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Effect of Hindlimb Unloading on Hamstring Muscle Activity in Rats
Alexander Popov1, Vsevolod Lyakhovetskii2, Oleg Gorskii2,3
1Pavlov Institute of Physiology RAS, Saint-Petersburg, Russian Federation, margeit@yandex.ru.
Brain, Behavior and Evolution
|February 27, 2024
Summary
Hindlimb unloading altered hamstring muscle activity, specifically increasing semitendinosus (ST) flexor activity during locomotion. This shift may model non-traumatic knee disorders by altering tibia torque.
Area of Science:
- Biomechanics
- Neuroscience
- Human Movement Science
Background:
- Knee axial rotation is crucial for preventing knee disorders.
- Support afferentation influences axial rotator muscles.
- Evolutionary changes in semitendinosus (ST) and biceps femoris posterior (BFp) innervation suggest hindlimb unloading (HU) may mimic these shifts.
Purpose of the Study:
- To investigate the effects of 7-day hindlimb unloading (HU) on the electromyographic (EMG) activity of the ST and BFp muscles.
- To understand how load-dependent sensory input influences these antagonistic hamstring muscles during different locomotor tasks.
Main Methods:
- Examined EMG activity of ST and BFp muscles before and after 7 days of HU.
- Assessed muscle activity during locomotion (stepping) and swimming.
Main Results:
- ST flexor burst activity increased during the stance-to-swing transition in locomotion and retraction-to-protraction in swimming.
- BFp flexor burst activity remained unchanged.
- Both ST and BFp showed increased non-burst extensor activity during stepping and decreased activity during swimming.
Conclusions:
- ST and BFp flexor burst activities respond differently to load-dependent sensory input.
- A shift in activity towards ST during the stance-to-swing transition may create excessive internal tibia torque, serving as a model for non-traumatic musculoskeletal disorders.
- The activity patterns of ST and BFp suggest a basis in reciprocal activity of homologous muscles and increased supraspinal control.
