Autogenic training to influence the flexibility of the hamstring muscles and perceived stress of healthy women: A randomized controlled feasibility study

Background
Stretching is widely used in sports and physiotherapy for improving flexibility, performance, and lowering the risk of injury. Recent research re-evaluated the effects and underlying mechanisms of stretching, challenging the belief that muscles would elongate. Currently, two main mechanisms are supported by evidence, (a) an altered sensation leading to a greater tolerance to stretch, and (b) changes in the viscoelastic properties of muscle tissue. Similar effects on the nervous system and muscles have been observed following relaxation therapy. Besides somatic effects, relaxation techniques have shown psychological effects, especially on stress and stress-related symptoms. Possible correlations between psychological relaxation and muscle flexibility have not been scientifically evaluated. The aim of this study was to pilot a study design to evaluate possible effects of Autogenic Training on functional flexibility, muscle activity, and muscle stiffness as well as perceived stress.
Methods
Twelve female participants (age: 23 ± 2) were randomly assigned to the relaxation (n = 6) or the stress group (n = 6). The relaxation group conducted the exercise the heaviness from the “Autogenic Training” relaxation therapy, while the stress group completed the “Montreal Imaging Stress Task”, a standardized stress induction protocol. Perceived stress, flexibility, activation, and stiffness of the hamstring muscles were measured before and after the interventions. Measurements consisted of the “Perceived Stress Questionnaire”, the “Toe Touch Test”, the “Passive Straight Leg Raise Test”, the normalized amplitude of surface electromyography, and the shear modulus of the biceps femoris and semitendinosus muscles.
Results
From baseline to post assessment perceived stress decreased significantly in the relaxation group, (p = 0.027), while perceived stress increased in the stress group, (p = 0.028). The relaxation group demonstrated a significant increase in functional flexibility measured with the “Toe Touch Test”, (p = 0.046), while the stress group showed no significant changes in any of the measures. There was no statistically significant correlation between perceived stress and the other outcome measures. No changes of muscle stiffness or activation in the hamstring muscles were detected.
Conclusion
Autogenic training appears to be a promising intervention to reduce perceived stress and improve functional flexibility in movements such as toe touching. In future research, the effects of long-term relaxation programs on flexibility should be evaluated.