Which Comes First, Cardio or Weights_ - Alex Hutchinson [50]
Why does this happen? There are various theories—for example, it’s possible that “looser” muscles and tendons aren’t able to transmit force to the bones as effectively, much like the ropes on a sailboat need to be taut in order to trim the sails. Or, on a microscopic level, it may be that individual muscle fibers are able to exert more force when they’re shorter. There is also evidence for “neuromuscular” effects, in which the after-effects of stretching disrupt the signal between brain and muscle calling for a contraction. Most likely, it’s a combination of these factors—that would explain why researchers at McMaster University found decreased strength related to neural signaling that lasted for about 15 minutes, along with weakness in the muscles themselves that lasted for up to an hour after a session of calf muscle stretching.
Of course, observations in the laboratory don’t always translate to the real world. So scientists and coaches at Louisiana State University’s NCAA-champion track team put the theory to the test with 19 of their star sprinters in 2008. Each athlete performed three 40-meter sprints in two different sessions separated by a week; they performed a dynamic warm-up before both sessions and added four static stretches of the calf and thigh muscles before one of the sessions. The result: they were significantly slower (5.62 versus 5.72 seconds) when they stretched, with most of the deficit coming in the second half of the sprint.
All of this evidence, along with related studies that show endurance may also be compromised, makes a compelling case that you should avoid stretching before workouts or competitions, says Jason Winchester, the lead author of the LSU study, whose consulting clients include National Football League teams and the U.S. national track team. Instead, incorporate light stretching after your workouts or on rest days. If you really prefer stretching before workouts, the slight loss of strength and speed is unlikely to make much difference, but if it’s a competition, leave as much time as possible between stretching and the start.
Do flexible runners run more efficiently?
Even if we can’t agree on what the “perfect” running form is (see Chapter 4), most of us do recognize when we see a runner who looks particularly smooth and effortless. Seeing it is one thing, but imitating it is another thing entirely—no one is quite sure how to develop a more efficient running style. One of the most common ways people try to do this is to increase flexibility with a regular stretching program, so that they won’t be held back by tight hamstrings or locked-up hips. This makes sense intuitively, but the evidence doesn’t back it up.
When researchers tinker with running form, they’re less interested in subjective outcomes like how smooth you look than in more objective measures like “running economy”—a concept similar to fuel economy in cars. Running economy tells you how much energy you have to burn to run at a given pace; the less energy you burn, the longer you’ll be able to continue at that pace. (It’s usually determined by measuring very precisely how much oxygen you breathe in and how much is successfully transported to your working muscles.)
Researchers have been sticking volunteers on treadmills for decades, trying to figure out which factors lead to good or bad running economy. As far back as 1990, studies were starting to suggest that the runners with the most trunk and lower-body flexibility had the worst running economy. A rigorous study of 34 world-class British distance runners in 2002 reached the same conclusion, using a simple sit-and-reach test, which involves sitting on the ground with your legs straight in front of you and reaching as far as possible toward your toes. Another study, at Nebraska Wesleyan University in 2009, found the same connection between better sit-and-reach score and