Don’t stretch before strength training or sports practice because it will compromise performance. Two performance areas that are profoundly diminished by stretching are maximal strength and jumping ability.
Various kinds of stretching have been shown to decrease athletic performance, including static stretching, PNF stretching, and contracting/relax methods. It’s very unlikely stretching prevents soreness or injury either, yet according to a 2009 study, 54 percent of 2,377 adults were still performing static stretching before exercise because they thought it would protect them from both.
In that study, self-reported injury and soreness was slightly diminished in people who stretched, but since it was self-reported, it’s hard to tell whether this was due to a protective effect of stretching, or an expectation that stretching would have a certain effect. Other studies show no injury prevention benefit to static stretching, especially in comparison to other warm-up options such as doing warm-up lifts or a sports-specific dynamic warm-up.
Performance is clearly compromised by static stretching, whereas doing a complex warm-up will likely improve speed and jumping ability. A recent study in the Journal of Strength and Conditioning Research showed that both static stretching and proprioceptive neuromuscular facilitation (PNF) decrease maximal strength by about 7 percent compared to performing no stretching. This study compared the effects of each stretching warm-up prior to a maximal strength test of the quadriceps and the group that performed no stretching lifted significantly more weight.
A second study in the same journal compared a variety of different styles of stretching on jump height. Researchers tested the effects of no stretching, static stretching, PNF, and contract-relax on jump height. The group that did not stretch performed best in all jump tests, whereas the static stretching group had a very significant drop in jump height. Neither PNF nor contract-relax stretching effected jumping ability significantly, but they did decrease muscle elasticity. They are not suggested prior to training or sports practice.
Rather than stretching, perform a complex warm-up using the same muscle groups to be used in your workout or sports training. For example, prior to speed work, or jumping, perform one set of a heavy squat exercise for a few reps. This will enhance neural drive to the legs and activate the elastic properties, allowing you to take advantage of the stretch-shortening cycle.
Similarly, a low load warm up in which you perform body weight or very light weight lifts to activate the muscles has been shown to improve strength and power by increasing “motor unit activity.” For best results, always perform warm-ups in which you are moving in a way that mimics the movements you intend to train.
The one proven benefit to static and PNF stretching is increased joint range of motion. Stretch regularly—a few times a week—for at least 30 seconds per stretch to increase flexibility. Range of motion is necessary for peak performance in some sports and to perform certain lifts such as deep squats. Stretch after training or in an entirely separate session that is at least 4 to 6 hours before you need to perform at your best so as not to compromise strength and power.
To read more about stretching issues, check out Stretching for Strength and Muscle Mass http://www.charlespoliquin.com/ArticlesMultimedia/Articles/Article/819/Stretching_for_Strength_and_Muscle_Mass.aspx.
Pacheco, L., Balius, R., et al. The Acute Effects of Different Stretching Exercises on Jump Performance. Jouranl of Strength and Conditioning Research. 2011. Published Ahead of Print.
Miyahara, Y., Naito, H., et al. Effects of Proprioceptive Neuromuscular Facilitation Stretching and Static Stretching on Maximal Voluntary Contraction.Journal of Strength and Conditioning Research. 2012. Published Ahead of Print.
Jamtvedt, G., Herbert, R., et al. A Pragmatic Randomized Trial of Stretching Before and After Physical Activity to Prevent Injury and Soreness.British Journal of Sports Medicine. 2010. 44, 1002-1009.