypoxic training, as any other component to a successful athlete’s program. Hypoxia is simply a form of physiological stress which may be utilised as a complement to existing training programs in order to alternate training stimulus and potentially enhance haematological indices.
Q: From your experience, what is the first sign of athlete overusing hypoxia? What are the recommendations for hypoxic exposure prior to major tournaments?
A: There is large individual variation in physiological hypoxic response- both related to the mode of training used, the severity of hypoxic stimulus and individual hypoxic tolerance and experience. Therefore, from a research perspective without repeatedly, individually testing different hypoxia ‘exit strategies’ in controlled, standardised environments, we are unable to prescribe an exact hypoxic dose or dictate a standard exit time prior to an event. However the recent consensus, taken from repeated practice in the applied field, is either to exit the hypoxic environment 2-3 days prior or ~2 weeks prior the planned event.
In my experience perhaps not the first, but definitely the most influential sign that an athlete is struggling with hypoxic dose during a LH-TL paradigm is a progressive worsening in sleep quality and the prevalence and severity of sleep disturbance; often related to an increase in reported ‘unexplained’ fatigue and lethargy. In extreme circumstances athletes who tend to ‘over do’ or ‘abuse’ the use of hypoxic training equipment can present with incredibly low levels of ferritin and display associated symptoms of anemia. That said, both of these conditions could be exhibited in athletes with heavy training loads- with no altitude exposure.
Dr Stefan Kluzek is a registrar in Sports and Exercise Medicine in the Oxford Deanery. He has special interests in human adaptive physiology.
Rachel Turner is a postgraduate student in Hypoxia and Performance Physiology from the University of Limerick.
Dr James Thing co-ordinates “Sport and Exercise Medicine: The UK trainee perspective” — a twice-monthly blog.