Foot numbness, or paresthesia, is a common experience for runners, often described as a temporary tingling or a “pins-and-needles” sensation that develops during a run. This feeling in the left foot is usually a sign of temporary nerve compression or a restriction in blood circulation that occurs during the repetitive motion of physical activity. Since the foot swells naturally while running, the nerves and blood vessels are more susceptible to pressure from external and internal factors. Understanding the mechanisms behind this sensation is the first step toward finding a simple solution.
Equipment and Fit: The Primary Culprits
The most immediate and common causes of foot numbness relate directly to the gear a runner uses, particularly the footwear. Running shoes that are too tight, especially across the midfoot or in the toe box, can compress the delicate nerves that run between the metatarsal bones. Because the foot expands in length and width during a run, a shoe that feels comfortable while standing may become restrictive after a mile or two, leading to nerve entrapment and the resulting tingling. Many experts suggest purchasing running shoes a half to a full size larger than your street shoe size to accommodate this natural swelling.
The way a shoe is secured also plays a large role in nerve pressure on the top of the foot. Tying laces too tightly can compress the dorsal nerves, which run just under the skin on the top of the foot, especially in runners with high arches. This pressure point is sometimes referred to as the anterior tarsal tunnel. To alleviate this, runners can employ alternative lacing methods, such as “skip lacing” to bypass a specific eyelet that rests directly over a painful spot, or using a “window lacing” technique to create more room over the top of the foot.
Socks can contribute to the problem. Overly thick socks take up too much space inside a properly fitted shoe, effectively making the shoe too small and increasing internal pressure. Socks that are too tight around the ankle or calf can also restrict circulation or put pressure on surface nerves.
Running Form and Underlying Nerve Compression
When equipment adjustments fail to resolve the numbness, the cause may be related to an individual’s running mechanics or an underlying nerve condition exacerbated by the activity. Issues with running form, such as overstriding, can increase the impact force transmitted through the foot with each step. This repeated, excessive impact can cause inflammation and mechanical stress that irritates or compresses the nerves over time.
Biomechanical factors, like overpronation (an excessive inward rolling of the foot after landing), can also contribute to nerve stress. When the foot rolls too far inward, it can stretch or compress tissues in a way that irritates the tibial nerve in the ankle. This can lead to a condition known as Tarsal Tunnel Syndrome, where the tibial nerve is compressed as it passes through a narrow channel in the ankle, causing pain, tingling, and numbness that often radiates into the sole of the foot.
A more localized issue, often presenting as numbness or a burning sensation between the toes, is Morton’s Neuroma. This condition involves the thickening of the tissue around a nerve, most commonly between the third and fourth toes, creating a small, painful mass. The repetitive pressure from the push-off phase of running, combined with the narrow forefoot of some shoes, stresses this nerve, leading to the feeling of stepping on a pebble or a fold in a sock.
Immediate Adjustments and When to Consult a Professional
If numbness begins during a run, the safest immediate action is to stop running completely. This pause allows the foot to relax and can relieve the immediate pressure causing the paresthesia. Simple, mid-run troubleshooting involves loosening the shoelaces, especially those over the top of the foot, and walking for a minute or two to restore normal circulation and nerve function. Performing a quick ankle circle or a gentle calf stretch can also help to decompress any tightness in the surrounding muscles that might be contributing to the nerve irritation.
While occasional, temporary numbness is usually benign, certain symptoms are red flags that warrant a consultation with a healthcare professional, such as a podiatrist or physical therapist. Numbness that persists for a significant period after the run has ended, is accompanied by sharp, burning pain, or is associated with noticeable muscle weakness requires medical evaluation. A professional can accurately diagnose underlying issues like Tarsal Tunnel Syndrome or a developing Neuroma and may recommend solutions like custom orthotics, physical therapy, or specific nerve block procedures. Ignoring persistent numbness can lead to a worsening of the underlying condition or a change in gait that causes secondary injuries.