Do you know what's better for your pelvic floor muscles: being able to squeeze strongly or being able to squeeze and hold for a long time? The answer is somewhere in the middle! Today we're going to talk about the different types of muscles and why we want both to be trained in our pelvic floor.
There are several ways to classify skeletal muscle fibers, but one way classify them is using slow-twitch or fast-twitch fibers (Scott, 2001). Fast twitch fibers are important for creating lots of strength but can't maintain this strength for very long. Slow twitch fibers aren't able to produce as much strength, but they can hold a muscle contraction for a much longer period of time. You can think about fast twitch fibers like a sprinter--they can run really fast for a short period of time. Slow twitch fibers are more like a marathon runner--their running speed may not be as quick as the sprinter, but they can sustain for longer periods and longer distances.
All of the skeletal muscles in our body have and use both types of fibers depending on our activity. Think about our glutes (butt muscles) for example. When we stand up from a chair or perform a squat, we use more of the fast twitch fibers. We need to create lots of strength to get us up from the chair or squat, but that task only lasts a second or two. When we are standing in one place, those same muscles are working to help keep us upright and stop us from falling over, but these muscles are working at a much lower resistance and need to work for much longer.
These same principles are true for our pelvic floor muscles. To explain why, let's first start by talking about the main roles that our pelvic floor muscles perform.
Support: The pelvic floor muscles sit at the base of the pelvis and help to support the pelvic organs. This includes the bladder and rectum as well as the uterus in those with a vagina and the prostate in those with a penis. These muscles need to have good strength, endurance, and tone to be able to support these organs throughout the day, especially as we are active.
Sphincteric: The pelvic floor muscles play a role in controlling when we pee or poop, and our ability to keep pee and poop in. While there are other involuntary muscles that assist in this job, the pelvic floor muscles have an important job. The pelvic floor muscles need to be coordinated to do the right thing at the right time. They need to squeeze to keep the urethra (where pee exits) and the anus (where poop exits) closed and they need to lengthen to open to allow pee, poop, or gas to exit.
Stability: The pelvic floor muscles work as a part of the core muscles. The core is like a barrel that helps to keep the spine, pelvis, and abdominal contents stable and secure. The diaphragm, our primary breathing muscles, makes up the top of the barrel. The transverse abdominus, a deep abdominal muscle, makes up the front of the barrel. The back of the barrel is made up of the multifidus muscles. The bottom of the barrel is the pelvic floor muscles. These muscles all need to work together to keep our bodies strong during activity.
Sexual function: In all individuals, regardless of gender, the pelvic floor muscles play a large role in sexual function. The muscles are active during sex and orgasms. They help with tone and sensation and maintaining erections. While tone can improve pleasure for both partners, the pelvic floor muscles need to be able to relax at the right times so that entry and sex are painless.
Each of these functions requires different levels of strength and amounts of time for the pelvic floor muscles to contract or engage.
Let’s take the sphincteric muscles for example. We need these muscles to have good resting tone throughout the day to ensure we aren’t leaking pee and poop as our body creates it, but that does not mean we need to squeeze and hold the muscles all day long (plus they would get very tired doing this). When we do something like sneeze, we need these muscles to be able to create much more pressure to close off the urethra and anus to ensure the change in our abdominal pressure does not force urine, gas, or stool out. This quick but short increase in the muscle strength would use more of the fast-twitch muscle fibers.
Remember that the pelvic floor muscles can be working even when we aren’t consciously engaging them. Think about your neck muscles, they hold up our head all day long without us having to think about it; however, we can move our head side-to-side if we think about it. The pelvic floor muscles work in a similar way. Actively engaging and squeezing the pelvic floor all day long can lead to too much tension and can cause pain the same way if we walked around with our head turned to one side all day long!
For a healthy pelvic floor that can do everything we expect of it, it’s important for both the slow-twitch and the fast-twitch fibers to be well-trained. Seeing a pelvic floor physical therapist or occupational therapist can be a great resource and they can provide you with individualized advice. Find a pelvic floor PT or OT near you at www.mypfm.com/find-a-pt.
Ready to learn more about pelvic health? Here are some helpful resources:
Subscribe to Pelvic Flicks for pelvic floor weekly workouts
Watch our YouTube playlist on Pelvic Floor Muscle Training
Learn more about the pelvic floor muscles with our book: My Pelvic Floor Muscles The Basics
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Visit our Instagram page for more on pelvic health.
For providers, check out myPFM Academy to learn more so you can better help your clients. With two membership options, you have access to courses, a growing library of patient handouts, hundreds of custom sharable images and infographics, and multilingual resources. At myPFM Academy you’ll find courses like:
Pelvic PT Evaluation of the Pelvic Floor Muscles with Dr. Samantha Richter, PT, DPT, WCS
Vaginal Weights: Evidence Based Research Review with Dr. Amanda Olson, PT, DPT, PRPC
New Structure for PFM Assessment Using ICS Terminology with Beth Shelly, PT, DPT, WCS, BCB-PMD
Written by Emily Reul, PT, DPT
References
Scott W, Stevens J, Binder-Macleod SA. Human skeletal muscle fiber type classifications. Physical Therapy.2001;81(11):1810-1816