In order to reduce the risk of injury, strengthening has been shown to be more protective by a bulk of evidence, most notably a large systematic review by Lauersen et al in 2014. You’ve probably heard, ‘you can’t go wrong getting strong,’ and it’s a fairly decent homage to the most powerful component to any rehabilitation program – strength. But do we throw the baby out with the bathwater? JUST strengthening everything, all the time, for all population groups, is maybe not the most efficient way forward. Similarly, performing massive amounts of flexibility training may have limited effect after a certain point for certain individuals.
Long-term flexibility training has been hypothesised to enhance muscle tendon unit compliance, theoretically increasing the ability to store and release elastic energy within the stretch shortening cycle of muscular performance (Ref). It has been demonstrated, however, that runners who are more flexible have a reduced running economy (Ref). It is obvious that some sports require more flexibility in order to perform to high levels (like gymnastics) and the requirement for flexibility training would seem obvious in these cases. Coaches/clnicians may employ flexibility training as a component of programming for any sport, however, and it is unclear as to the guidelines and most appropriate setting for this kind of training. Questions about flexibility training’s effectiveness and its place in high performance settings remain pervasive in the literature.
Generally, populations fit into a bell-curve distributions – otherwise known as ‘normal distribution’ – the athletic or ‘weekend warrior’ population is no different. For those at either end of the spectrum, there will be a world of difference between the effectiveness of flexibility programs. For those people who are very inflexible, effectiveness of flexibility training will undoubtedly be high – spend your time here, this is ‘bang for buck’ in order to accomplish increased range of motion (if that is desired for your task). For those who may have increased flexibility to begin with, flexibility training will not be as effective and would certainly be time-intensive and will not result in great gains.
To conclude, it is always worth asking, does this person need to be more flexible? Although it may not reduce my risk of injury when looked at in comparison to strengthening, but do not discount it. But if using it, what is the time-versus-reward ratio going to look like for your athlete or patient and is that time better spent doing something else?