How to Do Spider Curls Properly

The first time I heard about this exercise, I was confused.

Then, once I found out what these actually were, I realized why people were talking about them. It’s a phenomenal exercise to target and isolate the biceps, which is why spider curls have become so popular for arm development.

Now, if you’re not sure how to do them just yet ... don't worry. That’s what I’m here for: to teach you.

Not only will I teach you proper spider curls form, but also common mistakes people make when doing them. First, let’s go over what a spider curl actually is...

Key Takeaways:

Spider curls isolate the biceps by removing shoulder involvement and mechanical assistance.

Proper spider curls form keeps tension on the biceps throughout the entire range of motion.

Different grips shift emphasis between the biceps, brachialis, and brachioradialis.

Spider curls are more difficult than standing curls due to reduced leverage.

Programming spider curls strategically can accelerate muscle growth and arm development.

What Are Spider Curls, and How Are They Different From Regular Curls?

Spider curls are a type of bicep curl where you lie on an incline bench and do curls with your arms freely hanging down toward the ground. It’s not a very complicated exercise, but it is a little different than a traditional curl. Allow me to explain, so you know what to expect...

In most variations of the bicep curl, you have some support for your upper arm to push against for leverage. In a standing bicep curl, you might not realize it, but you activate your lats to hold your upper arm in place at your side. This gives you more leverage to pull more weight.

In a concentration curl, you set your upper arm against your leg for support.

In a preacher curl, you lay your arms on a pad for support.

In each of these cases, you have a bit of a mechanical advantage to lift the weight. That’s not the case with spider curls. When doing spider curls, your arms hang freely below you at an angle where you have a little less leverage. You have no support for your upper arms, and your biceps get a good stretch at the bottom. This makes it more difficult to pull the weight up. There’s another piece to this exercise that makes it harder...

Normally, people end up recruiting their deltoids to help pull the arm up in front of them. Bringing your arms in front of you while doing a bicep curl makes it easier to curl the weight up.

The bicep does this as well to a small degree, but it's not the same. When you see someone's upper arms way in front of their body during a bicep curl, the deltoid is doing a lot of the work. The spider curl makes involving your deltoid very difficult. So if your arms have less support and your deltoids are not a factor, your biceps have to work harder to move the weight.

That is, as long as you do them correctly. There is always a way to cheat the rep, but you’ll only be cheating yourself out of the benefits of the exercise if you do. That's where proper spider curls form comes into play.

To put it simply, the spider curl is harder than a normal curl, but the difficulty makes it better for muscle growth in many cases. So, in other words, if you want to start working toward building arms like Arnold, you better be doing spider curls!

What Muscles Do Spider Curls Work?

Spider curls are known for their ability to isolate the biceps, but other muscles get some work too ... especially if you consider the different variations and grips you can do.

Every grip you use for spider curls will target the biceps in some way ... with palms facing forward targeting them the most. Changing your grip switches the emphasis to another muscle, though.

If you turn your palms from facing forward to facing each other, you emphasize the brachialis. This muscle lies beneath the biceps and can help increase arm thickness. If you turn your palms again to face away from you, you are now targeting the brachioradialis. This muscle gives a lot of thickness to the upper forearm near the elbow.

All these muscles work together in every curl, but which muscle gets worked the most depends on your grip. Regardless of which grip you choose, though, it’ll help you develop some big, thick muscles in your arms.

So, for the most part ... spider curls are designed to primarily train your biceps.

Anatomical Breakdown of Spider Curls: Muscles Worked

Spider curls primarily target the biceps brachii, specifically the short head, due to the arm position in front of the body. The incline angle creates a stretch at the bottom of the movement, increasing tension during contraction.

Secondary muscles worked include:

Brachialis – adds thickness beneath the biceps
Brachioradialis – contributes to forearm size and elbow stability

Because spider curls eliminate shoulder momentum, the biceps must handle more of the load directly. This makes them highly effective for focused muscle growth.

But now that you know which muscles we’re working with, let’s dive into proper spider curls form.

Proper Spider Curls Form

Learning proper spider curls form is critical if you want to maximize muscle growth and avoid compensating with other muscle groups. Setting up to do spider curls is simple. The execution is where some people go wrong.

Step 1: Locate Equipment

All you need is a bench set up at a 45-degree angle and a pair of dumbbells.

Step 2: Choosing the Correct Weight

This is not an exercise to try to go super heavy on. If you do standing bicep curls with 40-pound dumbbells, I wouldn’t try that much here.

Remember, you have less of a mechanical advantage in the spider curl. That means the heavier you go, the more likely you are to cheat the rep in order to get the weight up.

Start with a weight you can complete 10-15 reps with fairly easily. That way, you can get your form down and feel how the movement is supposed to feel.

Step 3: Take Position on the Bench

With your dumbbells in hand, place your chest on the upper part of the bench. Try to keep your legs straight and the balls of your feet on the ground. Your dumbbells should be hanging freely below the bench without touching anything.

Also, be sure to pull your shoulders down and back. This puts them in a more stable position when you have weight in your hands.

Step 4: Choose Your Grip

Remember, the direction your palms face during a spider curl matters. It helps determine which muscle is used most to execute it.

If you want to focus on your biceps: Keep your palms facing forward throughout the entire set. Or start with your palms facing each other, and rotate the palms forward as you curl up.

If you want to build your brachialis to help with arm thickness: Keep your palms facing each other throughout the entire set.

If you want to focus on all 3 in every rep: Try doing zottman spider curls. This variation requires your palms to face forward on the way up, then you turn your wrists at the top so the palms face the ground on the way down.

Step 5: Execute

Proper spider curls form keeps tension directly on the biceps throughout the entire movement.

With your arms hanging straight down, engage your biceps in order to curl the weight up as high as you can get it.

When you reach the top of the exercise, squeeze your biceps hard for a second, and then slowly return back to the starting position. Repeat this for reps.

Spider Curls vs Preacher Curls

Spider curls and preacher curls both isolate the biceps, but they create tension differently. Preacher curls support the upper arm on a pad, reducing movement and minimizing cheating. However, the pad slightly reduces stretch at the bottom of the rep.

Spider curls allow the arms to hang freely, creating more stretch under tension and eliminating shoulder assistance. This increases difficulty and forces strict execution.

If your goal is maximum biceps isolation with stretch tension, spider curls may be superior. If your goal is strict support and beginner-friendly mechanics, preacher curls can be a great option.

Common Mistakes to Consider

Do your best to keep your upper arms from moving in any direction throughout the exercise. This helps to keep the emphasis on the biceps.

The most common mistake I see when doing the spider curl is pulling the upper arms back toward your body like you would when doing a row. This puts more emphasis on the lats, and your biceps don’t have to work as hard to curl the weight.

But ... if you’re doing the spider curl to grow your biceps, performing it this way will only make it harder to see progress.

In Closing

When programmed correctly, spider curls can be one of the most effective biceps isolation movements in your training split. It’s truly a great exercise to build up your arms, and it’s pretty fun.

There are so many ways to train your muscles, and it’s good to switch up the exercises when planning your workouts. Adding spider curls to your arm workouts or upper-body exercises can create new stimulus and break plateaus. Each one will hit the muscle a different way, and switching it up on your body is the key to seeing progress.

Spider Curls: Frequently Asked Questions

What muscles do spider curls work?

Spider curls primarily target the biceps brachii, with secondary emphasis on the brachialis and brachioradialis depending on grip variation.

Are spider curls better than preacher curls?

One isn't necessarily better than the other. Spider curls increase stretch and eliminate shoulder assistance, which can increase biceps activation. Preacher curls provide more arm support and may be easier for beginners.

How many reps should I do for spider curls?

Most lifters benefit from 8–15 reps per set. Because spider curls are strict and challenging, moderate weight with controlled tempo works best.

Can beginners do spider curls?

Yes, but beginners should start light and focus on proper spider curls form to avoid swinging or shoulder involvement.

Should I use dumbbells or a barbell?

DB spider curls allow independent arm movement and better mind-muscle connection. Barbells allow heavier loading but require strict form control.

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