Hello,

I read pretty much everywhere on English-language websites that bouncing when stretching should NEVER be done.
However even though every body keeps repeating this, no one ever explains why or cite any authoritative source to back up the claim that 'bouncing is harmful'.

I am wondering this because I have recently joined a kung fu club in Egypt where ALL stretchings are based on bouncing and pain. Their philosophy is that the more pain you feel, the better the results. They have me settle in a position where the muscle I'm working is stretched to its very limit (where I can already feel significant discomfort) and then push my back to make me bounce around beyond the point of pain.

I told them that this ran counter to everything I had heard, and they told me that the proof of the pudding in the eating (most of them can do the splits after this type of training).

Bottom line : I'm very very confused. Any opinion would be really appreciated.

Thanks! (and sorry for my poor English).

Very controversial subject among personal trainers, so please allow me to quote from 'Essentials of Athletic Injury Management'-William E. Prentice, pg69-70.(Required reading towards a degree in Physical Therapy).
"Ballistic stretching involves a bouncing movement in which repetitive contractions of the agonist muscle are used to produce quick stretches of the antagonist muscle. The ballistic stretching technique, although apparently effective in improving range of motion, has been criticized in the past because increased range of motion is achieved through a series of jerks or pulls on the resistant muscle tissue. The concern was that if the forces generated by the jerks are greater than the tissues' extensibility, muscle injury may result."
My instructor in the course (MD in Physical Therapy and the Athletic Director at the college) is very big on focusing on static stretching to avoid injury. The danger comes from 'bouncing' too far because you would have no control over being able to stop the motion before injury.

Here's some new data that you might want to present to your instructor.
No Pain, No Gain ? It's Really Not True!

We've heard it before, but people still believe they must "hurt" in order to
improve. Even some athletes and coaches follow the motto, "No Pain, No Gain." Most
fitness professionals know it is not true, but often do not understand why. While
muscle damage is a big issue, what about postural deviations while recuperating from
the pain?

A study in Denmark investigated this very thing. How we respond to environmental
and physical changes plays a significant role in the dynamic alignment and stability
of musculoskeletal structures. In testing this statement, researchers had 10
healthy men sustain isometric contraction of the quadriceps muscle group using 50%
of maximal force. EMG's were conducted before, immediately after, 24 hours and 48
hours after the exercise.

What was found was that the neuromuscular system was not able to activate like it
should in the quadriceps muscle group after performing the exercise as well due to
muscle soreness. This could potentially lead to injuries to connective tissue such
as ligaments and tendons, thus contributing to sports-related injuries.

So, while some coaches, trainers, and exercisers alike may think they are getting
stronger and faster by creating this delayed-onset muscle soreness, they are
actually increasing their risk of injury. Even daily activities can be risky?and
put them out for weeks or months from their training or workout.

Nosratollah Hedayatpour et al, "Delayed-Onset Muscle Soreness Alters the Response to
Postural Perturbations," Medicine and Science in Sports and Exercise. ACSM Volume
43, No. 6, June 2011, pp. 1010-1016.