When your sex life isn't what you think it should be, there could be several factors at play. In some cases, stress, depression or a bad sexual experience may be to blame.Or sometimes, the reason is primarily physical, such as fatigue or poor circulation to the genital region.Sexual problems can occur suddenly or develop over time. While it's hard to miss advertisements for sexual enhancers, such as Viagra, a more natural approach to better sex is exercise.Aerobic and strengthening exercises According to the University of California, Santa Barbara, physically fit people are more likely to enjoy sex and engage in it more frequently.Regular physical activity at any age increases your confidence, libido and your ability to have an orgasm, they explain.Exercise increases endorphins, endurance and blood flow to the genitals---in erectile dysfunction, for instance, the problem can be low blood flow in that region of your body.Also, push-ups and abdominal exercises strengthen the muscles you use during sex, explains Discovery Health, and increase your stamina.Kegels These exercises strengthen the pelvic floor muscles, which support the bowel, bladder and uterus, explains the National Institutes of Health (NIH).They increase sexual pleasure for both women and men. Kegels tighten vaginal muscles and improve orgasms, and make it easier for men to delay ejaculation.Practice kegel exercises while you're urinating by squeezing your muscles and stopping the flow for 10 seconds and then releasing.Or you can do them at any time by pretending you're urinating and tightening the muscles to hold it. During these exercises, it's important to keep the muscles of your abdomen, buttocks and thighs relaxed, advises the NIH.Flexibility exercises Being flexible increases your range of motion so you can be more creative in the bedroom. It also allows you to get in and out of sexual positions more easily, according to Kyle Ellen Nuse of Fox News.According to Nuse, flexibility exercises also improve blood flow and circulation. Add flexibility exercises, such as leg stretches, hip-flexing exercises and yoga, to your exercise routine to enhance your sex life.Pelvic tilts For greater flexibility and creativity, pelvic tilts are also effective. They may increase sexual arousal and help you reach orgasm more easily as well, explains Discovery Health.To do pelvic tilts, start by lying on your back with your legs shoulder-width apart and then bend your knees.With your feet flat on the ground and your arms resting at your sides for support, breathe in and raise your buttocks and pelvis.Keep your back straight and your abdominal muscles tight. Hold for a few seconds; then lower your back to the ground.