As most people know, when you get cold, you shiver. The shiver response is characterized as an increase in heat production via the contraction of skeletal muscles. This can increase to a level that is 500% more than resting metabolic rate (Jansky, 1998). If you haven’t been into the chambers at CrossFit X-treme San Jose, ask anyone who has: you shiver. You shiver hard. This means that every time you shiver, your body is using an increased caloric consumption just to maintain your body heat for survival.
Interestingly, there is another mechanism for heat production in the body: non-shivering thermogenesis. This is primarily down through the use of brown adipose tissue (BAT) that is often found in higher amounts in hibernating mammals and human babies. Lichtenbelt et. Al (2004) describe “temperature training” where the body learns to adapt and develop the “Thermal comfort zone.” The Thermal comfort zone is the ambient temperature range where the body can have regulatory changes in the body. So often in today’s society, climate control in our work places, homes and even cars, our body’s natural responses to changes in temperature get lazy. This could imply that our development and use of brown fat decreases!
During your first 3 minutes, we often explain how the extreme cold effects the nervous system. Often times, to distract you from the extreme experience your body has encountered, but also to educate you on what is going on. Morrison (2004) reports that this same activation of the nervous system causes BAT to increase fatty acid consumption, increases leptin levels and even breaks down white fat. Leptin is a hormone strongly related to appetite by cuing the body to feel full! White fat is the fat type that you pinch while looking in the mirror convincing yourself that you’re less beautiful than you actually are.
So there you have it! Come in for your temperature training and teach your brown fat to burn your white fat!
Sources:
Jansky, L. (1998) Shivering. In Physiology and Pathophysiology of Temperature Regulation (Blattheis, C.M., ed.), World Scientific
Lichtenbelt, W. V., Kingma, B., Lans, A. V., & Schellen, L. (2014). Cold exposure – an approach to increasing energy expenditure in humans. Trends in Endocrinology & Metabolism, 25(4), 165-167. doi:10.1016/j.tem.2014.01.001
Morrison. S. (2004) Physiology, 19 (2) 67-74. Central Pathways Controlling Brown Adipose Tissue Thermogenesis. DOI: 10.1152/nips.01502.2003
