Sauna Bathing for improved Athletic Performance
Nothing beats relaxing in the sauna after exercise. The peaceful seclusion of a natural space offers a much needed opportunity to stretch, breathe and be present in our bodies before we get on with the rest of our day. But emerging research suggests there’s more to be gained from a post-exercise sauna than simply relaxation: the physiological effects of sauna bathing can actually have powerful positive impacts on athletic performance too. In fact, regular sauna bathing post-workout has been shown to significantly improve endurance, enhance muscle recovery and even promote muscle growth. Here, we look at the science behind sauna bathing to improve fitness.
Blood, Sweat and Saunas
When we’re exposed to heat, our bodies send blood away from our organs towards our skin; this helps to prevent our core temperature from rising, and enables us to produce sweat (largely made up of plasma from our blood) to help us cool off. This process, while efficient at regulating our temperature, creates the need for more plasma, and so heat stress also causes blood vessels to dilate in order to increase blood flow and boost plasma volume to facilitate this process.
Interestingly, several studies have recently shown that repeated heat exposure actually results in a sustained increase in plasma volume in the blood, as our bodies adapt to prepare for future heat stress [1][2][3]. One study examined a group of well-trained cyclists and observed that after just four sauna sessions, the athletes experienced a 17.8% expansion of their peak plasma volume, compared to where it was during their normal training [1]. This significant increase in blood plasma volume also occurs through undertaking endurance exercise itself [4], so it seems when following exercise with a sauna bathing session, the benefits of this adaptation are two-fold.
So how does an increase in blood plasma volume affect health and athletic performance? Having a greater blood plasma volume essentially means we have more blood; and when this is the case, blood can be pumped with less effort, efficiently sending more vital oxygen and nutrients to muscles with less cardiovascular strain and a lower heart rate. This is a well established idea supported by studies that clearly demonstrate the link between increased blood plasma volume and faster time trials for cyclists [1][5]. As Fellman explains in his 1992 review in Sports Medicine,
“[increased blood plasma] can improve performance by inducing better muscle perfusion, and by increasing stroke volume and maximal cardiac output.”[4]
In effect, this physiological adaptation makes our cardiovascular system more efficient and better equipped for endurance exercise.
Sustained Improvements in Endurance
Studies into post-exercise sauna bathing have also shown that with sustained regular sauna sessions for a longer time period, blood plasma volume does begin to reduce a bit, though it’s still higher than training without sauna sessions [1][2]. However, with continued regular sauna use, another beneficial adaptation becomes apparent; our bodies start to generate more red blood cells due to the natural production of erythropoietin (EPO) being stimulated by the reduced blood supply to our kidneys in the sauna [7].
This is good news for athletes, because an increase in red blood cells also boosts cardiac output and facilitates an increased amount of oxygen being delivered to skeletal muscles we use when exercising [6]. A team of researchers in New Zealand conducted a study whereby they had six competitive distance runners undertake a three week period of normal training, then a three week period of their normal training plus a 30 minute sauna bathing session immediately post-exercise [6]. After each of these periods, the participants were required to run on a treadmill (at a pace determined by their fastest 5K time) until exhaustion. The study found that after supplementing training with sauna sessions, the runners had a 7.1% increase in blood plasma volume and a 3.5% increase in red blood cells [6].
But how did this translate to their performance? When the athletes supplemented their training with post-exercise saunas, their time to exhaustion was increased by 32% - this means they were able to keep running for 32% longer - and on average, this translated to cutting down their 5K race time by about 2% - certainly not an amount to be sniffed at in the world of competition [6].
Enhanced Muscle Recovery
As mentioned above, regular heat exposure in a sauna increases blood flow to skeletal muscles. This increases the delivery of glucose and oxygen to those muscles, which may reduce their dependence on glycogen stores by 40% – 50%, protecting against muscle fatigue [8]. Whats more, spending time in the sauna after exercise loosens muscle tension, preventing potential exercise-induced injuries [7].
Finnish researchers discovered that sauna bathing could also improve the amount of human growth hormone (HGH) produced by the body [9]. In a small study, the researchers found that after three days of two one-hour sessions (perhaps a bit extreme!) there was a 16-fold increase in the amount of HGH release in both male and female participants, which they report resulted in more muscle growth [9]. The mechanism of HGH is still not fully understood, but it is known to play an important role in the body’s growth and the repair of its tissues, including promoting protein synthesis in muscle [9]. Interestingly, a more recent study on rats found that individuals exposed to heat treatment showed a 30% improvement in muscle growth on average [10].
Better Thermoregulation
Another benefit of regular sauna use in terms of athletic performance, is improved thermoregulatory control. Studies have shown that regular sauna sessions help our bodies to acclimatise to the heat we generate during physical activity [1]. After several sauna sessions, our bodies start sweating at a lower core body temperature, and maintain a constant sweat rate for a longer period, which results in better cooling down during exercise [2].
Heat acclimatisation is perhaps particularly beneficial when training for a race in a warm climate; and exposing the body to heat stress (for example, through sauna use) has been shown to improve exercise tolerance for ultra-endurance runners in hot conditions [1][11].
Whether our goals are faster race times, improved muscle recovery, or simply better overall fitness, a traditional sauna could be the ideal way to boost our training - and as the weather turns colder here in Mid-Wales, there’s nothing quite like the promise of a post-exercise sauna to motivate us on the final stretch.
Sources
Stanley, J., Halliday, A., D’Auria, S. et al. (2015) Effect of sauna-based heat acclimation on plasma volume and heart rate variability. European Journal of Applied Physiology 115, 785–794. DOI: https://doi.org/10.1007/s00421-014-3060-1
Kirby, N.V., Lucas S.J.E., Armstrong, O.J., Weaver, S.R., Lucas, R.A.I. (2021) Intermittent post-exercise sauna bathing improves markers of exercise capacity in hot and temperate conditions in trained middle-distance runners. European Journal of Applied Physiology. 121(2):621-635. DOI: 10.1007/s00421-020-04541-z.
Heinonen, I and Laukkanen, J. A. (2018) Effects of heat and cold on health, with special reference to Finnish sauna bathing. American Journal of Physiology: Regulatory, Integrative and Comparative Physiology. 314: R629–R638. DOI: https://doi.org/10.1152/ajpregu.00115.2017
Fellmann, N. (1992) Hormonal and plasma volume alterations following endurance exercise: A brief review. Sports Medicine. 113(1):3-49. DOI: 10.2165/00007256-199213010-00004. PMID: 1553454.
Luetkemeier, M.J., Thomas, E.L. (1994) Hypervolemia and cycling time trial performance. Medicine and Science in Sports and Exercise. 26(4):503-9. PMID: 7515456.
Scoon, G.S., Hopkins, W.G., Mayhew, S., Cotter, J.D. (2006) Effect of post-exercise sauna bathing on the endurance performance of competitive male runners. Journal of Science and Medicine in Sport. 10(4):259-62. DOI: 10.1016/j.jsams.2006.06.009.
Hannuksela, M. L., Ellahham, S. (2001) Benefits and risks of sauna bathing. The American Journal of Medicine. 110(2):118-126. DOI: https://doi.org/10.1016/S0002-9343(00)00671-9.
Ketelhut, S. and Ketelhut, R. G. (2019) The blood pressure and heart rate during sauna bath correspond to cardiac responses during submaximal dynamic exercise. Complementary Therapies in Medicine. 44: 218-222. DOI: https://doi.org/10.1016/j.ctim.2019.05.002.
Leppäluoto, J., et al. (1986) Endocrine effects of repeated sauna bathing. Acta Physiologica Scandinavica. 128(3): 467-470. DOI: https://doi.org/10.1111/j.1748-1716.1986.tb08000.x
Selsby, J.T., et al. (2007) Intermittent hyperthermia enhances skeletal muscle regrowth and attenuates oxidative damage following reloading. Journal of Applied Physiology. 102.4: 1702-1707. DOI: 10.1152/japplphysiol.00722.2006
Costa, R. J. S., Crockford, M. J., Moore, J. P. and Walsh, N. P. (2012) Heat acclimation responses of an ultra-endurance running group preparing for hot desert-based competition. European Journal of Sports Science. 14(1): S131-S14. DOI: https://doi.org/10.1080/17461391.2012.660506