Pump Iron to Pump Up Your Libido?

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Q: Is weight lifting the best way to boost your sex drive or does all exercise increase testosterone levels?

A: Although the steroid hormone testosterone, present in both men and women, can affect your libido, so do many other factors. Studies have shown that regular exercisers report a higher sex drive. This may be related to surges of testosterone that can occur immediately after resistance training like lifting weights, or right after endurance training like running.

But testosterone levels can vary for many reasons. For one thing, the hormone seems to fluctuate throughout the day, depending on what are known as circadian rhythms. In men, levels are highest in the morning and concentrations are minimal in the evening. Women generally have lower levels compared to men, but levels can vary tremendously in both men and women. Women may have a different exercise response than men. Although there may be increased levels in men and women that can be detected immediately following certain workouts, overall levels may be decreased after other types of exercise, such as regular endurance training. Even food intake may play a role. If a person drinks a protein-carb shake before and after a workout, the levels can go down. And aging men, for example, have lower levels and may get a lower boost from a tough weight-lifting session than a younger man.

Plus, it's not only levels of the actual hormone that may affect a person, but the amount of receptors present on cells that can interact with the testosterone. Testosterone helps stimulate muscle growth, but different types of muscle fibers are more (or less) receptive to the hormone. This means that the effects of testosterone may also depend upon the proportion of muscle fibers a person may have (which is mostly genetically determined), and what kind of exercise they do to train the muscles.

Like everything else going on in the body, especially with hormones, the response of testosterone is highly complex: It's not like you just push a button by doing a bench press and Whoa! spurts of testosterone liven up your libido!

Plus, a revved up sex drive may also occur from other sympathetic hormones like epinephrine (adrenalin) that make a person more energized, or even opioids like beta-endorphins that can produce a "feel-good" effect. Or it may be that the psychological self-confidence that you get from being physically fit, accomplishing fitness goals (exercising on a regular basis, for example) or simply losing weight boosts your self-esteem and helps you to feel sexier. One recent study in the International Journal of Obesity found that overweight and obese women who lost weight by using the diet drug sibutramine reported improved sexual arousal and orgasms—and the more weight loss, the better.

No matter what, all types of exercise are good for you, and by keeping your body in good working order, everything should keep functioning the way it should! For more information on all the benefits of strength training read Designing Resistance Training Programs (Human Kinetics Publishing, 1997), by Steven J. Fleck and William J. Kraemer.

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Martica is a Manhattan-based exercise physiologist and nutritionist and an award-winning fitness instructor. She has written for a variety of publications including Self , Health , Prevention , The New York Times and others. Martica is the author of seven books, including her latest, Cross-Training for Dummies . (Read her full bio.)