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Thursday 5 December 2019

Exercise (Things We Don’t Know about Pregnancy Series #8)

I wasn’t sure how to break it to her. The midwife. That I was a climber.

My greatest fears in pregnancy was being told not to climb, abused by people for doing it anyway, and turfed out of climbing centres – and I had done my research: exercise is highly advantageous during pregnancy, and there are no controlled studies on climbing whilst pregnant.

The body changes during pregnancy

During pregnancy, your body changes and remodels itself to create a nest to house your foetus for 9 months. As the hormone relaxin floods your body, your ligaments relax and joints loosen. Your centre of gravity shifts, upsetting your sense of balance. Your need for oxygen increases, with an extra 20% of blood flowing through your body, and this can make your blood pressure drop, leaving you more prone to dizziness.

So you should definitely exercise – here’s why

Exercising is good when pregnant for the same reasons it's good when you're not, but it can have additional benefits, such as supporting circulation through you and your foetus, reducing cramping and back pain, and improving balance as your centre of mass shifts.

One literature review found that women who exercised at high intensity had a range of reduced pregnancy symptoms, including
  • 1/3 the rate of gestational diabetes
  • 2/3 the rate of preeclampsia
  • 1/4 the rate of low back pain
They also showed a better ability to tolerate heat stress, a higher foetal heart rate variability – or greater ability to adapt to physical stresses such as labour, and double the heart stroke volume in the mother.

Statistical analyses of competitive athletes (not climbers) has shown that women who are extremely fit are less likely to have overweight babies and equally likely to have underweight babies, with a slightly lower average weight. Since women who are very fit are less likely to be overweight, and overweight women tend to have heavier babies, this could just be a biased sample effect.

Some sports are also great for mental focus. Yoga is popular for this, but I'd argue climbing is better: an intensely psychological sport, it involves both managing your fear and physical problem-solving, both of which are good for reflection and coping with physical challenges – like labour.

Climbing whilst pregnant. © TWDK

Exercising benefits labour. Strengthening legs, stomach and pelvic floor can make natural delivery easier. In fact, the NHS offer specific advice on pelvic floor, pelvic tilt, and stomach exercises!

Fitter women were found to be less likely to request an epidural (down to 1/3) or have an abnormal foetal heart rate during labour, less likely to have umbilical cord tangling, to have labor induced (down to 1/4), or to have interventions like a caesarian section (down to 1/4). Labour was also shorter (65% delivered in 4 hours vs 31% of controls).

Postnatal exercise may reduce 'baby blues' – the natural plummet in mood caused by sudden changes in hormones (athletic women had 80% of the rate of postpartum depression compared to the general population). It also decreases risk of deep vein thrombosis.

But how many people know both about climbing and about pregnancy? I certainly wasn’t prepared to stop climbing because medical professionals who didn’t know the difference between top roping and lead climbing were afraid of it. As others have pointed out, most people who think climbing is unsafe know nothing about it, and perhaps haven’t realised that the risk of travelling by car is far greater (approximately a 1 in 20,000 risk of death in a given year compared with 1 in 79,500 for climbing).

Advice aimed at the inactive

Perhaps it comes as no surprise to learn that most exercise advice is aimed at people who don’t exercise at all.

Like, ever.

This isn’t particularly helpful for fitter women – it is completely biologically different to start exercising during pregnancy to continue it. If fitter women followed advice such as use stairs, walk to the shop, and get 150 minutes of moderate (sweating, out of breath, but able to talk) exercise a week, would mean reducing physical fitness.

This level of inactivity would in fact be impossible for me to achieve (how would I get to work?), and is probably rare in the UK unless you are disabled or live in the countryside. I also have problems with the advice because it recommends building up from 10 minutes of activity twice a day (140 minutes a week) to five 30 minute sessions a week (150 minutes) – not much of an increase, especially when interval training is so good for cardiovascular health[1].

But some of the advice is sound: beginners should pick whole body sports that don't involve moving in any very new way, like walking, swimming and running. I'd add not to let anyone pressurise you into a pregnancy-specific paid class like pilates – you don’t have to virtue signal to be a good mum – only go if they sound fun and worth the money.

If you do any instructed classes, tell your instructor you're expecting. Remember, pregnancy is not a handicap, but some things may need to be modified, just as they would for a dodgy knee cap.

One adaption I’ve made for climbing is using a full body harness, which takes pressure off the midsection and transfers it across the chest instead. Normally these harnesses are worn by very tiny children, but adult sizes are available. They’re not the most comfortable, but they’re their as a safety measure, not a luxury!

So, what exercises should you avoid – and why?

There are some things you should avoid in pregnancy, and these can be grouped into four categories: whacks, pressure, temperature, and mum.

Whacking the bump

Whacking the bump is not a good thing. The worst case scenario is placental abruption, when the placenta peels off the wall of the uterus and stops fending for the baby altogether, but any kind of damage is bad news.

Whacking the bump usually means getting hit or taking a fall, but some standing twist yoga positions are even contraindicated because they put on the abdominal cavity.

For this reason, contact sports (with risk of hits) like kickboxing, judo or squash are not recommended, nor are sports like cycling (except on stationary gym bikes), horseriding or parachuting (with risk of falls). For now, let’s set aside the relative safety of cycling or driving to work... Whilst “stuff where you go up or go fast” immediately meshes well with the idea of falls, the risk goes further – anything that makes you dizzy can make you fall over, including lying on your back for prolonged periods.

This is why so many yoga positions are contraindicated, such as inversions, which can cause dizziness in pregnant women who have a higher oxygen demand, and direct circulation away from the uterus.

But doesn’t climbing carry a falling risk?

Yes, and no.

Climbing is not inherently a high impact sport. Surprisingly, it is not designed around falling from great heights and slamming into things – in fact, the aim is not to fall (although all climbers should be trained in how to manage falls). If you are top- or bottom-roping, with a rope fixed at the top of the wall, the climber can sit back and rest their weight on the rope at any time. With a relatively taut rope, the “fall” you experience top roping provides about as much umph as flopping back onto the sofa – often less. Others have described these “falls” as jumping on a trampoline or jumping off a box onto a crash mat.

Belaying whilst pregnant. © TWDK
Lead climbing is different. It involves pulling up a rope behind you and because where it’s attached could be below the climber, falls tend to be bigger, exerting forces up to as much as about 7 kN (at a stretch, for a heavy climber and poor belayer). These kinds of forces and falls are not typical – but they’re possible. And you feel them if you’re the belayer ‘catching’ the climber, as well as if you’re the falling climber.

Beth Rodden conducted a survey of 339 pregnant climbers. Whilst some climbed up to delivery and others stopped altogether, most stopped leading at 12 weeks and otherwise limited their climbing from 20 weeks (half way), stopped training (pushing themselves) and doing abdominal exercises. Most stopped completely by 31 weeks (just over 7 months). Only 6% reported injuries.

There was more uncertainty about bouldering (low level climbing without ropes) – favoured by some and cut by others. In any case, climbing easy stuff and not ‘pushing your grade’ means you need never fall at all, only abseil serenely down, or downclimb on a bouldering wall.

Extreme pressure and the bump

Unborn babies can’t protect themselves against altitude and decompression sickness, and can even get embolisms, so entering extreme environments can be seriously dangerous. This means high mountain hiking (over 2,500 m) or scuba diving should be off limits. This does not really affect my recreation, and most women don’t go on extreme adventures so often that it would.

Heating the bump

Getting too hot and staying too hot for prolonged periods has been linked to malformations and birth defects in the baby, especially during the first trimester. This has led some people to avoid exercising hard. However, you’d have to run very fast for at least a couple of hours to get your body temperature anywhere near high enough to be risky. Studies on competitive athletes who work out at above 90% their recommended maximum heart rate have so far shown no increase in birth defects. “Hot yoga”, “hot pilates” and saunas, however, are deemed hot enough to pose some risk.


Since there is no evidence that too much exercise harms unborn babies, advice not to overdo it is primarily for the sake of mum. With loose muscles and joints, women can more easily injure themselves performing high-impact movements, bouncing or pushing themselves for prolonged periods, resulting in dislocations, pulled muscles, compression injuries and the like. As pregnancy progresses, most women find they need to ease off on the exercise.

Enough is enough

So, when is it time to stop exercising? How do you know?

In the past, pregnant women used to get told not to let their heart rate go above 140 beats per minute, but this arbitrary number has been slacked off as it doesn't really tell us much about safe limits. Instead, look out for signs that you're unwell, including
  • Dizziness
  • Headache
  • Extreme thirst
  • Swelling

Or, on the more worrying end,
  • Chest pain
  • Vaginal bleeding
  • Contractions

If any of these happen to you, please, please stop. These are not the normal consequences of exercising, and exercising, done right, should make you feel good. To show you what I mean, here are a few of the words that jumped out the page at me when reading articles by other climbers: grace, flow, focus, head space, identity, efficiency…

There are many unknowns when it comes to pregnancy, and over the next few months, I’ll be exploring more of them with you. Look out for my next blog post, which will be about alcohol and caffeine.

To read our full article on the things we don't know about pregnancy, check out our site. This article will be updated as we add posts across the coming months.

why don't all references have links?

[1] Kessler, Holly S., Susan B. Sisson, and Kevin R. Short. The potential for high-intensity interval training to reduce cardiometabolic disease risk. Sports medicine 42.6 (2012): 489-509.

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