Science Thursday: Exercise Physiology--Women vs Men

Intuitively, we know that women respond differently to exercise, training, and nutrition than men. Men are faster due to bigger hearts and more muscle mass (among other things). Women tend to recover faster from workouts, however, and may also have more endurance in ultra events. Also, women rarely get calf cramps while men succumb to these crippling stabs of pain. Men tend to lose weight faster than women; women hang on to body fat and have higher body fat percentages. Obviously, these are trends and observations. Surprisingly, little research has been done on the specific physiological differences between men and women during exercise.

Sidenote:
Women can be faster than men? There have been several instances of some women kicking men's asses, especially at the ultra endurance events. Check out Gertrude Ederle) who swam the English Channel faster than the 5 men who had done it before her. Lynne Cox , who swam in Antarctic waters, completing ultraswimming events where men who had tried before her died. Seana Hogan, ultracycling legend (yes, even better than men), and Pam Reed, bad-ass at Badwater and overall winner (several times!).

Back to the main story:
Recently, an article in the New York Times highlighted some of the differences in the physiology between men and women. We've all been hearing the hype about protein and muscle recovery after a workout. The idea is that muscle is made of protein. Working out breaks the muscle tissue down. It then recovers and rebuilds, coming back stronger than before. Studies have shown taking in a certain amount of protein within 30 minutes after a workout speeds up the recovery process, presumably by helping the muscle rebuild. That's why we've all been slugging chocolate milk after a good training session. Or at least, that's the excuse we've been telling ourselves for all the chocolate milk we've been guzzling (yum, yum). This study was first published by Rowlands et al., 2008 in Appl Physiol Nutr Metab.

Unfortunately, this study used all male subjects. Almost as an afterthought, Dr. Rowlands conducted a follow-up study, this time focusing on female subjects. Surprisingly, females did not respond like the males to ingesting protein after a cycling workout. They had no measurable benefit to the protein (Rowlands et al., 2010. Med Sci Sports Exerc). This may be due to the higher amounts of estrogen and lower amounts of testosterone in women vs men, although this is probably only a part of the total complex number of factors in the end equation.

This is not the first time gender differences have been observed with respect to physiology and training. For instance, studies have indicated that females do not respond to carbo loading like males do (See Tarnopolsky et al., 2001 J Appl Physiol). That well-intended, detailed meal plan you bought from the nutritionist to carbo load the week or two before your A race? If you're female, you may be simply wasting your time. The benefit of carbo-loading was not as great in women. For whatever reason (blame it on estrogen), women are not able to utilize the greater percentage of ingested carbohydrates to restock their glycogen stores, compared to men.

Finally, the heart-rate training you've been doing? If you're a woman, you may be using the wrong formulas. All those detailed books with numbers and percentages you're supposed to be a slave to in training were calculated based on studies using male subjects. Not to mention treadmill and their automatic heart rate programs. The ole' 220-age is not accurate. Apparently, this is about 8 beats too high for women, which may lead to premature fatigue and frustration if you're trying to adhere to a heart rate plan. Honestly, I think it's better to train based on feel and breathing anyway (I love the talk test but maybe because I love to talk). Researchers from the University of Colorado devised a more accurate formula for both sexes: 208-0.7*age (Tanaka et al., 2001. J Am Coll Cardiol). For more information, check out this article in the Times.

Basically, women should be wary when new recommendations arise for training, fitness, exercise and nutrition. Check out the source of the study. Was the gender of the subjects all male? If so, any conclusions should be taken with a pound of salt when it comes to changing up your program. Reynolds states in her article, As Dr. Rowlands says — echoing a chorus of men before him — when it comes to women, there’s a great deal that sports scientists “just don’t understand.” Afterall, women are not men. Thankfully.