The sensation of feet going numb while running, medically known as paresthesia, is a common complaint among runners. This feeling is often described as pins and needles or tingling. Paresthesia occurs when nerves are compressed or irritated, disrupting the transmission of sensory signals to the brain. The repetitive impact and mechanical stresses involved in running frequently trigger this issue. While the experience can be disconcerting, the causes are usually minor and related to external pressure or temporary tissue swelling.
Immediate Causes: Equipment and Mechanical Compression
External factors are often the simplest explanation for numb feet, acting directly to restrict blood flow or compress nerves. The most frequent mechanical cause is improper shoe fit, particularly a narrow toe box that squeezes the forefoot. Since feet naturally swell during exercise, a shoe that fits fine at rest can become constricting during a run. Choosing a running shoe that is a half-size larger or features a wider forefoot can alleviate this pressure.
Lacing technique is another common, easily correctable issue. Tying laces too tightly, especially across the top of the foot or instep, exerts excessive pressure on the dorsal nerves and blood vessels. This compression interferes with nerve function and circulation, causing numbness. Loosening the laces or utilizing alternative lacing patterns that skip the eyelets over the area of maximum pressure can resolve the tingling.
The thickness and material of socks can also contribute by taking up too much space within the shoe, effectively narrowing the fit. High-impact forces cause temporary swelling and fluid buildup in the feet. This tissue expansion pushes against the snug confines of the shoe, further compressing the nerves.
Specific Nerve Entrapment Conditions
When external causes are ruled out, numbness may stem from specific anatomical conditions where nerves are chronically irritated.
Morton’s Neuroma
One frequent condition is Morton’s Neuroma, which involves the thickening of tissue around a nerve leading to the toes, most often between the third and fourth toes. Repetitive impact and pressure on the ball of the foot during running can cause this nerve tissue to swell and become inflamed. This condition typically causes a sharp, burning pain in the forefoot, accompanied by numbness or the sensation of walking on a small stone.
Tarsal Tunnel Syndrome
Another localized issue is Tarsal Tunnel Syndrome, which involves the compression of the posterior tibial nerve as it passes through a narrow space behind the inner ankle bone. Running can exacerbate this condition because excessive pronation can increase the strain on the structures within the tarsal tunnel. Symptoms often manifest as numbness, tingling, or pain extending along the bottom of the foot. These conditions require specific treatments like orthotics, physical therapy, or injections to relieve the nerve pressure.
Contribution of Running Form and Biomechanics
The way a person moves can create internal stresses that lead to nerve compression, independent of equipment issues.
Excessive Pronation
Excessive pronation, where the arch of the foot collapses inward after landing, can stretch or compress nerves and overload the medial structures of the foot. This altered foot mechanics can contribute to conditions like Tarsal Tunnel Syndrome or place undue pressure on the plantar nerves. Supporting the arch with proper footwear or orthotics can help maintain better foot alignment and reduce nerve strain.
Impact Forces and Stride
The magnitude and location of impact forces during the stride also play a role in nerve irritation. Runners who overstride, landing with their foot too far in front of their body, often experience a heavy heel strike. This pattern increases the duration of ground contact and the mechanical stress transmitted through the foot, which can repeatedly compress nerves. Modifying the stride to a shorter, quicker cadence can shift the foot strike toward the midfoot or forefoot, reducing concentrated pressure. Insufficient strength or stability in the hips and core can also lead to poor mechanics that affect how the foot lands.
When Numbness Signals a Deeper Issue
While most cases of running-induced numbness are mechanical and temporary, certain signs suggest the need for professional medical evaluation. Numbness that persists long after the run is over, for more than 30 minutes, indicates that the cause is not just temporary mechanical compression. Symptoms accompanied by severe, sharp pain, muscle weakness, or changes in muscle function also warrant immediate attention.
Numbness that occurs even when a person is not running may point toward a systemic health condition. For example, peripheral neuropathy involves nerve damage caused by conditions like diabetes, leading to constant loss of sensation. Other possibilities include nerve impingement higher up the leg or in the lower spine, which can be irritated by running. Consulting a medical professional is appropriate when symptoms worsen or become more frequent, ensuring an accurate diagnosis and treatment plan.