Beyond the Hype: Exploring 6 Endurance Sport Myths

May 06, 2024

As you can imagine, I get asked a lot of questions about training. What’s the best type of training to improve V̇O2max? How much protein do endurance athletes need? Do I need to do strength training? How early should I taper? These are all great questions, and I love working with athletes to find the answer.

Alongside questions, there are a number of assumptions – or myths – that come up again and again when working with athletes, that I work hard to bust. In this blog, I am going to try and bust six of the biggest endurance sports myths.

Myth #1: Training the gut enhances carbohydrate use.

“I consume carbohydrates at high rates during training, to train my gut to digest and absorb carbohydrates at higher rates. That allows me to get more energy from sports drinks and gels during racing.”

Gut training – the practice of consuming carbohydrates at very high rates during training – has been investigated by researchers. The idea behind gut training is that it might allow athletes to tolerate higher rates of carbohydrate ingestion during competition, and therefore get more energy from carbohydrates in sports drinks and gels (1).

However, there isn’t really any evidence to suggest gut training works.

A recent systematic review (2) found that gut training may reduce gut discomfort during exercise with high rates of carbohydrate ingestion, and, possibly explaining that, reduced carbohydrate malabsorption (undigested carbohydrate making its way into the colon, which causes issues) (3–5). Gut training may therefore be a sensible strategy for those who really struggle to take on carbohydrates during exercise, and want to take on carbohydrates at very high rates during competition. That’s fine, although this latter point – the desire to take on very high rates of carbohydrate during exercise – is an objective that I think doesn’t hold water (see Myth #2).

However, for gut training to be useful beyond building tolerance – and therefore to be useful for those who don’t typically run into gut issues during training and racing – it needs to increase the rate at which you can get energy from the carbohydrates ingested in sports drinks and gels, which is measured as the exogenous carbohydrate oxidation rate.

There really isn’t evidence that training the gut increases exogenous carbohydrate oxidation rates, at least in any meaningful way. One study did find that 28 days of hard gut training increased this, although only by ~5 grams per hour (6). That’s a lot of work, for almost no reward.

Myth #2: The more carbs, the better.

“The more carbohydrate I can consume during exercise, the better my performance will be.”

I’ve written to try and dispel this myth quite a bit recently.

Excellent, early studies did find – and this has been replicated many times subsequently – that carbohydrate ingestion during endurance exercise enhances performance (7, 8).

We have a lot of data on the physiological effects of different carbohydrate dosing strategies, but surprisingly little on performance outcomes. The studies that have looked at performance do not provide strong evidence for a dose-response effect of carbohydrate ingestion during exercise. Physiologists proposed that these benefits were underpinned by glycogen-sparing effects of the ingested carbohydrates. Accordingly, many studies were done to ‘optimise’ carbohydrate ingestion during exercise, with ‘optimal’ identified as the highest exogenous carbohydrate oxidation rate (9). The proposal has been that the greater the rate at which ingested carbohydrates are metabolised, the greater their positive effects will be.

However, the issue with this thought process is that ingesting carbohydrates during exercise doesn’t seem to spare our muscle glycogen stores. That is, studies comparing muscle glycogen breakdown during exercise with and without carbohydrate ingestion during exercise generally hasn’t found differences (10, 11). Carbohydrate ingestion does seem to reduce the rate at which we chew through liver glycogen stores (12–14), which is useful as we break down liver glycogen to help maintain our blood glucose concentrations.

However, this understanding of the metabolic response to carbohydrate ingestion during exercise – no effect on muscle glycogen breakdown, sparing of liver glycogen breakdown – doesn’t suggest to me that more carbs should be better. Provided we are ingesting sufficient carbohydrate to maintain our blood glucose concentration, I don’t see why more should be better.

Surprisingly few studies have looked at the performance-enhancing effects of carbohydrate ingestion at different doses – i.e. whether more is better. The studies that are out there haven’t supported a strong dose-response effect (15, 16). In fact, a couple of studies have found some evidence of carbohydrate overdosing, or poorer performance at higher ingestion rates than lower ingestion rates, possibly due to accelerated muscle glycogen breakdown (17, 18). That’s exactly what you don’t want, especially when you consider high carbohydrate ingestion rates are likely to increase the risk of carbohydrate malabsorption and debilitating gut issues during competition.

More carbs therefore aren’t always better. From a performance perspective, ingesting some carbohydrates during exercise helps – enough to maintain blood glucose concentrations – but more doesn’t result in better performance. In fact, very high rates, beyond say 90 grams per hour so, may hasten muscle glycogen breakdown, decrease performance, and, plausibly, risk gut issues.

Myth #3: No pain, no gain.

“You know your training is working when it hurts.”

We train to stimulate physiological adaptations that improve performance – a bigger, stronger, more powerful heart, a greater capacity to transport oxygen in the blood, increased mitochondria for aerobic metabolism in muscles, and so on. We generate these adaptations by subjecting the body to the stresses associated with exercise during training. It is therefore understandable that the myth emerged that training must be hard – and therefore physiologically stressful – to result in the adaptive gains we seek. However, “no pain, no gain” is one of the most pervasive, and damaging, myths in the endurance sports world.

Figure: The adage "No pain, no gain" suggests it's always more advantageous to push yourself to a higher intensity. However, it's crucial to note that higher intensity doesn't always equate to better training gains.

Low-intensity, low-stress training is hugely beneficial. There is some evidence that low intensity training is an important stimulus for generating adaptations in our type I, slow-twitch muscle fibres (19), and also a fair bit of descriptive data showing that elite endurance athletes do most of their training – 70-90% - at low intensities (20–22). Low intensity training is useful because it doesn’t require much recovery time (23, 24), and therefore allows athletes to accumulate massive overall training volumes without becoming fatigued and falling over. I consider training volume as one of the key pillars of endurance training, so low stress, pain-free training is a really useful tool and fundamental component of a quality training programme. In support, some studies have reported better responses to training programmes focused on low-intensity work – polarised or pyramidal training – rather than training programmes focused on quite-hard, threshold-type work (25, 26).

That’s not to say that all training has to be easy. High-intensity interval training, which generates a high degree of stress for adaptation, is an important part of an endurance training programme (27). It’s just that we need to be careful and selective with how much of this training we do, given the fatigue it generates and the recovery it requires.

Myth #4: Drink to offset body mass losses.

“I try and estimate how much I’m going to sweat to ensure I drink at least that much during racing. I don’t want to get dehydrated.”

The origins of this myth are interesting – and perhaps related to the 1996 American College of Sports Medicine guidelines for athletes, which recommended they drink as much as possible during endurance events, and to avoid any body mass loss through dehydration (28).

These guidelines are just plain wrong, and unnecessary. In fact, the more recent guidelines, published back in 2007, now suggest the goal of hydration during exercise should be to avoid becoming dehydrated by more than 2% of body mass (29). Sure, becoming extremely dehydrated can worsen performance, and push your heart rate up, but these guidelines now acknowledge that it is not necessary to avoid dehydration completely.

Aside from anything else, it’s not practical. How do you predict sweat rates and fluid loss, other than by performing the same exercise in the same conditions, beforehand? Fluid losses also change over the duration of an endurance event. E.g. you fluid loss during the first 1 hour of the bike, will likely be very different to the fluid loss in hours 3, 4 or 5 during an Ironman bike leg.

In cooler conditions, my advice is to drink to thirst. Plan your race day, or training, hydration strategy to have plenty of water available to you and drink it as you see fit. Do try and take fluids on early, but don’t worry about predicting losses. If you are racing in hot conditions like Kona for example, the rate limiting step here is most likely going to be the rate of gastric emptying (36). For most people, this will be anywhere between 750 ml, and 1.3 L per hour. Exceeding that will likely lead to bloating and a feeling of excessive fullness.

There’s no need to drink to fluid losses.

Myth #5: Sodium intake during exercise reduces cramping.

“I take salt tablets during long training sessions to ensure I don’t cramp.”

This is an interesting one. Cramp can be debilitating for some athletes but doesn’t seem to ever bother others. As it seems to occur during more demanding, longer-duration events, which are also characterised by dehydration and electrolyte losses, it has long been thought that cramping is caused by dehydration and electrolyte losses, and that taking salt tablets during exercise reduces the risk of cramping.

Unfortunately, the data to support that contention – and solution – is not compelling.

For example, recent studies have found that crampers do not lose more sodium in sweat, or become more dehydrated, than non-crampers (30, 31). If salt losses were at the root of the problem, one would expect that athletes who start to cramp would be losing more salt in sweat and urine.

I should add that a recent experimental study did find that consumption of an electrolyte-containing drink in cramp-prone volunteers made it harder to induce cramp through artificial stimulation but didn’t prevent it completely (32). As such sodium may have a small contributing factor to cramping, but it certainly isn’t the major one.

I acknowledge that the effect of sodium intake on cramping is extremely hard to study, but to my eyes there isn’t good data to suggest that athletes who don’t have problems with cramping should make an effort to ingest more sodium than is found in standard sports drinks and gels.

Myth #6: Salty sweaters need more sodium during exercise.

“I’m a salty sweater, so I need to consume more sodium during training and racing.”

On that note, another persistent myth is that so-called salty sweaters need to consume for sodium during exercise than normal sweaters, as they lose more sodium in sweat.

The amount of sodium lost in sweat does vary between-athletes. However, this is probably largely to do with the sodium content of your diet – with those who consume more sodium letting more leak out in sweat than those who eat less sodium in the diet (33, 34). Studies have explored the day-to-day fluctuation in sweat sodium concentration, revealing variations of approximately 15% even with consistent daily sodium intake. Considering this level of variability, how can such data have meaningful practical implications?

Sodium, and all electrolytes, are incredibly important to our physiology. Accordingly, we don’t just let it go easily. If our sodium stores are running low, we make a greater effort to hold on to it and sweat sodium concentrations go down. If we ingest lots of sodium, we let it go more easily, and sweat sodium concentrations might go up. Of course, sodium is important in day-to-day life, but for exercise its importance has been largely over exaggerated. In a review published in 2018, it was concluded that minimal evidence that sodium ingestion during exercise improves endurance performance (35). But of course, more work still needs to be done in this area.

Take home point, salty sweaters probably just consume more sodium. If your sweat is salty, don’t rush out to buy more salt tablets.


Navigating the realm of endurance training and sports nutrition can feel overwhelming at times. The crucial strategy is to prioritize the essential elements and avoid getting caught up in marketing or media hype. Many times, things are simpler than they appear at first glance.


  1. Jeukendrup AE. Training the gut for athletes. Sports Medicine 47: S101–S110, 2017. doi: 10.1007/s40279-017-0690-6.
  2. Martinez IG, Mika AS, Biesiekierski JR, Costa RJS. The effect of gut-training and feeding-challenge on markers of gastrointestinal status in response to endurance exercise: A systematic literature review. Sports Medicine 53: 1175–1200, 2023. doi: 10.1007/s40279-023-01841-0.
  3. Lambert GP, Lang J, Bull A, Eckerson J, Lanspa S. Fluid tolerance while running: Effect of repeated trials. Int J Sports Med 29: 878–882, 2008. doi: 10.1055/s-2008-1038620.
  4. Miall A, Khoo A, Rauch C, Snipe RMJ, Camões-Costa VL, Gibson PR, Costa RJS. Two weeks of repetitive gut-challenge reduce exercise- ­associated gastrointestinal symptoms and malabsorption. Scand J Med Sci Sports 28: 630–640, 2018. doi: 10.1111/sms.12912.
  5. Costa RJS, Miall A, Khoo A, Rauch C, Snipe R, Camões-Costa V, Gibson P. Gut-training: the impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance. Applied Physiology, Nutrition, and Metabolism 42: 547–557, 2017. doi: 10.1139/apnm-2016-0453.
  6. Cox GR, Clark SA, Cox AJ, Halson SL, Hargreaves M, Hawley JA, Jeacocke N, Snow RJ, Yeo WK, Burke LM. Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling. J Appl Physiol 109: 126–134, 2010. doi: 10.1152/japplphysiol.00950.2009.
  7. McConell G, Snow RJ, Proietto J, Hargreaves M. Muscle metabolism during prolonged exercise in humans: Influence of carbohydrate availability. J Appl Physiol 87: 1083–1086, 1999. doi: 10.1152/jappl.1999.87.3.1083.
  8. Coggan AR, Coyle EF. Reversal of fatigue during prolonged exercise by carbohydrate infusion or ingestion [Online]. J Appl Physiol 63: 2388–2395, 1987.
  9. Jeukendrup AE, Jentjens RLPG. Oxidation of carbohydrate feedings during prolonged exercise: current thoughts, guidelines and directions for future research. Sports Medicine 29: 407–424, 2000.
  10. Coyle EF, Coggan AR, Hemmert K, Ivy JL. Muscle glycogen utilization during prolonged strenuous exercise when fed carbohydrate. J Appl Physiol 61: 165–172, 1986.
  11. Jeukendrup AE, Raben A, Gijsen A, Stegen JHCH, Brouns F, Saris WHM, Wagenmakers AJM. Glucose kinetics during prolonged exercise in highly trained human subjects: Effect of glucose ingestion. Journal of Physiology 515: 579–589, 1999. doi: 10.1111/j.1469-7793.1999.579ac.x.
  12. Bosch AN, Dennis SC, Noakes TD. Influence of carbohydrate ingestion on fuel substrate turnover and oxidation during prolonged exercise [Online]. J Appl Physiol 76: 2364–2372, 1994.\npapers2://publication/uuid/F479B870-C0EE-4489-A686-39EA1EA057F1.
  13. McConell G, Fabris S, Proietto J, Hargreaves M. Effect of carbohydrate ingestion on glucose kinetics during exercise. J Appl Physiol 77: 1537–1541, 1994.
  14. Jeukendrup AE, Wagenmakers AJM, Stegen JHCH, Gijsen AP, Brouns F, Saris WHM. Carbohydrate ingestion can completely suppress endogenous glucose production during exercise. Am J Physiol Endocrinol Metab 276: E672–E683, 1999.
  15. Baur DA, Schroer AB, Luden ND, Womack CJ, Smyth SA, Saunders MJ. Glucose-fructose enhances performance versus isocaloric, but not moderate, glucose. Med Sci Sports Exerc 46: 1778–1786, 2014. doi: 10.1249/MSS.0000000000000284.
  16. Smith JW, Zachwieja JJ, Péronnet F, Passe DH, Massicotte D, Lavoie C, Pascoe DD. Fuel selection and cycling endurance performance with ingestion of [13C]glucose: evidence for a carbohydrate dose response. J Appl Physiol 108: 1520–1529, 2010. doi: 10.1152/japplphysiol.91394.2008.
  17. King AJ, O’Hara JP, Morrison DJ, Preston T, King RFGJ. Carbohydrate dose influences liver and muscle glycogen oxidation and performance during prolonged exercise. Physiol Rep 6: e13555, 2018. doi: 10.14814/phy2.13555.
  18. King AJ, O’Hara JP, Arjomandkhah NC, Rowe J, Morrison DJ, Preston T, King RFGJ. Liver and muscle glycogen oxidation and performance with dose variation of glucose–fructose ingestion during prolonged (3 h) exercise. Eur J Appl Physiol 119: 1157–1169, 2019. doi: 10.1007/s00421-019-04106-9.
  19. Skelly L. E, Gillen JB, Frankish BP, MacInnis MJ, Godkin FE, Tarnopolsky MA, Murphy RM, Gibala MJ. Human skeletal muscle fiber type-specific responses to sprint interval and moderate intensity continuous exercise: acute and training-induced changes. J Appl Physiol 130: 1001–1014, 2021.
  20. Seiler KS, Kjerland GØ. Quantifying training intensity distribution in elite endurance athletes: Is there evidence for an “optimal” distribution? Scand J Med Sci Sports 16: 49–56, 2006. doi: 10.1111/j.1600-0838.2004.00418.x.
  21. Tønnessen E, Sylta Ø, Haugen TA, Hem E, Svendsen IS, Seiler S. The road to gold: Training and peaking characteristics in the year prior to a gold medal endurance performance. PLoS One 9: 15–17, 2014. doi: 10.1371/journal.pone.0101796.
  22. Seiler KS. What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform 5: 276–291, 2010.
  23. Seiler S, Haugen O, Kuffel E. Autonomic recovery after exercise in trained athletes: Intensity and duration effects. Med Sci Sports Exerc 39: 1366–1373, 2007. doi: 10.1249/mss.0b013e318060f17d.
  24. Stanley J, Peake JM, Buchheit M. Cardiac parasympathetic reactivation following exercise: Implications for training prescription. Sports Medicine 43: 1259–1277, 2013. doi: 10.1007/s40279-013-0083-4.
  25. Stöggl T, Sperlich B. Polarized training has greater impact on key endurance variables than threshold, high intensity, or high volume training. Front Physiol 5: 1–9, 2014. doi: 10.3389/fphys.2014.00033.
  26. Neal CM, Hunter AM, Brennan L, O’Sullivan A, Hamilton DL, DeVito G, Galloway SDR. Six weeks of a polarized training-intensity distribution leads to greater physiological and performance adaptations than a threshold model in trained cyclists. J Appl Physiol 114: 461–471, 2013. doi: 10.1152/japplphysiol.00652.2012.
  27. Buchheit M, Laursen PB. High-intensity interval training, solutions to the programming puzzle: Part I: Cardiopulmonary emphasis. Sports Medicine 43: 313–338, 2013. doi: 10.1007/s40279-013-0029-x.
  28. Convertino VA, Armstrong LE, Coyle EF, Mack GW, Sawka MN, Senay LC, Sherman WM. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc 28: i–vii, 1996. doi: 10.1097/00005768-199610000-00045.
  29. American College of Sports Medicine, Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc 39: 377–390, 2007. doi: 10.1249/mss.0b013e31802ca597.
  30. Martínez-Navarro I, Montoya-Vieco A, Collado E, Hernando B, Panizo N, Hernando C. Muscle Cramping in the marathon: Dehydration and electrolyte depletion vs. muscle damage. J Strength Cond Res 36: 1629–1635, 2022. doi: 10.1519/JSC.0000000000003713.
  31. Szymanski M, Miller KC, O’Connor P, Hildebrandt L, Umberger L. Sweat characteristics in individuals with varying susceptibilities of exercise-associated muscle cramps. J Strength Cond Res 36: 1171–1176, 2022. doi: 10.1519/JSC.0000000000003605.
  32. Earp JE, Stearns RL, Stranieri A, Agostinucci J, Lepley AS, Matson T, Ward-Ritacco CL. Electrolyte beverage consumption alters electrically induced cramping threshold. Muscle Nerve 60: 598–603, 2019. doi: 10.1002/mus.26650.
  33. Braconnier P, Milani B, Loncle N, Lourenco JM, Brito W, Delacoste J, Maillard M, Stuber M, Burnier M, Pruijm M. Short-term changes in dietary sodium intake influence sweat sodium concentration and muscle sodium content in healthy individuals. J Hypertens 38: 159–166, 2020. doi: 10.1097/HJH.0000000000002234.
  34. McCubbin AJ, Lopez MB, Cox GR, Caldwell Odgers JN, Costa RJS. Impact of 3-day high and low dietary sodium intake on sodium status in response to exertional-heat stress: a double-blind randomized control trial. Eur J Appl Physiol 119: 2105–2118, 2019. doi: 10.1007/s00421-019-04199-2.
  35. McCubbin AJ, Costa RJS. Impact of sodium ingestion during exercise on endurance performance: A systematic review. International Journal of Sports Science 8: 97–101, 2018.
  36. Leiper JB. Fate of ingested fluids: factors affecting gastric emptying and intestinal absorption of beverages in humans. Nutrition Reviews, Volume 73, Issue suppl_2, Pages 57–72, 1 September 2015. 



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