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Training in the Heat – Some good news

Training in the Heat – Some good news

Yes, we all know how difficult and uncomfortable it is to train in the heat so why should we? Gyms are air conditioned (mostly) so why not simply avoid the heat and use their running, rowing, cycling, etc equipment to train? Easy solution you might think, and yes it will work but perhaps there are real and additional benefits to staying outside quite apart from the aesthetic benefits of the great outdoors. In fact, there are real fitness benefits to be gained from training in hot conditions so get out there and train. Need I say more?
For those that require further explanation I’ll start with some very basic physiology that relates to those benefits so you can understand why and where you can gain improvement. Muscles need fuel to perform and that fuel is supplied in the form of glycogen1. Depletion of glycogen levels, without sufficient replacement of carbohydrate, leads to the phenomenon athletes call ‘hitting the wall’2. As blood glycogen levels approach depletion and demand exceeds supply at the muscles (remembering that brain function requires energy as well2), i.e. supply from the liver cannot be maintained at a rate sufficient to support muscle and brain function, then muscles start to consume the glycogen stored within (Costill et al. 1971, King et al. 1985). Glycogen released in this process differs slightly to glycogen acquired from the liver. Consequently, muscles function less efficiently on muscle-derived glycogen and performance declines.
Now for the good news (if you are a football player)! Buchleit et al. (2013) found that as little as 1 week of heat training produces a substantial increase in running performance and an increased haemoglobin mass (more red blood cells) among elite Aussie Rules players. More haemoglobin means a greater capacity to deliver glycogen to muscles. Moreover, benefits of their heat training were still evident 4 weeks later, so no excuses for not performing well when you travel to a cooler environment to compete!
A further benefit to training in the heat is, contrary to what you might feel, that your rate of sweating reduces once you are acclimated to hotter conditions relative to first experiences with increased heat and the sodium concentration in your sweat decreases3 similarly once acclimated (Buono et al. 2007). Heat acclimation also has a positive effect on the retention of crucial minerals that can be lost in sweat (Chinevere et al. 2008), so overall, acclimation to hot conditions has positive benefits for muscle and body function.
In Summary: Training in the heat is good for you but always take appropriate precautions, particularly if this approach is new to you. If unsure always seek medical opinion before taking on an exercise regime.


  1. Our bodies store energy in the form of glycogen (one form of energy storage) (Wasserman 2009). Glycogen is a form of glucose that is primarily stored in the liver although about some is stored in muscle tissue. Glycogen is the most ‘available’, i.e. readily accessible, form of energy stored in our bodies. Glycogen is delivered to muscles by our red blood cells2. (Salway 2004). In fasted individuals the bloodstream only carries around 4 grams of glucose and around 60% of that blood glucose is needed to maintain brain function at rest (Wasserman 2009).
  2. Hitting the wall can be slowed during extended exercise sessions through regular ingestion of carbohydrate with a high glycemic index, through specialised adaptations and training to increase fuel use efficiency and percentage of fatty acids utilised as fuel (McDonald 2009a, b) and ‘carb loading’ to increase glycogen storage (Costill et al. 1971) although contemporary research suggests carb loading is not the ideal option for endurance athletes according to sports nutritionist Steph Lowe from the Natural Nutritionist (more to come on this research in a later post).
  3. Sodium is crucial for correct functioning of muscles and nerves. Consequently loss of sodium through sweat (can also occur through over-hydration) can lead to depleted sodium levels with consequential muscle failures such as cramp or more serious problems. Extreme sodium depletion (hypernatremia) can adversely affect vital organs such as kidneys or even be fatal (Lee et al. 2014, Williams et al. 2016).

Disclaimer: The information delivered here was sourced primarily from peer reviewed publications and represent the interpretations of the author, Ross Johnston (BSc, Hons).


Buono MJ, Ball KD, Kolkhorst FW (2007) Sodium ion concentration vs. sweat rate relationship in humans. J Appl Physiol 103:990–994
Chinevere TD, Kenefick RW, Cheuvront SN, Lukaski HC, Sawka MN (2008) Effect of heat acclimation on sweat minerals. Med Sci Sports Exerc 40:886–891
Costill D, Bowers R, Branam G, Sparks K (1971) Muscle glycogen utilisation during prolonged exercise on successive days. J Appl Physiol 31
King DS, Costill DL, Fink WJ, Hargreaves M, Fielding RA (1985) Muscle metabolism during exercise in the heat in unacclimatized and acclimatized humans. J Appl Physiol 59:1350–1354
Lee JJY, Kilonzo K, Nistico A, Yeates K (2014) Management of hyponatremia. CMAJ 186:E281-6
McDonald L (2009a) Methods of Endurance Training Part 2: Miles Build Champions.
McDonald L (2009b) Methods of Endurance Training Part 1.
Salway JG (2004) Glycogen metabolism. Metab a glance 40:14–15
Wasserman DH (2009) Four grams of glucose. Am J Physiol Metab 296:E11–E21
Williams DM, Gallagher M, Handley J, Stephens JW (2016) The clinical management of hyponatraemia. Postgrad Med J 92:407–411

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