What’s happening when we increase range of motion?
Yuval asks, “Could you shade some light on the subject of the term “stretching”? What exactly is being stretched in a yoga pose? Muscle? Connective tissue? Both? The terminology is confusing — stretching, lengthening, [increasing range of motion] etc. And from what I hear, stretching per se is not necessarily a positive action. Or is it?”
This is a great question! Let’s break this question down a bit and start by looking at the word “stretching”. Stretching is a single word that we use to cover what is actually a complicated process with multiple different aspects. A more specific description of what we’re really talking about is increasing range of motion (ROM).
What is range of motion?
Range of motion is defined as the full range through which we can move an individual joint. It is described in degrees of a circle. Our available range of motion comes from a combination of connective tissue tension, nervous system stimulation, and the bone shape and angle that create our joints. There are some parts of this combination that we can affect and change with yoga. Those are things like the amount and type of tension in our connective tissue and possibly our nervous system stimulation. The aspect of range of motion that we can’t change is the shape of our bones and the angle at which they meet to create our joints. Our range of motion is also affected by things like injuries to the joint or swelling of tissues around the joint.
When might we want to increase range of motion?
The reality for most of us is that we do activities during the day that have the effect of decreasing our range of motion in certain actions. The range of motion in our hips may decrease if we spend most of the day sitting at a desk or if we spend a lot of time doing sports like running or cycling. If we did a lot of weight-lifting or simply spent time carrying our children around, then the range of motion in our shoulders might be limited. When range of motion is reduced, there is potential for that increased tension to be felt elsewhere in the body. So, if reduced range of motion is contributing to reduced functionality in our body or contributing to pain even, then we might want to consider increasing that range of motion.
That said, there is some research that suggests there is a short-term reduction in muscle function (voluntary muscle contraction) immediately after stretching (Avela et al., 1999). Behm, 2016 also suggested that reduced muscle activation immediately after stretching were responsible for short-term reductions in athletic performance that occurred when measured immediately after stretching. So, if you are stretching before an athletic event, you might want to give yourself a little time in between pre-event stretches and the event itself.
How do we increase range of motion?
In order to increase our range of motion we need to impact, not just our connective tissue, but how our nervous system interacts with our connective tissue. For this reason it makes sense to me that the more effective time to try to lengthen or stretch connective tissue is when we are relaxed. That is, stretch when we are not telling our nervous system to contract the muscles that we want to lengthen. It just wouldn’t make sense to try to stretch our biceps brachii, for example, in the same moment that we are engaging them to pick up a heavy object, right?
What is happening when we stretch in yoga?
What actually happens when we stretch in yoga, meaning the mechanisms that are involved in changing our range of motion, is not fully understood (Holtzman Weppler and Magnusson, 2010). Researchers have suggested several different mechanisms. But no one single mechanism for creating change in range of motion has been identified. Some mechanisms that have been suggested are that stretching: reduces muscle and/or tendon stiffness, creates change in neural adaptations (Behm, 2016; Holtzman Weppler and Magnusson, 2010), alters sensation, or creates other types of change in connective tissue or muscle cells (Holtzman Weppler and Magnusson, 2010).
How much stretch in yoga do we need to increase range of motion?
Although it’s often debated, there really is no one amount of time that research suggests that you should hold a stretch in yoga or otherwise, to make it effective. It’s true that if we don’t go far enough or hold it long enough, no change will happen. However, a recent review paper from 2018 suggests that one key aspect of stretching for increased range of motion, is frequency of stretching per week (Thomas et al., 2018). They reported that stretching five days per week had far more impact on increased range of motion than holding a stretch for a long time in a single session (Thomas et al., 2018). The type of stretching (static stretching, dynamic stretching, or proprioceptive neuromuscular facilitation [PNF]) does not seem to matter with respect to increasing range of motion (Behm, 2016; Thomas et al., 2018). All three types of stretching increased range of motion.
Behm, D.G., A.J. Blazevich, A.D. Kay, and M. McHugh. 2016. Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy individuals: a systematic review. Applied Physiology Nutrition and Metabolism. 41:1-11.
Thomas, E., A. Bianco, A. Paoli, and A. Palma. 2018. The relation between stretching typology and stretching duration: the effects on range of motion. International Journal of Sports Medicine. 39(4): 243-254.