Constant torque stretching in ankle contractures results in greater changes in range of motion than constant angle or dynamic stretching: A systematic review and meta-analysis

OBJECTIVES: To investigate the acute (directly post-stretching) and long-term (≥1 week of treatment) effects of stretching type, duration, and intensity on joint range of motion (ROM) and stiffness in ankle contractures.

DATA SOURCES: PubMed, Embase.com, Clarivate Analytics/Web of Science Core Collection, EBSCO/SPORTDiscus, and EBSCO/CINAHL were searched for studies published in English from inception until September 12, 2023.

STUDY SELECTION: Fifty-five studies that met the inclusion criteria were included, covering observational, controlled and non-controlled studies.

DATA EXTRACTION: Pre and post-treatment ankle ROM and stiffness, and stretching duration, intensity and type were extracted from each eligible treatment group by one reviewer.

DATA SYNTHESIS: Most studies did not quantify stretching intensity and its effect was not tested. For the acute effects on ROM, fifteen effect sizes were obtained from eleven studies. ROM increased more after constant-torque (95% CI [1.35, 2.15]) than after constant-angle (95% CI [0.44, 1.40] or dynamic stretching (95% CI [0.50, 1.01]), F=11.99, p=.004, I2=0%, and increased with duration (95% CI [0.00, 0.05]), F=5.12, p=.011, I2=55%. Acute effects on joint stiffness could not be assessed. For the long-term effects, fifty-four and twelve effect sizes were estimated from forty-four and ten studies, for ROM and stiffness, respectively. No effect of stretching duration on either outcome was found (F=0.32, p=.57, I2 =78% and F=0.74, p=.409, I2=5% respectively). No effect of stretching type on stiffness was found (F=0.02, p=.888, I2=0%). Not enough information was available to assess the long-term effects of stretch type.

CONCLUSIONS: We conclude that constant-torque stretching acutely increases ROM more than constant-angle and dynamic stretching. To assess if these superior acute effects result in more substantial adaptations over time, future long-term studies should define stretching type more clearly. Also, torque and angle during stretching should be recorded as measures of intensity in future studies.