The advantage of the single leg curl is that it forces each leg to work on its own. That way, asymmetries in strength between legs is discouraged.
Hammerstrength | Legs | Lever | Plate | Pulley Cable
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An advantage of iso-lateral exercises is that the stronger side cannot help the weaker side thereby letting the weaker side stay weak and risking injury to the stronger side because it is overworked. In this exercise analysis (Quicktime ipod compatible 11.4MB; streaming Google flash video), Nancy Arnold and I (Bud) present the hammerstrength single leg curl. This exercise works the ham strings of each leg separately to help avoid promoting strength differences between the two legs.
As Nancy demonstrates in the video, machine set up is a little more complex than for some other exercises. You have to set the weight stack for each side separately. Then you have to move the pad for one knee to kneel on and lean forward to grip the front handles for stability. Finally, as I illustrate in the photo strip at right, you perform the exercise by curling the extended (non-kneeling leg) as tight as you can. Generally, in hamstring exercises, we shoot for a contraction that gets well beyond the 90 degree mark. If you cannot achieve that, you should drop weight.
As for setting initial weight, my technique on a new machine is to start very low and do a test rep to see what the machine is like. I then increase it until I think I am getting something that requires the level of effort stipulated by our program. Nancy and I have been working together long enough that I sometimes use her weight to guesstimate a starting weight for myself.
Additional Links
- Interestingly, the Houston Texans trainer concurs with our analysis of the benefits of iso-lateral leg exercises. He also does an interesting analysis of the leg press as squat substitute.
