Too often, athletes show up late to a group workout and just jump in on the fast swimming, running or riding with no warm-up. Others are pinched for time, trying to squeeze a workout into a busy schedule, so they skip the warm-up figuring the main set of the workout is more important anyway.
Is a warm-up really necessary? What constitutes a "good" warm-up?
A warm-up activity serves two major purposes—to enhance performance and prevent injury. Consequently, a warm-up is both physical and mental.Relaxed, sitting in your chair and reading this column produces a relatively low 15- to 20-percent of blood flow to your skeletal muscles. Most of the small blood vessels (capillaries) within those muscles are closed. After 10 to 12 minutes of total body exercise, blood flow to the skeletal muscles increases to some 70 to 75 percent and the capillaries open.
Along with more blood flow comes an increase in muscle temperature. This is good because the hemoglobin in your blood releases oxygen more readily at a higher temperature. More blood going to the muscles, along with more oxygen available to the working muscles, means better performance.
An increase in temperature also contributes to faster muscle contraction and relaxation. Nerve transmission and muscle metabolism is increased, so the muscles work more efficiently.
Scientific studies on linking warming up with injury prevention are difficult to administer. Few athletes want to go through a muscle stress test to see what it takes to tear a muscle.
Old studies on animal subjects determined that injuring a muscle that has gone through a warm-up process required more force and more muscle length than a muscle with no warm-up. This study is in line with the anecdotal data that acute muscle tears occur more often when the muscles are cold or not warmed up.
There have been human studies on sudden, high-intensity exercise and the effects on the heart. One particular study had 44 men (free of overt symptoms of coronary artery disease) run on a treadmill at high intensity for 10 to 15 seconds without any warm-up. Electrocardiogram (ECG) data showed that 70 percent of the subjects displayed abnormal ECG changes that were attributed to low blood supply to the heart muscle. Yikes!
The abnormal changes were not related to age or fitness level.
To examine the benefit of a warm-up, 22 of the men with abnormal results did a jog-in-place at a moderate intensity for two minutes before getting on the treadmill for another test of high-intensity running. With that small two-minute warm-up, 10 of the men now showed normal ECG tracings and 10 showed improved tracings. Only two of the subjects still showed significant abnormalities.
It is not known if a more thorough warm-up of 10 to 20 minutes would have made more improvements. It would have been interesting to see the results if the scientists would have taken the experiment that additional step.