Acute changes in passive stiffness of the individual hamstring muscles induced by resistance exercise: effects of muscle length and exercise duration

• Published in: European journal of applied physiology Vol. 123; no. 3; pp. 655 - 666
• Main Authors: Kawama, Raki, Hojo, Tatsuya, Wakahara, Taku
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-03-2023; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Biomedicine; Elastic Modulus - physiology; Elasticity Imaging Techniques; Exercise; Hamstring Muscles - physiology; Human Physiology; Humans; Male; Muscle contraction; Muscle, Skeletal - physiology; Muscles; Occupational Medicine/Industrial Medicine; Original Article; Physiology; Range of motion; Range of Motion, Articular - physiology; Resistance Training; Sport science; Sports Medicine; Torque; Stiff-leg deadlift; Shear modulus; Ultrasound shear wave elastography; Eccentric-only exercise; Time-course change
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-022-05092-1

Purpose
A previous study revealed that resistance exercise with eccentric contraction and a wide range of motion (ROM) can acutely decrease muscle stiffness of a specific muscle. To explore further approaches to decrease the stiffness, we examined the acute changes in passive stiffness of the individual hamstring muscles after eccentric-only resistance exercise with different combinations of muscle lengths and exercise durations.
Methods
Thirteen healthy young male participants performed three sessions of eccentric-only exercises that comprised stiff-leg deadlift with different muscle lengths and exercise durations (duration per repetition × the total number of repetitions) on separate days as follows: (1) short muscle lengths with a short duration (SS); (2) long muscle lengths with a short duration (LS); and (3) long muscle lengths with a long duration (LL). Maximal joint ROM, passive torque, shear modulus of each hamstring muscle, and maximal isometric torque of knee flexion were measured before, and at 3, 30, and 60 min after each session.
Results
The shear modulus of the semimembranosus was significantly lower at 3 min post-exercise (129.8 ± 22.7 kPa) than at pre-exercise (140.5 ± 19.1 kPa,
p
 < 0.01) in LL, but not in SS or LS. No significant differences were observed in the shear moduli of the biceps femoris long head or semitendinosus between pre-exercise and 3 min post-exercise in any session.
Conclusion
The combination of long muscle lengths and a long duration during eccentric-only resistance exercise is important to immediately decrease the stiffness (shear modulus) of a specific muscle.