Sex-Specific Biological Factors That Can Impact Your Workout

Women store fat differently than men. While women's lower centers of gravity and smaller muscle-to-mass ratio make it harder to bang out pull-ups, their tendency to store "gluteofemoral fat" (fat in the hips, butts, and thighs) gives women a huge leg up: A 2010 study from Oxford University found that body fat in the thighs and backside, as opposed to storing excess fat around the midsection, helps protect against heart disease and diabetes.

"Don't be concerned about a little (or more than a little) subcutaneous body fat, especially on your lower body," says Mark Sisson, author of The Primal Blueprint and a paleo fitness expert. "If you've been trying in vain to lose fat in specific areas, consider that it might be there for a reason. Even if you're not interested in having a child, it's likely that the presence of lower-body fat indicates good health (and the ability to get pregnant)," he says. "The research outlined above suggests that classically female patterns of fat deposition are healthier than classically male patterns."

According to the American Academy of Orthopaedic Surgeons, women are two to 10 times more likely to suffer a knee injury than men, thanks to a biomechanical difference in the angle of the hips to the knees called the "Q-angle."

"Because of wider hips, women's knees are more vulnerable to high-impact activities like plyometrics, sprinting, or sports like soccer that require quick changes of direction," says Steve Toms, head of personal training for Lifetime Fitness and corrective exercise specialist. (More here: Why Women Are At a Higher Risk of Tearing An ACL)

Since you can't change your bone structure, Toms suggests strengthening the muscles that surround your pelvis to boost core stability. It sounds counterintuitive, but for many women, the key to ameliorating knee pain is building strength in the glutes and hips. Try adding frontal-plane lunges to your routine and working your way up to single-leg exercises to build stability in the hips, Toms advises.

You might want to be extra careful working out during your period. Australian researchers found that female athletes are more likely to get injured during their periods than any other time of their cycle. Why? Low estrogen at the beginning of the menstrual cycle (when you're actually bleeding) causes reduced muscle tone and impairs coordination, making you more susceptible to injury, especially in the knees, feet, and ankles.

It's not just your physiology that suffers. Rachel Cosgrove, in her book The Female Body Breakthrough, adds that "more than one study has shown that exercise feels harder the week before and the week of women's periods because of increased levels of progesterone and decreased levels of serotonin." You may find that your workouts feel harder than usual and that you're more tired, but don't beat yourself up if you don't set a personal best this week. "Just get in and get it done," says Cosgrove. (Related: 6 Things to Know About Working Out On Your Period)

If you want to make the most of menstruation, power through those weight routines. According to Cosgrove, your body's fat-burning potential peaks during this time. And there's more good news: Taking birth control can help counter the negative effects. "There's now quite a global body of research saying that the pill actually is protective of injuries. It protects you from injuries, improves performance, and improves muscle function," according to the Australian researchers. Birth control as a performance enhancer? Double win!

Thanks to the flexibility of "birthing hips," women can pop a baby out without splitting in half. But those same pliable ligaments can cause pain and injury, especially in the joints connecting the hips to the spine (the sacroiliac joints), says Diane Lee of Diane Lee & Associates, a physiotherapy clinic that specializes in helping women heal pelvic pain. Unlike most joints, the sacroiliac joints are fused together with a very small range of motion. Increasing that range of motion—as often happens during pregnancy—can destabilize the entire pelvic girdle.

"Sacroiliac joint dysfunction occurs in both genders, but it's far more common in women," Lee says. Your pelvic girdle is the primary stabilizer of all movements, so when your pelvis is out of alignment, everything else follows. "It's like having your pantyhose twisted; everything needs to be aligned to work properly."

SI pain can have many different causes, so Lee cautions that "there is not one prescription for healing." Each case is individual. Her expert recommendation: Find a physiotherapist who has experience working with women and get an evaluation.

If you think wearing a weight vest amps up your workout, try strapping 30+ pounds to your abdomen for nine straight months. Okay, so you don't start out 30 pounds heavier, but you get the point: Pregnancy is the ultimate form of weight lifting. It's also the primary way in which men and women differ. What does that mean for your workout? Aside from the obvious added resistance, experts recommend that pregnant women take the following precautions during exercise: stay hydrated, don't allow yourself to overheat, avoid any activity that could cause you to fall on your stomach, and tone down your weight lifting in the third trimester to avoid straining already loosened ligaments.

These restrictions will certainly impact your workout, but they don't mean you need to skip exercise altogether. Research on the topic concludes: "In the absence of any obstetric or medical complications, most women can maintain a regular exercise regimen during pregnancy. Some studies have found a greater sense of well-being, shorter labor, and fewer obstetric interventions in physically well-conditioned women as compared with other women." (This comprehensive guide has all the need-to-know info on exercising while pregnant.)

Shin splints are every runner's nemesis, but women are three times more likely to be afflicted than men, according to Australian researchers. Plus, a study of female athletes published in the Journal of the American Medical Association found that women's shin splints are up to three-and-a-half times more likely to progress to stress fractures than men's.

Additional risk factors for shin splints include flat feet and overpronating (excessive inward roll of the foot after landing)—both conditions that also affect more women than men. Researchers speculate that this may be due to increased prevalence of osteoporosis in women, the effects of the pregnancy hormones in relaxing ligaments in the feet and legs, and/or the prolonged wearing of heeled shoes. So if you're feeling pain during your Saturday morning runs, you may want to ditch your heeled boots on Friday.

Anyone who's gone on a diet with their partner knows the frustration of watching them shed pounds simply by ditching beer while you pull out all the stops and still don't see results. But women's metabolisms are more efficient for a good reason. In times of scarcity, women maintain their body mass and are better at utilizing fat stores than men, allowing women to keep the species going. This has benefits in a non-neanderthal setting too. A 2000 study published in the Canadian Journal of Applied Physiology found that women are better at burning fat (as opposed to carbs) to fuel their cardio sessions than men. (Related: 12 Small Changes You Can Make to Increase Your Metabolism)

It might seem like your entire body is working against you and your fitness goals, but there are steps you can take to protect your body and maximize your performance, starting with these three strategies.

1. Monitor Your Menstrual Cycle

Track your cycle with a period-tracking app, like Clue. Also, pay attention to how workouts make you feel all month, says Kathryn Ackerman, M.D., the medical director of the Female Athlete Program at Boston Children's Hospital. After 12 weeks, you’ll see patterns that can help you exercise more effectively.

2. Train Smarter

Women typically have wider hips, bigger breasts, and a lower center of gravity than men do, which puts more strain on their knees and joints and increases the risk for injury, says Jacky Forsyth, Ph.D., an exercise physiology professor at Staffordshire University in England. To counteract this risk, add neuromuscular training—like balance and plyometrics—to your routine. Also, do moves that strengthen the muscles around the pelvis, like clamshells and bridges, and do jumping exercises, suggests Dr. Ackerman.

3. Find Your Tribe

“Women are more likely than men to drop out of their sport after getting injured because they lose their confidence,” says Dr. Ackerman. Join a community like a run club or a workout studio. The trainers and friends you make will become part of your support system, so if you do get injured, you’re more apt to bounce back.