Can't Straighten Your Arm After a Workout? Here's Why

Sore arms and biceps after a challenging upper-body workout are normal — maybe even to be expected, since sore muscles are part of the natural muscle-repair process that ultimately makes you stronger.

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 they can't straighten their arms all the way. Their elbows just won't do it.

Lingering biceps pain, especially when you can't straighten your arm, is generally rooted in inflammation and damage — typically the result of new stress placed on your biceps muscles.

Why Can’t I Straighten My Arms After a Workout?

Here’s why your arms might feel stiff and painful after a workout and what you can do to resolve the issue.

Delayed-Onset Muscle Soreness

Tough workouts cause microtears within your muscle fibers, leading to delayed-onset muscle soreness, or DOMS, a day or two after intense exercise.

"To repair the damage done to the neuromuscular system, blood flow to the area increases," says Todd Buckingham, PhD, a visiting professor of exercise science at Grand Valley State University in Allendale, Michigan. "This creates inflammation and edema, or swelling."

The increase in circulation is ultimately beneficial because your blood carries nutrients that aid healing. "It regenerates muscle tissue, increasing performance and overall strength," says Jonathan Mike, PhD, a professor of exercise science and sports performance at Grand Canyon University in Phoenix, Arizona.

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

The pain and swelling in your arms can then prevent you from fully straightening your elbow joint. The pressure against your nerve fibers is so intense that your brain tells your arm not to straighten any more. (This all happens through your autonomic nervous system, so it's not something you can consciously control.)

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

Cellular Damage

Another potential reason why you can’t 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)," says Buckingham. The SR plays a key role in allowing you to contract and relax your muscles. It releases calcium into your muscle cells, which acts as a key to unlock your muscles and allow them to move.

"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."

3 Workout Habits That Lead to Biceps Pain

Experiencing lasting biceps pain, especially when you can't straighten your arm, is generally rooted in the inflammation and damage detailed above. But these are often the result of a few common scenarios you may encounter during your workout.

1. You Pushed Too Hard

Overdoing it during a workout increases the chance of being unable to elongate your muscles afterward.

"If a muscle is stressed past its limits due to repeated contractions against a heavy load, it causes neuromuscular injury," Buckingham says. This can be a sign you went too hard, so you might want to take things slower the next time, he says.

Upping the intensity little by little will lead to better long-term results. Moving forward, be sure to increase the intensity of exercise gradually, so that you're not loading on more than you can handle.

2. You Tried New Exercises

If you haven't worked out in a while or you do a different type of workout than usual, you might also end up with inner elbow pain.

You’ll experience more microtears when you’re doing an activity you’re not used to, Buckingham notes. "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."

But there's no reason to avoid new exercises if they don’t aggravate a current injury or lead to a new one. Just make sure you ease into them.

3. You Worked Your Muscles Eccentrically

Pain and difficulty extending your arms is also more likely to happen after exercises that involve eccentric actions. "Eccentric contraction is the forced lengthening of a muscle," Buckingham says.

For instance, during hammer curls, raising your hand up to your shoulder is a concentric action, or contraction — your biceps muscle is getting shorter. 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, consider limiting how many eccentric exercises you do in a given workout — for example, stick with one per workout at first.

When to Talk to a Doctor

Should you be worried about not being able to straighten your arms? Not necessarily — it's normal to be a little sore after a workout. 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.

"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 or brown urine
• Severe muscle aches
• Weakness

Also consider talking to your doctor if you have severe or long-lasting inner elbow pain. This could mean a tendon injury, says Buckingham. You may have strained the tendon that attaches your biceps muscle to the bones — luckily, this usually resolves on its own.

When Will I Be Able to Straighten My Arm Again?

Most likely in a day or two. Still, things could draw on a bit longer, depending on 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 says.

If you're so sore you can't move, it's probably best to consult a medical professional, as you may have injured yourself during your workout.

Treatment and Prevention Tips

If you're sure you're dealing with normal soreness and don't need to see a healthcare professional, you can try these treatments — and prevention — suggestions on your own.

1. Adjust Your Workout

Too much too soon is a common cause of muscle soreness and stiffness, especially for beginners.

The best long-term solution is to reduce your exercise intensity. Decrease the amount of weight you're lifting, or lower your number of sets and reps. A rule of thumb: The last two reps of each set should feel comfortably challenging.

2. Move and Stretch

Wondering if you should work out while you're sore? Don't jump right into another training session, but it's okay to keep moving. “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, freehand.

• Biceps curls
• Triceps extensions
• Arm circles
• Shoulder presses
• Y raises

Overhead Dynamic Triceps Stretch

• Skill level: All levels
• Time: 30 seconds
• Body part: Arms and shoulders

1. Raise your left arm straight above your head and bend your elbow to lower your palm to your back.
2. Place your right hand near your raised elbow and gently pull it toward your body and down.
3. Pause, then release and straighten your arm back overhead.
4. Continue for 30 seconds.
5. Repeat on the other side.

Wrist Flexion and Extension Drill

• Skill level: All levels
• Time: 30 seconds
• Body part: Arms

1. Hold your left arm straight out in front of your body at shoulder height with your palm facing up.
2. With your right hand, pull back on the fingers of your left hand to feel a gentle stretch in your left forearm.
3. Hold here for 10 to 15 seconds.
4. Use your right hand to gently pull your left palm toward you.
5. Hold here for 10 to 15 seconds.
6. Repeat on the other side.

Forward Overhead Swing

• Skill level: All levels
• Body part: Arms and shoulders

1. Start by standing with your arms by your sides and your feet about shoulder-width apart.
2. Take one small step forward with your left foot as you swing both arms overhead.
3. Swing your arms back down as you step back.
4. Repeat, this time stepping forward with your right foot.
5. Continue alternating feet for 30 seconds.

3. Refuel

You also want to make sure you're getting enough protein. Protein helps repair exercise-induced muscle damage, which is how you get stronger. Aim for 1.4 to 2 grams (g) of protein per 2.2 pounds (lb) of body weight a day.

For easier math, many people simply plan to eat 1 g of protein per pound of their body weight each day.

The Takeaway

• Inflammation and damage to the cellular structures in your biceps muscles are common causes of pain that prevents you from extending your arm after a workout.
• Pushing too hard during a workout or trying workouts you're not used to are more likely to result in this type of damage.
• Stretch, get proper nutrition, and ease up on your workout intensity to heal and avoid this type of injury in the future.
• If the pain lasts for longer than two days, it’s a good idea to see a doctor to rule out conditions that require more support to heal.