Strength training during pregnancy is good for mother and baby

Geschatte leestijd: 11 minuten I have never imitated Schwarzenegger in his role in the movie Junior (1994) and thus, as a man, I have no idea what it’s like to be pregnant. However, I do know that there are many misconceptions and uncertainties when it comes to strength training for pregnant women. The direct reason for this article is a study that will soon be published (in the Journal of Strength and Conditioning Research) which again demonstrates the safety of specific strength training during pregnancy [1]. This article will discuss this newly published research, but as usual, I will also address other studies on this topic for a comprehensive overview.

The benefits of strength training during pregnancy

For clarification: All forms of sports, including strength training, involve certain risks. Just the fact that as a mother you also have the responsibility for two lives increases this risk. When I refer to strength training in this article, I assume the correct form of training, with the correct technique and intensity. Furthermore, I assume a normal pregnancy without known complications. It’s a standard phrase, but especially in this case, it’s always advisable to consult a doctor first to check if there are no special circumstances that would prevent you from training. In the case of expected multiples or complications in previous pregnancies, there may be reason to advise against training [3]. Except for these circumstances, exercising during pregnancy offers various benefits.

“Effects of pregnancy comparable to effects of training”

Did you know that the changes in your body during pregnancy are somewhat comparable to the changes during and through training [2]? When you are pregnant, for example, your maximum oxygen consumption at rest is increased by about 30% [3], you also produce more carbon dioxide and breathe in and out faster [4]. The amount of air your lungs breathe in and out per minute increases by 50%, similar to the amount of blood that increases by 40-50 percent [2]. The amount of blood your heart pumps per minute (“cardiac output”) increases by 30 to 50 percent [3]. This “cardiac output” is maximized to increase blood flow to the placenta and the fetus [5].

Cardio poses higher risk during pregnancy than strength training

Although both strength training and cardio can have these effects, this occurs mainly with cardio. It’s somewhat logical that cardio creates more “cardiovascular stress” (the extent to which the heart and lungs have to work), it’s not called “cardiovascular training” for nothing. Additionally, cardio leads to higher heat production, making it less well-tolerated by the pregnant body than strength training [6]. The most recent research that will be published soon aimed to specifically check this point: Whether strength training indeed does not cause excessive cardiovascular stress [1]. Does this also apply, for example, to strength training for the lower body, which most people will know requires more energy (including for the heart and lungs) than the upper body?

Research Brazil: “Strength training during pregnancy safe in terms of cardiovascular stress”

Brazilian researchers compared the effects of strength training between 10 pregnant, healthy women (average age 25, 22-24 weeks pregnant) with 10 healthy young women who were not pregnant (also average age 25). They had the ladies do pec-deck flyes for the chest and leg extensions for the legs. They did one and three sets of 15 repetitions with a resistance/weight of 50% of their estimated maximum (fairly standard training except for the number of exercises). They measured various things after doing one and three sets such as blood pressure, heart rate, and oxygen consumption. By comparing both groups, the researchers found that the group of pregnant women reacted almost the same to the exercises and there were no dangerous effects from the training.

We concluded that the pressure response was unaffected by pregnancy and showed to be safe during the performance of resistance exercises. R. Bgeginsk, Federal University of Rio Grande do Sul

Considerations for exercising during pregnancy

In addition to the mentioned changes that make cardio pose an increased risk, there are also other effects that need to be considered. These are mainly hormonal in nature.

Hormonal changes during pregnancy

For example, the hormone relaxin produced during pregnancy to relax the pelvic tendons for an easier delivery. However, this hormone also affects other tendons in the body, making them smoother/less stiff and therefore providing less stability. This, combined with a changed balance due to an increase in size and weight of the belly, makes it unwise to do sports with rapid explosive movements [4,5]. Think of it like a race car with a piano placed on top of the roof and at the same time, the tight race suspension is replaced by the soft suspension of an off-road vehicle. The car would dangerously lean in every turn. Unfortunately, this example shows that I am a man, but unfortunately, I couldn’t come up with a metaphor involving horses, dancing, or high-heeled shoes.

Increased Insulin Production

During pregnancy, insulin production is increased [4]. Insulin regulates the amount of glucose in the blood. Increased insulin production means that more sugar is taken up from the blood and used by the muscles or stored as fat. This means that there is less sugar in the blood. If this is not taken into account with diet and training causes even more sugar to be used, this can lead to hypoglycemia (low blood sugar). This can lead to nausea, dizziness, fatigue, and fainting.

Increased hydration requirement

A concern for training during pregnancy is that blood used to sustain activities (by, for example, providing oxygen to the muscles) comes at the expense of the blood that should go to the fetus [2]. This can result in an increased heart rate of the fetus [2,8,9]. This can be limited by drinking enough and limiting the intensity of the training (see further). It is always important to drink enough, but especially when exercising during pregnancy [10,11]. Dehydration during exercise can lead to an increased risk of premature birth [4,12].

General Benefits of Strength Training During Pregnancy for Mother and Child

Although there are certainly some considerations and special cases where strength training is not recommended, in general, there is a negative correlation between training and complications in the fetus [13]. The risk of complications actually decreases. There are many different benefits attributed to exercising during pregnancy. For the mother:

• Better heart and lung function [14]
• Smaller increase in weight and fat mass [14]
• Better mental well-being [2,14]
• Easier to be active [14]
• Faster recovery [14]
• Greater overall fitness [14]
• Lower blood pressure [2]
• Better prepared for childbirth due to extra effort required for breathing during training [2,3]
• Less muscle soreness and less tired muscles at rest [2,7]

For the child:

• Lower percentage of body fat [14]
• More resilient to stress in general [14]
• More resilient to the stress of childbirth [14]
• Improved “maturation” of nerves and brain [14]
• The baby is more alert at birth and calms itself more easily (“self-quieting”) [12,14]
• By the age of five, children appear to be leaner and mentally (slightly) better developed [14]
• Better protected against heart and vascular diseases in childhood and adulthood (although these studies are controversial) [20,21]

Which Exercises During Pregnancy?

Although you can continue to do most strength exercises for the usual reasons during pregnancy, there are some muscle groups that deserve extra attention during pregnancy.

“Easier” Delivery Through Leg Muscle Training

As a man, I may use the term “easier” too easily. However, by training specific muscle groups, you can prepare them for their role during childbirth [4]. This includes training the quadriceps, hamstring exercises, buttock exercises, adductors, and abductors (the muscles that move the legs inwards and outwards).

“Kegel Exercises”

You probably get these during pregnancy gymnastics and the like, but I’ll mention them anyway. Kegel exercises (named after Arnold Kegel) are exercises for the pelvic floor muscles where you work with rhythmic contractions (contracting for a certain number of seconds and then releasing). These ensure that your pelvis is better prepared for childbirth because you are better “aware of these muscles and how to contract and relax them” [17]. Moreover, they help the body return to its pre-pregnancy state more quickly [4].

Back Muscles to Offset Increased Weight of the Abdomen

As the weight of the abdomen and breasts increases during pregnancy, this poses an additional burden on the extensor muscles of the back. Especially training the rhomboids, trapezius, and back of the shoulders can compensate for this [4].

Recommended Training Volume and Intensity for Strength Training During Pregnancy

The most important thing to remember is that during pregnancy, you are not training to make gains, but to limit the loss of previous results [2]. Although there are guidelines for training volume (how much you do) and intensity (how heavy you do it), this largely depends on the mother’s level of fitness prior to pregnancy [7,15]. In this regard, it does not differ from a random visitor to a gym who approaches an instructor for a schedule. It also depends on the previous level of fitness (“non-mover,” “low-mover,” “high-mover”). You should start at a level “that does not result in pain, shortness of breath, or excessive fatigue” [2]. Then this could be increased as long as it does not lead to “significant discomfort” [5]. However, I think this depends on previous fitness levels. If you have never trained and start during pregnancy, you will not yet come close to what you could do maximum, pregnant or not. For example, you could build this up to 80% of what you could do without pregnancy. However, if you already train intensively and are already at 100% of your current capacity that you normally try to expand, this will only decrease as the pregnancy progresses, although gains are still possible in the first months. As a general recommendation, moderate intensity is suitable for all women with a normal, complication-free pregnancy. Higher intensity, for example for trained athletes, is advised only after consulting a doctor and not after the start of the third trimester of pregnancy [5]. Competition is also only recommended after consultation.

Recommendations for Volume and Intensity According to Research

Several publications have been made with guidelines on this [2,6,14,15,16,22,]. If you look for the similarities, the following recommendations emerge from these studies:

• Train three days a week
• Half an hour per session (possibly with build-up from 15 minutes)
• Do one to three sets of 10 to 15 repetitions each (in total, so one set per exercise)
• Resistance/weight: 50% to 70% of your (estimated) 1RM (the maximum weight with which you can do one repetition of the exercise).

This should therefore take into account the level of fitness. Untrained women could start with fifteen minutes per session and build up to 30 minutes. As you can see, the workouts are shorter than usual when you are used to a regular, full strength training schedule where you train two muscle groups per day and do three to four exercises per muscle group.

Training Tips for Strength Training During Pregnancy

A few general tips:

• Breathe controlled. Especially do not hold your breath, which can cause pressure (such as when you try to breathe hard while the airways are closed) [2]
• As mentioned: Avoid explosive/ballistic movements (due to relaxin, but also to keep the risk of injury low)
• Avoid too heavy resistance. Choose a weight with which you can do at least 10 to 12 repetitions.
• Choose machines/equipment where loose weights pose a risk. Think, for example, of bench pressing where, for example, there is a risk that the weight/weights could fall on the stomach or squatting where you can fall with weight on your back.

Avoid Exercises Lying on the Back (“Supine Position”):

• Avoid this especially after the first trimester of pregnancy. This can cause too much compression of the inferior vena cava due to the weight of the fetus. This so-called inferior vena cava ensures the return of blood to the heart [5,18,19,22].
• Abdominal exercises performed lying on the back can cause a tear in the abdominal muscles [4]
• The previously mentioned cardiac output, the amount of blood your heart pumps per minute, decreases by 9% when lying on your back [2,22]. This is increased during pregnancy to supply the placenta with enough blood and is therefore limited when lying on your back (and therefore also when doing exercises from this position).

“Crossfit Moms: It’s Okay to Take It Down a Notch”

An extra warning is probably necessary for Crossfitters. I wrote something about choosing machines instead of free weights before. The biggest risk mentioned in various studies is “blunt force trauma,” getting a hard blow [23]. When looking for images for this article, I quickly came across photos of a pregnant woman deadlifting. I thought then, “Nice picture, but actually an example of how not to do it.” The whole feeling of “look-at-me-being-hardcore” that I got from this also immediately made me suspect that this was someone who does Crossfit. It’s possible you already know that one of my biggest objections to Crossfit is the fact that Crossfitters almost always want to let everyone know that they do Crossfit. Sometimes it almost seems like a cult with, for example, people doing a Crossfit WOD (workout of the day) during their wedding (really, I’m not making it up, google crossfit wedding). Earlier, I saw a video in which a man had his baby strapped to his front and was doing a barbell shoulder press, and I thought, “You must not accidentally strain yourself now or get scared by a mouse or whatever, because then that baby will have a Grand Canyon in its fontanelle. So it really wasn’t surprising at all that when I clicked on the picture, it turned out to be a Crossfit lady who proudly posted this image on Facebook and then received over 6000 comments, mainly from people who thought this wasn’t very smart. Although the discussion in many cases was about strength training in general, I want to make the distinction again between machines and free weights. If you do an exercise with a heavy barbell or kettlebell above your head, there is always a chance that it will fall. Of course, there is a difference between a dumbbell curl with a relatively light dumbbell on the one hand (like the picture at the top that I found fitting for the article) and heavy squats on the other hand. So use your common sense! You don’t have to agree with me that Crossfit can lead to injuries faster than usual strength training. Research has not been able to show this so far (although only one study has been conducted based on surveys filled out by Crossfitters). Even if you do “normal” strength training, you have to take a step back with some things. Then it seems wise to apply this in Crossfit as well.

Conclusion

Strength training during pregnancy offers many benefits for both mother and child. Both mother and child are better prepared for childbirth as a result of strength training, but also benefit long after from the strength training. However, careful consideration must be given to some safety tips. It is always advisable to consult a doctor first, especially if there have been complications during this or a previous pregnancy.

Part II:

Training after childbirth, how fast, how often, and how heavy? You have read that strength training during pregnancy ensures, among other things, that the body can be returned to its pre-pregnancy state more quickly after childbirth. In the next part, I will therefore discuss how you can further speed up this process through training. How soon do you start again after childbirth and how intense? Can and should you then do cardio again? You will read about it soon on Fitsociety.

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