The last couple of physiotherapy articles discussed the structures that are involved in stretching, the different types of stretching and the process of tissue lengthening, namely stress, relaxation and creep.

Studies have shown that stretching of the muscle-tendon unit does produce a lengthening of this structure.

As previously described, the muscle cells, strong inelastic tissues surrounding them and tendon elongate as a result of a rearrangement of collagen fibres and sliding muscle-cell filaments.

This produces an increase in the joints' range of movement. However, the effect is short lived as the tissues slowly return to their original length within three to 60 minutes.

Interestingly, it has also been found that when range of movement is measured after this period of return to baseline levels, increases in flexibility remain.

The reason for this apparent paradox is that the stretch produces an increase in the body's tolerance for pain or stretch sensation, so that, when the stretch is repeated the muscle-tendon unit can elongate further.

But the tissues have not undergone any permanent change. The body can now tolerate a greater stretch before pain consciously makes the body stop.

Is stretching, then, achieving what we want it to achieve? In particular a greater range of movement, decrease in post-exercise soreness and assistance in injury prevention.

The answer to the latter two is probably no.

Research has not conclusively shown that stretching assists in the reduction of post-exercise soreness or prevention of injury.

Warm-up is a different matter as this activity has been demonstrated to decrease tissue stiffness (particularly in the calf muscles) which lessens the resistance of tissue to elongation, hence, less strain is placed on tissues especially at the musculo-tendinous junction.

These are issues that may be discussed at a later date.

With regard to increasing the range of movement of joints. If the muscle-tendon unit was permanently lengthened, either of two things would happen.

Firstly, the tissue would sag between the origin and insertion of the muscle as the length of bone has not changed proportionally.

Secondly, the contractile tissue would increase the overlapping of its sliding filaments in order to maintain its resting tension.

Both of these processes would necessarily produce a decrease in the force produced by the contracting actin/myosin filaments resulting in reduced sporting performance.

So the desirability for long, maximally stretched muscle-tendon units may not be advantageous after all.

Studies have found that the efficiency of movement is, in fact, greater in those stiffer, less flexible runners and stretching prior to the event had no effect on the speed in a sprint race.

But if a stretching regime is required to produce the greatest temporary gains in range of movement the following parameters may be considered:

• Walk/jog/cycle for 10-15 minutes before stretching.
• Stretch for five to 45 seconds - most lengthening occurs in the first 20 seconds.
• Four-five stretches - repeated stretches up to 30 seconds apart produce progressively less stiffness.
• Stretch to strong tension sensation.
• PNF stretches may produce greater results.
• Stretch often as lengthening effect reverses in approximately one hour.
• References for this article are available on request

Capt Ross Railton