To do the prone dumbbell spider curl with good form, lie chest-down on a bench set to about 45 degrees (anywhere from 30 to 60 works) and let your upper arms hang straight down.
Curl the weights up using only your elbows, with palms facing forward and a light load, and lower each rep over 2 to 4 seconds without letting your upper arms swing or row back. Keep reading for a more detailed explanation of setup, weight, technique, and the mistakes to avoid.
What the Spider Curl Does and Why It Feels Different
The spider curl works mainly the biceps brachii, the muscle that bends your elbow and turns your palm up. Two helpers, the brachialis and brachioradialis, also bend the elbow, while your forearm flexors work isometrically to keep the wrist neutral.
What sets this lift apart is where the resistance peaks. With your upper arm hanging vertical, the weight sits directly below the elbow at the bottom, so the torque there is close to zero.
It builds as you curl and peaks when your forearm reaches horizontal, which makes the lift hardest from mid-range to the top. A preacher curl is the opposite, since it's hardest near the bottom.
That has a practical payoff for your form:
- The useful part of each rep is roughly the upper half to three-quarters of the range.
- Swinging out of the bottom skips the easy part and sets up momentum for the rest of the rep.
- Cutting the top short throws away most of the work, since that's where the load is heaviest.
You'll also see the claim that the spider curl isolates the short head of the biceps. The reasoning is that the arm hangs in slight shoulder flexion, which puts slack in the long head.
Another view says the opposite: on a low-angled bench, the short head gets too shortened to produce much force, which shifts emphasis toward the long head and the brachialis. Nobody has measured it directly, so treat short-head isolation as a hypothesis rather than a fact.
The exercise also has some history. The original spider bench had a narrow chest pad set at 15 degrees, and lifters used a narrow false grip about 8 inches (20 cm) apart. Most gyms now have an adjustable incline bench instead, which works well for the version you'll learn here.
Setting Up the Bench and Your Body
Start with the backrest at 45 degrees. Anywhere from 30 to 60 degrees works, and the right spot depends on your arm length. Go too low, close to flat, and the lift turns into a seal-row pattern.
Go too upright and it becomes a standard curl, since your arms no longer hang in front of your body. Taller lifters with long arms may not manage 45 degrees and can drop toward 30, though going too low may stress the shoulders.
Use one quick test to confirm the angle: with your elbows fully extended, the dumbbells should hang freely without touching the floor or the bench frame. If they do, adjust the angle before you add a single rep.
Body position, from the ground up
- Set the dumbbells on the floor within reach before you lie down.
- Place your chest and upper stomach against the pad. The top edge should sit around armpit or upper-chest height, with your head and neck just over the top.
- Put the balls of your feet or your toes on the floor, legs long with a slight knee bend. Stance width varies with your height, limb length, and bench model.
- Pull your shoulder blades back and down, and keep them there for the whole set. Brace your core lightly.
- Keep your head still and neutral with your eyes forward, or tuck your chin slightly. Don't crane your neck.
- Let your arms hang straight down, about shoulder-width apart and slightly in front of your torso rather than beside your ribs.
If your feet slide back during the set, brace them against a board or plate placed in front of the rear bench leg. Smaller lifters who can't reach the floor comfortably can kneel on the seat instead.
Choosing Your Dumbbells and Grip
Go clearly lighter than you would for standing curls. You have less leverage in this position and no body english to help, so a good starting point is about 70% of your standing-curl weight.
While you're learning the movement, pick a load you can move for 10 to 15 fairly easy reps. Once the pattern feels solid, move to a working weight where the last one or two reps are hard but still clean. If your form breaks down early, go lighter.
Dumbbells suit this lift for two reasons: each arm works on its own, which exposes left-right imbalances, and your wrists can rotate during the rep. Other implements are mostly a matter of comfort.
One EMG comparison found that EZ-bar and straight-bar curls produced modestly higher biceps activity than dumbbell curls in some phases, but it didn't use a spider position, so it doesn't change the choice much.
Grip options
- Standard grip: fully supinated, with your palms facing forward.
- Active supination: drive through your pinky and ring fingers. Grip toward the outside of the handle and think about turning your pinkies outward as you curl.
- Alternative: start with your palms facing each other and rotate to palms-forward on the way up.
Whichever you choose, keep your wrists neutral or bent back very slightly. Curling them inward hands the work over to your forearms.
Step-by-Step Execution, Tempo, and Breathing
The rep, step by step
- Lie on the bench with your feet planted and your shoulder blades back and down. Pick up the dumbbells with a supinated grip and let your arms hang with the elbows fully extended.
- Take a breath and brace your core lightly.
- Exhale and bend your elbows to curl toward your shoulders. Only your forearms move, and your elbows keep pointing at the floor.
- Stop when your forearms are about vertical and the dumbbells sit near your collarbones or neck without touching. The bare minimum is forearms parallel to the floor, but most coaches want you to go higher.
- Squeeze your biceps hard for about a second. Some coaches say a pause isn't required, but they agree the top is the hardest point of this curl.
- Inhale and lower slowly until your elbows are fully straight. Don't bounce the weights or let them drop.
- Pause briefly at the bottom so the dumbbells don't swing into the next rep.
Tempo and range of motion
Lower the weights over 2 to 4 seconds. A sample tempo is 2 seconds up, a 1-second squeeze, and 3 seconds down. The slower lowering phase adds time under tension without needing more weight.
Use the full range in both directions. Half reps are a major mistake here, because tension is very low at the bottom and the top is where most of the work happens. Stopping short at either end cuts out the part of the rep that matters.
Breathing
Exhale as you curl up and inhale as you lower. Don't hold your breath for the whole set.
Elbow drift
The defining rule is that your upper arms stay still and roughly vertical, and your elbows never move backward. Coaches differ on the last few degrees. Some want your elbows frozen in space.
Others allow a slight forward shift near the top, just enough for your forearm to reach vertical, as long as your elbow never passes the weight.
Common Mistakes, Fixes, and Form Cues
The big one: rowing or dragging
Letting your elbows move back toward the bench is the most common error on this lift. It shifts the work to your lats and takes it off your biceps.
A related version, the drag curl, rows the weights toward your abdomen and then slides them up the bench. To fix it, keep your elbows under or slightly in front of your shoulders, curl toward your neck, and lower the weight. Treat any backward elbow movement as a failed rep.
Other common errors and their fixes
- Swinging and momentum: This often starts when you let gravity drop the weight on the way down. Lower slowly, stop at the bottom, and cut the load if you can't hit your target reps cleanly.
- Going too heavy: Heavy loads push work onto other body parts and invite cheating. Start near 70% of your standing-curl weight and use moderate-to-high reps.
- Wrong bench angle: A bad angle also makes a neutral head and stable feet harder to hold. Start at 45 degrees and adjust within 30 to 60 for your arm length.
- Partial reps: Straighten your elbows fully at the bottom and curl to a full contraction at the top.
- Rushing: Lower the weights over 2 to 4 seconds.
- Elbows drifting forward into shoulder flexion: This brings in your front delts and lowers tension on the biceps. Allow only a slight shift at the very top.
- Wrists curling in: Keep them neutral.
- Craned neck or moving head: Set your head position before the first rep.
Cues worth repeating to yourself
- “Upper arms are pillars.”
- “Elbows point at the floor.”
- “Curl toward your neck, not your belly.”
- “Chest stays glued to the pad.”
- “Lead with the pinky.”
- “Slow down, full stop at the bottom.”
If you can't feel your biceps working or the dumbbells hit the floor, adjust the bench angle before changing anything else.
Programming the Lift and What the Research Says
How to program it
Aim for 2 to 4 sets of 8 to 15 reps, with a lowering phase of about 3 seconds and a one-second squeeze at the top. End each set 1 to 2 reps shy of form breakdown.
Before every set, run through this checklist: bench at 45 degrees, chest on the pad, head still, shoulder blades back and down, feet planted, arms vertical, palms forward.
What the research says
No peer-reviewed study has tested the spider curl itself. The closest evidence comes from studies on related curls in untrained people, so treat the findings below as indirect.
- Preacher vs. incline curls: In an 8-week trial, 63 untrained women trained either preacher curls (30 women) or incline curls (33 women). Incline curls grew the upper arm slightly more (0.08 cm difference), while preacher curls grew the lower arm more (0.10 cm difference). Each group also got stronger on its own exercise.
- Early vs. late range: In a study of 19 women, the arm trained in the early range (0 to 68 degrees of elbow flexion) gained more distal biceps size and full-range 1RM than the arm trained in the late range (68 to 135 degrees).
- Shoulder position: In a 10-week trial, 15 young men (average age 25.6) did single-arm cable curls twice a week for 3 to 5 sets of 8 to 12RM, with the shoulder flexed or extended about 50 degrees. Biceps thickness rose about 6% to 7% on one side and 9% on the other, with no significant difference.
Put together, these results suggest shoulder position matters less for growth than where in the range the load peaks. The spider curl barely loads the stretched bottom position, so pair it with a curl that does, such as the incline dumbbell curl.
Finally, be skeptical of claims like “constant tension” or “hits the biceps harder than any other curl.” Those are marketing, not proof.
Conclusion
The spider curl rewards clean form more than heavy weight. Set the bench near 45 degrees, keep your upper arms vertical, and lower each rep slowly through the full range.
Start light, treat any backward elbow movement as a failed rep, and pair the lift with a curl that loads the stretched position for a more complete biceps routine.
