Abstract
OBJECTIVE:How much force is needed to stretch skeletal muscle is still unknown. The aim of this study was to develop a device that mechanically stretches rat muscle to compare the force (N) required to stretch the soleus muscle of young and aged rats and the tibio-tarsal angle joint at neutral and stretched positions.METHODS:Twelve female Wistar rats were divided into two groups: a young group (YG, n=6, 311±11 g) of rats 3 months old and an aged group (AG, n=6, 351±43 g) of rats 15 months old. The left soleus muscle was mechanically held in full dorsal flexion and submitted to mechanical passive stretching: 1 bout of 10 repetitions, each repetition lasted 60 seconds with an interval of 45 seconds between repetitions, performed once a day, twice a week, for 1 week. The force required during stretching was measured by a load cell, and the tibio-tarsal angle joint was measured by photometry.RESULTS:The load cell calibration showed excellent reliability, as confirmed by the intraclass correlation coefficient value of 0.93. A decrease in delta force was found in the comparison between YG and AG (0.11±0.03 N vs 0.08±0.02 N, p<0.05, repeated measures ANOVA). There was no difference between the YG and the AG in the tibio-tarsal angle at resting position (87.1±3.8° vs 87.1±3.5°, p=0.35, Kruskal Wallis) and at the end of the stretching protocol (43.9±4.4° vs 42.6±3.4°, p=0.57, Kruskal Wallis).CONCLUSION:The device presented in this study is able to monitor the force necessary to stretch hindlimb rat muscles. Aged rats required less force than young rats to stretch the soleus muscle, and there was no difference regarding the tibio-tarsal angle between the two groups.
Highlights
Muscle stretching is defined as an exercise that involves the application of a force to improve the resistance of connective tissue by increasing the length of a muscle-tendon unit and the range of motion (ROM) [1]
There was no difference between the first and the last values registered by the load cell related to the force applied to stretch the soleus muscle of the YG or the AG (Table 1)
The delta force was similar between the YG and the AG in each repetition, but when the delta force of all repetitions was compared, the YG had a higher mean than the AG (0.11±0.03 N vs 0.08±0.02 N, p=0.00) (Table 2)
Summary
Muscle stretching is defined as an exercise that involves the application of a force to improve the resistance of connective tissue by increasing the length of a muscle-tendon unit and the range of motion (ROM) [1]. This type of exercise promotes physical benefits in young and old people, including enhanced flexibility and/or ROM [2,3], fascicle length [4], functional capacity [5], and performance [6]. Received for publication on February 7, 2018. Accepted for publication on April 10, 2019
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
