Part 2: Why the mechanical argument for tight muscles doesn’t make sense when it comes to pain
Traditional physiotherapy has often looked to find “deficits” in someones function and then suggested those deficits are what is causing pain. Deficits are typically any type of physical functions or attributes that deviate from averages. Typical examples being altered postures when you are standing that deviate from neutral (e.g your head might be forward, your pelvis might be tilted more anteriorly than average, some muscle is weak or range of motion is less than average).
A very common and fully unsupported explanation for all sorts of pain problems would be the lower crossed syndrome. This completely made up and unsupported “dysfunction” suggests that people have pain because their hip flexors and back muscles are tight and their ab and butt muscles are weak. This then theoretically (but without evidence) causes the pelvis to anteriorly rotate forward. I’ve written a lot about this before (see the Blog about Bullshit Butt Theories here) so don’t want to re-litigate this fairy tale of a pain explanation but wanted to talk about why muscle and joint stiffness is mostly irrelevant for this proposed boogeyman. Meaning the ideas underpinning the lower crossed syndrome theory don’t make any sense.
I’m not new to this topic. My first question ever on a form of social media was in 1998 on this topic. The answers told me to not worry about it. Yet, we are still having this discussion somehow.
The Mechanical Argument for not worrying about stiff and restriction muscles and joints
Reason #1: Posture isn’t related to pain
We could probably just discuss this and not go any further. In general, static posture (anterior pelvic tilt, lumbar lordosis, forward head position, “text neck”) are not related to pain (text neck debunked here and here, forward head posture explored here and Todd Hargrove’s blog here is excellent). Sure, sometimes it hurts when you stand for a prolonged period and if your back is arched it feels better to lift your foot up on something and flex your spine more. Super. Variety is good. Or sometimes if you are at a computer screen and you are slumped forward it feels better to sit up straight. But the converse is also true. After sitting up straight for awhile it feels great to slump. Here is an old blog of mine on not worrying about sitting posture
Your body is robust. Why should you care if your pelvis anteriorly tilted? The argument is that there is greater load on the back. So what? Load is good dummy. Load and stress is what causes us to adapt. That’s why we exercise, that’s why squats are good and jumping and running. The load on the spine just standing or sitting is very low. We are capable of tolerating very high loads and yet we freak out over some potentially tiny increase in load because your back is a little bit arched? Or your hip flexors are supposedly “tight”. Again, any load that your hips flexors put on your back is tiny compared to all the wonderful loads that we place on our backs when we are active.
Reason #2: Muscle stiffness is a poor determinant of posture
Posture is probably more of a habit rather than being determined by stiff or loose muscles. Or it’s determined by the shape of your bones. But, even if the muscles are contributing to your posture I will tell you why stiffness and trying to address that stiffness is mostly irrelevant.
First, the definition of joint stiffness is a joint’s resistance to movement. This could be created by muscle, tendon, joint capsules or any connective tissue. It’s typically measured by moving joint through its ROM and measuring how much force you apply and measuring the ROM. You then plot the two and that gives you a joint stiffness curve. In the picture below you will see two curves. The red curve is more stiff than the blue curve. It takes more force to bend that joint. Notice how with a joint you initially have a lot of movement with very little force applied. Because in most joints at the start of movement there isn’t a lot of stiffness. The increasing stiffness occurs later in the movement. If stretching were to decrease joint stiffness we would see a shift in the curve to the right. i.e the same force would equal more ROM. But surprisingly we don’t regularly see that after long term stretching programs (naturally, the research is mixed on that).
It is assumed that a “tight” or “stiff” muscle will pull your joint into some new resting position. So if you have tight hip flexors they will “pull” the pelvis anteriorly when you are standing. The problem with this is that when you undergo a long term stretching regime we increase our range of motion but we often don’t change the joint stiffness (see this blog here or here). A number of studies suggest that there isn’t any mechanical changes in the tissue so we actually aren’t any less stiff (here is a review but you should know that you will find some exceptions. Nothing is that cut and dry). This means if there is no change in the stiffness of a joint at rest then it won’t be “pulling” any differently on the structures to cause a change in posture.
It seems like we are able to change our joint mobility without consistently changing joint stiffness (again there are some exceptions - see this fantastic PhD thesis which shows that after 24 weeks of stretching your ankles they will be slightly less stiff but after 24 weeks of stretching your hamstrings there is no change in stiffness - despite both increasing their ROM). What people have argued is rather than there being this structural change after stretching we have nervous system change - You have merely improved your tolerance to stretch. This means the joint has the ability to move farther but at a certain position it isn’t pulling with less force on the bones. That’s what stiffness is. Caveat some studies do show a change in stiffness but it seems small and inconsistent across studies (don’t Pubmed bomb me) and the primary means for changing mobility seems to be via nervous system adaptations.
To reiterate, when you stretch your hip flexors your mobility might change but they aren’t less stiff in the long term (they are less stiff in the short term - i.e minutes). So, in the long term stretching and mobility work doesn’t lead to the hip flexors pulling forward less on the pelvis thus posture doesn’t change. This has been studied. If you stretch the hamstrings you won’t see a change in kinematics (aka dynamic posture) when you run (reference here), if you stretch the hip flexors you will see a change in mobility but you won’t see a change in running kinematics (reference here) and if you stretch and strengthen you won’t see dramatic changes in postures during functional tasks (reference here).
We aren’t puppets where you can loosen and tighten strings to “pull” us into different positions (Gosh, I wrote the same thing 10 years ago - G*damn Groundhog day)
Reason #3: Joint “Stiffness” is not creating unnecessary or too much tension on your joints
I hear this one a lot. It’s the idea that a stiff muscle is “pulling” on a sensitive part of your spine or even on a stress fracture. Or you need to loosen up the flexor muscles in the forearm to stop “pulling” on a sensitive elbow tendon. So a therapist has to come along and “release” that muscle to offload the joint, tendon or the stress fracture. Or teach you to relax and decrease the tension and stress on your joints. This is attractive to those with pain because it often fits with what we feel. We feel stiff. We feel tightness and we will feel pulling when we move. It’s easy to assume that a muscle or joint is stuck and it needs to be loosened. And sometimes these interventions help with pain but I’d suggest its not because they are decreasing the stress on a sensitive structure. There a few problems with this:
1. We can’t always trust what we feel. The body lies sometimes. Especially when in pain. Pain corrupts who we are and how we feel our joints and muscles. (that was the whole point of the first blog). This is seen in the work of Brusco et al (2020) below. They found that after 6 weeks of static stretching joint range of motion increased (stretch tolerance), with no change in joint stiffness and the person felt the stretch later i.e. they felt less stiff. Even though no change in objective measures of stiffness were seen. We changed our perception of the sensation without actually changing the joint stiffness.
If we aren’t truly tight or that much stiffer when in pain (again, I’m sure there are exceptions - especially when we naturally or unnaturally guard and brace) it means we really aren’t putting a lot of extra force on our joints. Related…
People are asked to respond when they feel the stretch. After long term stretching they feel it later even though there is no change in stiffness
2. There isn’t a lot of resistance to movement (i.e stiffness) when in normal postures.
This means that even if we are stiffer we wouldn’t be putting extra stress on our joints from that stiffness because we don’t “see” that extra stress until you start moving away from your resting posture. Meaning, if extra stiffness was really there it is tiny and would only show up when you start moving through greater ranges of motion. When I had Frozen Shoulder I didn’t know it was stiff until I moved to about 70% of my previous max ROM. During most activities it was fine. The stiffness just showed up when it was near end ROM.
Related, even if there was more stiffness who cares? Stiffness is just a little bit of load. Load and stress is good for us. It was causes us to adapt. Many sport scientists would even argue that joint and tendon stiffness is a good thing. Its often associated with better performance. Strength training increases stiffness and strength training is often universally recognized as one option to help people with pain.
What’s the harm in worrying about muscle stiffness and tension?
For most people, there is no harm at all. But for some, we ruminate. We can perseverate. We might always be looking for someone to decrease that tension or “release” some muscles. You spend hours stretching, foam rolling, getting massages and trying to change something that is not pathological. It’s like trying to breath through the proper side of one nostril. We are chasing something that can’t be caught.
So, why does it feel stiff?
One way to reframe stiffness is what you already know. You are in pain. You are sensitive and sore. So now, normal movements where your muscles are either actively working to move a joint or where your muscles are being stretched become irritating and painful. Muscles are stupid. They are just ropes that can only pull. When you arch your back your back muscles pull you into that position. When you bend forward your back muscles are pulled on as you flex forward. In both cases the muscles produce tension where they attach and to the structures near them. You feel tension because your muscles are being tensioned. That is their only job! You are feeling a normal pulling sensation but because you are in pain it can now feel problematic. And if you think it’s problematic it the feeds into the problem. The feeling of tension may not be the true problem here. It’s whatever is driving your sensitivity and pain that we want to focus on.
As always, there are exceptions. In Part 3 we will talk about where trying to change how you move (e.g more relaxed, might be helpful)
Reason #4: Range of Motion Increases don’t influence resting posture and inconsistently influence dynamic posture (aka Kinematics)
What about muscle ROM? Well, this was only studied 31 years ago yet we still promote this tripe. Here we see a study showing no relationship between anterior pelvic tilt and hip extension ROM (link here). This has also been shown in runners but only 21 years ago. I guess people promoting this drivel should be given more time to find it. These authors found that the amount of hip extension measured with the Thomas Test was not related to Anterior Pelvic Tilt when running (reference here). We have also seen that increasing hamstring ROM won’t change lumbar posture either (reference here). Oh and remember when I said that the original lower crossed syndrome theory suggested that Anterior Pelvic Tilt was related to muscle strength. Well that’s been studied and there isn ‘t any relationship either (references here, here and here)
A caveat might be mobility training and movements where you near end range. If I raise my arms over my shoulder to reach something and my shoulder flexion is limited I will reach the end range of shoulder movement and will have to extend more at my spine to reach my goal. If I stretch my shoulders for months I might then be able to reach the higher overhead and my back won’t have to arch. You could call this a change in posture but it’s only relevant when you get to end ROM for specific joints. This last example is where Part 3 will pick up. Trying to find examples where mobility and stiffness might be relevant for pain and injury. This blog is becoming a tad too much of a polemic. I don’t want to be an absolutist and say that stiffness or mobility are never relevant. That would be unfair and not accurate. Nor do I want to say that stretching and foam rolling are never helpful for people. That too would be inaccurate. See you soon.