The stability ball leg curl is one of those exercises that lifters often dismiss because it looks too easy. Don't be fooled. Seasoned lifters often clutch their legs in agony when first attempting it.
Think of this ham curl as a way to balance out the volume you're placing on all the quad work you do. Whenever my knees get cranky, it's a reminder to refocus my efforts on these.
And despite how challenging it is, it can be part of a lower body warm-up since it hits the low back, glutes, hamstrings, and calves. Lastly, using the appropriate progression for your level can build some serious strength and size.
We'll get to some great progressions in a bit, but first here's a refresher on how to do the standard version:
The Standard Stability Ball Ham Curl
- Start with your calves on the ball, legs straight, and arms out to the sides for support.
- Raise your hips off the ground by squeezing the glutes while keeping the abs braced and ribs down.
- Simultaneously pull your heels in as you extend your hips upwards. Avoid overarching your back.
- At the top of the movement there should be a straight line from your knees to your hips. Now lower down to the starting position in control by keeping the hips up while straightening the legs.
Now check out these variations that you might not have tried yet:
Single-Leg Ham Curl
This is the most challenging variation because only one leg is working and the hips stay elevated the whole time.
2-Up, 1-Down Ham Curl
Using only one leg on one phase of this exercise is still going to be more challenging than the standard, bilateral version, but it won't be quite as hard as doing it with one leg during both phases.
Low-Hip to High-Hip Ham Curl
The lowered-hip position of the leg curl is an easier variation of this lift. So this would be a great regression if you don't quite have the standard version down yet.
Even if you do, lowering your hips will shift the emphasis to knee flexion to complete the movement, which might be exactly what you're going for.
The biceps femoris consists of a long and short head. Unlike the other hamstring muscles, the short head of the biceps femoris doesn't cross the hip joint, so it only assists in knee flexion. Therefore, it will be increasingly recruited in this variation.
Low-Hip Ham Curl
A lowered hip position is considered the easiest, so you could use this as a regression and work your way up to harder variations. You could even try this as part of a drop set, which you'll see below.
Bomb-Proof Hamstrings Drop Set
Combine all these variations for a nasty drop set that's sure to pump up your leg biceps.
- A1 – Single-Leg Curl x 5-10 reps per leg
- A2 – 2-Up, 1-Down Leg Curl x 5-10 reps per leg
- A3 – Double-Leg (Standard) Curl x 5-10 reps
- A4 – Low-Hip Up, High-Hip Down x 5-10 reps
- A5 – Low-Hip Leg Curl x 5-10 reps
Do this series for 1-3 sets, striving to add a rep or two each week.
Why Your Foot Position Matters
The hamstrings consist of the semimembranosus, semitendinosus (inner), and biceps femoris (outer) muscles. The semitendinosus and semimembranosus assist in medial rotation of the leg, so doing leg curls with the feet slightly turned in can place greater emphasis on those muscles.
The biceps femoris assists in lateral rotation of the leg, so doing leg curls with the feet turned out slightly can emphasize this outer portion of the hamstring. For balanced development, experiment with feet turned in, turned out, and neutral.
Whichever position feels most challenging likely needs extra attention.
How to Program It
- Stability ball hamstring curls work well in a warm-up for a lower-body focused session. Pick the progression that would allow you to comfortably get 1-2 sets for 10-20 reps.
- During a workout focused on strength and muscle building, pick a variation that permits 3-4 sets for roughly 6-15 reps. Focus on controlled negatives during your sets.
- As an accessory or a finisher, pick a variation that allows 1-3 sets for 15-plus reps. Try experimenting with the drop set as well.
You can recover from these relatively quickly and tolerate a higher frequency during a training week. This exercise is simple to do anywhere and it's anything but easy. Built hamstrings and healthy knees will be your reward for doing them!
Related: The Bodyweight Leg Extension
- Jenkins, D. (2002). Hollinshead's functional anatomy of the limbs and back (8th ed.) Philadelphia: Saunders.