Your biceps brachii muscle responds well to both isometric and dynamic exercises. So wouldn't it be ideal if you could perform an exercise that's isometric and dynamic?
Static arm curls, which are popular with people who do the P90X program, are like regular arm curls except that you keep one arm isometrically contracted while performing dynamic curls with your other arm. Then you switch arms and reverse the motion.
Let's take a closer look.
Related: Isometric bicep exercise
Static bicep curl exercise details
- Also Known As: Iso curls
- Main Muscles: Biceps brachii
- Secondary Muscles: Brachialis, brachioradialis, forearm flexors
- Exercise Type: Strength
- Exercise Mechanics: Isolation
- Difficulty Level: Beginner
- Equipment Needed: Dumbbells
How to do static arm curls correctly
- Hold a pair of dumbbells by your sides with a supinated grip.
- Curl the dumbbells up until your elbows reach a 90-degree angle.
- Hold this contracted position with one of your arms while you perform 5 reps of full range of motion (ROM) curls with your other arm.
- Complete the 5 reps and then switch arms.
- Perform 10 total reps per arm.
Benefits of curl holds
The iso curl helps to improve your mind-muscle connection by testing you're isometric bicep strength. So if you want to increase your work capacity and improve your lactic acid tolerance, then you should definitely give isometric curls a go in your next workout.
Increased isometric strength
The isometric bicep curl combines static muscle contractions with high-intensity curl repetitions to blast your biceps and make them grow. Hence they're popular with P90X enthusiasts, who, based on their videos, are getting excellent results from this exercise.
Static arm curls force you to contract your biceps for 10-20 seconds at a time, which can really help to strengthen your mind-muscle connection. After all, if you can squeeze your biceps for that long, just imagine how easy a regular 1-2 second muscle contraction will feel!
In other words, along along with negative curls, the static dumbbell curl is the training drill to do if you want to feel your biceps working more during your regular exercises.
Ultimately, this increased isometric strength will have a significant carryover to any movement that requires you to contract your biceps intensely.  Chin-ups, rows, and curls are prime examples of such exercises.
Better biceps pump
Did you know that muscle contractions are the cause of the sensation that's known as the pump?
For this reason, iso bicep curls will really pump up your arms because you're combining both types of muscle contractions—isometric and dynamic—into one movement.
As soon as your bicep is done with curl holds, it gets blasted by 5 full reps of dynamic curls (no half bicep curls, please). This creates an intense pump because your biceps are already fatigued and full of lactic acid by the time they get to the normal bicep curl.
The pump that you get from doing isometric bicep curls will make your arms look leaner and more vascular while you're training, which will definitely motivate you to get in shape and push through those challenging final sets.
Enhanced bicep endurance
If you're a bodybuilder or powerlifter, then you might not care that iso curls can enhance your bicep endurance. However, you really should.
After all, if your biceps have good endurance, they can tolerate more reps and sets, which is to say higher amounts of training volume. 
This actually means that static curls are an excellent muscle-building movement because increasing your training volume generally also boosts your rates of muscle growth. So by making your biceps more fatigue-resistant, you'll also be able to make them grow faster by increasing their volume tolerance.
Read More: Eccentric standing curl
Conclusion: Should you do static curls for your biceps?
The aptly named iso curl isolates your biceps in an isometric fashion. If you want to pump up your biceps and increase their volume tolerance, static arm curls are one of the most effective exercises for the job. This is because they get you used to holding the weight in a contracted position for extended periods of time—then they force you to smash out a set of full ROM curls.
So don't hesitate to throw some curl holds into your next workout if you want to build muscle. While iso curls may not be the best mass-builder of all time, they're great for burning out your biceps and increasing your ability to perform more sets, which we know is good for muscle growth.
- Isometric exercises: Good for strength training? (2020, March 21). Mayo Clinic. https://www.mayoclinic.org/healthy-lifestyle/fitness/expert-answers/isometric-exercises/faq-20058186?reDate=23052021
- Wiggins, M. (2020, March 26). Strength-Endurance Training: Be Stronger. . . Longer. Bodybuilding.Com. https://www.bodybuilding.com/content/strength-endurance-training-be-stronger-longer.html