Maternal Strength Training: Part 2 - The Myths

(Image used with permission from Emily Breeze)

In part 1 we discussed the benefits of exercise and strength training during pregnancy.

If you've not yet read it, I suggest you do. It's only a 10 minute read but sheds some light on why pregnant women should continue to exercise vigorously during the entire term.

If you, a friend or family member are still anxious at the thought of exercising during such time, then part 2 should help debunk the common myths.

Ultimately, the health of both mother and baby is a paramount consideration when deciding whether to exercise during pregnancy. Until recently, most advice on the matter was based on the 1985 recommendations put forward in the publication of American College of Obstetrics and Gynecologists (ACOG), which lacked scientific support and were overly precautious in their recommendations. It's a shame that old and irrelevant information still finds its place in conversation today.

Bizarrely, many of the recommendations within this publication were misguided and based on studies involving various animal species. Animals have different physiological responses to training than humans, and many of the studies used involved pushing unfit species to the point of physical exhaustion—far beyond the exercise intensity employed by the majority of pregnant women (Stevenson, 1997).

Fortunately, a wealth of research has been conducted on humans in more recent years, and the vast majority of studies appear to indicate that maternal exercise is safe when carried out by otherwise healthy women (ACOG Committee Obstetric Practice, 2002; Royal College of Obstetrics and Gynaecologists, 2006).

Newer ACOG guidelines now state that, in the absence of medical complications, 30 minutes or more of moderate exercise on most if not all days of week is both safe and recommended for pregnant women (ACOG Committee Obstetric Practice, 2002).

The Myths


There appears to be a belief that exercise-induced hyperthermia can have detrimental effects on the fetus. Similarly to the above named publication, initial concerns on these risks were based on research in animals, where heat stress during early stages of pregnancy led to an increased occurrence of neural tube defects (McMurray, et al., 1993; Ezmerli, 2000).

Studies in humans, however, do not support this conclusion (Jones, et al., 1985; McMurray, et al., 1993). Stevenson (1997) reported no evidence that prenatal exercise induces hyperthermia nor did it have any negative effects on the fetus.

Larsson and Lindqvist (2005) found that low impact maternal exercise of up to 70% of maximal heart rate shows no significant increase in core temperature from pre-exercise levels, and none of the subjects even approached a dangerous body temperature.

The cause for concern with too high a heart rate has to do with the muscles pulling all the oxygen and not enough going to the fetus, however, the 140bpm guidelines come from outdated research, which was understandably cautious.

We now know the heart rate can be pushed higher than this without worry.


One of the biggest exercise-related concerns among some pregnant women is miscarriage.

By most accounts, abortion is not associated with the level of physical activity (Clapp, 1989; Magann, et al., 2002; Aittasalo, et al., 2008).

Latka et al. (1999) actually showed that those who exercised during pregnancy had a lower rate of abortion compared with those who were inactive. A study comparing resistance training with a non-exercise group showed that exercise was not associated with premature delivery and had no negative effects on gestational age (Barakat, et al., 2009).

These results have been shown to extend to vigorous exercise too. Clapp (1991) reported that previously fit women who continued to train at a level above current guidelines during pregnancy showed no difference in rate of abortion, congenital abnormalities, or implantation problems. Kardel (2005) has also stated that a high volume and/or intensity of training in initially fit women poses no adverse risks to the mother or baby.

Joint Related Injuries:

A concern with maternal exercise is the risk of a soft tissue injury to the joints. During pregnancy, there is an increase in joint laxity brought on by an increased secretion of the hormone called relaxin (Artal and O’Toole, 2003). This makes joints less stable, heightening the possibility of strain and tear of muscles, tendons, and ligaments.

Despite this, however, research does not show an increased incidence of maternal exercise- related injury (Clapp, 1993; Vladutiu, Evenson, and Marshall 2010) and specifically resulting from participation in resistance training programs (Baechle, Earle and Wathen, 2008; Barakat, et al., 2008), provided proper guidelines are followed.

Any body can become injured from performing an exercise incorrectly, however pregnancy does not increase the risk of it occurring.

Sternfeld et al. (1995) showed that muscle and joint complaints actually decreased among during pregnancy.

Given that resistance training has been shown to increase connective tissue strength (Fleck SJ and Falkel, 1975; Stone, 1988), it would seem to be a particularly beneficial method for reducing injury risk in pregnant women.

Strength training increases joint stability. There's no doubting it. A properly planned strength training program will help reduce aches and pains that are common in pregnancy, such as lower and upper back pain, ultimately by keeping posture in more optimal alignment. And yes, if you’re new to strength training you can absolutely start during pregnancy. If you're unsure of what to do, look into working with us online or in-person and we'll help teach you solid movement patterns and progress you appropriately.

Damage to the Abdominal region:

I’ve come across articles/blogs that advise pregnant women to let their abdominals get “nice and soft” before and during pregnancy. The advice is to even stop abdominal training whilst trying to become pregnant, just so you don’t risk abdominal separation.

This is not good advice.

Correct abdominal and trunk training is so important during pregnancy because of your ever-changing posture and additional weight being added to the anterior (front) aspect of the body. As discussed previously, strength training can help to minimise hyperextension (arch) of the lower back and place the pelvis in a better position.

Abdominal separation is a real thing that many women in pregnancy experience, it’s called Diastasis Recti (DR). DR occurs because of the growing fetus pressing onto the abdominal wall. The rectus abdominis (6-pack muscle), will stretch because of this and the connective tissue holding it together can get very thin and soft, ultimately leading to separation between the muscles.

The good news? A stronger trunk can help reduce the size and severity of DR and set you up for a speedier recovery post birth.

If part 1 and part 2 haven't helped convince you that maternal strength training is not only safe but extremely beneficial, wait for part 3 (coming soon) where we discuss the considerations for correct training programmes and methodologies for pregnant women.

#prepostnatal #pregnancy #exercise #maternity #resistancetraining #strengthtraining #benefits #prenatalexercise


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Aittasalo M, Pasanen M, Fogelholm M, Kinnunen TI, Ojala K, and Luoto R. Physical activity counseling in maternity and child health care—A controlled trial. BMC Womens Health 14: 14, 2008.

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