Thursday, August 21, 2008

Stretching & Beyond

Musculoskeletal injures such as muscle strains and tears are extremely common in sports injury. The overall result of muscle injury is not only influence on athlete performance but is also the source of pain. As muscle tightness is one of the predisposing factor for injuries, preventive measure such as stretching exercise have been wildly practiced from amateur players to elite athletes. It becomes an integral part of any sports activity.

Warm-up and cool down exercises are highly recognized as essential parts of any sports activity. The aim of warm-up is designed to increase muscle-tendon suppleness, stimulate blood flow to peripheral, increase temperature of body, muscle tendon and connective tissue; and enhance free, coordinated movement. Examples are jogging, cycling, massage, stretching. Past researchers have investigated the effect of various modes of warm-up, such as jogging, cycling exercise, massage, heat, stretching, isometric contraction and proprioceptive neuromuscular facilitation(PNF).

There are some recommendations by sports scientist:

Stretching technique
Static stretching is more recommended than PNF among the techniques. But it is only showed beneficial when multiple intervention is implemented. A study by demonstrated that isometric contraction would produce same relaxation effect as passive stretching. As lengthening of connective tissue occur in both routines. The author also suggested that combination of contraction and stretching is even more effective to promote relaxation. As research findings related to PNF is uncertain, the use of PNF in injury prevention is still controversial.

Holding Period
Most of the literature suggested stretch holding period range from 10 to 30 seconds. Some stated that 30 second or less is recommended. During the stretch one should felt the stretch, but with no pain and within comfortable zone. As pre-disposing injury such as microscopic muscle tears due to over-stretching may contribute to the subsequent muscle injury. Moreover, 12-18 seconds is recommended by since stress relaxation occurs in that period. Other suggested that 15 seconds stretch is as effective as 45 seconds and 2 minutes stretch on hip abduction range.

Repetition

The first 4 repetition is shown to be most effective . A repetition of 2 to 4 times is also recommended by another author. Other opinions such as 5 to 6 times in improving hip, knee and ankle flexibility are said to be effective.

PNF
Specifically for PNF technique contract- relax, literature suggested that one should contract and hold 6-8 seconds, then relax and stretch for other 6-8 seconds. This maneuver should be repeated 3-6 times.

Points of Consideration

  • Stretching should be done 15-20 minutes before exercise, and 5-10 minutes after exercise.
  • Holding period can be vary due to difference in viscoelasticity of different muscle at different temperature, difference in muscle architecture, and arrangement of connective tissue.
  • Stretching exercise should be carried out throughout the season as well as off-season. Only long-term stretching program can improve overall flexibility.
  • Balance in flexibility should be considered. Stretching should be done on both agonist and anti-gonist on both limbs.
  • Care should be taken when implement stretching program with athletes whom processed hyperlaxity. There are 3 clinical tests which is recommended to assess athletes' hyperlaxity.
  • As elasticity of slow-twist fiber is greater than fast-twist fiber, therefore the fast-twist fiber is more susceptible to injury. Athletes participate in high intensity sports such as sprinting may require stretching more than an endurance runner.

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