Exercise-induced leg numbness

A common reason for referral to a sports medicine specialist is leg or foot numbness or tingling with exercise.

Symptoms that can arise from muscle, nerve conditions, and medical conditions such as diabetes or even central nervous system problems.

Perhaps the most common condition is “stepper’s foot” when a persons foot goes numb while using a step masters or elliptical machine. The most common cause for this is constant pressure on the foot.

This steady pressure causes the nerves that pass between the toes to go temporarily numb. Once the person steps off the machine for a few seconds to up to a minute, the tingling quickly resolves.

This is typically not a serious problem. Solutions include loosening laces, shoes with more forefoot cushion, an orthotic with a metatarsal button, lifting your feet off the pedals like you would when walking normally, cross training with different machines and good calf flexibility.

Occasionally, the nerve between the toes (the interdigital nerve) can get impinged and cause pain and electric shocks to the toes and foot. This can develop into a neuronal or thickening of the nerve and be quite painful. Usually, this can be detected on history and careful physical examination and may require adjustment of your activity, modified footwear, and treatment with medications or injections.

Muscle and joint fatigue

Muscle and joint fatigue or aches can mimic tingling and numbness in the foot. Occasionally, a foot joint or bone problem causes pain in the foot and the leg muscles fatigue much quicker. When this occurs, the athlete reports the foot feels weaker and occasionally feels numb or tingly.

Another condition that requires a little more investigation is called chronic exertional compartment syndrome. This is an overuse problem and athletes typically complain of increasing pain, numbness and weakness of the foot or leg with running.

The symptoms usually start part way through a run and are not present normally at the start. Often it will make the athlete stop running and take minutes and sometimes hours to fully settle.

As this syndrome progresses, it can cause pain even at rest and especially the night after the run. Other symptoms can include exercise related numbness into the top or sole of the foot and even a drop foot. This is caused by elevated pressure in one or more of the three muscle compartments in the calf. Strength and nerve testing at rest is normal

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Test the pressures

The key here is to test the pressures in the compartments once immediately after exercise and then one and five minutes later. If the pressures in the calf are too high, you have your diagnosis.

Treatment involves relative rest, determining if orthotics are required, a graduated return to activity, and occasionally surgical release of the high pressure compartment in chronic cases.

Tarsal tunnel syndrome is a relatively rare condition that presents with burning pain and numbness in the soles of the feet. It is often worse at night and the neuropathic burning character or electric shocks is a clue to the diagnosis. It is usually worse with pronation and stretching the sciatic nerve during a walking physical exam.

Typically, this condition starts slowly but increases to the point of not just tingling, but also numbness and burning sensations.

Before treatment is initiated, it is important to make the correct diagnosis. Patients are often treated for plantar fasciitis, tendinitis, stress fractures and metatarsal before a correct diagnosis is made. Nerve testing can be done to confirm the diagnosis and imaging is sometimes required.

Treatment includes orthotics to decrease stretch across the tarsal tunnel during heel valgus, rest, anti inflammatories, possible steroid injections and even surgical decompression in cases where there is a lesion compressing the nerve.

In older athletes, exertional weakness or numbness in the foot or leg could be the sign of spinal stenosis. Athletes usually, but not always, have a history of low back complaints.

The classic pattern is the numbness or weakness is worse with walking or running, and better with sitting. Just stopping and standing usually doesn’t help as much as sitting does.

Athletes may report they can run uphill easier than downhill. This is due to the fact that you normally lean a little more forward running uphill and lean back running downhill which tends to further narrow the spinal canal. This clue might not be of much help here on flat Cayman, though.

A careful history, physical and neurological exam followed by appropriate testing is key to making the diagnosis.

It is important to remember that numbness, tingling and weakness can arise from the nerves in the foot, leg, thigh, back or even the spinal cord or brain. Occasionally even non-neurological structures can mimic these symptoms.

If these symptoms are persistent and, in particular, are getting worse, seek advice from your doctor, as there are often things that can be done to further investigate and then treat the underlying problem.

Dr. O’Connor is a physiatrist, nerve specialist (EMG), and sports medicine physician practising in the Cayman Islands.

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Some people feel numbness from the continual pressure when using elliptical machines.
PHOTO: FILE
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