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I talked with a female friend about how to lose her small fat tummy. I suggested to her that she do sit-ups every day. She read in a book that doing sit-ups is harmful to women, because they may have some bad effect on the uterus and possibly cause infertility.
Is there any scientific basis for what she claims about sit-ups?
A friend of mine was told she couldn't train judo because it would somehow harm her reproductive organs. (At no time was she asked whether this mattered to her.) We know that even as recently as the 1970s, women were barred from marathons on similar grounds:
I'm sure many physicians trained in that era are still spouting the same horseshit. Exercise-induced infertility is one of the oldest anti-woman canards in the history of misogyny. Alarm bells should go off when we hear it.
How many scaremongering news stories do you hear about male infertility caused by judo, or sit-ups, or football? Practically none, despite the fact that the testes are much more exposed to external injury and are damaged by overheating. Likewise, how many stories of infertility (or uterine prolapse) do you hear among the women who lift weights, run marathons, do step aerobics, play judo, or CrossFit? How many incidents are reported nationwide each year? Millions of women train hard. We would be seeing an epidemic if these activities carried significant risks.
Another answer claims that sit-ups cause uterine prolapse, which is a serious condition. The idea is that sit-ups increase intra-abdominal pressure, pushing the uterus down into the vagina. What is left unmentioned is the degree to which this is a risk factor compared to the other causes: "aging, time-related weakening of the ligaments holding the uterus up; having had vaginal deliveries; and a drop-off in estrogen production".
What else causes intra-abdominal pressure? A vast array of common activities, not just hard exercise. Something as everyday as taking a poop is sufficient. The article warns against sit-ups for this woman--not all women--because she recently experienced a uterine prolapse. This does not contraindicate sit-ups for women. That's just plain put-the-woman-back-in-the-kitchen scaremongering BS.
Similarly, the idea that sit-ups cause infertility strikes me as silly. They're not a particularly rough exercise. Are women's ovaries really that weak? I think not.
In contrast, we do see that extensive exercise can, for some women, in some circumstances, cause irregularities in menstrual cycles. (It should be noted that not exercising will of course have negative effects as well.) A brief PubMed search resulted in nothing suggesting that sit-ups are particularly harmful towards women's health.
The reason to avoid sit-ups is not for any of these anti-woman tropes, nor nonexistent dangers. It's because the exercise itself just isn't too great. Sit-ups are not that efficient at training the abs, and they can put stress on the lower back.
More importantly, spot reduction is a myth, so it won't help reduce belly fat any more than squats or bicycling would.
Your friend shouldn't do sit-ups, but she shouldn't do them because she's too busy lifting heavy weights, running, or boxing, not because they constitute some danger to her frail womanly nature.
@DaveLiepmann. It does help a lot. Exercises is necessary, but must find a right way. Excessive exercises doesn't give any benefits to anyone.
Apparently sit-ups (and other exercises that create pressure in the lower body) can cause problems with the pelvic floor, including promoting pelvic floor weakening, with the most extreme form of that being uterus prolapse, where the uterus is pushed down into the vagina. However, from what I've found, this is not a concern for all women, but specifically for women who already have a weak pelvic floor due to either recent pregnancy, a genetic predisposition, or other factors such as certain childbirth events.
To quote one article:
"lifting a heavy weight increases pressure inside the abdomen, which in turn pushes down on to the pelvic floor. Sit-ups, curl-ups and double leg lifts, traditionally recommended as abdominal strengthening exercises, also raise internal abdominal pressure....If the pelvic floor isn't strong and co-ordinated enough to quickly lift and hold to counter this internal pressure during exercise, then pelvic organ prolapse, or misalignment, is promoted."
This article also describes some pelvic floor strengthening exercises to help counteract this issue, which is important to note, since it seems to provide a way to do sit-ups more safely if you are doing these compensatory exercises.
Another article, specifically in the case of a 60 year old woman with a uterine prolapse, mentioned:
Things that contribute to uterine prolapse — a dropping down of the uterus into the vagina — are aging, time-related weakening of the ligaments holding the uterus up; having had vaginal deliveries; and a drop-off in estrogen production...Activities that increase intra-abdominal pressure can make the uterus fall farther. Sit-ups increase intra-abdominal pressure, as does straining to eliminate stool. You can do other exercises for weight loss: walking, jogging, biking, swimming.
So, perhaps the take-home here is that, sit-ups are not necessarily harmful provided they are done properly and the appropriate pelvic floor strengthening exercises are done along with them. If one has a particular condition such as mentioned above, one might want to consult one's physician about it before undertaking a regimen with sit-ups.
I've read about exercise inducing amenorrhea.
...exercise-induced amenorrhea is a temporary condition that occurs when the energy demands of strenuous exercise cause your body to go into "starvation mode" and shut down unnecessary functions, including ovulation, to keep your basic life functions going.
Another resource suggests that exercise in otherwise sedentary people will increase your fertility, as long as it isn't taken too far. Too far is defined when you have:
Yet another resource suggests that sit-ups are safe into early pregnancy, but due to blood vessel constriction not in the second or third trimesters.
In fact the only resource I could find that would support your friend's concern was someone who was asking a similar question due to information from their acupuncturist. In other words, the association is from holistic sources, and not from traditional medical sources.
The conclusion
Exercise is important, and can improve fertility in both men and women. There are several types of exercise, and the frequency and intensity of your exercise has more influence on your fertility than any single exercise.
If your friend is not currently trying to have a child, any potential mal-effect of sit ups would only be temporary and gone in a couple days from ceasing that activity. If your friend is currently trying, but not successfully, take a look at a host of things, not just sit-ups:
Anything more than that, and your friend might need to see a fertility specialist.
