The preacher curl machine might be the most underrated piece of equipment in your gym. While everyone crowds around the dumbbell rack, this machine sits waiting to deliver one of the purest bicep contractions you'll ever feel.
I've been using preacher curl machines for over a decade, and they've been instrumental in building the bicep peak I always wanted. Let me show you exactly how to use this machine to its full potential.
Why the Preacher Curl Machine Works So Well
The genius of the preacher curl machine lies in what it prevents: cheating. When you do standing curls, it's incredibly easy to swing your body, use momentum, or recruit your front deltoids to help lift the weight. Your biceps end up doing maybe 60-70% of the actual work.
The preacher position changes everything. Your upper arms are locked against an angled pad, typically set at about 45 degrees. This position does several things simultaneously:
First, it eliminates momentum. You physically cannot swing when your arms are braced against a pad. Every ounce of force must come from your biceps brachii contracting.
Second, the angle creates a different strength curve than standing curls. You'll feel the hardest part of the movement in the stretched position at the bottom, which research suggests may be particularly effective for muscle growth.
Third, machines provide consistent resistance throughout the range of motion. Unlike free weights where gravity only pulls straight down, the cable or cam system maintains tension even at the top of the movement.
Setting Up the Machine Correctly
Proper setup makes or breaks your results on this machine. Here's how to dial it in:
Seat height: Adjust the seat so your armpits sit right at the top edge of the pad. If the pad hits your chest, you're too high and will limit your range of motion. If it hits mid-bicep, you're too low and your shoulders will want to take over.
Arm placement: Your entire tricep should rest flat against the pad. There shouldn't be any gap between your arm and the padding. If there is, the seat needs adjusting.
Grip: Most machines have handles with a supinated (palms-up) grip built in. Grip firmly but don't death-grip the handles—excessive squeezing can fatigue your forearms before your biceps.
Shoulder position: Pull your shoulders back slightly and keep them down. Don't let them round forward or shrug up as you fatigue.
Executing the Perfect Rep
Starting position: Arms extended but not locked. Keep a slight bend in your elbows—maybe 5-10 degrees. This protects the joint and keeps tension on the muscle.
The curl: Initiate the movement by flexing your biceps, not by pulling with your hands. Think about driving your pinky fingers toward your shoulders. Curl until your forearms are roughly vertical or slightly past—most machines have a natural stopping point.
The squeeze: At the top, pause for a full second and contract your biceps as hard as possible. This peak contraction is where a lot of the magic happens.
The lower: This is where most people mess up. They let the weight drop. Instead, lower under control for 2-3 seconds. This eccentric phase causes significant muscle damage (the good kind) and should never be rushed.
The stretch: At the bottom, feel a full stretch in your biceps before initiating the next rep. Don't bounce out of the bottom position.
Common Mistakes That Kill Your Gains
Going too heavy: This is mistake number one. When the weight is too heavy, you'll start using your shoulders, cutting range of motion short, and swinging. Check your ego and use a weight you can control for 10-12 quality reps.
Partial reps: If you're only going halfway down, you're missing the stretched position where much of the growth stimulus occurs. Full range of motion, always.
Rushing: Each rep should take about 4-5 seconds total. If you're banging out reps faster than that, you're using momentum instead of muscle.
Lifting your elbows: As fatigue sets in, you might start lifting your elbows off the pad to help complete reps. This shifts work to your shoulders. If you can't keep your arms planted, the set is over.
Holding your breath: Breathe out during the curl (concentric), breathe in during the lower (eccentric). Holding your breath spikes blood pressure unnecessarily.
Programming the Preacher Curl Machine
For most people, here's what works:
Frequency: 1-2 times per week. Your biceps recover relatively quickly, but they also get worked during all your pulling movements (rows, pulldowns, etc.).
Volume: 3-4 sets of 10-15 reps. Biceps respond well to moderate-to-higher rep ranges. Save the heavy 5-rep sets for compound movements.
Placement in workout: Do preacher curls after your compound pulling movements. If you fatigue your biceps first, your rows and pulldowns will suffer.
Progressive overload: Add weight when you can complete all sets at the top of your rep range with good form. Even 2.5-5 pounds is progress.
Preacher Machine vs. Free Weight Preacher Curls
Both have their place. The machine provides more consistent tension and is generally safer—you can push closer to failure without worrying about dropping a barbell on yourself.
Free weight preacher curls require more stabilization and may activate slightly more muscle fibers. They also let you adjust your grip angle more freely.
My recommendation: Use both. The machine is excellent for controlled, high-rep work and learning the movement pattern. Free weights are great for progressive overload and variation.
The Bottom Line
The preacher curl machine is a powerful tool for bicep development when used correctly. Focus on proper setup, controlled reps, full range of motion, and progressive overload over time.
Don't be the person who loads up the stack and swings through partial reps. Be the person who uses moderate weight with perfect form—and watch your biceps grow.