There are only two reactions to “core exercises” – either you LOVE them or you HATE them. The muscles that are commonly referred to as the “core” are the front abdominal muscles – the rectus abdominis (6-pack), transverse abdominis, and obliques. They’re what everyone wants, but are incredibly hard to achieve without a strict and clean diet…or an incredibly high metabolism. What’s not commonly thought of as the “core” though, are the OTHER muscles and structures that make it up. The core is made up of your respiratory diaphragm at the apex of the abdomen, the abdominal muscles in the front, the lumbar paraspinal muscles in the back, and the pelvic floor muscles at the base. These groups together help keep your body strong and stable, as well as performing other duties we won’t touch on here. And these muscle groups can be exercised in a myriad of ways – both the traditional “core” exercises (such as crunches) and not so commonly thought of exercises (such as squats). What I seek to do with this blog is hit on 4 commonly performed exercises that strengthen the core and how they impact the pelvic floor. These exercises are: low front planks, sit-ups (butterfly), bird dog, and squats.

Low Front Plank

The plank is great for activating the spinal muscles as well as the abdominal muscles. However, is an exercise that brings to mind a “NEVER do that” connotation. Many believe that due to the impact this exercise can have on the pelvic floor, it’s an exercise that should NEVER be done. But I don’t believe that are true “nevers” in life. Planks can really help wake up the abdomen – whether used as a warm-up or a strengthener. To say you can “never again” do a plank is ridiculous. But at the same time, jumping into a 5 minute plank 2 weeks postpartum is also ridiculous. It’s something that needs to be consistently performed and increased at a safe progression.

The reason the pelvic floor can be affected is because of possible pressure created on it while in the plank position. If your abdomen and low back isn’t taking the brunt of the demand, then your pelvic floor may take on more of that work. So, rather than jumping straight into an “as long as possible” plank, maybe do short intervals first – making sure the pelvis is tucked and there isn’t sag in the low back. Then progress from there!

Sit-Ups

This is what first comes to mind when trying to predict what others will think of when considering “core” exercises. What I think of first when I consider a sit-up in a workout is “why do I want to add a sit-up in?” If it’s because I want them to get better at sit-ups or because they have a sit-up test coming in the future, then I’ll likely throw it in there. If it’s because I want them to feel like they’re really moving, but also be able to slow down the amount of movement, then I’ll likely throw them in there. If the reason is because I want to do core work, I might choose another exercise that will bank in on more muscle groups at the same time.

The sit up will target specifically the abdominal muscles – and possible the hip flexors depending on how you’re set up in this movement. It doesn’t really activate the low back or the pelvic floor as much – meaning it won’t assist in co-contracting different muscle groups. Because of the increase in intra-abdominal pressure, it also means that if you’re not strong enough for this exercise it will put more pressure on the pelvic floor. If the pelvic floor (like with the plank) isn’t ready for that demand, then it’ll cause issues (either in incontinence or eventual pain).

There’s some concern with diastasis recti with sit-ups. With a diastasis recti, there’s a split in the rectus abdominis muscle – what is traditionally considered the “6-pack muscles.” This occurs in 100% of women in the 3rd Trimester, due to the amount of space required for the growing fetus. However, in most women it either resolves completely or is asymptomatic. Diastasis remains in 32-46% of women, causing pelvic floor dysfunction or low back pain. However, what we’re looking at when deciding on if sit-ups are appropriate is the absence or presence of that pelvic floor dysfunction or low back pain. In the absence of low back pain/pelvic floor dysfunction, with a baseline strength, and with having a benefit to performing sit-ups, then get it!

Bird Dogs

Bird dogs is one of my favorite exercises for “core” – it encompasses so many parts. It challenges balance, it challenges the abdominal muscles, it challenges the low back muscles. It’s versatile, you can add so many things to it – from combining bands to weights to increasing hold times. You can add pelvic floor contractions with it, and add pelvic floor relaxation to it. Like I said, it’s incredibly versatile!

The biggest benefit there is to adding a bird dog in, whether as a warm-up to ensure the low back and abdominal muscles are firing well before getting into movement, or as part of a core-circuit, is that it enhances co-contraction behaviors in the muscles. This muscular co-contraction means everything is going to work and move together better. With the core being made up of specifically 3 different muscle groups – this is vastly important when considering a “core” workout.

Squats

Squats are likely the least-thought of core-exercise. However, studies show that squats – especially heavy squats – increase the activation of low back muscles (especially the lower portion of the back). And that activation of the trunk musculature on heavy squats, creating a ballooning effect, can increase the stability within the squat. However, now that we’re getting into heavy squats and the intra-abdominal pressure pattern for heavy squats – it’s a great time to talk about what happens to the pelvic floor with this activity.

When the breath is held in the lungs, the diaphragm is kept in a descending position. Because of its relationship to the pelvic floor, that means the pelvic floor is held in a stretched position throughout the movement. Like any other muscle group, if it’s held in a stretched position it has a harder time contracting and assisting to hold up. Meaning that incontinence within this movement is likely – or pressure creating prolapse – due to the forces on the pelvic floor. Does this mean it will definitely happen to you? NO! But like everything else in this blog post, you have to train for that. You can’t move from squatting 105# to squatting 300# and not expect things to fail out on you or at the very least to have some sort of issue. It also means that you need to train specific motions within the squat to keep your pelvic floor from failing (which in itself would be a separate blog post).

SO! We’ve gone through the 4 core-muscle strengthening exercises that I chose. What do you do with this information now? Use it! Plan your programming with your core in mind – plan your patient’s exercises with the core in mind. What the core actually does, what muscles actually make it up, how it works in conjunction with other muscles, and the multiple ways that the core can be challenged. A body goes through a myriad of movements throughout the day – and most of the time they aren’t the exact same movement. Meaning you, your patient, your athlete – their life is variable, and as such – their exercises need to include variability!

References:

Gluppe, S., Hilde, G., Tennfjord, M., Engh, M., Bo, K. Diastasis Recti Abdominis in Postpartum Primiparous Women: A Randomized Controlled Trial. Phys Ther, 2018; 98 (4): 260-268

Ko, M., Song, C. Comparison of the effects of different core exercises on muscle activity and thickness in healthy young adults. Phys Ther Rehabil Sci; 2018, 7(2), 72- 77

Tillaar, T., Saeterbakken, A. Comparison of Core Muscle Activation Between a Prone Bridge and 6-RM Back Squats. Journal of Human Kinetics, 2018; 62, 43-53

Olsson, A., Kiwanuka, O., Wilhelmsson, S., Sandblom, G., Stackelberg, O. Cohort study of the effect of surgical repair of symptomatic diastasis recti abdominis on abdominal trunk function and quality of life. BJS Open, 2019; 3: 750-758

Garcia-Waquero, M., Moreside, J., Brotons-Gil, E., Peco-Gonzalez, M., Vera-Garcia, F. Trunk muscle activation during stabilization exercises with single and double leg support. Journal of Electromyography and Kinesiology, 2012, doi: 10.1016/j.jelekin.2012.02.017

Hamlyn, N., Behm, D., Young, W. Trunk muscle activation during dynamic weight-training exercises and isometric instability activities. Journal of Strength and Conditioning Research, 2007; 21(4): 1108-1112