Can't Straighten Your Arms After a Workout? Here's Why (and What to Do About It)

If you can't straighten your arms after the gym, inflammation and damage to your muscle structures may be to blame.
Image Credit: Mladen Zivkovic/E+/GettyImages

Feeling sore after a challenging workout is normal — maybe even to be expected. After all, sore muscles are a natural part of the physiological repair process that ultimately makes you stronger and fitter.

But some people experience a strange post-exercise phenomenon that goes beyond basic aches and pains. After lifting weights — usually a hefty dose of biceps and pulling exercises — they find that they can't straighten their arms. Their elbows just won't do it.

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Wondering, "why can't I straighten my arms after a biceps workout?" We don't blame you for being concerned, frustrated or just plain confused if you can't extend your elbow.

Luckily, we're here to deliver answers. Find out why you might not be able to straighten your arms after a workout and what you can do to resolve the issue. Here's the long and the short of it.

2 Physiological Causes of Not Being Able to Straighten Your Arm After a Workout

1. Increased Blood Flow and Inflammation

Doing a tough workout causes microtears within the muscle fibers (and their nerves), leading to delayed-onset muscle soreness, or DOMS, a day or two after intense exercise.

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"To repair the damage done to the neuromuscular system, blood flow to the area increases," says Todd Buckingham, PhD, lead exercise physiologist for the Mary Free Bed Sports Performance Lab. "This creates inflammation and edema, or swelling."

Ultimately, the increase in blood circulation is a good thing, because your blood carries nutrients that assist with healing. "It regenerates muscle tissue, increasing performance and overall strength," explains Jonathan Mike, PhD, a professor of exercise science and sports performance at Grand Canyon University.

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But it can also come with some less-than-pleasant side effects. "The inflammation from extra blood flow pushes on your nerve fibers, which detect pain," Buckingham says. That's why your muscles feel so tender.

The pain, in turn, can prevent you from fully straightening your elbow joint. Once you reach a certain point, the pressure against your nerve fibers is so intense that your brain tells your arm not to straighten any more. (This all happens in your autonomic nervous system, so it's not something you can consciously control.)

Inflammation can physically limit your range of motion by several degrees, according to Buckingham. "The inflammation acts like a blockade preventing you from full extension," he says.

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2. Cellular Damage

Another potential cause of not being able to extend your elbow: damage to the structures supporting your biceps muscles.

"Each of your muscle cells has a net-like structure surrounding it, called the sarcoplasmic reticulum [SR]," Buckingham says. The SR plays a vital step in allowing you to both contract and relax your muscles. It releases calcium into your muscle cells, with that calcium acting like the key that unlocks your muscles and allows them to move. So, to lengthen your biceps muscles and extend your arms, the SR has to release calcium.

"But if you damage your SR during heavy exercise, it won't release calcium and so there won't be any relaxation of the muscle," Buckingham says. "This can lead to stiffness and pain and can prevent you from straightening out the muscle."

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3 Reasons for Extra Inflammation and Damage

1. Pushing Too Hard

Overdoing it during a workout increases the chance of being unable to elongate your muscles afterwards. "If a muscle is stressed past its limits due to repeated contractions against a heavy load, it causes neuromuscular injury," Buckingham says.

"This is an indication that you went too hard, so back off a bit next time." Upping the intensity little by little will lead to better long-term results. Moving forward, be sure to increase the intensity of exercise in a stepwise fashion, so that you're not loading on more than you can handle.

2. Trying New Exercises

Along those lines, if you haven't worked out in a while or you do a different type of workout than usual (say, you go to your first ever barre class, or lift weights for the first time in ages), you're also at greater risk.

"When you are unaccustomed to the activity, you will experience more microtears in your muscles than if it's something you do routinely," Buckingham says. "The reason is that your muscles have to build themselves up stronger so that the next time you do the same activity, they won't have as much damage."

That's no reason to avoid new exercises. Just ease into them.

3. Doing Eccentric Work

It's also more likely to happen during exercises that involve eccentric actions. "Eccentric contraction is the forced lengthening of a muscle," Buckingham says.

For instance, during biceps curls, raising your hand up to your shoulder is a concentric action or contraction — your bicep muscle is getting shorter. Holding the dumbbell in place at the top of the lift is an isometric contraction, meaning there is no change in muscle length. When you lower your hand back down, this is an eccentric contraction, elongating your muscle.

"Eccentric contractions produce the most muscle damage because you are working against gravity," Buckingham says. "Instead of simply letting your hand fall down to your side, you have to control the descent."

Eccentric exercises are great for building muscle, so don't feel like you have to avoid them. Instead, limit how many eccentric exercises you do in a given workout. Try limiting yourself to one per workout before increasing further.

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Should I Be Worried About Not Being Able to Straighten My Arms?

Not necessarily. As long as it clears up within 48 hours or so, you should be fine. That said, it probably means you pushed yourself too much. After all, if you're so sore or your movement is inhibited to the point where you can't work out for days, you're missing out on the benefits of regular exercise.

"Consistency is key if you want to see improvements in fitness," Buckingham says.

If your symptoms do linger longer than two days, you should get checked out by a doctor to rule out more serious conditions like rhabdo.

"Rhabdomyolysis is when you have extreme damage to the muscle," Buckingham says. "It breaks down and releases proteins into the blood, which can harm your heart and kidneys, and is potentially life threatening." Signs of rhabdomyolysis include dark red urine, severe muscle aches and weakness.

Also consider talking to your doc if you have severe or long-lasting inner elbow pain.

"This could signify injury to the tendon, which attaches the bicep muscle to the bones at the inner elbow," Buckingham says. "You might have strained the tendon by lifting too much weight." It typically resolves on its own.

"It could also be a condition called tennis elbow," Mike says. "It is often due to overuse of the forearm muscle and is extremely treatable." According to the American Academy of Orthopaedic Surgeons, the vast majority of people with tennis elbow feel better with rest, over-the-counter pain meds and physical therapy.

When Will I Be Able to Straighten My Arm Again?

Most likely in a day or two.

Still, things could draw on a bit more, depending the type and overall volume of your recent training session, Mike says. “It also depends partly on genetics, and partly on how well you are resting and recovering," Buckingham adds.

Can't Extend Your Arms? Here's How to Fix It

Because the causes of not being able to straighten your arms after a workout largely have to do with pushing super, if not too hard, the best long-term solution is to back off of your exercise intensity. Slowly progress your workouts so your muscles are able to adapt, recover and grow back stronger between each lifting session.

Speaking of recovery, it's vital to both preventing future pains and easing the ones you've already got.

"Doing gentle range of motion movements will increase blood flow to the affected area and aid in recovery," Buckingham says.

He suggests repeating the same type of movements that caused the issue, only without weights. So if you can't straighten your arm, try the following: biceps curls, triceps extensions, arm circles, shoulder presses and Y raises.

But, all in all, the strategies for straightening your arms once more aren't all that different from those used to get rid of regular cases of DOMS. Rest your muscles, get protein and eat up lots of antioxidant-rich fruits and veggies.

Your Complete Guide to Workout Recovery

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