Runners deal with their share of complaints mid-workout — calf cramps and foot numbness included. And though you may experience both at once, they usually have separate causes.
The two most common causes of numb feet when running is a lack of blood flow or nerve injury that creates a loss of sensation in one or both feet. Meanwhile, a calf cramp while running usually signal an issue with muscle contraction.
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"Muscles are supposed to contract to help us get from A to B, but when it's an involuntary, excessive contraction, that's when we get that pain," says Larry Nolan, DO, a primary care sports medicine physician at The Ohio State University Wexner Medical Center.
If either (or both) of these sound familiar, read on for potential causes and what you can do about each of them.
Causes of Calf Cramps While Running
1. Dehydration and/or Electrolyte Imbalance
Some experts believe that dehydration and/or electrolyte imbalances contribute to cramping. However, the topic is somewhat controversial in the medical literature, says Omar Yaldo, MD, an orthopedic foot and ankle surgeon at the Hoag Orthopedic Institute.
Water helps circulate blood and nutrients to your muscles when running. It's thought that dehydration slows this flow, interfering with normal muscle contraction and increasing your odds of cramps.
And electrolytes are minerals you lose through sweat and include calcium, chloride, magnesium, phosphorus, potassium and sodium, per Medline Plus. They affect muscle function and the amount of water in your body.
It's thought that losing too many electrolytes via sweat — especially sodium — causes an imbalance, which makes it hard for muscles to contract well while running. This may cause cramping.
The dehydration and electrolyte imbalance theories have been challenged over the years. That said, it couldn’t hurt to keep these bases covered and see if that helps your cramping, Dr. Yaldo says.
Fluid needs vary, but aim to drink 11 to 13 eight-ounce glasses of water per day, as recommended by the Institute of Medicine of the National Academies. Sip a sports drink to replenish electrolytes when running longer than 60 minutes, suggests the Mayo Clinic. And be especially mindful of fluids and electrolytes when running in the heat.
2. Increase in Uphill Running
Running on inclines may be less stressful for the knees than running on level ground, but it's pretty tough on the calf and Achilles tendon (a thick band of tissue that connects the calf muscles to the heel bone), says Simon Brossier, PT, DPT, a physical therapist at NYU Langone Health.
If you're not used to running hills, your calves can fatigue quickly. Once your muscles pass a certain level of fatigue, they may respond by cramping. It's essentially a sign that your muscle has exceeded its capacity to perform a task, which, in this instance, is uphill running, Dr. Brossier says.
Switch up your running routes to reduce uphill running volume. Moving forward, aim to make gradual increases in volume. Brossier suggests no more than 10 percent per week.
3. Muscle Imbalances
If you're getting calf cramps nearly every run, it's time to consider muscle imbalances. It's not uncommon for runners to have stronger quads (the muscles in the front of the thigh) and weaker glutes, hamstrings (the muscles in the back of the thigh) and calves, Yaldo says.
When these posterior-chain muscles aren't strong enough to handle the same amount of work as other muscles, your calves in particular wind up tiring out earlier in your run. "That's when you would start getting those calf cramps," Yaldo says.
Perform a resistance-training workout at least twice per week and include exercises that target the posterior chain, Yaldo says. Calf raises, hamstring curls and glute bridges are all fantastic options.
Causes of Foot Numbness While Running
1. Poorly-Fitting Running Shoes
If your feet get numb while running, your first step is to check how your running shoes fit. You should have room in the toe box to move your toes. If the top of your shoe feels like it's pressing on the top of your foot, you may have found the source of your problem.
"Having shoes that are too tight or poorly fitting — or even wrapping the laces too tightly — constricts blood flow to the foot and compresses some of the nerves," Yaldo says.
Replace your running shoes. Look for a pair with a wide toe box so your toes don’t get squished. The shoes should also feel comfortable right away when you try them on: “There’s no need to ‘break-in’ a shoe,” Brossier says.
2. Flat Feet
Believe it or not, having flat feet may increase your odds of numbness. Every time your foot lands, the blood vessels in the bottom of the foot get compressed. If your feet are flat, you have more surface area that makes contact with the ground, which means more blood vessels getting compressed with every step, Yaldo says.
You can’t change the fact that your feet are flat. However, you can reduce the surface area by adding an orthotic to your running shoe.
“Sometimes, you can start with an over-the-counter arch support or get a shoe with built-in arch support and see if that helps,” Yaldo says.
3. Pinched Nerve
Foot numbness can originate in other areas of your body, such as your lower back. And foot numbness in relation to the lower back often points to a pinched sciatic nerve.
The sciatic nerve starts in the lower back and runs down the back of each leg, per the Hospital of Special Surgery. This nerve can get pinched (compressed) by surrounding tissues, especially if you use bad mechanics during exercise and daily life. Running can cause the pinched nerve to become more exacerbated and inflamed.
"In turn, that inflammation can affect the nerves that run all the way down to your feet, causing numbness," Yaldo says.
If you have foot numbness accompanied by tingling, pain or a dull ache in the lower back, get your back checked out by a medical professional. Physical therapy and, in some cases, medications, can take pressure off the nerve, Yaldo says.
4. Longer Stride Length
Sometimes, your running form plays a role in foot numbness. Your stride length, in particular.
"Having a longer stride length can cause your heel to hit the ground with more force, and that can then cause some numbness in the heel," Yaldo says.
Plus, a March 2014 study in Clinical Biomechanics found that longer stride length increases the stress on the knee joint when running. This added stress may boost your risk of developing patellofemoral pain syndrome, also called "runner's knee," according to the American Academy of Orthopaedic Surgeons.
Try shortening your stride to see if that relieves numbness, Yaldo says. Focus on taking shorter, quicker steps when you run.
Cause of Calf Cramps and Foot Numbness
If you experience both calf cramps and foot numbness while running, it may be due to a combination of the causes discussed above. Alternatively, it could be due to overtraining. Running too much without sufficient recovery is a recipe for burnout and injury.
"With overtraining, your muscles and nerves get fatigued, and I could see that causing a multitude of issues," Yaldo says. Calf pain and numb feet included.
Switch to cross-training activities like cycling or swimming until your symptoms improve. After that, increase your running mileage by no more than 10 percent from one week to the next, Yaldo says. Making small, gradual bumps in mileage can help prevent issues from overtraining.
When to Consult a Doctor
If you've tried simple fixes on your own and still haven't seen improvements, it's time to get checked out by a doctor. And you should see your doctor immediately if you have foot numbness that seems random and/or wakes you up at night with electric shock sensations.
"I would be concerned that it's neuropathy," Yaldo says. Neuropathy occurs when the nerves that carry signals to and from the spinal cord to the rest of the body don't work correctly, per MedlinePlus. When this happens, you may feel tingling, burning, pain and/or numbness that often starts in the feet.
Neuropathy is often caused by diabetes, but there are many other potential culprits. In fact, one of the main causes of neuropathy is idiopathic, "meaning we just don't know the reason," Yaldo says.
Depending on the cause of your foot numbness and/or calf cramps, you may need to work with a physical therapist, primary care physician, or endocrinologist.