Behind the Back Smith Machine Wrist Curls
What Are Behind the Back Smith Machine Wrist Curls?
Behind the Back Smith Machine Wrist Curls are an isolation exercise that primarily targets the forearms, specifically the wrist flexors on the palm side of the forearm. They are a beginner-level movement: you stand with a Smith machine bar held behind your hips, arms straight and palms facing backward, and raise the bar by bending only at the wrists.
The main purpose is building strength and size in the wrist flexors. Your fingers hold the bar throughout, so the finger flexors also work to keep it in your hands, but the movement trains wrist flexion rather than grip itself. That makes it a useful accessory for forearm development, usually placed at the end of a pull or arm session with a light load and moderate to high reps, rather than a replacement for direct grip work.
The Smith machine is what sets this version apart. The bar runs on a fixed track, so there is nothing to balance, and the hooks let you set the bar at hip height instead of having to pick a bar up behind your back. Safety stops set just below the bottom of the rep catch the bar if your grip gives out. The trade-off is that the track only moves straight up and down, so you stand close to the bar and keep your arms hanging straight for it to travel smoothly. Behind the Back Barbell Wrist Curls use a free bar instead, and Behind the Back Cable Wrist Curls use a cable.
Holding the bar behind your body works the same wrist flexors as a seated Barbell Palms-Up Wrist Curl, in which the forearms rest on the thighs or a bench. Neither version is clearly better: the standing one needs no bench, while the seated one braces the forearms so the elbows and shoulders cannot help. Pairing either with a Barbell Palms-Down Wrist Curl trains the wrist extensors on the other side of the forearm. Beginners can start here with a light load, and anyone with wrist or inner-elbow discomfort can start with a seated Dumbbell Palms-Up Wrist Curl, which allows smaller load increments.
Muscles Worked
- Flexor Carpi Radialis
- Primary
Instructions
- Set the Smith machine bar on the hooks at about the height of your upper thighs, just below your glutes, and set the safety stops just below where the bar will sit at the bottom of each rep.
- Stand upright with your back to the bar, close enough that it almost touches the backs of your legs, feet about hip-width apart.
- Reach back and grip the bar with your hands about shoulder-width apart, palms facing backward, away from your body.
- Stand tall and rotate the bar to release it from the hooks. Let your arms hang straight at your sides with your shoulders down.
- Keeping a firm grip, let your wrists bend back and lower the bar as far as is comfortable. This is the starting position.
- Curl your wrists to raise the bar as high as they allow, moving only at the wrists.
- Pause briefly at the top, then lower the bar slowly to the starting position.
- Repeat for the desired number of reps, then rotate the bar back onto the hooks.
Common Mistakes
Using Excessive Weight
A bar that is too heavy cuts the range of motion short and turns the rep into a jerk from the shoulders, so choose a load you can curl through the full wrist range with control.
Bending the Elbows or Shrugging
Bending the elbows or shrugging the shoulders to help lift the bar takes work away from the wrist flexors, so keep your arms straight and your shoulders down while only the wrists move.
Cutting the Range Short
Stopping well before full wrist extension at the bottom or full wrist flexion at the top leaves much of the movement untrained.
Dropping Into the Bottom
Letting the bar fall into wrist extension instead of lowering it slowly loads the wrist and inner elbow suddenly and wastes the lowering phase.
Skipping the Safety Stops
Training without the safety stops set just below the bottom position leaves nothing to catch the bar if your grip gives out behind your back.
Injuries
Behind the Back Smith Machine Wrist Curls are a low risk exercise when performed with proper technique. The load is light, the bar runs on a guided track, and safety stops set just below the bottom of the rep catch the bar if your grip slips.
The main strain points are the wrist at the end of its range and the inner elbow, where the wrist flexors attach. Both are overuse problems more than acute ones, usually from loading too heavy, dropping into the bottom of each rep, or stacking a lot of wrist and grip work into one week. Choose a weight you can control through the whole range, lower the bar slowly, and never force the wrists further back than they comfortably go. Stand close to the bar so it can travel straight up and down, rather than pulling your wrists out of line.
If the standing position feels awkward on your wrists, regress to a seated Dumbbell Palms-Up Wrist Curl with your forearms supported on your thighs. Progress with small load increases or a slower lowering phase, or move to Behind the Back Barbell Wrist Curls once you no longer need the machine's guidance.
Stop the set if you feel sharp pain in the wrist, pain at the inner elbow that lingers after training, or numbness or tingling in your fingers, and get it checked if it keeps coming back.
- Primary Focus
- Forearms
- Equipment
- Smith machine
- Modality
- Strength
- Difficulty
- Beginner
Alternative Exercises
Frequently Asked Questions
- Q: Is the behind-the-back version better than a seated wrist curl?
Neither is clearly better. Both train the same wrist flexors through the same wrist motion, so pick the setup that feels best on your wrists: the seated Barbell Palms-Up Wrist Curl braces your forearms on your thighs, while this version needs no bench.
- Q: Can I use a barbell instead of a Smith machine?
Yes, using a barbell offers a similar movement pattern, but you’ll need to balance the weight yourself, which can make the exercise slightly more challenging.
- Q: Should I let the bar roll down to my fingertips?
It is optional. Letting the bar roll toward your fingertips adds finger work and a little more range, but it loosens your hold on the bar and raises the chance of straining the wrist or losing the bar, so use a light load and keep the safety stops set if you try it.
- Q: How often should I do this exercise?
Once or twice a week is enough for most people, especially if your routine already includes other grip-heavy movements. Add volume gradually, and back off if your wrists or inner elbows stay sore between sessions.
- Q: Will wrist curls help my deadlift grip?
They can help indirectly. Holding a heavy deadlift depends mostly on your fingers keeping the bar closed in your hands, so if grip is what limits you, add direct grip work such as a Dead Hang or a Dumbbell Farmers Carry.