Stretching is a well known technique used to remedy muscle tension and tightness. Tight hamstring muscles? Stretch. Tight hip flexor muscles? Stretch. So how effective is stretching, really? And are there greater benefits to some stretching techniques over others?
Our bodies thrive on movement and movement is dependent on the range of motion available at any given point in time. Anatomically, there are two major contributors that limit range of motion: muscles and joints. A reduction in range because of joints is often owing to the surfaces of the joint as well as the structures in the joint capsule. In contrast, muscles impact range by means of their length. Any increase in muscular tension, or muscle ‘tightness’, can alter the range of motion available.
Muscular ‘tightness’ becomes apparent when there is an increase in tension from active or passive mechanisms. Passive mechanisms are dependent on the structural properties and make up of the muscle. This includes the elastic-like properties of the muscle that provide tension or tone while at rest. Passively, muscles can become shortened through prolonged postural adaptation or scarring following trauma or injury.
Active mechanisms stem from the reflex properties of the muscle. These reflexive properties can lead to shortening as a result of muscle spasm or contraction. Active tension occurs with dynamic muscle contraction – when you activate your muscles to perform a physical activity.
Stretching is used with the aim of reducing muscle tightness by focusing on increasing the
length of the muscle. With stretching, increased muscular tension generally means
decreased muscle length. Conversely, decreased muscular tension means increased muscle
length. With this comes the belief that stretching, in essence, increases the distance of the
muscle between its attachment points.
Types of stretching:
There are three main categories of stretching techniques: Static, Dynamic and Pre-Contraction. The most common and perhaps most widely used is Static stretching, where a certain position that creates muscle tension and thus a stretching sensation is held for a sustained period of time. Think reaching for your toes with an outstretched leg while sitting on the floor.
Dynamic stretching is further divided into Active and Ballistic stretching. Active stretching entails taking a limb through its full available range and repeating in a cyclical motion. This is commonly seen in leg swings or arm circles. Ballistic stretching involves fast pace alternating movements with a ‘bouncing’ technique at the end of range. Given it’s increased risk of injury, Ballistic stretching is no longer recommended.
Pre-contraction stretching occurs when a muscle is contracted, or switched on, prior to being stretched. The most common of this technique is termed Proprioceptive Neuromuscular Facilitation (PNF). Under the umbrella of PNF, there are several approaches aimed at
increasing range. These include ‘contract-relax’, ‘hold-relax’, and ‘contract-relax agonist contract’ where the opposite muscle to the one being stretched (agonist) is switched on. Often, the degree of muscle contraction is upwards of 75% maximal effort and then held for 10 seconds prior to relaxing, however the contraction can be as low as 25% and provide benefits.
So how effective are all these stretching techniques?
There have been many studies that have set out to answer this question. Generally the research measures effectiveness by determining changes in range of motion, where a positive outcome would be an increase in joint range. It is clear that static stretching does in fact increase joint range of motion. However the reasoning behind this is not necessarily what we would expect. It is likely that this increase in range is not a result of increased muscle length but rather an increased tolerance to the stretch. While one study has found 8 weeks of static stretching increased muscle extensibility, most of the research indicates that
increase in range following static stretching is owing to an ability to withstand more stretching force rather than increased muscle length.
During a static stretch, the greatest amount of increased range occurs within 15-20 seconds
and no further improvements are seen after 2-4 repetitions. Despite its benefit in increasing
range, static stretching has been shown to negatively affect muscle strength with running or
jumping activities. Termed ‘stretching induced strength loss’, static stretching prior to
explosive activities is no longer recommended. Interestingly, performing a maximal
contraction prior to the stretch as with PNF stretching may remedy this by decreasing the
effects of ‘stretching induced strength loss’.
Dynamic vs Static…
A comparison between static and dynamic stretching found that they were equally effective in increasing joint range both acutely and over time. In contrast to static, dynamic stretching pre-exercise is not associated with strength deficits and has been found to improve power, running and jumping performance. With this, it appears that dynamic and PNF stretching are most favourable prior to exercise. On the other hand, static is perhaps more suited post exercise to increase joint range, or as a part of rehab to align collagen fibres during muscle healing.
So, do you need to stretch?
Overall, stretching is effective for increasing joint range. Likely, such increase is owing to an increased tolerance to stretching as opposed to an increase in length of the muscle from its attachment points. Static stretching is recommended to be held for 15-20 seconds, with 2-4 repetitions. Prior to exercises, dynamic stretching and PNF stretching are preferable over static to eliminate any ‘static induced strength loss’. Have a chat to your physiotherapist about stretching and how it can best be tailored to you.
