Spider curls: what they do, how to do them, and who they are worth it for

The spider curl is a biceps curl you do face down on an incline bench, with your arms hanging straight toward the floor. That position removes any chance of cheating with a hip swing or a lean back, so the biceps gets the work your back and shoulders would otherwise steal on a standing curl. Here is what it actually does, how to perform it, and who it genuinely earns a slot for in a program.

What the spider curl actually trains

The biceps has two heads. The long head crosses the shoulder joint, the short head does not. When your upper arms sit in front of your torso, as they do on a spider curl, the long head is already shortened, so more of the work shifts to the short head and to the brachialis, the muscle underneath that pushes the arm out in width as it grows.

The second factor is the resistance curve. On a standing dumbbell curl the hardest point is around 90 degrees of elbow flexion, and in the last 20 to 30 degrees the resistance almost disappears because the dumbbell drifts over the elbow. On a spider curl the arms hang vertically, so the lever arm is longest right at the top. The muscle is loaded hardest in the shortened position. That is why this is not a replacement for standing or incline curls, but a complement from the other end of the curve.

Rule of thumb: incline curls hammer the bottom, spider curls hammer the top, standing curls sit in the middle. Two different angles per week is plenty.

Setup and technique, step by step

1. Set the incline bench to 30 to 45 degrees. Below 30 your chest slides down the pad, above 45 your arms stop hanging vertically.
2. Lie chest down with your chin just over the top edge of the pad and your feet flat on the floor, hip width apart. If the bench rocks, brace it against a wall or a rack.
3. Pick up dumbbells or an EZ bar and let your arms hang straight down. Pull the shoulders back and down and do not let them roll forward.
4. Bend only at the elbow. The upper arm stays exactly where it started for the whole set.
5. With dumbbells, actively rotate the palm up (supinate) through the last third of the rep, like turning a key. That adds biceps involvement.
6. Hold the top for 1 second with a deliberate squeeze, then lower for 2 to 3 seconds to a fully straight elbow.
7. Do not pause at the bottom for more than half a second if your elbows are cranky. Reach full extension and reverse.

Common mistakes

• Too much weight. The first tell is your shoulders creeping forward and the top of each rep turning into a jerk.
• Bench too steep. At that point it is just a chest supported curl and the whole reason for the exercise is gone.
• Half reps. If you never straighten the elbow you are training only the top third, which throws away the strength curve you came for.
• Holding your breath. Your head is down and pressure climbs quickly. Exhale on the way up, inhale on the way down.

Sets, reps and how much weight

• Reps: 10 to 15. Below 8 the exercise stops making sense, because the load required breaks the position.
• Sets: 2 to 4 per session, 1 to 2 times per week. Total direct biceps work should land around 8 to 14 sets per week including every other curl variation.
• Load: start at 50 to 65 percent of your standing curl weight. If you curl 15 kg per hand for 10 reps standing, start here with 8 kg and build from there.
• Rest: 60 to 90 seconds. There is no reason to rest longer on an isolation move.
• Progression: once you hit 3 sets of 15 clean reps, add 1 to 2 kg per hand and drop back to 10 reps.
• Placement: at the end of the session, after rows and pull ups. Put it first and you weaken your grip for everything else.

Who it is worth it for, and who should skip it

It is worth it if your biceps lags behind your back, if you catch yourself turning every curl into half a sit up, or if your elbows dislike heavy standing work. It is also useful for home training with light dumbbells, because a spider curl with 8 kg feels closer to a standing curl with 12 kg.

Skip it if you are a complete beginner with under 3 to 6 months of training. Pull ups, rows and plain dumbbell curls will do more for you right now. Skip it too if you already run 5 separate biceps exercises in a week, because a sixth only adds time in the gym. If you have a shoulder problem, the arms forward position bothers some people, so test one light set of 15 reps before committing.

Growth is not only about exercise selection. Without roughly 1.6 to 2.2 grams of protein per kilogram of bodyweight per day and enough sleep, no curl angle will do much.

When to see a doctor

• If you heard or felt a pop at the front of the shoulder or in the crook of the elbow, followed by sudden weakness and bruising, get seen urgently. That can be a torn biceps tendon.
• If elbow pain lasts longer than 2 to 3 weeks despite backing off curls.
• If there is swelling, warmth, or loss of motion at the elbow.
• If you get tingling or numbness in the fingers, especially the little and ring fingers.
• If you take fluoroquinolone antibiotics or corticosteroids, tendons are more vulnerable, so check in before adding load aggressively.

The short version

• The spider curl keeps the upper arm in front of the torso and loads the biceps hardest at the top, exactly where a standing curl gives up.
• Bench at 30 to 45 degrees, arms vertical, movement only at the elbow, 1 second squeeze at the top and a 2 to 3 second lower.
• 2 to 4 sets of 10 to 15 reps, once or twice per week, at about 50 to 65 percent of your standing curl load.
• It helps most if your biceps lags or you cannot stop swinging, and least if you are a complete beginner.
• A pop, swelling, finger numbness or pain lasting past 2 to 3 weeks is a reason to get checked, not a reason to add a set.