Leg cramps, problems catching your breath, overall fatigue, dehydration - all of these things can happen during sex. On top of these issues, you might suddenly in the midst of passion, think of all of your woobly bits - the parts of your body you dislike. Maybe, to make matters even worse, you realize the position you are in and your partner's perspective of your body. "Ugh!" you sigh.
Sex can be physically tiring, just like any other physical activity, particularly if it's sustained for a long duration. With the spring around the corner, and people's thoughts turn to love (and lust), now is a good time to think about exercise. The link between physical fitness and sex is an interesting one, and one that should not be underestimated.
Getting enough sleep, eating right and reducing stress are all important for having a satisfying sex life, but they are also really obvious and talked about elsewhere at length. What is less discussed is the importance of getting exercise before you end up in bed with your special someone.
Exercise that is performed over a sustained time leads to a so-called "runner's high," caused by the release of endorphins. These endorphins are stimulating, and as well as causing us to feel great, they stimulate the release of sex hormones. The added bonus is that exercise causes us to feel better. It elevates our mood and creates a feeling of calmness (albeit after we have had a chance to cool off and relax). The lowering of heart rate, improved digestion, lowered blood pressure and lowered stress hormone levels combine with the feelings of well being caused by the endorphins. Add to that an increase of another hormone, oxytocin, and the result is a relaxed, content, person.
For women, the link between exercise and sex has been explored by Cindy Meston and her colleagues. Their results indicate that working out - albeit vigorously - primes women's bodies for sexual activity. It is not simply that exercise increases genital blood flow or makes women sexually aroused. Instead, there seems to be something, as of yet unidentified, that prepares women's bodies. After working out, she found that women's bodies respond faster and more intensely to sexual content (such as an erotic film). Her findings are exciting because they counter the long held belief that relaxation is necessary for a good sexual experience, and assumption that might be due to the link between anxiety and erectile problems for men. I should mention that so far these effects have been documented immediately after exercise and seem to diminish quickly- indeed, they seem to be the strongest 15 minutes after exercise and fade fast.
As for men, sexual experiences also benefit from exercise. White and colleagues (1990) had two groups of men, whose average age was 48 years, all of whom were sedentary but healthy at the start of the study. One group engaged in walking, while the other in aerobic exercise. The latter group reported higher levels of sexual intimacy, more satisfying orgasms, and more reliable sexual functioning. Thus, men who are physically inactive and then aerobically exercise three or four days a week, regularly, for at least an hour at a time, soon report more sex and better sex. However, all men experienced an improvement, leading the researchers to conclude that enhanced sexuality is directly correlated with their improvement in physical fitness.
Satisfying sex lives isn't just about the nuts and bolts of biology - it also involves self image. People who exercise often have a positive self body image, which might make them simply enjoy their bodies more, too. Penhollow and Young (2004) found frequency of exercise and physical fitness enhanced attractiveness and increased energy levels. They write that those who exercise are more likely to experience a greater level of satisfaction and a positive perception of self, which may cause them to believe they are more desirable and may perform better sexually
One last thought - sex itself is a physical activity and burns calories and increases fitness. Many factors influence how many calories are spent during sex, but most reports seem to indicate about 85 for a half hour to hour session, which is about the same as bowling (see this link for calorie counts). Unlike bowling, though, sex can also increase self-esteem, cardio-vascular health, emotional intimacy, improve sleeping, and increase immunity!
Penhollow, T. M. & Young, M. (2004). Sexual desirability and sexual performance: Does exercise and fitness really matter? Electronic Journal of Human Sexuality, 7, http://www.ejhs.org/tocv7.html.
White, J., Case, D. A., McWhirter, D., Mattison, A. M. (1990). Enhanced sexual behavior in exercising men. Archives of Sexual Behavior, 19(3), 193-209.
To see a short summary on female physiology and exercise and further references: http://www2.psych.ubc.ca/~bglab/female.html