Dynamic stretching is a form of stretching beneficial for running and in sports since it utilizes momentum from range of motion in an effort to propel yours muscles into an extended range of motion not exceeding their static-passive stretching ability. Dynamic stretching should be part of a comprehensive warm-up before your running workouts.
On the other hand, static stretching - where you hold a stretch for a longer period time - should not be used before your run or activity bout. Rather, it should be used afterwards.
Let's have a look at why...
Static Stretching Slows Down Gymnasts
Although warm-up and stretching exercises are routinely performed by gymnasts, it is suggested that stretching immediately prior to an activity might affect negatively the athletic performance.
One study, looked at the acute effect of a protocol, including warm-up and static and dynamic stretching exercises, on speed during vaulting in gymnastics. Eleven boys were asked to perform three different protocols consisting of warm-up, warm-up and static stretching and warm-up and dynamic stretching, on three nonconsecutive days. Each protocol was followed by a "handspring" vault.
The results showed a significant difference in gymnasts' speed, following the different protocols with the gymnasts mean speed during the run of vault being significantly decreased after the application of the static stretching protocol. These findings support the notion that static stretching has an inhibitory role in speed and power development.
Dynamic Stretching Improves Muscular Power
Japanese researchers studied the effects of static stretching for 30 seconds and dynamic stretching on leg extension power in eleven healthy male students. Each subject performed static stretching and dynamic stretching on the 5 muscle groups in the lower limbs and nonstretching on separate days. Leg extension power was measured before and after the static stretching, dynamic stretching, and nonstretching. No significant difference was found between leg extension power after static stretching and after nonstretching.
However, leg extension power after dynamic stretching was significantly greater than that after nonstretching. These results suggest that static stretching for 30 seconds neither improves nor reduces muscular performance and that dynamic stretching enhances muscular performance.
Dynamic Warm-Up Improves Power and Agility
A 2006 study compared the effect of a dynamic warm up (DWU) with a static-stretching warm up (SWU) on selected measures of power and agility. Thirty cadets at the United States Military Academy completed the study (14 women and 16 men, ages 18–24 years).
On 3 consecutive days, subjects performed 1 of the 2 warm up routines (DWU or SWU) or performed no warm up (NWU). The 3 warm up protocols lasted 10 minutes each and were counterbalanced to avoid carryover effects. After 1–2 minutes of recovery, subjects performed 3 tests of power or agility (T-shuttle run, underhand medicine ball throw for distance, and 5-step jump).
Not surprisingly, the results of the study revealed better performance scores after the DWU for all 3 performance tests, relative to the SWU and NWU, leading the researchers to conclude that, as part of a warm up routine, "the use static stretching as a stand-alone activity should be reassessed."