A randomized crossover design was used to investigate the effect of the two SS protocols on ROM and muscle stiffness of the dominant leg, which was determined by kicking a ball. Our choice of SS intensity and duration was based on previous research Freitas et al. All measurements were performed within about 3 min after stretching.
A total of 18 healthy young adults males, 11; females, 7 who did not play sports or have a high activity daily participated in the study age, In previous studies, the effect of SS has not been investigated separately for men and women Ryan et al. Therefore, this study did not separate men and women. Participants were excluded if they had a history of surgery on their back or lower body, lower-extremity contracture, neurological disorders, or if they took hormone or muscle-affecting drugs.
Written informed consent was obtained from all participants. In addition, this study was approved by the Ethics Committee at our institution Participants were seated in an isokinetic dynamometer Biodex system 3. We adjusted the seat position to prevent the heel raise during passive dorsiflexion, and the ankles of participants were fixed to the footplate by two adjustable belts firmly.
Furthermore, we visually confirmed no heel raise during the passive stretching. The participants were instructed to relax and stop the dynamometer at the point of the feeling of discomfort. All participants performed the familiarization session 1—2 weeks before the experimental trials.
Two trials were performed and the greatest dorsiflexion or passive torque at DF ROM was used for further analysis Blazevich et al. A previous study showed that the reliability of shear elastic modulus measurements used by the elastography device was very high [ICC 1,1 was 0.
Ultrasound image measurements were performed twice in long-axis image of MG. The analysis of shear wave speed in ultrasound images was performed using image analysis software MSI Analyzer version 5. The measurement of shear wave speed Vs was set as the region of interest in the area as large as possible in MG, and the average value of the shear wave speed inside this region was obtained Figure 1.
The average value of shear elastic modulus obtained from two ultrasound images was used for analysis. Figure 1. Typical examples of measurement of shear wave speed Vs before A and after B stretching. The measurement of shear wave speed was set as the region of interest in the area as large as possible in MG, and the average value of the shear wave speed inside this region was obtained.
The colored region represents the shear modulus map with the scale right the images. The static stretching was performed for one session of s high-intensity and short-duration condition or one session of s low-intensity and long-duration condition.
We performed two stretching conditions randomly with an interval of more than 1 week and less than 3 weeks. The test-retest reliabilities were investigated for all variables in seven healthy young adults.
Moreover, we calculated the minimal detectable change MDC using the standard error of the mean. We assessed the normality of the data by the Shapiro-Wilk test.
Therefore, the parametric tests were applied to the data of the DF ROM, but the nonparametric tests were applied to the data of the passive torque at DF ROM, the shear elastic modulus, and the relative change for all variables. POST and conditions high-intensity and short-duration protocol vs. For the relative change for all variables, Wilcoxon signed-rank test was performed to compare between the conditions.
Using the t -value and sample size, the effect size ES was calculated when the outcome was applied to parametric tests. On the other hand, using z -value and sample size, ES was calculated when the outcome was applied to non-parametric tests.
All statistical analyses were performed using R2. All variables in both protocols are presented in Table 1. Table 1. We investigated the effects of high-intensity, short-duration and low-intensity, long-duration of SS with the same total work on DF ROM and shear elastic modulus of MG. Our results showed that DF ROM was increased significantly for both conditions, and DF ROM after the high-intensity and short-duration condition was significantly greater than that after the low-intensity and long-duration condition.
Conversely, passive torque at DF ROM changed significantly after both protocols, with no significant difference between the two protocols. Shear elastic modulus was decreased significantly for both conditions, and shear elastic modulus after the high-intensity and short-duration condition was significantly greater than that after the low-intensity and long-duration condition. Our results showed that DF ROM significantly increased after both high-intensity and short-duration SS and low-intensity and long-duration protocol.
Interestingly, our study showed that DF ROM at POST in the high-intensity and short-duration protocol was higher than that in the low-intensity and long-duration protocol. Freitas et al.
Generally, the mechanism of the increase in ROM is the increase in the capacity to tolerate loading prior to stretch termination the increase in stretch tolerance and the changes in viscoelastic properties of the muscle-tendon unit Behm et al. The results in the current study showed that passive torque at DF ROM was significantly increased and shear elastic modulus was significantly decreased after SS at both protocols.
Kay et al. Moreover, Freitas et al. Therefore, it is possible that the superior change in DF ROM in high-intensity and short-duration protocol than low-intensity and long-duration protocol could be because SS at higher intensity was more effective on stretch tolerance. Thus, our results suggest that the stretching intensity could be more important for changes in DF ROM than stretching duration with the same load of intensity and duration.
This study showed that shear elastic modulus of MG was significantly decreased after both SS protocols. Nakamura et al. Furthermore, in previous studies, the mechanism of the decrease in muscle stiffness could be resulted in the change in connective tissue Morse et al. Therefore, in this study, the change in the shear elastic modulus could be contributed to the change in the connective tissue property.
On the other hand, in this study, the relative change in shear elastic modulus of MG in the high-intensity and short-duration was greater than the low-intensity and long-duration. Sato et al. Therefore, it is considered that intensity and duration of SS above a certain level is required to decrease shear elastic modulus.
Practice To recognise vertically opposite, alternate Z , corresponding F and interior angles Practice. A trapezoid has 4 sides and exactly 1 pair of parallel sides. Enlargement Objectives: C GradeEnlarge a shape by a fractional scale factor Compare the area of an enlarged shape with the original shape Find the centre. Similar presentations. Upload Log in. My presentations Profile Feedback Log out.
Log in. Auth with social network: Registration Forgot your password? Shear strain is defined as the ratio of relative displacement between the surfaces to the separation between the surfaces. For instance, in the above diagram, the shear strain is given by:. The shear modulus is a quantity that describes how difficult if is for a material to be deformed by applying a shear stress.
The shear modulus for a material is defined as:. When you cut a piece of paper with a pair of scissors, you are giving a shear stress to the paper. One side of the scissors attempt to pull the paper in one direction, the other side of the scissors attempt to pull the paper in the other direction. Scissors cut papers by applying a shear stress. Forces causing tensile stress are at right angles to a surface. Forces causing shear stress act parallel to a surface. Shear stress causes one surface of an object to displace with respect to the surface opposite to it.
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