An easy way to increase the eccentric (negative) loading is to do the concentric or lifting part of the rep with both legs, then the lowering part with one leg. After you hit failure with the single-leg eccentrics, continue the set by using both legs and a controlled negative.
Alternate legs on each rep. Make sure to do the eccentric portion in a controlled fashion to take advantage of the overloading effect. Don't just let your leg freefall when lowering the weight. Do 4 sets of 8 reps.
Now that the New Year is upon us, many people are looking for effective ways to regain the size and strength they might have inadvertently lost. After all, it's damn tough to stay on track with your training during the months when that jolly, red-suited fella who looks suspiciously like a wino shows up in the middle of the night. (No, I'm not talking about your Uncle Steve.)