Summary
The static stretching is one of the easiest methods is to improve the elasticity of joints or to avoid the shortening of muscles. The effectiveness of the implemented methods for elasticity improvement is indisputable, however there is a range of attainted results. One of the possible explanations can be hormonal fluctuations, which occur during the menstrual cycle.
Abstract
There are many more or less sophisticated methods to improve the elasticity of their joints or to avoid the shortening of muscles. One of the easiest methods is static stretching, which does not require any additional accessories, but merely time and consistency. The most frequently evaluated area of the therapeutic intervention is the hamstrings. Their shortening correlates with a number of biomechanical disorders of lower extremities and an increased risk of knee injury. The effectiveness of the implemented methods for elasticity improvement is indisputable, but the range of the attainted results should prompt a search for causative factors of this differentiation. One of the possible explanations can be hormonal fluctuations.
The aim of the study was the assessment of the effectivity of static stretching of the hamstrings in various phases of the menstrual cycle with special reference to changes in stiffness, strength, and elasticity.
Material and method. Initially the study group consisted of 534 young women, but after applying inclusion criteria only 48 of them have been accepted (mean age 21,4±0,4 years, mean body mass 60,34±7,51 kg, mean body height 167,34±6,14 cm, mean BMI 21,49±1,93). Inclusion criteria for the study were a reduced elasticity of the hamstring muscles and a regular menstrual cycle. Chosen biomechanical parameters such as length, passive stiffness, and strength of hamstring muscles were examined. The whole study included filling in an original questionnaire, non-invasive body composition estimation using bioelectric impedance analysis, and twofold examination of selected biomechanical parameters before and after the therapeutic intervention. Static stretching (3 x 45 seconds) was performed by a physiotherapist. All the measurements were carried out three times in particular phases of the menstrual cycle.
Results. Statistically significant influence of static stretching upon the length of hamstring muscle was revealed. A change in the passive knee extension test was 13,34 %; SD = 10,97, and in active knee extension test was 8,46%; SD = 9,26. Static stretching turned out to be effective in reducing the passive stiffness of the examined muscles. In the lacking-angle test an improvement of 7,21% SD = 19,68 was noted. The hamstring strength did not change after intervention, both in stretched position (p = 0,708) and relaxed position (p = 0,635). All measured biomechanical parameters demonstrated no differences in various phases of the menstrual cycle. However, in the luteal phase the lacking-angle test result was lower than active knee extension test results (p = 0,041) and the passive knee extension test result (p<0,001). Similarly in the ovulatory phase the lacking-angle test result was also lower, but only in reference to the passive knee extension test (p=0,022).
Conclusions. Static stretching is an effective tool for improvement of the elasticity of the hamstring muscle in young women. Among its benefits both the change of the muscle length as well as the modification of passive stiffness were observed. No Stretching Induced Strength Loss was found after intervention, regardless of the position applied. The menstrual cycle phases have no significant impact on results of measured biomechanical parameters.