Different Stretches for Different Purposes
We all know we’re supposed to stretch. Some of us even do it from time to time. But are we stretching right?
There is more than one way to stretch. Most of us grew up doing static stretching – the stretch that you hold without moving for 10-60+ seconds. But there are A LOT of ways to “stretch”. And just like how running at different effort levels induces different physiological changes in our bodies, different type of stretching do different things.
First off, let me start by saying there are very few things that are either blanketly “good” or “bad” for you when it comes to physical fitness and athletic performance. It’s often more productive to think in terms of what physiological stimulus different things provide.
Let’s start off really old school: ballistic stretching. This is when you stretch by bouncing at the end of range of motion, getting a little more range of motion out of the tissue using gravity or momentum. Not the best idea to do this on cold muscles. This form of stretching was mostly abandoned due to the high risk of injury when using this technique on cold muscles. Cold muscles aren’t typically the most elastic, and so they’re more likely to suffer damage. Literally ripped apart when you reach the end of their range of motion and then force it further. That being said, you can commonly see this approach being used on WARM muscles, especially with stretches like leg swings. (What does it do physiologically?)
Static stretching is the (now) classic stretch that generally replaced ballistic stretching at some point in the dark ages of athletic training and performance. The basic idea is to stretch a tissue to close to the end of range of motion, and then hang out there for a while. This is typically used in both warming up (due to the lower risk of injury than ballistic stretching), as well as during cool downs to help mitigate some of the discomfort we feel the day after a hard workout. It can work to functionally increase the length of a muscle fiber by essentially getting the actin and myosin fibers within the muscle cell to add some extra bits on the end, making themselves longer. These are the proteins that actually ratchet past each other to get the muscle to contract. By making these protein chains longer, the muscle can actually contract from a longer state, providing a bigger functional range of motion. The connection points between actin and myosin fibers are like a bunch of little ratcheting heads on the myosin that crawl along the actin fibers. This process takes energy, and by wearing it out you can actually get the ratchet heads to let go, which is why this kind of stretching can be used to help reduce muscle tone (how flexed the muscle is in its resting state).
Foam rolling and flossing are typically thrown in with stretching, since one of the goals is to help increase the functional range of motion of the tissue or joints. While both of these methods can be used to get a little stretch out of a tissue by forcing the muscle fibers to have a longer path between one end and the other, they’re mostly used to help break up adhesion between muscle fibers so that they can actually slide past each other like they’re supposed to. These techniques can also be useful for working on the nerves that conduct information back to the central nervous system from the muscle tissue, helping to reduce muscle tone and decrease the perceived level of discomfort.
While ballistic stretching has pretty much gone by the wayside for most folks, there are a couple of forms of dynamic stretching that are commonly used today. Active Isolation (AI), PNF stretching, and derivatives of them, are pretty common place. Dynamic stretching is useful for getting around the muscles reaction to tense up in an effort to protect itself when being stretched. This is a natural and normal reaction that helps us not rip muscles in half when we move. But if we are intentionally trying to stretch the muscle to increase its functional range of motion, then we probably need to push it a bit past the point where the muscle is comfortable hanging out. Static stretching overcomes this by essentially wearing out that response. Dynamic stretching typically short-circuits the response in some way so that it doesn’t kick in. These methods of stretching also use movement throughout the muscle’s range of motion, which is why they’re called dynamic.
AI stretching works using the idea that it’s hard to contract a muscle if it’s antagonist is contracted coupled with the knowledge that the protective contraction doesn’t kick in for 3-5 seconds after a muscle is stretched. In practice, this means that it’s harder for your hamstring to actually contract if you are really cranking down on your quads. By using a 4-5 second cycle for a number of reps (normally between 10 and 15), you can normally get progressively deeper stretches and end up with a bigger range of motion than if you just employed a static stretch. If we use the hamstring/quad example again we can demonstrate this: Laying on our back with a strap around our foot (so that we can lay flat and still stretch it), we engage the quad to pull the leg as high as we can on the 1-3 counts, on the 4 count we give the rope just a bit of a tug before relaxing the quad on the 5 count and starting over. If I'm not mistaken, I believe ultrarunner legend and physical therapist Scott Jurek is an avid promoter of AI stretching, using it himself several times a day to stay flexible and injury free.
Proprioceptive Neuromuscular Facilitation, or PNF stretching, is pretty similar looking to AI stretching, but is focused on tricking the proprioreceptors in the tendons on each end of the muscle. These nerve sensors are what actually detect a muscle being stretched, and initiate the protective contraction reaction. Again, this is a VERY useful system for us to have. But if we are stretching under controlled circumstances, we can intentionally tinker with those receptors so that they don’t wig out until the stretch is greater, allowing us to get a bigger range of motion and the subsequent lengthening of actin and myosin. This is also typically done in a 4-5 count cycle for some number of reps. The difference is when we are get to the 5 count in the cycle, we’re going to intentionally contract the muscle that we’re stretching, backing it up in the range of motion just a bit. By engaging the muscle at the end of range of motion, it helps provide a little more stimulus to the actin and myosin filaments to lengthen, so that there is more overlap (and thus greater ability to apply force) at that range of motion). If we go back to the hamstring stretch, this looks very similar to the AI stretch with us laying on our backs with a strap around our foot. We’ll lift the foot as high as we can on the 1-3 counts, give the rope a tug on the 4 count, and then engage the hamstring on the 5 count before we start over.
In my personal experience, a lot of folks who are think they are doing AI or PNF stretching are really combining the two. Both of these can also be done with a partner to assist by providing that extra bit of stretch and some resistance while contracting with the PNF stretching, but be careful. It can be very easy to hurt someone if you aren’t paying attention and you’re the “helper”.
There are a lot of other dynamic stretches as well that have become pretty popular to include in any warm up routine. These stretches pretty much all fall into the camp of gentle movement that works a muscle through the complete range of motion in a slow and controlled manner. Examples of these include the walking knee hugs, walking hamstring stretches, walking lunges, etc. The idea is that we are both gently warming up the muscles we’re going to use for the workout in a similar fashion to the work we’re about to do while priming the central nervous system to keep everything coordinated. So we’re not just stretching, but we’re engaging the muscles as well. We’re getting warmed up and working on range of motion at the same time. And who doesn’t like being time efficient when working out, right? The key here is that the motions mimic what the workout will demand, they’re controlled and smooth, and progress from easy to hard.
Each style of stretching is most useful for different things, depending on what the goal of the stretch is at the physiological level. Most athletes use a combination of these techniques, depending on when in the workout they are doing them and what they need. If we’re needing to increase the length of the actin and myosin filaments within the muscle fibers, then we probably need to be doing some kind of static stretching, or preferably AI or PNF stretching. If we need to get tissues moving and grooving again, then we probably want to spend some time flossing and rolling to break up the adhesions that are preventing that. If we need to get the central nervous system fired up so that the muscle is responding the way we want it to in a coordinated manner, we probably need to be doing some dynamic stretches in our warm up routines. And almost all of these will help to one degree or another in helping flush waste products out of muscle tissue after our workout to help start the recovery process.
This was a fun one to write. It got me to do a little bit of reading and digging to double check that I wasn’t giving you guys a goofy mixed up understanding. Let me know if you found this helpful, and don’t be afraid to ask questions if there’s something specific you’d like to know. I’d rather write these articles about topics people need/want to know about than just geek out once a week. What forms of stretching are you currently using? Are you going to change how you stretch to better address your needs? Train smart!