What is Stretching and What Does it Do?

Stretching is a movement to increase muscle flexibility and/or joint range of motion. It results in elongation of muscles and soft tissues (ligament, tendon etc.)

When tissues are held at a constant force, tissue deformation occurs to achieve a new length (“stress relaxation response”). Stretching also reduces/inhibits nerve sensitivity and responses to make lengthening possible.

Types of Stretching:

• Static Stretching: involves holding a muscle in a lengthened position on tension.

• Dynamic Stretching: involves moving a limb through its full range of motion repetitively (active stretching) or moving a limb through rapid, alternating movements at end-range of motion (ballistic stretching).

• PNF Stretching: involves a contraction of the muscle against a resistance (partner or elastic band).

The Effect of Stretching on Flexibility:

• “The duration of increased flexibility after stretching is from 6 to 90 min, although an extensive program of several weeks duration has produced increased flexibility that persists for several weeks.” (Thacker et al, 2004)

• Static stretching is effective at increasing ROM. The greatest change in ROM with a static stretch occurs between 15 and 30 seconds…no increase in muscle elongation occurs after 2 to 4 repetitions. (Page, 2012)

• “Static stretches held for 30 seconds and performed for three repetitions have been reported to increase muscle length… this increase in muscle length was maintained for at least 24 hours, with the greatest increases being maintained during the first 15 minutes...” (Woods et al, 2007)

The Effect of Stretching on Performance:

FOR:

• “… static flexibility training increased bench press performance by 5.4%, in accordance with a decrease in active muscle stiffness by 7.2%.” (Weerapong et al, 2004)

• “…moderate improvements of 2.1% were observed for jump performances, whereas repetitive actions such as running or sprinting or agility showed a small 1.4% improvement with dynamic stretching. (Page, 2012)

AGAINST:

• “We found a 2.8% decrease in torque and a 3.2% decrease in power as a result of the static and PNF stretching exercises…static stretching as part of a warm-up immediately prior to exercise has been shown detrimental to muscle strength and performance in running and jumping.” (Page, 2012)

• “Static Stretching (–3.7%), Dynamic Stretching (+1.3%), and PNF Stretching (–4.4%) induced performance changes when testing was performed soon after the stretching. (Behm et al, 2015)

The Effect of Stretching on Injury:

FOR:

• “…the occurrence of muscle/tendon-related injuries and low back pain was statistically significantly lower (2.5% vs 6.9%) in the stretching group.” (Amako et al, 2003)

• “…poor flexibility was associated with 2.5 times the risk of injury as compared with average flexibility…” (Pope et al, 2000)

AGAINST:

• “With respect to risk of injury, the combined risk reduction of 5% indicates that the stretching protocols used in these studies do not meaningfully reduce lower extremity injury risk...” (Anderson, 2005)

• “…a pre-exercise stretching programme of 11-12 weeks did not reduce the risk of exercise-related injury.” (Weerapong et al, 2004)

Conclusion:

It simply depends on what your aim is. Research suggests that stretching will increase muscle flexibility and will most likely prevent injury.

In regard to influencing performance, I think it depends on what activity is going to be performed. For activities requiring power/strength immediately after stretching, then it would appear that dynamic stretching is best (as it not associated with strength or performance deficits). In longer duration activities (eg long distance running), static stretching and PNF seem best to achieve a greater range of motion (greater ROM has been demonstrated to reduce injury and improve muscle/running economy).

Most importantly, listen to your body!