Last updated September 2026
To flex or not to flex? Not your biceps. Your spine.
In strength training we’re taught to lift with a flat back, and for heavy lifting that’s good advice. But at Seriously Strong Training we question everything, and we’ve found that only ever training your back flat may not be the best way to build a resilient spine. That’s where the Jefferson curl comes in.
The short version
- What it is: a slow, controlled, rounded-back toe touch while standing on a box, holding a light weight. It moves your whole spine through flexion and back.
- Why do it: it strengthens your back through a range most exercises skip and improves mobility in your hamstrings and spine.
- How heavy: very light. Start with a dowel or empty bar and add no more than 5 lb at a time.
- Who should skip it: anyone with a current back injury or diagnosed disc problem, unless their physician or physical therapist clears it.
What is the Jefferson curl?
It’s like a straight-leg deadlift taken to the extreme. Instead of keeping your back flat, you roll down one segment at a time, letting your spine round from your neck to your lower back, then roll back up.
It looks scary at first, but it makes sense when you think about how muscles get stronger: they get strongest in the positions and ranges you train them in. Train your back only in neutral, and you’ll be strong in neutral. The Jefferson curl adds strength and control in the rounded positions you end up in during everyday life, like picking something up off the floor.
Important: don’t do this exercise if you have a back injury without talking to your physician or physical therapist first.
How to do the Jefferson curl
- Stand on a sturdy box or bench at least 12 inches high, toes at the edge, feet hip-width apart.
- Hold a light barbell or a pair of dumbbells (start with a dowel or PVC pipe).
- Tuck your chin and slowly roll down, one segment of your spine at a time, keeping the weight close to your legs and your knees slightly bent.
- Go as low as your flexibility allows. At first that may be around your toes; over time you’ll reach below the box.
- At the bottom, breathe all the way out, then breathe in.
- Roll back up just as slowly, stacking your spine from the bottom up, keeping the weight close.
Coach’s cue: slow is the whole point. Take 3–5 seconds down and 3–5 seconds up.
Film yourself and compare it to our video. It usually takes a few tries to get the feel.
How to progress it
| Stage | Load | Sets x reps |
|---|---|---|
| Weeks 1–2 | Dowel or PVC pipe | 2 x 8–10 |
| Weeks 3–4 | Empty bar or light dumbbells | 2 x 8–10 |
| After that | Add 5 lb at most, only when every rep is slow and pain-free | 2–3 x 6–10 |
You’re training your spine in its weakest position, so there’s no need for heavy loads. This exercise is about the quality of the movement, not the weight on the bar. Do it at the end of a workout, 1–2 times a week.
Why it works
Strength comes from two things: bigger muscles and a nervous system that uses them better.
- Muscle size: muscles grow best when they’re loaded through a full range of motion. Most core exercises keep your lower back still, so those muscles never train through their full range. The Jefferson curl does.
- Nervous system: you get strongest in the exact range you train. Gains carry over somewhat beyond that range but drop off the further you go. Train only in neutral, and you’ll be strong only near neutral.
Injuries often happen when you’re in a vulnerable position and not paying attention, or when you lift past your limits. Being strong in more positions helps cover your bases. For a deeper look at lifting with a rounded back, see this article by Sam Spinelli, and for the science of size and strength, this one by Greg Nuckols.
Can the Jefferson curl help low back pain?
For some people, yes. Low back pain is common and has many causes. For most people, getting stronger is one of the best things they can do for it. The two contributors we see most often in our clients are:
- Weakness: when the muscles around your spine lack strength, they can stay tight to protect it, which can feel like a constant, nagging back. If one side always feels tighter, there may be an imbalance.
- Stiffness and limited range: a back that only ever moves a little often feels worse. Gentle, loaded range of motion can help it feel better.
The Jefferson curl, combined with good core training, can help with both. But back pain has many causes, and this exercise isn’t right for everyone.
When to see a professional first
See a physician or physical therapist before trying the Jefferson curl if you have back pain that came from an injury, pain that shoots down your leg, numbness or tingling, or pain that’s getting worse. Stop if the exercise causes sharp pain.
Coach’s tip
Treat the Jefferson curl like mobility work with a little weight, not a strength lift. The people who get the most out of it are the ones who stay patient with the load and never chase the number.
Frequently asked questions
Is the Jefferson curl safe?
For healthy people who start very light and progress slowly, it’s generally considered safe. If you have a back injury, get cleared by your physician or physical therapist first.
What muscles does the Jefferson curl work?
The spinal erectors along your back, with your hamstrings and glutes stretched and working at the bottom.
How heavy should Jefferson curls be?
Light. Start with a dowel, then an empty bar or light dumbbells, and add no more than 5 lb at a time.
How often should I do Jefferson curls?
One or two times a week, 2–3 sets of 6–10 slow reps, at the end of a workout.
Related posts
- Core Training Guide: The 4 Types of Core Exercises
- Your Strength Training Has Left This Muscle Weak
- 6 Best Low Bar Squat Accessory Exercises
Want a coach to check your Jefferson curl and build it into a safe plan? Book a free strategy session at our Tallahassee, St. Petersburg or Tampa gym.