Sweating Down - Rationale for "turning up the heat" in training
Firstly it should be said that, as with many strategies in boxing, there is a compromised to be reached between the advantages that may be gained by achieving a certain weight, physique, and body composition, compared with the negative impacts these may have on our performance and health. Undoubtedly dehydration impairs athletic performance (as little as 2% bodymass), as well as concentration and cognitive function. Indeed a recent fMRI study showed that dehydrating 3 kg (modest by the standards of many boxers) can reduce the volume of fluid around the brain by as much as 30% (Dickson, et al., 2005). I am not yet aware of any studies that indicate how efficiently this brain fluid is replenished when we rehydrate. However, there is method to this madness. Here are some of the reasons some may choose to "dry out"...
Amateur boxing rules aim to prevent disparities on club shows over 2kg; that's how much size matters! When one considers that lean mass (ie our muscle) is 74% water, you can see how feasible it is to artificially "make a weight" far below your natural size. In addition, carbs in the muscle are stored with an excess of water in a ratio of 3:1 (Mackay, 1932). This means that when fully "carbed up" your muscles and liver may hold up to an additional 500g of carb and 1.5L of water – a total of 2Kg. This is on top of normal cellular hydration. If you've sweat-down as well, you can see how fighters like Ricky Hatton can pile on 6-8Kg in the 24 hr between weigh-in and fighting.
Killer Calorie Control
Exercising in the heat really can "burn off" the pounds. For example, populations in tropical climates often have a basal-metabolic rate 5-15% higher than those in cooler climates (Henry, 2005). Observations are frequently made that, for exercise carried out at the same power-output (e.g. running at a predefined speed), an increase in temperature can increase energy expenditure by over 5% (CONSOLAZIO, 1961; Pugh, Corbett, & Johnson, 1967). This is often a whole weight-category (ie the difference between welter and light-welter). This is thought to happen by a process called cardiovascular drift. Your blood-vessels relax in order to dissipate the extra heat, meaning your heart has to beat faster to maintain the flow to your muscles – even though your running-speed/exercise intensity may be the same.
Not only does exercising in the heat require more energy and so help with energy-balance, but the it stimulates your body to burn fat (Cheung & McLellan, 1998). This means that instead of using carbs or muscle tissue, fat is the fuel of choice, meaning you lose weight in an effective manner.
Train hard, fight easy!
This mantra favoured by old-school boxing coaches has some "real weight behind it" when it comes to physiological adaptations. Training in a depleted state is known to enhance adaptations to endurance training, while "heat shock proteins" released in training at high temperatures are known to switch on genes involved in aerobic and anaerobic fitness adaptations and to impact on inflammation (Morton, Kayani, McArdle, & Drust, 2009). Training in these conditions will decrease the subsequent negative effects of inflammation and muscle break-down (Morton, et al., 2009), meaning that if you suffer in the short term, you'll be a cool, calculating fighter come fight-night.
Freddy Brown is an Elite Sports Nutritionist currently working with Professional Rugby Clubs, having supported GB wrestling, GB boxing and a host of professional boxers. Currently working for the RFU's head nutritionist under his Perform and Function banner.
- Cheung, S. S., & McLellan, T. M. (1998). Heat acclimation, aerobic fitness, and hydration effects on tolerance during uncompensable heat stress. J Appl Physiol, 84(5), 1731-1739.
- CONSOLAZIO, C. S., R; MASTERSON, JE A. (1961). Energy Requirements of Men in Extreme Heat. Journal of Nutrition, 73.
- Dickson, J. M., Weavers, H. M., Mitchell, N., Winter, E. M., Wilkinson, I. D., Van Beek, E. J., et al. (2005). The effects of dehydration on brain volume -- preliminary results. Int.J.Sports Med., 26(6), 481-485.
- Henry, C. (2005). Basal metabolic rate studies in humans: measurement and development of new equations. Public Health Nutrition, 8(7a), 1133-1152.
Mackay, B. B., M. (1932). THE RELATION BETWEEN GLYCOGEN AND WATER STORAGE IN THE LIVER
- Morton, J. P., Kayani, A. C., McArdle, A., & Drust, B. (2009). The exercise-induced stress response of skeletal muscle, with specific emphasis on humans. Sports Med, 39(8), 643-662.
- Pugh, L. G., Corbett, J. L., & Johnson, R. H. (1967). Rectal temperatures, weight losses, and sweat rates in marathon running. J Appl Physiol, 23(3), 347-352.