The real reason you ache after exercise, and why stretching exercises won't help...

It's common for many people, especially when they're just starting an exercise program, to feel sore for the next day or two after exercise.

To prevent delayed-onset muscle soreness (DOMS for short), we're always told to spend a lot of time on stretching exercises immediately after exercise.

But does it really help?

Not according to a team of Danish researchers. They found that stretching before and after exercise has no effect on muscle soreness.

Stretching exercises

Publishing their findings in the Scandinavian Journal of Medicine and Science in Sports, the researchers persuaded seven healthy (but untrained) women to take part in two experiments.

• During the first experiment, the women exercised their right quadriceps (the group of muscles in the front of your thigh) to exhaustion. Ratings of muscle pain were taken for the next seven days.

• In experiment two, the women performed the same type of exercise. This time, however, they spent 90 seconds stretching before and after exercise. Again, muscle pain was assessed for seven days.

Contrary to popular belief, results showed that the stretching exercises had no effect on muscle soreness, which reached a peak two days after exercise.

So, what actually causes the soreness?

A bout of exercise causes inflammation, which leads to an increase in the production of immune cells (comprised mostly of macrophages and neutrophils).

Levels of these immune cells reach a peak 24-48 hours after exercise. These cells, in turn, produce bradykinins and prostaglandins, which make the pain receptors in your body more sensitive.

The result?

Whenever you move, these pain receptors are stimulated. Because they're far more sensitive to pain than normal, you end up feeling sore.

This doesn't mean that you shouldn't perform any stretching exercises after exercise. But if you're only doing it to ease muscle soreness, there's little evidence to show it makes any real difference.

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Reference
Lund, H., Vestergaard-Poulsen, P., Kanstrup, I.L., & Sejrsen, P. (1998). The effect of passive stretching on delayed onset muscle soreness, and other detrimental effects following eccentric exercise. Scandinavian Journal of Medicine and Science in Sports, 8, 216-221