The triceps reflex is an involuntary contraction of the triceps muscle at the back of your upper arm, triggered when a clinician taps the tendon just above your elbow with a reflex hammer. It tests the nerve pathway running through the C7 and C8 segments of your spinal cord, making it a quick and reliable way to check whether those nerves are functioning normally. Along with a handful of other deep tendon reflexes, it’s a standard part of neurological exams.
How the Reflex Works
The triceps reflex is what’s called a monosynaptic stretch reflex, meaning the signal only crosses one connection point inside the spinal cord. When the tendon is tapped, the triceps muscle fibers are stretched suddenly. Tiny sensors inside the muscle detect that stretch and fire an electrical signal up through the radial nerve, entering the spinal cord at the C7 level (and to a lesser extent C6 and C8).
Inside the spinal cord, that incoming signal directly activates a motor nerve cell, which sends a return signal back down the radial nerve to the triceps. The muscle contracts and your forearm extends slightly at the elbow. At the same time, the spinal cord actively inhibits the opposing muscle group (the biceps), allowing it to relax so the triceps can move freely. This entire loop happens in a fraction of a second, without any input from your brain.
How Clinicians Test It
To test the triceps reflex, a clinician supports your arm so the elbow is bent at about 40 degrees, roughly midway between fully bent and fully straight. Using the broad end of a Taylor reflex hammer, they strike the triceps tendon just above the bony point at the back of your elbow (the olecranon). The expected response is a visible contraction of the triceps and a small extension of the forearm.
If the reflex is hard to elicit, you may be asked to perform a reinforcement technique. The most common version, called the Jendrassik maneuver, involves interlocking your fingers and trying to pull your hands apart, or clenching your teeth, while the clinician taps. This increases background nerve activity throughout your body and can bring out a reflex that otherwise seems absent. It helps distinguish a truly absent reflex from one that’s simply subtle.
The Grading Scale
Reflexes are graded on a standardized 0 to 4 scale:
- 0: No response at all. Always considered abnormal.
- 1+: A slight but definite response. May or may not be normal depending on context.
- 2+: A brisk response. This is considered normal.
- 3+: A very brisk response. May or may not be abnormal.
- 4+: A single tap causes repeating, rhythmic contractions (called clonus). Always abnormal.
A grade of 1+ or 3+ isn’t automatically a problem. Clinicians compare your reflexes on both sides and look at the overall pattern across multiple reflex sites before drawing conclusions.
What an Abnormal Triceps Reflex Can Mean
Diminished or Absent Reflex
A weak or absent triceps reflex points to a problem somewhere along the nerve pathway between the spinal cord and the muscle itself. The most common cause is cervical radiculopathy, a condition where a nerve root in the neck is compressed, usually by a herniated disc or bone spur. When the C7 nerve root is affected, the triceps reflex is specifically impacted. Cervical radiculopathy typically causes arm pain (present in 97% to 99% of cases), along with numbness, weakness, and reflex changes (seen in 71% to 84% of patients).
An especially telling sign is the “inverted triceps jerk.” Normally, tapping the triceps tendon produces elbow extension. In an inverted response, the elbow flexes instead. This happens when the nerve fibers feeding the triceps reflex arc are damaged, but the biceps pathway remains intact, so the biceps contracts unopposed. It localizes the injury specifically to the C7 segment.
Exaggerated Reflex
An overactive triceps reflex suggests a problem higher up in the nervous system. Your brain normally sends signals down the spinal cord that keep reflexes in check. When that pathway is damaged (called an upper motor neuron lesion), reflexes become exaggerated because the braking system is gone. Conditions that can cause this include multiple sclerosis, spinal cord injury, ALS, traumatic brain injury, brain infections, and even vitamin B12 deficiency. Exaggerated reflexes usually appear alongside other symptoms like muscle stiffness, weakness, and clonus.
How It Fits With Other Reflexes
The triceps reflex doesn’t get tested in isolation. It’s part of a set of upper extremity reflexes that each map to different spinal cord levels. The biceps reflex tests C5 and C6, while the triceps tests C7 and C8, and the brachioradialis reflex covers C5 and C6. By comparing the results across all of these, a clinician can pinpoint which level of the spinal cord or which nerve root is involved in a problem.
For example, if the biceps reflex is normal but the triceps reflex is absent on one side, the issue likely involves the C7 nerve root rather than C5 or C6. If both reflexes are exaggerated, the problem is probably above both nerve levels, somewhere in the brain or upper spinal cord. This mapping ability is what makes reflex testing so useful. A few taps with a hammer can narrow down the location of a neurological problem before any imaging is ordered.