Sleep is for winners

In addition to being able to squeeze in a few extra miles of running, one of the biggest changes that I was able to make in my training regimen when I finished my PhD and became a full-time athlete was getting a lot more sleep. Endurance athletes push their bodies to the limit when training and preparing for competitions, and it is widely accepted in the running community that getting enough rest is critical to let your body recover and adapt after hard workouts so that the training can have the desired effect and lead to improved performances. Additionally, getting enough sleep is associated with good health in the general population and government organisations (e.g. the NHS in the UK and CDC in the US) typically offer advice on improving sleep habits in order to get sufficient amounts. I can't know exactly how much of an impact the extra sleep had on my running, but I definitely improved my performances over the next 2 years and I also very rarely found myself missing training sessions due to illness. Recently I haven't been managing to get quite as much sleep as usual, and I believe that this was probably a contributing factor to the sinus infection which led to me dropping out halfway round the NYC Half Marathon last month. In addition to less sleep, I was also exposed to more potential pathogens than normal as I was commuting on public transport to a temporary work placement. I'm no longer working, have been trying to make sure that I get more sleep, and thankfully seem to have returned to full health again.

Following this recent experience, I decided that I would like to know a little bit more about the effects of sleep deprivation - both on our abilities to train and perform optimally in sports, and also on our general health. I have to admit that this isn't something that I had given a great deal of thought to in the past, mainly because the requirement for sleep seemed too obvious to justify spending much time thinking about the reasons behind it. In a similar way to the feelings of hunger which remind us that eating is crucial to our health, there is a homeostatic drive to sleep which becomes greater the longer that we stay awake - i.e. we feel increasingly tired. The importance of sleep is further demonstrated by the fact that over time this homeostatic drive becomes strong enough to initiate brief 'microsleeps' even when a person is active¹ and sleep at that moment may in fact be dangerous, as in the case of drivers falling asleep at the wheel. However, although there are numerous scientific articles which demonstrate the depth of research carried out in the field (and at least one journal dedicated entirely to sleep), there currently does not seem to be a definitive answer to the question of why we sleep. What is clear is that this research has created an ever-growing body of evidence which indicates that sleep deprivation plays a role in a multitude of health issues.

One side effect of sleep deprivation, which I had already heard about, is an increased risk of obesity and diabetes². There is in fact a bidirectional relationship between lack of sleep and these diseases: sleep deprivation can lead to metabolic and hormonal changes which cause insulin resistance and increases in appetite, but pyschological factors and anatomical abnormalities (e.g, sleep apnea linked to excess weight) in diabetic and/or obese people can then interfere with sleep quality and lead to a worsening of health problems. Although weight gain is not usually something that an athlete running 100+ miles a week has to worry about, probably of greater interest to the endurance athlete are the immune effects of sleep deprivation which are associated with an increased risk of insulin resistance and also cardiovascular disease. Results vary between different studies, but it is generally found that sleep deprivation leads to an increase in the circulating numbers of blood cells involved in inflammatory immune responses, as well as raised levels of inflammatory signalling molecules (cytokines)³. This raised inflammatory state in subjects getting inadequate levels of sleep has the potential to affect sporting performance, and is one reason why sleep should be a high priority for all athletes.

Increased levels of inflammatory cytokines such as interleukin-6 (IL-6) are hypothesised to play a role in the development of overtraining syndrome - unexplained fatigue and underperformance in athletes during training periods⁴. This underperformance, and the related but less severe condition referred to as overreaching, generally occur as a result of heavy training volumes without sufficient rest and recovery. When the stress of heavy training is amplified by additional stress factors, such as the pressures of major competitions or a lack of adequate sleep, an athlete's training load is more likely to result in the development of symptoms of overreaching. Although the increased inflammatory immune response associated with sleep deprivation is likely to be one component involved in development of this syndrome, many other factors are thought to play a role as well. In fact, there is also evidence for a role of immune suppression or modulation in the development of fatigue⁵. This actually highlights another method for sleep deprivation to lead to overtraining syndrome, because in addition to a general state of increased inflammation a lack of sleep is also associated with disrupting the the balance of protective immune responses. The seemingly conflicting affects of reduced sleep are in part due to the fact that the sleeping period is split into different stages, during which different biological processes occur. The early stage of sleep is actually associated with induction of protective inflammatory immunity, which is then dampened down in later sleep stages prior to waking⁶. Disruption of sleep can therefore impede the generation of protective targeted immune responses, while simultaneously causing additional health problems through the generation of widespread non-specific inflammation.

The importance of a non-disrupted sleep cycle for the initiation of protective inflammatory immune responses takes us back to the idea that adequate sleep is desirable to help prevent athletes from missing training and races due to illness. Experimental evidence for an impact of sleep on the development of immunity has been demonstrated in studies that have found an association between sleep after vaccination and the generation of a protective immune response ^7,8. Although more research does need to be carried out, there is definitely evidence to suggest that getting sufficient sleep can improve our bodies' abilities to fight off infections and remain healthy. Indeed, the International Society of Exercise and Immunology mentions sleep in a list of 'practical guidelines for prevention of infections among athletes':

• Check athletes are updated on all vaccines needed at home and for foreign countries should they travel abroad for training and competition
• Minimise contacts with infected/sick people, young children, animals, and potentially contaminated objects. 
• Keep at a distance from people who are coughing, sneezing, or have a 'runny nose'; and, when appropriate, wear or ask them to wear a disposable mask.
• Wash hands regularly, before meals, and after direct contact with potentially contagious people, animals, blood, secretions, public places, and bathrooms. Carry alcohol-based gel with you where lavatories are not available or not clean enough.
• Use disposable paper towels and limit hand to nose/mouth contact when suffering from upper respiratory tract or gastrointestinal symptoms.
• Do not share drinking bottles, cups, towels, etc.
• While competing or training abroad, prefer cold beverage from sealed bottles, avoid crude vegetables, and meat. Wash and peel fruits before eating.
• Quickly isolate a team member with infection symptoms and move out his/her roomate.
• Protect airways from being directly exposed to very cold and dry air during strenuous exercise, by using a face mask.
• Ensure adequate levels of carbohydrate intake before and during strenuous or prolonged exercise in order to limit the extent and severity of the exercise-induced immunosuppression phase.
• Wear proper out-door clothing and avoid getting cold and wet after exercise.
• Get at least 7 hours sleep per night.
• Avoid crash dieting and rapid weight loss.
• Wear flip-flop or thongs when going to the showers, swimming pool and locker rooms in order to avoid dermatological diseases.
• Keep other life stresses to a minimum.

(Taken from Walsh et al. Position Statement Part two: Maintaining immune health. Exercise Immunology Review. 17: 64-103, 2011).

As can be seen from the length of the above list, sleep is only one of a large number of factors that can impact the immune health of athletes. However, it is also one aspect of training that is often quickly neglected due to other pressures and commitments. Most people want/need to work and have some kind of social life outside of sport, but if you're serious about achieving your athletic targets then sometimes you might need to say no to that Happy Hour drink after work, drag yourself away from Facebook/Twitter and tuck yourself into bed an hour or two earlier!

¹Poudel et al. Losing the struggle to stay awake: Divergent thalamic and cortical activity during microsleeps. Human Brain Mapping. 2012 Sep 24 (Epub ahead of print).
²Lucassen et al. Interacting epidemics? Sleep curtailment, insulin resistance, and obesity. Annals of the New York Academy of Sciences. 1264(1): 110–134, 2012.
³Mullington et al. Sleep Loss and Inflammation. Best Practice & Research: Clinical Endocrinology & Metabolism. 24(5): 775-784, 2013.
⁴Kreher and Schwartz Overtraining Syndrome: A Practical Guide. Sports Health. 4(2): 128-138, 2012.
⁵Silverman et al. Neuroendocrine and Immune Contributors to Fatigue. PM&R. 2(5): 338-346, 2010.
⁶Besedovsky et al. Sleep and Immune Function. Pflugers Archiv. 463(1): 121-137, 2012.
⁷Lange et al. Sleep after Vaccination Boosts Immunological Memory. Journal of Immunology. 187(1):283-90, 2011.
⁸Prather et al. Sleep and Antibody Response to Hepatitis B Vaccination. Sleep. 35(8): 1063–1069, 2012.

A healthy addiction to avocados

Along with making sure that you get enough rest and recovery, one of the best ways to help ensure that you get the most benefit from the hard work of your training (while also staying fit and healthy) is by maintaining a healthy and nutritious diet. Eating and drinking the right things means that you can be better fuelled up and prepared for your workouts, and that your body can repair itself and become stronger as a result of the training. Carbohydrate and protein are very important for the fuelling and repair processes, but a certain amount of fat is also critical for a healthy endurance athlete's diet. Gram for gram, fat contains twice the calories of carbohydrates and can therefore help to ensure that an adequate amount of energy is taken on board during periods of high volume training. The best types of fat to consume are unsaturated fats, as found in nuts, seeds, vegetable oils, and fish. These contain essential fatty acids, which our bodies need to stay healthy and which they can't manufacture.
I eat at least a portion of nuts every day, but another of my favourite sources of 'good' fat is avocados. I'm always experimenting and looking out for ideas for different ways to use avocados, and was particularly excited a few months ago when I discovered this recipe for rather tasty avocado truffles. Recently, a glut caused by some over-enthusiastic avocado purchasing led to me investigating the addition of avocados to my post-workout stack of breakfast pancake. They got the thumbs up from my husband, so I've put the recipe below for anyone who fancies giving them a try.

Avocado Banana Pancakes

 120g wholemeal flour
1tsp baking soda
1/4tsp baking powder
1 small avocado (the flesh of mine weighed 90g)
1 small banana (mine weighed 110g peeled)
Juice of half an orange
200mL milk
1 egg
50g yoghurt

• In a large bowl, mix together flour, baking soda and baking powder.
• In another bowl, mash together the avocado and banana into a purée.
• Add orange juice, milk, egg, and yoghurt to the avocado/banana purée and beat together with a fork.
• Add the wet ingredients to the dry, and stir until combined. Depending on how thin you like your pancakes, you may wish to add a little more milk at this point.
• Heat a large flat-based frying pan/griddle on medium and brush with a little bit of oil.
• Drop large spoonfuls of batter onto the preheated pan and cook until bubbles appear on the surface. Flip pancakes and cook other side until browned.
• Transfer pancakes to a plate and keep in a warm oven while you cook up the rest of the batter.
• Serve with fresh fruit/honey/syrup/yoghurt.

Is running really good for your health? (An immunologist's perspective)

There seems to be a general acceptance in the running community that we will spend a certain amount of time suffering with injuries, and this is particularly true of marathoners pushing themselves through week after week of high mileage and intensive training. There are a number of things that can be done to minimise injury risk, including the use of adequate rest and nutrition strategies, general strengthening work and physiotherapy/soft tissue treatment. However, many runners will still find themselves injured at some point in the season. Or at the very least, resorting to cross-training for a few days in order to prevent a minor 'niggle' from progressing into a full-blown injury. This has often led to conversations between myself and fellow athletes in which we jokingly wonder why we put our bodies through all of the trauma, which is a question that my knees in particular would like to know the answer to as they seem to have born the brunt of most of my marathon training cycles!

Setting the issue of injuries aside, the general opinion of running and other forms of exercise is in terms of a positive impact on health. This is a logical viewpoint to take, as are the recommendations that organisations such as the NHS and CDC give for regular physical activity in order to improve general health and well-being. The picture changes somewhat if we move from considering a moderate level of exercise undertaken with the aim of staying fit and healthy, and into the world of elite endurance athletes pushing their bodies to the limit in pursuit of their perfect performances. My own experiences in the athletics world have caused me to associate high training volumes with an increased incidence of illness, and I personally seem particularly sensitive to developing a sore throat as I approach the end of a hard training block, or even after a tough race (particularly in cold weather). I am not alone in having developed this perception of the side-effects of intense training, and several reviews of the subject (including the 2011 Exercise Immunology Review Position Statement¹) note that athletes and coaches generally believe that there is an increase in upper respiratory tract infections (URTI) associated with intensive exercise.

Having spent several years studying for a PhD in the field of immunology, I could come up with a reasonably educated guess about some of the potential immunological explanations for a link between hard training and increased vulnerability to infections. However, I have also occasionally wondered how many of my own symptoms were really signs of infection, and to what degree they  were due to running-related allergy and other inflammatory effects. Recently, after finally taking the plunge and beginning to carry out some research on a subject with which I should probably already be much more familiar, it was comforting to discover that even among experts there is a degree of uncertainty about the level of URTI in athletes versus non-infection-related Upper Respiratory Symptoms (URS). A large part of this uncertainty is due to a lack of investigation into the causes of symptoms reported by athletes, of which sore throats are the most common¹. There is a greater amount of published scientific literature concerning the more general effects that endurance training has on the functioning of the immune system, which is likely to have an impact on susceptibility to disease. So much literature, in fact, that these effects will have to be the subject of future blog posts.

Regardless of whether the URS experienced by athletes are caused by infection or other inflammatory stimuli, evidence from several studies does indicate that symptoms are more prevalent in endurance athletes during high intensity training or competition². Further research needs to be carried out to determine the level of any impact that URS have on an athlete's performance in training and racing, in order to gain a better understanding of any potential negative consequences from this side-effect of extended intensive training.

You'll be pleased to know that there's no need to hang up your trainers just yet, well not for your immune system's sake anyway. In addition to the well-publicised general health benefits of regular, moderate, exercise, there is  also evidence of a positive impact on the immune system and possible reduction in URTIs (more on this in future posts). These findings have led to  the hypothesis of a J-shaped relationship between exercise and upper respiratory infection³:

As with so many of my favourite things in life, it seems that moderation is also the key to getting the maximal health benefits from exercise. I don't think I'll be letting that stop me from running a few more marathons in the future though (or occasionally having that extra glass of red wine and piece of dark chocolate)!

¹ Walsh, N et al. Position Statement Part one: Immune function and exercise. Exercise Immunology Review 17: 6-63, 2011.
² Shephard, R Overview of the epidemiology of exercise immunology. Immunology and Cell Biology 78: 485-495, 2000.
³ Nieman, D Exercise, infection, and immunity. International Journal of Sports Medicine. 15: S131-141, 1994.

Chopping up tonsils

I have been thinking about writing a blog for some time, after all there are only so many hours of the day that can be spent running and baking - particularly as I have chosen not to train for any marathons this spring. The only problem has been deciding how to get started and what to write about. You wouldn't think that would have been such a difficult problem for an Olympic marathon runner with an immunology PhD, but in the end I got the necessary inspiration following a conversation with one of my pool-running friends. We spoke briefly about illness and runners, and I mentioned that I thought it was common for people to pick up infections after running a marathon as the stress of the race lowered their immunity. As I was walking home from the pool I realised that I had never made much of an effort to combine my two interests, and did not really know much about the specifics of the immunological effects of endurance running. A brief search on PubMed and Google revealed that there is actually a society dedicated to exercise and immunology (The International Society of Exercise and Immunology), and their journal seemed like it would provide perfect reading material to inspire my first blog posts.

It turns out that there is rather a lot of reading to be done on the subject of exercise and immunity, and so I'll be saving that for my next post and for now I'll just stick with plain old immunology. I have been involved in a few media interviews since becoming an international athlete, and I have occasionally been asked what exactly my PhD was about. Unfortunately, I have found that condensing over 3 years of scientific research into a few sentences that are understandable by a non-scientist is not an easy job. My default response has therefore been to jokingly say that I pretty much spent my time chopping up human tonsils, and then to add that I was working in a meningitis research lab. That seemed to keep most interviewers happy, but I think that it's now time for me to actually make a real attempt at explaining my PhD for people without a background in biology.

My PhD research was focused on one specific cell type, called dendritic cells, which play a key role in controlling the way our immune system responds to encounters with both harmful and non-harmful foreign material. Dendritic cells are often referred to as the 'sentinels' of the immune system, as their role is essentially to patrol their local environment and assess it for potential danger. The cells constantly sample the material surrounding them, and have receptors which are able to detect the presence of material including components from disease-causing organisms. If a dendritic cell discovers a harmful presence, it alerts another type of immune system cell called a T cell. The T cells then release a variety of signalling factors, which initiate the appropriate immune response to protect against the threatened infection. My research examined how dendritic cells responded to the presence of the Neisseria meningitidis bacteria (one of the leading causes of bacterial meningitis), and how they subsequently interacted with and directed the response of the T cells.

Dendritic cells (DC) detect the presence of potential danger and alert T cells, which then direct the immune system's response.

So why all of the gory chopping up of tonsils? The reason is that the initial site of colonisation by N. meningitidis is in the back of the throat or nose, and the immune tissue closest to this area is the tonsils. This means that the dendritic cells in the tonsils will be among the first immune cells to encounter the colonising bacteria. As tonsils are removed fairly regularly in routine tonsillectomy operations, we had the opportunity to access tissue containing the dendritic cell subset of particular interest to this research. Even though it seems unlikely that anyone would be too attached to their tonsils following removal, we did of course obtain informed consent from the patients or their parents/guardians before conducting any research!