About me Archives - Tom Hollis https://www.tomhollishealth.com/category/featured/about-me/ Expert sports nutrition and running coaching from a registered Dietitian and UK Athletics qualified Running Coach Wed, 30 Oct 2024 19:42:32 +0000 en-US hourly 1 https://wordpress.org/?v=6.7.1 https://www.tomhollishealth.com/wp-content/uploads/2024/08/cropped-Favicon-new-32x32.webp About me Archives - Tom Hollis https://www.tomhollishealth.com/category/featured/about-me/ 32 32 Hydration hydration hydration: everything you need to know about hydration in endurance running https://www.tomhollishealth.com/hydration-hydration-hydration-everything-you-need-to-know-about-hydration-in-endurance-running/?utm_source=rss&utm_medium=rss&utm_campaign=hydration-hydration-hydration-everything-you-need-to-know-about-hydration-in-endurance-running Thu, 09 Jun 2022 20:11:57 +0000 https://www.tomhollishealth.com/?p=1309 I was given a last minute place at Hackney Half a couple of weeks ago which meant (full disclosure here) that I ran under someone else’s name, thereby committing one of running’s seven deadly sins. I haven’t yet come up with a list of the other six, but perhaps that’s a blog for another day… […]

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I was given a last minute place at Hackney Half a couple of weeks ago which meant (full disclosure here) that I ran under someone else’s name, thereby committing one of running’s seven deadly sins. I haven’t yet come up with a list of the other six, but perhaps that’s a blog for another day…

I did it as a progressive tempo training run, aiming to finish in something like half my target marathon time for London in October. Naturally, I got slightly overexcited towards the end (big crowds, banging tunes etc.) and sped up a bit, finishing about a minute ahead of schedule in 1h17.

It was the first time I’d run Hackney, and while this blog isn’t intended as a race review, the atmosphere was great, and I’ll run it again one day (under my own name) – just not as a PB race. For one, the course is quite winding and not particularly flat. But most importantly, being at the end of the spring race season in late May, it always seems to be roasting hot in East London.

I watched my girlfriend (now wife) run in it in heatwave conditions back in May 2016, and it really wasn’t much cooler this year. I have been lucky that most of my target half and full marathons over the years have been on the cool side, and in fact I can say with certainty that these were the hottest conditions I’ve done anything more than a 10k race in.

On the day of the race, I posted an Instagram story about how I thought the Hackney emergency services would be in for a busy day, and sadly this was very much the case. I received response after response to that story confirming they’d seen people literally dropping like flies around the course.

In the (enormous) race village, all the pre-race chat coming over the loudspeaker had been about ‘hydration, hydration, hydration’, but besides ‘drinking a lot’, what does this really mean, and why is it so important in hot conditions? What does the evidence say about hydration in endurance sport, and how can we apply that to ourselves? It’s undoubtedly a tricky area and one that so many runners get wrong, especially when race conditions aren’t kind.

First then, why hydrate? i.e. what happens if we don’t?

Good hydration is essential, both for health and exercise performance. A quick GCSE biology recap: when we exercise, muscles generate heat as a by-product. Sweating is one of our go-to physiological responses to counteract this; the evaporation of water from the skin surface allows us to lose heat from blood vessels near the skin surface. The lost water needs to come from somewhere though, so if this process continues unchecked (i.e. without rehydration), blood plasma volume will reduce significantly (hypovolaemia) or core body temperature will steadily rise (called hyperthermia when exceeding 40 celsius), or both.

As a lot of those Hackney runners found out, this can result in heat-stroke, which at its worse can be fatal. However, well before this grim endpoint is reached, evidence suggests that, although there is huge individual variability, dehydration even at the level of >2% of body weight (i.e. 1.4kg of fluid loss for a 70kg runner) can affect aerobic performance and also cognitive function in hot conditions. This latter effect might be particularly important in the context of, say, decision making about fluid intake or pacing, and exacerbate the problem. These effects all increase as dehydration worsens, and when we reach 6-10% bodyweight loss, cardiac output, sweat production and muscular blood flow can all be compromised. Nasty.

How much to drink?

So, what can we do to prevent this? In general, it’s best to start a race (or hard training session) in a state of ‘euhydration’, that being one of neither over- nor under-hydration, with pale, straw-coloured urine. Clearly, starting in a dehydrated state would be a bad idea, whereas overhydration can cause GI discomfort and unwanted mid-run toilet trips!

During the run / race itself, hydration advice has shifted in the past decade or so. The traditional viewpoint used to be that ‘drinking to thirst’ was unsafe, because if you’re already thirsty, you’re already dehydrated, with runners therefore advised to pre-empt and avoid thirst by drinking early and regularly.

However, this method has its own risks, chiefly that of overhydration and exercise-associated hyponatraemia (EAH). This is known to be very common among recreational endurance athletes, and is essentially when the blood becomes diluted (specifically with regard to sodium content), due to replacement of fluid but not electrolytes (which I will get to later). Without wanting to sound too dramatic, again, at its most severe, EAH can be fatal.

Endurance runners are now advised, therefore, that following their instinctive thirst mechanism is a useful starting point to avoid EAH. There is phenomenal variability in sweat rates (anywhere from around 300ml to 2.5L / hour), both between and within individuals, depending on conditions and exercise intensity. However, for the majority of endurance runners, a range of 400-800ml fluid intake per hour is appropriate, with the higher end applied to faster or heavier athletes or hotter conditions (and vice versa).

Again though, this range remains just a starting point. A dietitian can help individualise the plan, but an athlete should also learn through their own experience about what they need. Sweat rate and lab composition testing can be helpful, but runners can also get into the habit, from time to time, of weighing themselves pre and post run (naked, wiping off any skin surface sweat) and working out sweat losses per hour in different conditions (accounting for any drinks consumed during the session, of course).

What to drink?

So now we know roughly how much to drink – or at least how to go about learning how much. What about what to drink? Let’s kick that off with another quick GCSE biology recap by way of some key definitions. These terms are thrown around freely in relation to sports drinks, but are, in my experience, quite poorly understood:

Hypotonic (e.g. water, dilute squash)

  • less concentrated than blood
  • best for rapid hydration

Hypertonic (e.g. hydrogels, most ‘recovery’ drinks)

  • more concentrated than blood
  • best for recovery and rapid carbohydrate delivery

Isotonic (e.g. most traditional sports drinks)

  • similar concentration to blood
  • all-rounder: compromise between hydration and carbohydrate delivery

When we talk about concentration, what we are really referring to here is the amount of sugars and salts (electrolytes) per litre. And when we consider our drink of choice, it’s important we can understand and weigh up the options, because ultimately it becomes a trade-off between optimal hydration and optimal carbohydrate delivery.

During a run, if rapid (re)hydration is needed above all else (e.g. from a safety perspective), a hypotonic solution such as water could be prioritised. If energy (carbs) are an urgent priority (but no other options e.g. gels are immediately available), then a hypertonic, sugar-heavy drink could be chosen.

However, in most other circumstances, isotonic is the way to go during a run. The rehydration rate is not far behind that of a hypotonic drink, and you have the added bonus of a gentle infusion of carbs (to be factored in alongside your race day fuelling plan) and electrolytes. In fact, current endurance sport guidelines consider the sodium levels found in most isotonic sports drinks to be optimal during prolonged exercise, for most athletes. Again though, there is great variability in sweat composition. Some people regularly see white salt marks on clothes or have salty-tasting sweat. In such ‘subjectively salty sweaters’ (or those that have lab-tested their sweat composition), alternative electrolyte plans are likely to be needed, especially when these runners also have either naturally high sweat rates and / or hot or humid conditions.

Remind me what electrolytes are?

Before moving on, a very quick recap on electrolytes and why they are important. Sodium is the one we hear most about, but potassium, calcium, magnesium, chloride and phosphate are all crucial too. Electrolytes are so called because they carry electric charge across cell membranes, and when this balance is disturbed, heart, nerve and muscle function can all be compromised.

And what about post-exercise rehydration?

One of the other important roles that electrolytes (especially sodium) play is regulating fluid balance, which takes us on nicely to post-exercise rehydration. Despite the pre-run and mid-run hydration guidance above, it is expected that any prolonged endurance exercise is likely to end up with some bodyweight fluid deficit (especially in conditions like Hackney) and the recommendations are to rehydrate with 150% of that lost weight. So, if you’re 1 kg lighter after the run, drink 1.5L.

The most efficient and optimal way to do this is with a surprisingly salty drink. Guidelines state that >60 mmol sodium per litre is optimal for fluid absorption, and it should be pointed out that this is where commercially available sports drinks really don’t cut it. They fall well below this level, because it wouldn’t be palatable to the general consumer and wouldn’t exactly fly off the shelves! So this is where my homemade special recipe comes in handy (and cheap):

  • 500ml orange juice
  • 500ml water
  • 2/3 of a tsp of salt

…mix together and enjoy the salty smugness of optimal rehydration!

Very concise summary of recommendations:

  • Pre-run: start euhydrated (pale straw urine)
  • Mid-run: drink to thist is an acceptable starting point
  • Most fall within 400-800ml / hour range (higher end if heavier, faster or hotter)
  • Isotonic usually wins for mid-run
  • Individualised plans (for volume and electrolytes) are best
  • Rehydrate post-run with 150% of lost weight, and go homemade for optimal results

Right, so there you have it. Hopefully that is a one-stop-shop with everything you needed to know about hydration in endurance sport, but as ever, your friendly sports dietitian (me) can help make sure you’re getting everything right with an individualised hydration plan. Anyone else thirsty?

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Where ICU meets sports nutrition https://www.tomhollishealth.com/where-icu-meets-sports-nutrition/?utm_source=rss&utm_medium=rss&utm_campaign=where-icu-meets-sports-nutrition Sun, 22 Nov 2020 14:09:25 +0000 https://www.tomhollishealth.com/?p=838 Isn’t it bizarre how trivial conversations or moments can stick in your head? I often think back to such a moment in September 2019… Despite having promised to myself in 2013 that my life in academia was finally over, having qualified as a Registered Dietitian, there I was in the classroom again, ready for Exercise […]

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Isn’t it bizarre how trivial conversations or moments can stick in your head? I often think back to such a moment in September 2019…

Despite having promised to myself in 2013 that my life in academia was finally over, having qualified as a Registered Dietitian, there I was in the classroom again, ready for Exercise Physiology – the first module of my Applied Sports Nutrition postgrad.

Most of the students on my side of the course had a nutrition background of some description (while the other side had a sports background), including a sprinkling of dietitians with differing levels of clinical experience. I was the only one coming from a critical care (ICU) background though, and this caused a few eyebrows to raise. At least two or three of my new coursemates asked ‘why would an ICU dietitian be interested in sports nutrition’ or stated that ‘you couldn’t pick two more different ends of the dietetic spectrum’. I knew that this wasn’t the case, but I could also see why someone who didn’t work in critical care might make these assumptions…and no doubt there are others visiting my website who will be thinking the same. So these conversations stayed with me, and I’ve been meaning to write this blog ever since.

I make no secret of the fact that I specialise in critical care and endurance sports nutrition (plus plant-based nutrition, but I’ve covered that in lots of other blogs so won’t mention here), and I feel lucky to have found two areas of nutrition that I feel so passionate about. Importantly though, there are huge areas of overlap that mean that, far from being totally separate entities, a greater understanding in one really benefits my practice in the other.

  1. Precision nutrition

ICU is all about numbers, data, and precision – or at least the pursuit of precision – and this is certainly part of the appeal. This is true for everything from biochemistry to ventilation settings, and certainly for nutrition too. Patients are generally fed via enteral feeding tube or intravenously, and every ml of delivered nutrition is documented. That’s not to say that how we set our nutrition targets is without some controversy, nor that feeding always goes to plan (there are always interruptions and unexpected breaks in feed), but as long as everything is accurately documented and analysed, we can monitor and react to those individual nutritional ‘balances’ (comparing feed prescription to delivery), as we seek to optimise that patient’s nutritional status.

The same can be said for sports nutrition. As with ICU, there may never be absolute consensus on how we calculate athletes’ nutrition requirements, but as the evidence base continues to grow (and it’s my job to stay on top of this), there is now undoubtedly greater precision and specificity in the guidelines. Through electronic food diaries, we can then quantitively track a client’s progress against these targets and be extremely precise in our recommendations. In my experience, this is what clients want, and it’s great to be able to provide this with confidence.

  1. Periodisation

In a similar vein to the point above, there is a broad acceptance that nutrition advice on critical care needs to be periodised, adjusting for different stages in a patient’s journey from early acute illness (where substrate utilisation is impaired) through to the late acute and then chronic and rehab phases, when physiology and metabolism shifts dramatically.

A major outstanding question in critical care nutrition is how to recognise the flow between these different phases. Fortunately, this is not a problem in sports nutrition, where the evidence and guidelines allow for nutrition advice to be neatly periodised around far more clearly defined phases, both on a ‘macro’ level in terms of training seasons and race build-ups, but also on a ‘micro’ level, in terms of key nutrient intake windows around individual sessions and rest days: essential to getting the best adaptation from all that hard work in training.

  1. Body under stress

I mentioned earlier the acute phase of critical illness and how this impacts on nutrition. Critical illness puts a huge amount of stress on the body, and, certainly in its earliest stages at least, induces a hypoxic and catabolic state where the metabolism of glucose, fatty acids and amino acids is all likely to significantly altered.

The same is true in sports, of course, where we push ourselves to the limit and induce physiological stress, albeit deliberately! We deprive our working muscles of adequate oxygen to respire aerobically, tipping us into and beyond our anaerobic or lactate thresholds. We also need to remember that exercise alone (whether resistance or cardio) is catabolic, and it only becomes an anabolic (i.e. muscle-building) process when combined with adequate nutrition. I’ve often come across statements such as ‘one day on ICU is like running a marathon’, and this is all rooted in the massive overlap here in terms of stress on the body.

I look out for rising blood lactate, electrolyte depletion and reduced oxygen saturation in all my ICU patients. It’s no coincidence that these are all also key elements  of exercise physiology and performance nutrition!

  1. Rehab and recovery

As ICU medical management improves, so do patient survival rates. And with this being the case, in recent years there has been an ever-increasing emphasis on achieving far more than just ‘survival’. Post Intensive Care Syndrome (PICS) is a dreadful but all-too-common combination of cognitive, psychological and physical impairments that persist for months, if not years, after ICU. One benefit of the current pandemic has been the increased media attention (and clinical funding) that post-ICU has received, but the reality is that this is not an issue specific to COVID-19.

We have the most fantastic post-ICU MDT recovery clinic at my hospital, where patients have access to a consultant, nurse, physio, occupational therapist, psychologist, pharmacist, and of course, a dietitian – me! I feel very privileged to be able to guide these incredibly vulnerable patients through their rehabilitation and recovery, as they deal with a bewildering mix of symptoms and changes in appetite, intake and body composition.

The language overlap with sports nutrition in terms of ‘rehab’, ‘recovery’, and ‘muscle wasting’ is immediately obvious, and in fact, this is another area where the evidence base in critical care rehab nutrition lags behind and actually borrows from the comparably well-defined guidance for sports and performance nutrition. Logic suggests, for example, that the ‘muscle full effect’ of protein dosing and timing that is so well described in performance nutrition should also apply to the rehabilitating post-ICU patient. I do therefore often adopt a similar strategy in my post-ICU clinic, but the reality is we don’t yet have the data in this population to confirm the theory. Watch this space, hopefully…

The other benefit of working in the post-ICU clinic is that I get to actually speak to my patients (!), many of whom have no idea that my colleagues and I were also providing their nutritional care when they were sedated, mechanically ventilated and tube-fed on the ICU a few months earlier. Given that all of my sports clients are awake (hopefully), it’s probably no bad thing that I’ve been keeping up my clinic skills, not least negotiating goals that work around individual patient lifestyles and schedules.

  1. Holistic physiology

Working on a mixed medical and surgical ICU means that every patient that comes through the door is completely different, and critical care dietitians, perhaps more than any other, need to be experts on the body as a whole. Organ systems don’t fail in isolation; a patient might have respiratory, kidney and GI failure simultaneously, for example, and each of these has nutritional implications that we interpret and respond to. It’s sometimes incredibly complicated and may mean prioritising one component over another, but coming from a biology background, I relish the opportunity to think so holistically.

Once again, this really benefits my work in sports nutrition, where it’s all about different organ systems working together. Of course, there are the fundamental and overlapping roles of the working muscles, lungs and heart. But we also need to consider, for example, the complex relationship between exercise and the GI tract, and the massive impact of the central nervous system on performance. All of these can be influenced by or impact on an athlete’s nutrition and hydration strategy, and this is what usually occupies my mind when I’m running (genuinely!), and certainly when I’m advising clients.

Hopefully I’ve managed to convince you that, far from being alien ends of the nutrition spectrum, there is a HUGE overlap between the wonderful worlds of critical care and sports nutrition, and that expertise in one massively benefits the other.

 

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Dietary nitrates and endurance exercise – intro blog https://www.tomhollishealth.com/dietary-nitrates-and-endurance-exercise-intro-blog/?utm_source=rss&utm_medium=rss&utm_campaign=dietary-nitrates-and-endurance-exercise-intro-blog Thu, 20 Feb 2020 20:51:51 +0000 http://www.tomhollishealth.com/?p=555 As a curious runner but sceptical scientist, I’m easily drawn to news pieces about enhancing running performance, particularly those that relate to nutrition. I try to view the articles through two pairs of eyes – my own (to critique the evidence and how it’s presented), and perhaps more importantly, those of a running friend or […]

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As a curious runner but sceptical scientist, I’m easily drawn to news pieces about enhancing running performance, particularly those that relate to nutrition. I try to view the articles through two pairs of eyes – my own (to critique the evidence and how it’s presented), and perhaps more importantly, those of a running friend or potential client. It’s vital to consider how they would interpret the article, and what questions might soon come my way.

Beetroot  juice is a fine example of running nutrition grabbing the headlines in recent years. I had already been following the media stories with interest, but studying for my postgrad in sports nutrition gave me the perfect excuse to delve deeper into the science. In fact, I recently chose beetroot juice and endurance exercise as my topic for a literature review, and having just received my highest ever mark for a piece of coursework (!), I feel as well placed as I ever will to give a brief(ish) synopsis of my take on the research here…

…but clearly not brief enough that it doesn’t warrant three separate blog posts! This first one will act as a general introduction and set the scene for the next two, which will discuss some of the more subtle trends emerging from the literature.

The first key point to clarify is that it’s not really just beetroot juice (or even beetroots) that we should be focusing on, but rather the dietary nitrates held within. There are plenty of other good dietary sources of nitrate, including spinach, rocket and swiss chard, but beetroot juice is easily the most heavily researched and therefore tends to dominate the news articles (perhaps because the juice volumes and therefore nitrate concentrations can be more closely controlled).

When we consume nitrate, it is first converted to nitrite (with a little help from bacteria in our mouths), then to nitric oxide – an incredibly useful and unique molecule that already has various applications in medicine. In intensive care, for example, we often see it used as a vasodilator (widens blood vessels) in the treatment of severe cardiovascular conditions. When you discover that nitrates are also linked to improvements in mitochondrial efficiency (the energy powerhouses of our cells), muscular blood flow and oxygen efficiency, it becomes easy to see why they have been so extensively researched in endurance sport over the past ten years or so.

Most of the articles in the popular media have reported very positive impacts from nitrates (usually beetroots) on exercise endurance, speed and general performance:

Telegraph

Independent

FT

But how accurate are these claims, and how much difference could beetroot juice, or any other nitrates, really make to the likes of me or my friends at the running club?

Since this is not intended as an academic piece, I won’t formally reference individual studies here as that would quickly get far too clunky for a blog, but will provide links as appropriate. Rest assured though that this is all based on the scientific literature (including meta-analyses),  and please feel free to contact me if you’d like any more info or detail.

Going back to the early studies, the key headline that emerged was that beetroot juice can improve running economy. This attracted huge attention, firstly since economy (or efficiency) is one of the three fundamental components that predict endurance performance (alongside maximum oxygen consumption (VO2 max) and lactate threshold), and secondly because economy had previously been considered a relatively fixed variable for athletes. In other words, nitrates might impact on a crucial performance element that very little else could touch.

Nitrate research falls into three exercise test categories: ‘time trial’ (time taken to complete a given distance), ‘time to exhaustion’ (open-ended assessments at fixed but sub-maximal work rates) and ‘graded exercise tests’ (often combining progressive exercise intensity and time to exhaustion).

Of the three, time trial is considered the most reliable indicator for real competition performance, but unfortunately this is where the results for nitrate are least consistent and convincing. Overall though, the evidence from endurance time trial meta-analyses (i.e. merging the results of many smaller studies) points towards a small but not statistically significant improvement with nitrates compared to placebo. There were similar overall findings for graded exercise tests.

Time to exhaustion tests are considered an inferior indicator of pure performance, as they are more susceptible to psychological factors such as motivation and boredom. Nonetheless, they remain heavily used in sports research, and the overall results for nitrates are quite convincing, suggesting moderate, statistically significant endurance improvements with nitrates compared to placebo.

But if the statistically significant effects are only seen in time to exhaustion and not time trial, does this detract from the ergogenic (performance-enhancing) claims for nitrates? Not necessarily. First, improved running economy, even at sub-maximal rates (as per time to exhaustion tests), can have real benefits for training, and therefore indirectly improve race performance. Second, and more important, is that even small, non-statistically significant effect sizes in time trial could have a meaningful impact on competition. To put this into context, overall effect sizes in meta-analyses with nitrate have been 0.8-0.9%, and the difference between winning gold and finishing twelfth in the London 2012 Olympic men’s 10,000m running final was only 0.66%. Clearly then, even small effects from nitrate have the potential to be pivotal in the context of the narrow margins of competition. In addition, dietary nitrate can be considered a low risk intervention, with adverse effects across the research generally limited to discolouration of urine or stool (to which most people who have eaten much beetroot in the past will already be accustomed!)

So, we can already start to see that dietary nitrates could be a safe, useful tool for endurance athletes. The next couple of blogs will cover some of the more subtle and interesting trends in the research, as well as practicalities for the athlete.

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