6 Weird Side Effects of Running and How to Fix Them

This was it. This was the summer I would get off the couch and start running consistently. I was a little intimidated but nonetheless committed. I knew it wouldn’t be easy. I was expecting a challenge and honestly, that was part of the appeal of this running journey. What I wasn’t expecting was all the interesting, sometimes annoying, and occasionally alarming ways my body reacted to this new endeavor.

There was the unrelenting side stitch that I was convinced was appendicitis, and the embarrassing toilet break that I always had to take about ten minutes into my run. More than once, I questioned if I was really cut out for this running nonsense.

If you’re a new runner and this sounds familiar to you, rest assured that it’s completely normal for your body to have some weird reactions during that first month or two of logging miles. There are even scientific reasons for what you’re experiencing. Here are some of the most common reactions, why they happen, and how you can endure—and possibly avoid them.

1. Side Stitches

Let’s start with one of the most common responses that new runners experience and my personal nemesis: the side stitch. Exercise-related transient abdominal pain (ETAP) is the medical name for the stabbing, cramping pain you might feel under your ribs while running. And it’s generally triggered by shallow breathing, which could potentially limit the oxygen that your muscles get. This includes your diaphragm, a large muscle under your lungs that helps with breathing. When your diaphragm doesn’t get enough oxygen, it becomes fatigued faster and cramps up.

“Side stitches can also occur when your breathing is out of sync with your running pace, which can cause your lungs to press down on the diaphragm at the same time that forces from running’s jostling impact move up to your core,” says Dr. Laura Ankrum, DO, a family medicine physician, marathoner, and 2000 U.S. Olympic Trials qualifier. “As a result, your diaphragm becomes fatigued and spasms.”

To avoid side stitches, practice syncing your breathing with your running pace. For easy runs, try using a 3:3 pattern (inhaling for three steps and exhaling for three steps) or a 4:4 pattern. As you get faster, switch to a 2:2 pattern.

If you’re in the middle of a run and you get a side stitch, walk for a few minutes and focus on taking deep belly breaths. The side stitch should disappear within 15 minutes or less.

2. Surprise Bathroom Breaks

It turns out that I’m not the only one with the urge to use the bathroom shortly after starting a run. According to Ankrum, it’s very common.

“This is primarily due to blood flowing away from your digestive system to deliver more oxygen to your working muscles. This temporary decrease in blood may irritate the intestines,” Ankrum says. Running also jostles your intestines and gets your digestive system moving, so food will pass through faster. This can lead to a sudden urge to go that sends you sprinting to the nearest toilet.

“Ten to 15 minutes into the workout is when it is probably going to hit you, so a good strategy is to warm up by doing a loop or two in close proximity to a bathroom so that you can be back within that window.”

You can also help your digestive system adapt. Initially, don’t eat anything for two hours before you run. Once your digestive system can tolerate that, start decreasing the duration until you can tolerate eating up to 20 minutes before you run.

“Everybody’s a little different, but it usually takes a few months for your digestive system to naturally adjust to running,” Ankrum says.

3. Appetite Swings

You finish your run, and you know you should refuel, but for some reason, the thought of eating immediately after your workout almost makes you gag. Then, two hours later, you are so hungry that you’re tempted to eat everything in sight. Don’t worry, extreme appetite swings are normal.

Immediately after a run, you may experience a loss of appetite because of how running diverts blood flow away from your gut. Running also reduces the production of ghrelin, the hunger-stimulating hormone, while simultaneously elevating satiety hormones like peptide YY (PYY) and glucagon-like peptide 1 (GLP-1).

“Because of that hormonal response, you may not have an appetite after your run, but your body still needs to replace the calories you burned so you can be ready for your next workout,” says Chris Clark, a former NCAA DII All-American and professional track athlete and private running coach with a master’s degree in exercise science.  Even if it’s 40 minutes after your run, consume some simple carbohydrates that are easy to digest, like bananas, bagels, and rice. You also need protein, but your body can access amino acids any time of day, so consume that once you cool down, and that delayed, sometimes extreme hunger kicks in.”

4. Shin Splints

Medial tibial stress syndrome, or shin splints, is a common overuse injury that impacts the tibia, or shin bone. Typically, the painful throbbing from shin splints will be felt in your left and right shins at the same time.

Repetitive stress from running creates microscopic tears in the muscle fibers and bone tissue. When the rate of this micro-damage outpaces your body’s ability to adapt and heal, inflammation and pain occur as shin splints.

“This is very common with beginner runners because they tend to ramp up the miles too soon or do too much speed work before their bodies have adapted,” Clark says. “Sometimes shin splints come down to your connective tissue not getting a variation of stimulus when you train. Instead of running on the same track or hard surface all the time, add in some variety and run on different surfaces, like grass, sand, or dirt trails if you can.”

He also recommends making sure your shoes are well-cushioned and fit your feet properly.

“You can run through shin splints, but you’ll need to rest more and decrease the mileage and intensity of your workouts until you heal,” adds Ankrum. To mitigate the pain from shin splints and encourage your body to adapt, try wearing compression socks, or using kinesiology tape or even old-fashioned athletic tape on your shins. Post-run, gently foam roll and stretch your calves to release muscle tension and ice your shins to reduce inflammation.

With modified activity, most people feel better within two to four weeks. But if shin pain continues on only one side, visit your doctor to rule out a stress fracture or other structural injury.

5. Twitches and Muscle Spasms

At some point on your newbie journey, your leg muscles may involuntarily spasm or twitch while you’re resting. This usually occurs within 12 to 16 hours after longer runs and can be especially common in the evenings.

“There’s still some debate over what exactly causes a twitch, but it’s usually the result of an overexertion of the muscle that’s spasming,” Ankrum says. “It can also be related to dehydration or an electrolyte imbalance on the cellular level.” Electrolytes dictate how muscle fibers contract and relax, and how nerve cells fire. When these minerals are out of balance, the electrical signaling misfires and muscles lock up as a result. To avoid post-run muscle spasms and twitches, focus on balancing your electrolytes and hydrating properly.

“After a hard workout, you might still get the twitching at night, even if you get your hydration and electrolytes right. Although this is most common in the calves, you can get these spasms anywhere,” Ankrum says.

Post-run twitches and muscle spasms should settle down after a couple of minutes. And they should occur less frequently after a few weeks of training. “If they keep occurring on easy days or rest days, you might be missing something nutritionally. In this case, see your healthcare provider to determine the exact cause.”

6. Blisters and Chafing

Nothing sabotages a good run (and the next one and the one after that) quite like a blister on your foot. Friction, typically from ill-fitting shoes or socks that literally rub you the wrong way, can cause your skin’s upper layers to separate.

“That fluid-filled bubble you see is actually your body’s way of creating a natural cushion to protect the underlying tissue while it’s healing,” Ankrum says. “It will usually be a clear fluid, but if you keep running on it, it can sometimes break a blood vessel, causing a blood blister. Over time, your body will absorb the fluid in your skin layer. You will likely develop a callus and stop getting blisters on your foot’s hot spots.”

Until then, you can apply moleskin, or an anti-chafing balm or lubricant, to those hot spots. Popping a blister is also a popular remedy, but it can be risky.

“The blister acts as a barrier against infection, but if it is extremely painful or likely to burst anyway, use a sterile technique to pop it,” Ankrum advises. Clean the blister and the surrounding area with mild soap and water, followed by rubbing alcohol. Sterilize a needle in the rubbing alcohol for a minimum of 20 seconds before piercing the blister near its base or outer edge. Use a clean cotton swab or gauze pad to gently press down on the blister and drain it. Then apply a topical antibiotic and a non-stick bandage over the area to prevent infection.

To reduce the friction that causes blisters, make sure that your shoes fit properly. They shouldn’t be too loose or too wide around your heels, which could cause rubbing. And the toe box should allow your toes to splay naturally. Don’t underestimate the power of quality running-specific socks made of moisture-wicking fabrics. For blister protection, look for socks with an anatomical fit to prevent them from slipping down. Since seams can exacerbate hot spots, socks with seamless construction are a plus.

Like blisters, chafing is a common and painful irritation caused by the repetitive rubbing of clothing or skin on skin. Further aggravated by heat and sweat, chafing frequently occurs between the inner thighs, at the waistline or underarms, or anywhere clothing creates friction against the skin. To avoid this dreaded chafing, wear moisture-wicking apparel and consider applying anti-chafing balms to hot spots.

From your skin to your shins, the physical responses that the body has to running can range from just plain weird to incredibly painful. As a new runner, understanding the science behind these normal reactions and familiarizing yourself with some ways to prevent them can help you enjoy every mile of your running journey. Trust that your body will adapt and embrace these responses as a rite of passage.

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