Depending on the study that you sign up for, testing will take between 1 and 3 hours. Most testing will consist of 3 measures: ankle arthrometry, transcranial magnetic stimulation, and peripheral nerve stimulation.
The instrumented ankle arthrometer is designed to measure the amount of laxity, or “give”, in your ankle. You will be asked to lay on a table and your foot will be placed in the arthrometer and clamps will be secured so that it fits snugly, but is not uncomfortable. From here, we will apply a load on your ankle consistent with the clinical tests that are used to diagnose ankle sprains. This force will be applied gradually and should not be uncomfortable.
Transcranial Magnetic Stimulation
Transcranial Magnetic Stimulation (TMS) involves the application of magnetic pulses over the brain to evoke a response in the leg muscles. We are then able to see how big those responses are, how they responses increase with stimulation intensity, and at what intensity we begin to get a response. These values tells us about the excitability of the primary motor cortex, or how strong the connections between the cortex and leg muscles are. In theory, somebody with greater cortical excitability would have an easier time recruiting the muscles necessary to stabilize the joint.
TMS testing will consist of 3 phases. First, sensors will be placed on the legs to measure muscle activity. Second, we will apply pulses to the head while moving the coil in a small area to find the “hotspot” – the best spot to activate the lower extremity muscles. Finally, apply pulses across a wide range of pulses to measure the excitability of your brain, perhaps while you perform a task
While stimulating the brain may sound intimidating, the sensation you will feel is as if you are being “tapped” on your head. Some taps will be harder than others, but none would be described as painful. With each tap, we will get a degree of contraction from your legs, but you may also blink. This is normal and is related to the coil’s proximity to the muscles of your face. To ensure the safety of each participant during testing, we must exclude subjects on certain medications, or those that have a history of seizure or other medical conditions. To understand if you qualify, please consult this questionnaire (PDF, 168 KB) and indicate if you answered “Yes” on any questions when expressing interest. This will not automatically exclude you, but Dr. Needle will follow up and see if you still qualify.
Peripheral Nerve Stimulation
By stimulating your nerve, we can determine the strength of your spinal reflexes. This is similar to a doctor checking your reflexes with a reflex hammer, except that we can control the intensity of the pulse, and measure the exact response.
For this testing an electrical probe will be placed behind your knee. We will briefly search for the exact location of the nerve, before providing stimulation over gradually increasing pulses, until a maximum response is observed. The pulses will be brief (<1 millisecond), as will any residual sensations (tingling or muscle contraction) in your leg.