Arnold’s Favorite Biceps Exercise (Made Better)
Summary
Jeff Cavaliere revisits Arnold Schwarzenegger’s classic 21 curl biceps exercise and improves it by applying the science of the strength curve. Rather than using a single weight for all three phases, he introduces a “cube set” approach using three progressively lighter dumbbells to better match the body’s natural strength levels throughout the movement. This method maximizes effort and muscle stimulus across every portion of the curl.
Key Points
- The traditional 21 curl consists of 7 reps in the bottom half of the range of motion, 7 reps in the top half, and 7 full reps — a technique popularized by Arnold Schwarzenegger.
- The strength curve of a curl means tension peaks in the middle of the movement, making that range the hardest and both the bottom and top halves comparatively easier.
- Using a single dumbbell for all three phases forces you to select a weight based on your weakest point, under-loading the easier portions of the curl.
- The “cube set” method solves this by using three different dumbbell weights — one for each phase — so the load better matches your actual strength at each range.
- Start heavier than your normal 21 curl weight for the bottom portion, then step down in weight for each subsequent phase.
- This approach ensures you are squeezing out maximum effort at every point in the rep, rather than coasting through the easier ranges.
- The overall principle is to mirror the strength curve with your loading, getting more out of a single set than traditional fixed-weight methods allow.
Exercise Details
21 Curls — Cube Set Method
Target Muscles
- Biceps brachii (primary)
How to Perform (Example with 35 lb working weight)
- Pick up dumbbells two increments heavier than your normal 21 curl weight (e.g., 45 lbs)
- Perform 7 reps in the bottom half of the curl (from full extension up to roughly 90°)
- Set down the 45s and immediately pick up the middle weight (e.g., 40 lbs)
- Perform 7 reps in the top half of the curl (from roughly 90° up to full contraction)
- Set down the 40s and pick up your base weight (e.g., 35 lbs)
- Perform 7 full range-of-motion curls
Key Form Cues
- Control each half-rep deliberately — do not swing or use momentum
- Maintain awareness of where the hardest point (mid-range) falls as you transition between phases
- Keep transitions between dumbbells quick to maintain the intensity of the set
Common Mistakes to Avoid
- Using the same single dumbbell for all three phases, which underloads the bottom and top portions
- Choosing a weight that is too heavy for the full rep phase, which causes form breakdown at the end
- Not increasing weight on the easier bottom-half phase — this leaves mechanical tension on the table
Sets/Reps
- 7 reps per phase × 3 phases = 21 total reps per set (specific set count not mentioned)