Effects of High-intensity Static Stretching on Range of Motion, Performance, Muscle Activation and Architecture

The acute effects of static stretching on strength and power are conflicting as research has shown that it can reduce strength and power or have no effect. A variable of static stretching that has received little attention is the intensity of static stretching.

The first study within this thesis was a systematic review of 18 studies which examined the effects of different intensities of static stretching on ROM, strength and power. The findings revealed conflicting results. ROM increased no matter the intensity, some studies showed that strength and power decreased regardless of static stretch intensity, and some showed that high intensities led to a greater decrease. It was also revealed that there were methodological inconsistencies between the studies on how they measure the intensity of the static stretches.

The following study within this thesis was a questionnaire to examine the current practices athletes and coaches participating in sport in the UK on their use of static stretching and specifically static stretching intensity. Results from the questionnaire of 147 athletes and 19 coaches revealed that static stretching prior to sport performance is still undertaken despite recommendations from previous research (78%). In addition, to the author’s knowledge this is the first study to investigate if the intensity of static stretching is considered within sport in the UK. It was shown that athletes are less likely to consider the intensity of stretches (68%) whereas coaches are more likely to consider it when programming static stretching exercises for their athletes (70%). This study also showed that there is a variety of methods of measuring the intensity of static stretches and is often not considered by athletes due to this reason.

The following study presented in this thesis aimed to examine the reliability of a 120% point of discomfort static stretch of the hamstrings as a high intensity static stretch. Results showed that this was a reliable method of generating a high intensity static stretch when compared to subjective discomfort ratings. In addition, knee extension ROM increased pre to post (p=0.043) and knee flexion MVIC was decreased following the high-intensity static stretch intervention (p=0.02), however, hamstring passive stiffness and single leg jump power remained unchanged.

The final study within this thesis aimed to build on the findings from the previous study and compare different durations and intensities of static stretching (100%*30s, 120%*30s, 120%*60s) on hamstring range of motion, strength, power, muscle architecture and muscle activation via surface electrical myography (EMG). The results showed that all three conditions led to increases in knee extension ROM with a greater increase occurring following the 120%*60s condition (p=0.024). None of the conditions led to changes to knee flexion MVIC or single leg jump power. Furthermore, there were no changes following any of the stretch conditions on EMG and muscle architecture.

In conclusion, performing a 120% static stretch of the hamstring is a reliable method of generating a high-intensity static stretch and is also a reliable method of increasing knee extension ROM. No conclusions can be made on the effects of high-intensity static stretching on strength, power, EMG, fascicle length and angles results have differed across the studies presented within this thesis.