I Can’t Flex My Bicep

Flexing your bicep is a great way to show off gym gains and is even a workout in itself. But what if one day you can no longer contract or flex your right or left bicep despite it being the same size? 

Is lifting still safe as long as the rest of your body is fine? Is it something you should be concerned about? If you want to know the answer to these questions, you’ve come to the right place. 

I had the same problem before, and I’ll guide you the best way I can as a licensed personal trainer. Here’s what you need to know about muscle flexing and why you can’t flex your bicep. I’ve also included tips on how you can flex your biceps correctly. 

Let’s get started!

I Can’t Flex My Bicep. Should I Worry About It?

My answer depends on the cause. If your body is not used to the tension, there’s no need to worry. Your muscles will get used to it after a few weeks. However, ensure you include enough rest days in between, depending on your fitness level or experience.

But if the reason why you can’t flex your bicep is that you have ruptured a tendon. In that case, immediately seeing your doctor is essential because you may need immediate surgical repair. 

If you didn’t straighten your arms a few days after bicep curls, it would be best to call the doctor, as it is a sign of rhabdomyolysis. Below are other reasons why you can’t flex your biceps.

All About Muscle Flexing and Biceps Muscle: 7 Reasons Why You Can’t Flex Your Bicep

I Can't Flex My Bicep

1. Pinched nerve

One of the reasons you can’t flex your bicep muscle is you may have a pinched nerve in the neck or arm. When surrounding tissues compress nerves in these parts of your body, it causes weakness, numbness, tingling, or pain.

Home treatment, time, and rest relieve most pinched nerves. However, treatments like physical therapy and cervical collars can help when they don’t. A manipulation from a chiropractor or a deep tissue massage is another solution. 

Otherwise, see your doctor if signs and symptoms last for several days.

2. Poor grip strength

If you can’t flex your biceps or can’t handle any more weight, it could be that your grip is weak at the moment. A 2016 study in the sports science journal Shoulder & Elbow indicates that weak grip strength indicates shoulder health.

Before I had weak grip strength, I added grip training to my workout. You can use resistance bands, dumbbells, or grip masters to challenge your muscles or incorporate exercise into your daily activities. The dead hang is another excellent exercise to improve your grip strength gradually.

For instance, you can try balancing a few tin cans on the palm of your hand for 30 minutes. Before drinking it, lift a water bottle to improve wrist muscles or practice wringing out a wet cloth.

[See Related Post: Best Grip Strengthener]

3. Distal biceps injury

The distal biceps muscle in the front of your arm helps you twist your forearm and bend your elbow. Unfortunately, it can be prone to a tendon injury, whether partial or complete ruptures. 

Distal biceps injury often occurs in the dominant hand of middle-aged adults. Sometimes, those with distal biceps injury report hearing a “pop” from the front of the elbow. 

Unanticipated loading of the biceps tendon is another common mechanism of distal biceps injury as the biceps muscle contracts, yet the elbow is rapidly straightened. 

Restoring the distal biceps tendon

Various options are available to treat a torn distal biceps tendon, such as operative interventions or conservative treatment. Physical therapy often focuses on maintaining the full motion of the elbow as well as reducing the pain.

4. Poor mind-muscle connection

If you can’t flex your biceps muscle, it could be because you have a poor mind-muscle connection on one side—often in your non-dominant hand.

An excellent method to improve your ability to create forceful muscle contractions and build dense muscle is to train your mind to train the muscles. It’s also called the mind-muscle connection. This functional training could include sensory concentration, movement focus, and pump direction. 

I can’t flex my left bicep as well as my right arm

Avoid barbell exercises until you achieve a solid mind-muscle connection to use both evenly. Focus on improving your mind-muscle connection on the non-dominant hand. Slower reps also help. Concentrate on both concentric and eccentric motions as well.

5. Bad bicep insertion genetics

Like the other muscles in the body, the bicep is composed of tendons and muscle bellies. The muscle belly is the central part of the muscle, and it increases in size in bodybuilding. On the other hand, the tendon is the part that attaches or connects the muscle to the bone, allowing movement.

The muscle-to-tendon ratio shows that long muscle bellies and short tendons (long biceps) have more potential to achieve muscular size than long and short muscle bellies (short biceps). This concept is also called “muscle insertion.”

So, having lousy bicep insertion genetics may be why you can’t flex your bicep. While you can’t change genetics, you should not let this limit your training.

[See Related Post: Why Don’t My Biceps Get Sore After a Workout?]

6. Muscle rigidity

There are about 600 muscles in your body. When you need to move one body part, the brain sends a nerve signal to the muscles on that part. As a result, it causes the muscle to contract.

After muscle contracting, the muscles relax again until the next time you use them. However, muscle rigidity happens when a group of muscles or a muscle in one arm, for instance, stays contracted for an extended period. 

The brain is still sending nerve signals, telling the muscle to contract even if the muscle is no longer needed for movement. 

Muscle rigidity can also last for hours or sometimes days. And the longer the muscles remain contracted, the more pain one feels.

7. Microscopic tears in the tendon

The last possible reason you can’t flex your bicep is that you already injured the tendon either in your left arm (left bicep) or right arm (right bicep), yet you kept working it.

Remember that microscopic tears in the tendon can happen when you lift too fast or too heavy as it cheats with momentum to move too much weight. So, when you flex your arm like a bicep curl, you’ll “hit the wall.” 

Fitness terminology is a feeling of intense exhaustion. It can also be a point where your body will start telling you that you are overdoing it and should take the much-needed rest. So, give it at least two weeks until you regain your full range of motion.

How to Flex Biceps Correctly

Muscle flexing, in general, improves blood circulation. And when blood flow is improved, it relieves headaches and symptoms of conditions like digestive problems and high blood pressure. 

Here’s a brief guide on how you can flex your biceps correctly:

Step 1. Make a fist
Stand or sit upright in a chair with your shoulders down and relaxed. Allow your shoulder blades to spread to keep your back wide. Next, make a fist with the arm that you want to flex. 

Even the simple act of forming a first already tightens your muscles. You can do this with your other arm to determine what needs improvement.

Step 2. Extend one arm out to your side
Straighten your arm to the side or down to be at its most expanded state.

Step 3. Bend your elbow toward your body
The next step is to bend your elbow toward your body while tightening your right or left biceps muscle. Go slowly to build the tension through your bicep muscles as it tightens.

Make sure the arm angle is good. Next, rotate the forearm to flex the bicep muscles. You can clench your thumb into your first, so you have something to grab. Avoid holding a flex for too long.

Step 4. Don’t forget the surrounding muscles
No matter your fitness experience or size, don’t neglect the surrounding muscles: lats, traps, chest, and shoulders. Showing off the entire package while flexing your biceps is also great.

Using barbells or dumbbells to build your biceps

If you plan to add a significant arm size, choose whichever type of weight you are most comfortable with or is available. Use barbells to work both of your arms at the same time, or use dumbbells to exercise each arm on its own. You can do dumbbell curls, for instance.

Of course, each piece of equipment has its advantages and limitations:

  • Barbells are an advantage because they allow you to lift more weight since your stabilizing muscles do not have to work as hard, even in a single rep training for powerlifting.
  • However, a drawback to the barbell is that you may grow your muscles unevenly because you may work more in one arm than the other.

But whatever equipment you choose, don’t go too heavy on chest and back days, so you don’t have to lift heavy weights when training the biceps directly. I prefer to go light but do a lot of reps.

[See Related Post: Dumbbell Forearm Exercises]

The Bottom Line

I Can't Flex My Bicep

Most muscle-flexing problems are temporary and eventually get better with conservative treatment. By learning why one can’t flex their biceps muscle, you can focus on ways to address your concern and finally flex your biceps the right way.

I find occasionally stretching helpful or taking frequent breaks from the activity to prevent a bicep tear. And if you genuinely want to boost your biceps, playing hard is only sometimes the best strategy. 

Giving your bicep muscle full attention, just 20 to 30 minutes weekly in workouts is enough. Doing this will provide the best result without damaging the recovering muscle fibers you’ve worked hard to build. 

Best of luck with your training!

Disclaimer: If your forearm limits your strength workouts or you’ve been feeling pain in your biceps for days, a doctor could diagnose you much better.

If you like this article, please read our other reviews at ExpertFitness.org.

Nathan Lloyd, MSc

I’m a personal trainer, based in Boulder, Colorado.
I service clients physically in the Boulder area, mainly in the ONE Boulder Fitness Gym, but am also available for online consulting and coaching.

If you’re interested in my personal coaching programs, please contact me via the contact page.