Is there a relationship between flexibility and athletic performance? And, if there is a relationship, is more necessarily better?
Flexibility and Performance
There’s a difference between movement quantity and movement quality. Speed, strength, power, balance, and stability are qualitative aspects of movement. For functional movements, i.e., sports performance, quality of movement is more important than quantity.
Most elite athletes have extraordinary levels of strength, power, endurance, or balance. And, while there are elite athletes with exceptional flexibility, there are others with only average flexibility. Ultimately, it’s less about the extent of your range of motion (ROM) and more about how you use (what you do with) what you have.
The average person probably has the necessary range of motion to execute most sports movements. Their deficiencies usually have little to do with range of motion. The issue is typically attributable to strength, power, mobility, or coordination, not flexibility.
Iashvili (1983) found that active (dynamic, movement-based) ROM and not passive (static) ROM was more highly correlated with sports performance. Arguably, any further passive static ROM developed through passive static stretching will not provide any extra benefit.
There is a considerable body of research that discourages pre-activity static stretching — due to its potential to reduce strength and power output — in favor of dynamic warmup. Studies show that flexibility in the muscles of the posterior chain (glutes, hamstrings) is related to slower running and diminished running economy. Interestingly, it has been shown that stiffer leg muscles in endurance athletes may make them more economical in terms of oxygen consumption at sub-max speeds.
Flexibility and Injury Prevention
The relationship between flexibility and injury prevention is mixed, at best. Two studies involving soccer and hockey players revealed that players with more flexible groins do not suffer fewer groin injuries, while players with stronger adductors had less strains. There is actually more evidence to support that lateral imbalances in strength and stability are a better predictor of injury than lack of flexibility.
There are some studies suggesting that musculoskeletal tightness may be associated with an increased likelihood of muscle strain injury. Other studies, including Knapik, J.J. et al. 1992, found that subjects in the least flexible and most flexible quintiles were equally likely to get injured — 2.2-2.5 times more than subjects in the middle quintile (average flexibility).
The reality is that sports injuries are produced by a lot of different factors, and flexibility (or lack thereof) is only one of them. It would be inappropriate to assign a level to the importance of flexibility as it relates to injury prevention.
For most athletes in most sports, there is probably little to be gained by increasing flexibility or range of motion. Athletes are better off developing additional strength and stability within a particular range of motion.
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