It all starts as orders from the brain. Special cells called neurons carry electrical messages from the brain through the nervous system to the muscles you want to activate. If you're running, your brain tells your legs to move and your arms to pump. As soon as the messages get to their targets, the muscles react. You're cruising.
Skeletal muscles are the kind that attach to bones. They do most of the work when you exercise. Skeletal muscles are made up of long, twisted cells called fibers. Proteins inside the fibers help your muscles contract and relax. These muscle movements allow you to run, jump, skip, and throw a Frisbee, swim, and more.
With exercise, muscle fibers grow and multiply. The more you work out, the stronger and bigger your muscles get.
When you stretch, you lengthen muscle fibers. It then takes longer for messages from the brain to travel through them. Stretched muscles also seem to be more sluggish than unstretched ones. They don't spring back as readily. And every time you stretch, you may be tearing your muscle fibers a teeny bit.
Stretching before you exercise is particularly risky, experts say, because stretched muscles are less stable. That makes it harder for them to bounce back from the jarring impact of running, jumping, or weaving around other players on a soccer field.
WHAT TO DO ? - Instead of stretching before an activity, it is recommend warming up by starting slowly to get blood and oxygen flowing to your muscles. Warming up is also a natural way of stretching your muscles just enough to prepare them for more intense activity.
"If you're going to play soccer, jog a bit beforehand, if you're going to play baseball, swing the bat before a game."