Which Comes First, Cardio or Weights_ - Alex Hutchinson [49]
The weak link in the chain of logic is the assumption that being more flexible protects you from injury. Most muscle injuries occur within the normal range of movement during “eccentric” contractions (while the muscle is lengthening, for instance when you’re lowering a biceps curl). In other words, you’re most likely to pull your hamstring while sprinting or changing direction, not while trying to do the splits (unless you’re a ballerina or a hockey goaltender, in which case static stretching is in fact important). “If injuries usually occur within the normal range of motion,” McGill University sports doctor Ian Shrier asked in a widely cited editorial in the British Journal of Sports Medicine in 2000, “why would an increased range of motion prevent injury?”
Literally hundreds of studies have tried to answer that question, and the Centers for Disease Control and Prevention reviewed 361 of them in 2004 in search of an answer. “Stretching was not significantly associated with a reduction in total injuries,” they concluded. Moreover, “use of stretching as a prevention tool against sports injury has been based on intuition and unsystematic observation rather than scientific evidence.” Subsequent reviews, most recently in 2008, have reached the same conclusion. One example of the “unsystematic observation” used to justify stretching is that several influential early studies compared one group that warmed up and stretched to another group that did neither. The problem with this study design is that warming up—for example with a gentle jog and some movement drills within the expected range of motion—reduces injury risk whether you stretch or not.
It’s important to note that the lack of proof that stretching prevents injury isn’t the same as proving that it doesn’t work. It may be that stretching programs have to be tailored to the individual needs of each person or each activity, so studies of a generic stretching program are doomed to produce ambiguous results. Imagine testing your prescription eyeglasses on 1,000 random people and using the results to judge whether eyeglasses help people see more clearly. So if, like Bracko’s hockey players, you’re deeply attached to your stretching routine, there’s not enough evidence to compel you to give it up—but there are some compelling reasons to think very carefully about when and how you stretch.
Could stretching before exercise make me slower and weaker?
Until the debate about whether stretching prevents injuries is settled, many people will keep it as part of their exercise routine—so it’s worth considering whether stretching has any other effects that might influence when you choose to stretch. One major change that has already taken hold is the realization that you shouldn’t stretch a “cold” muscle. Experiments with leg muscles from rats at the University of Michigan, for example, have shown that even mild stretching is enough to damage unprepared muscle fibers. Since stretching is typically incorporated as part of a pre-exercise warm-up routine, experts now recommend that you first start with a gentle jog (or bike or swim) to warm up your muscles and make them more compliant. You should also avoid overstretching to the point of pain.
Even if you follow this advice, a series of studies in the last few years suggests that you’ll still suffer from temporary after-effects that make you weaker, slower, and less efficient. This phenomenon isn’t yet fully understood, but some experiments have found that it can last up to two hours after stretching—not exactly the ideal preparation for a workout or competition where you want to be at your best. Consider, for example, a 2010 study by researchers at the University of Milan, published in the Journal of Strength and Conditioning Research. A group of 17 volunteers performed a series of vertical jumps from different squatting positions, with or without stretching their leg muscles beforehand. The height of the jumps,