Reciprocal vs. Autogenic Inhibition
Two neuromuscular reflexes every strength & conditioning coach candidate must know cold — how they work, how they differ, and how they show up in stretching, lifting, and exam questions.
The 30-second summary
- Reciprocal inhibition — when an agonist contracts, its antagonist is neurally inhibited so it relaxes. Driven by the muscle spindle (Ia afferents).
- Autogenic inhibition — a muscle inhibits itself when tension in its tendon rises sharply. Driven by the Golgi tendon organ (GTO) (Ib afferents).
Reciprocal inhibition (in depth)
When you contract the biceps to flex the elbow, the CNS simultaneously sends an inhibitory signal to the triceps so it doesn't fight the movement. This is a spinal-level reflex mediated by muscle spindles and Ia afferent fibers, which synapse on inhibitory interneurons in the spinal cord that suppress the antagonist's alpha motor neurons.
Practical use: Contract-relax-antagonist-contract (CRAC) stretching leverages reciprocal inhibition — actively contracting the opposing muscle helps the target muscle relax deeper into a stretch.
Autogenic inhibition (in depth)
The Golgi tendon organ sits at the musculotendinous junction and monitors tension. When tension climbs high (or is sustained), Ib afferents fire, inhibiting the muscle's own alpha motor neurons — the muscle relaxes to protect the tendon from avulsion.
Practical use: PNF hold-relax and contract-relax stretching use a 6-second isometric contraction of the target muscle to trigger GTO-mediated relaxation, then push into a deeper stretch.
Side-by-side comparison
| Feature | Reciprocal Inhibition | Autogenic Inhibition |
|---|---|---|
| Receptor | Muscle spindle | Golgi tendon organ (GTO) |
| Afferent | Ia fibers | Ib fibers |
| Stimulus | Stretch / agonist contraction | High musculotendinous tension |
| Muscle inhibited | Antagonist | Same muscle (self) |
| PNF technique | CRAC | Hold-relax / contract-relax |
Exam-style example
Q: A 6-second isometric contraction of a stretched hamstring, followed by a deeper passive stretch, primarily relies on which mechanism?
- A. Reciprocal inhibition via muscle spindles
- B. Autogenic inhibition via Golgi tendon organs
- C. Stretch reflex potentiation
- D. Reduced sarcomere cross-bridges
Answer: B. Sustained tension activates GTOs (Ib), inhibiting the hamstring itself and allowing deeper ROM.
Common exam traps
- Mixing up receptors: spindle → length, GTO → tension.
- Assuming the GTO reflex means "shutdown." It's inhibition, not paralysis — the muscle simply relaxes enough to protect the tendon.
- CRAC vs. hold-relax: both are PNF, but they exploit different reflexes.