All the information in today’s literature about flexibility is enough to make your head spin. Static stretching vs. dynamic stretching; mobility vs. flexibility; motor control vs. length-tension relationships… the list goes on and on. So today I want to break down some important facts about flexibility.
First and foremost, we must understand the difference between flexibility and mobility. Tony Gentilcore, co-founder of Cressey Sports puts it best:
Mobility is how a joint moves, while flexibility is the length of a muscle.
The difference between the two lies in the understanding that muscles, such as hamstrings, have a certain length to them, whereas joints have a range of motion. Our brains are amazing machines and control everything that happens in our bodies. Your brain will decide if you have enough strength and stability to even control the flexibility or range of motion that you actually have access to. The body oftentimes moves through it’s path of least resistance to function, so if you lack range of motion or mobility in one area, the body will simply steal it from another area that moves better. All of this happens without you even being aware of it.
One example of this is the relationship between the hip and the spine. Oftentimes, our hip joints lose range of motion over the course of our lives due to sedentary and uniplanar lifestyles. When a hip loses the ability to properly extend or rotate, the body will find another area to make up for that loss of motion… and usually it is the lumbar spine. If your back begins to take on the job of motion that the hip should normally perform eventually it will break down and begin to hurt. It’s one of the reasons that lower back pain affects more than 65 million Americans.
Another example is when we purposely limit a joint’s range of motion with braces or splints. It was common practice years ago (and sometimes still is today) for basketball players to tape their ankles or wear high top sneakers, which limited ankle mobility. What happens when you take away mobility at one joint? Well another joint has to make up for it and, in this case, it was usually the knee. Ask yourself how many basketball players you know who have knees that are shot? (No pun intended.)
Another important factor affecting flexibility (or our perception of flexibility) is our nervous system. Our nervous system basically runs the show for what happens in our bodies. To put it simply, the nervous system gives us permission for movement and therefore flexibility is the result of what our nervous system will allow.
Let’s take hamstrings for example. “My hamstrings are soooo tight…” is probably one of the most common complaints I get from clients. And when that client tries to touch their toes it does appear they have limited hamstring flexibility. However, when you passively stretch their hamstrings in supine (lying on their back) they present with 80-90 degrees of hamstring flexibility; well within normal range. Now, why can they not touch their toes and always feel tightness in their hamstrings? The nervous system. To put it in blunt and basic terms, the nervous system senses that you are not safe at the end range and allowing you to access that end range may result in an injury. Because our brains are such amazing machines they say “Wait…no way…this guy is going to hurt himself if we let him go there, so I am going to protect him and keep him out of harm by limiting your movement.” Hence, the hamstrings batten down the hatches, tighten up and limit the ability to touch the toes. Think of the nervous system as an overprotective parent trying to keep their kids out of harm’s way: a parent would not let their 14-year-old drive a car… not because they physically can’t, but because it is dangerous and they may get hurt.
Now, why does your nervous system hit the brakes? There could be a number of reasons for this. Maybe it’s poor core control of the lumbar spine, inability to flex the hips in a weight bearing position, core muscles that are too rigid (yes that does exist and it is not necessarily good in the way your are thinking), or poor lumbar flexion… the list goes on and on. As qualified healthcare practitioners and physical therapists, we must determine the underlying cause of the compensatory pattern in order to properly correct it. Doing hamstring stretches does nothing to fix the problem, because remember the hamstrings are not really tight, they are simply compensating for something else. So, if you have been stretching your hamstrings, or IT band, or plantar fascia for years with no improvement and want to lay blame on those muscles for being so tight remember, they are not necessarily at fault, they’re simply at the mercy of your brain.
Christa Gurka, MSPT, PMA®-CPT