“Wow, your baby has great muscle tone!”. Anyone ever heard that? It’s meant as a compliment. But does that mean that a baby can have…bad muscle tone? Let’s dig a little bit deeper and lay out exactly what parents really need to know about this muscle tone thing…

To put it scientifically (feel free to skip to next paragraph) – someone’s muscle tone is determined by what’s called their Golgi tendon organ (GTO). It’s a type of sensory receptor in our body that gives us information on what our muscles are doing. The GTO is who you can thank for your leg kicking out when your knee gets tapped at the doctor’s office – they’re checking for the Golgi tendon reflex (GTR). The presence of the GTR assures us that the GTO is functioning properly – that your muscle is in fact receiving important sensory input, relaying it to your spinal cord and back out to your muscle with a message that say’s “Yup, I felt that!”. Well, what it would really say is something like “I just felt a change in the resting tension of my quad muscle, but I’ll go ahead and put it back the way it was thank you very much”. The GTO responds to change in tension, i.e. stretch, placed on a muscle, and so it’s also called the stretch reflex. This is what lies at the heart of why people have different muscle tone.

To put it simply – someone’s muscle tone is determined by their sensitivity to a muscle’s change in length, which is known as their stretch reflex. The stretch reflex is why we don’t need to think about the fact we’re sitting up straight. Think about it – you may have poor posture, like me, but does sitting up at all require any actual mental effort? Do you ever need to remind yourself of sitting up because otherwise you might fall right out of your chair? How about keeping your head centered while you walk - ever cross your mind? Of course not! That’s because the stretch reflex has you covered. Without it our heads would be flopping all over the place, and when sitting down we’d look like one of those inflatable tubes creatures at car dealerships. As a matter of fact, the stretch reflex is pretty darn underrated!

So now we have established that we’re all born with the stretch reflex, and the presence of this reflex, more sensitive in some of us than others, determines our muscle tone. Some people get their knee tapped with a mini-hammer, there’s a little pause, they give a little kick. Others, perhaps with higher muscle tone, get their knee tapped and their leg kicks out almost simultaneously; one can imagine that this induvial is the more likely of the two to sit with better posture – they have a more excitable stretch reflex – and so when sitting at their desk their core muscles are responding more rapidly to every slouch (change in muscle position) gravity is causing. This kicks on the stretch reflex and they’re sitting up straight. Does this mean they’re stronger? Absolutely not! Do you see where this is going?

Babies are no different. Well actually they are different. They’re different in the sense that they haven’t mastered how to make use of their muscle tone yet. The baby who gets placed in tummy-time, but they’re arms, and legs go rigid and they look like superman…high muscle tone. The baby who gets picked up and their arms and legs stay limp, and they and conform to your shoulder like memory foam…low muscle tone. Most babies are somewhere in between. In any case though, the point is that whether your baby has higher or lower muscle tone, our job is to give them opportunities to feel and understand their own muscle tone, so they can integrate it with purposeful movement, and become efficient movers; because moving is learning! So how do we do that?

Well, let’s say your baby is on the high muscle tone end of the spectrum. When you put your baby in tummy time, they appear rigid. When you try and put them on their back, they scrunch up into a ball – it looks like they can’t relax. Gravity is putting a stretch on their muscles, and their stretch reflex is doing its job, and then some.  For this baby, we need to position them in a manner that gradually introduces them to what their own stretch reflex feels like. We need to put them in positions for play and provide interaction that puts them at an advantage.

For the baby on the low muscle tone end of the spectrum – the one who gives the extra good snuggles – the one you can plop down on the floor and they go full starfish - for this baby we need to do what we can to activate that stretch reflex, illicit a solid muscle contraction and get your baby using those muscles so that muscle recruitment becomes more natural. In short, this baby needs every opportunity to weight-bear through their arms and legs, while also stimulating their core muscles and posterior chain.

In summary, to provide your baby with opportunities to become more in-sync with their own muscle tone you need to set them in positions that provide the “just-right” challenge, and simultaneously offer them developmentally appropriate play opportunities; easier said than done. To learn how you can achieve this with each passing month as your baby continues to change, sign up for our monthly email subscription. It’s completely free and provides parents with expert insight on how to get the most out of every month from birth to one, and empowers you with strategies that will have a lasting impact on your baby’s development.

February 13, 2020 — Matthew Breen