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Temporal shift in task factor influence across the stretch reflex
Frida Torell1,2, Robin Rohlén1,3, Michael Dimitriou1
1Department of Medical and Translational Biology, Umeå University, Umeå, Sweden.
Plos One
|June 1, 2026
Summary
Mechanical perturbations trigger arm reflexes like the stretch reflex (SLR and LLR). Task factors such as load and target direction influence these responses, especially in shoulder muscles during delayed reaches.
Area of Science:
- Neuroscience
- Biomechanics
- Motor Control
Background:
- Mechanical perturbations to the arm elicit rapid reflexive actions.
- The stretch reflex comprises short-latency reflex (SLR) and long-latency reflex (LLR) components.
Purpose of the Study:
- To investigate how task factors influence SLR and LLR components during a delayed-reach paradigm.
- To analyze the effects of mechanical load, preparatory delay, perturbation, and target direction on reflex responses.
Main Methods:
- Utilized multiple linear regression (MLR) analysis.
- Analyzed electromyographic (EMG) activity from seven right arm muscles.
- Examined main effects and two-factor interactions of task variables.
Main Results:
- Shoulder girdle muscles showed task-dependent engagement; biceps and triceps acted as stabilizers.
- SLR modulation was observed in shoulder muscles, influenced by load and perturbation.
- Late LLR demonstrated significant task-dependent modulation, shaped by perturbation and target direction interactions.
Conclusions:
- Reflex responses, particularly LLR, are dynamically modulated by task parameters in a delayed-reach context.
- Findings highlight the differential control of reflex components based on task demands.
- Results provide insights into stretch reflex modulation and inform future research designs.
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