Understanding the Reflex Test
When people go for check-ups, doctors usually use a tool to see how patients’ reflexes respond to that tool. This is called the reflex test.
What is a Reflex?
A reflex is an automatic body reaction. It means that your body involuntarily reacts to a certain impulse. This specific impulse lets the senses send signals to the spine in which the brain and the nerves will allow the muscles in your body to react. For example, you’re a parent with a 6-month old son who is hyperactive and crawls a lot. You’re doing household chores while he plays in the crib in his room. Moments later you come back to his room to check on him and see him hanging from the rail guard of his crib about to fall off. You almost teleport to his position just in time to catch him—that is reflex.
Reflex tests measure the strength and appearance of a number of reflexes. These tests are actually part of a neurological exam done for spinal cord injuries or neuromuscular conditions—to check whether or not the nerves in the spine are still functioning. A so-called “deep tendon reflex” is included in the examination; it mainly measures the reliability of the body’s motor system—muscular reactions to activities such as walking, running, dancing, etc.
There are six major locations for testing the reflex to ascertain the health of the spinal cord. These are the ankle, knee, abdomen, forearm, biceps and triceps. The ankle is connected to the nerves of the first and second backbones. The knee is connected to the nerves of the second through the fourth backbones. The abdomen is connected to the nerves of the eighth through the twelfth backbones. And finally, the forearm, biceps and triceps are connected to the nerves of the fifth, sixth and seventh backbones. In order to see if the nerves are fully functional, these major locations are lightly tapped using a rubber hammer to see if there is a reflex to each part. For example, a “knee-jerk” suggests that the nerves in the lower part of the spine are functioning well.
Another reflex test is called the Babinski Test, which we shall discuss in my next article.
The Reflex Hammer
The tool being used for these reflex tests is called a reflex hammer. It is a medical tool that physically checks the overall condition of the nervous system.
The hammer was invented in 1800 by a Scottish physician named Sir David Barry, and was mainly used for pounding. In 1870, two physicians named Wilhelm Heinrich Erb and Carl Friedrich Otto Westphal discovered the “deep-tendon reflex” and decided to use the hammer to test the knee reflex. In 1888, a Philadelphia neurologist John Madison Taylor invented the first certified reflex hammer. Since then, it has been medically used for various reflex tests all over the world. Basically, neurologists or physicians are permitted to use this tool.
But don’t worry—it’s not going to hurt since it’s just a small hammer with a rubber head and a metal handle. In fact, you can check yours or your family members’ reflexes at home. All you need is the reflex hammer.
How the doctor conducts the reflex test
The (adult) patient is seated straight at the edge of a checkup bed, arms and legs are relaxed with one hand on top of the other. The patient should be calm and relaxed.
1. Biceps. On one arm, doctor places thumb on the biceps and then the thumb is struck with the reflex hammer. The same thing is done on the other arm. If both arms jerk similarly that means the nerves connected to the biceps are completely normal and functioning well.
2. Forearm. The patient relaxes both arms. Doctor then strikes the forearm tendon on one arm three inches from the wrist, will then do the same on the other arm. If both reflexes respond similarly, it means that the nerves connected to the forearms are normal and functioning well.
3. Triceps. The doctor will hold the patient’s arm with one hand and strike the tendon directly with the reflex hammer. The same thing is done on the other arm. If both arms respond similarly, then the nerves connected to the triceps are normal and functioning well.
4. Knee. This is where the “knee-jerk” comes in. Patient hangs the lower leg freely from the edge of the checkup bed. Doctor strikes the large tendon located just above the kneecap (quadriceps tendon) with the reflex hammer. The same thing is done with the other knee. If the reactions are the same, then the nerves connected to the knees are normal and functioning well.
5. Ankle. Doctor holds the relaxed foot with one hand and strikes the Achilles’ heel with the reflex hammer. he same thing is done with the other foot. If the reactions are the same, then the nerves connected to the ankles are completely normal and functioning well.
Why it is important to have reflex tests
Reflex tests help doctors recognize brain damages, spinal injuries and neuromuscular conditions. Doctors are then able to recommend that patients see neurologists or specialists who can further assist them with their illnesses.
And as always, the best way to achieve a healthy life is to have do daily exercises, eat nutritious food, and take vitamins that are good for the brain, spine, nerves and muscles.
- “Reflex Tests,” Encyclopedia of Children’s Health; last accessed 2/13/2020
- “The Neurological Examination,” UCSD’s Practical Guide to Clinical Medicine; last accessed 2/13/2020
- “Reflex Hammers: History, Current Use and How to Buy,” All Heart; last accessed 2/13/2020
- “Deep Tendon Reflexes,” The Precise Neurological Exam; last accessed 2/13/2020