A practicing physician for more than 40 years and a radio talk show host for 25, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is one of a very few doctors board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology.
He is a frequent contributor to Roadcyclist.com a bi weekly newsletter provided free to anyone who subscribes. He and his wife ride over 100 miles a week and he's over 70 years old. His website and newsletter are full of training tips that have been gleaned from sports and medicine journals. As I take my blog in a new direction, I will be referring to his research and qouting from his newsletters frequently.
In his latest newsletter he speaks about cold drinks during training. Something most of us never think about beyond preferring col cytomax to luke warm gross sports drinks.
Dear Dr. Mirkin: Does taking cold fluids improve exercise performance in hot weather?
Yes; drinking cold fluids lowers body temperature. More than 70 percent of the calories that you use to convert food to energy are lost as heat. So the more intensely you exercise, the more heat you produce. A rise in body temperature slows you down because the heart has to work harder to pump extra blood from your hot muscles to your skin to dissipate the heat. Seven studies show that cold beverages lower body temperature and improve performance by an average of 10 percent.
He had a previous post about drinking colas and training which I also found interesting;
The limiting factor in endurance racing is the time that it takes to get enough oxygen into muscles to burn food for energy. Anything that reduces oxygen requirements allows you to race faster. Sugar stored in muscles, called glycogen, requires less oxygen than fat or protein. Anything that helps you keep sugar in muscles longer gives you greater endurance.
A study from Georgia State University shows that drinks that contain both glucose and fructose burn more carbohydrates than those containing only glucose, and allow cyclists to ride much faster over 60 miles (International Journal of Sport Nutrition and Exercise Metabolism, April 2010).
Most soft drinks are sweetened with high fructose corn syrup (HFCS). Both HFCS and conventional sugar (sucrose) contain a mixture of two sugars, glucose and fructose, in nearly the same concentrations: HFCS has 55 percent fructose/42 percent glucose, while sucrose is a 50/50 mixture. So the relative concentrations of glucose and fructose are not significant. However, the fructose in sucrose from cane or beet sugar is bound to glucose and must first be separated from it, so it is absorbed more slowly into the bloodstream. The manufacturing process for HFCS frees the fructose from glucose to makes it into a free, unbound form that is absorbed more rapidly into the bloodstream. This could cause a higher rise in blood sugar ((Pharmacology, Biochemistry and Behavior, March 18, 2010) and provide more sugar for muscles during exercise. We need to wait for more research to know if HFCS drinks improve endurance more those made with cane or beet sugar.
Caffeine increases endurance (Medicine & Science in Sports & Exercise, July 2010) by increasing absorption of sugar by muscles (Journal of Applied Physiology, June 2006). Those who took sugared drinks with caffeine were able to absorb and use 26 percent more of the ingested sugar than those who took the same drinks without caffeine.
On long rides, we drink colas for their sugar and caffeine. However, you should take sugared drinks only when you exercise and for up to an hour after you finish. Contracting muscles remove sugar from the bloodstream rapidly without needing much insulin. Taking sugared drinks when you are not exercising causes higher rises in blood sugar that increase risk for diabetes and cell damage.
On a recent training ride I experimented with using half a water bottle of coke mixed with my usual peformance drink. As far as performance, I had plenty of energy that day. I found that you really had to shake the bottle before riding to flatten the carbonation but as I mentioned; there was no noticable difference in my power output and possibly I had more than usual. It's hard to tell in one ride and so further experimentation is needed and will be carried out.
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Hey, Thanks.
ReplyDeleteI am not sure to whom you are referring to when you say “most of us never think about beyond preferring cool cytomax to Luke warm gross sports drinks” but I always use bottle with frozen ice in the bottom and ice warm. All the athletes I work with do the same. I use ice to keep me cool during warm ups, and stay the hell out of the sun.
Cytomax?
Waste of money.
I've always been told that it's better to drink warm water/drinks because cold water takes energy to warm to your body temperature. I included that blurb because it's different from what I've been taught thus far.
ReplyDeleteCytomax?
It works for me.