I have used the Single Leg Dumbbell Lift (SLDL) extensively during the last year to improve running performance. In my opinion, there IS a correct technique to this exercise that is motivated by the GOAL of the exercise.
In my case, the primary goal of this exercise was to improve lateral stability and balance throughout the ankle, knee, and hip, while increasing flexibility. The secondary goal was to increase strength.
Therefore, the "right" technique is one that best promotes the development of stability, balance, and flexibility. To me, photos 1, 2, and 3 all meet my definition of the "right" technique. In photos 4, and 5, the individual may be able to lift more weight, but they will not be getting the stability and flexibility benefits.
Specifically, I recommend the following for this exercise:
- Keep back flat.
- Standing leg slightly bent.
- During the "bend" don't let the lifted leg droop down (like the man in photo 4).
- On the recovery phase of each rep, try not to let the lifted foot touch the ground so that you are balancing on one foot for the whole set (this is harder than it sounds).
- Use light weights (or even no weights) until you can complete a full set without losing your balance and maintain good form throughout.
- Don't let the weights rest on the ground during the "bend".
(1) and (2) promote good flexibility. (3) through (6) promote stability and balance.
The tendency when we get tired or lazy is to droop the lifted leg and/or allow the weights to rest on the ground during the bending portion of the exercise. The other tendency is to use too much weight, which subsequently requires us to put the lifted foot on the ground in between reps.
I don't stress about weights in one hand or two. . . I say switch it up to get some variability in the exercise.
My best suggestions for correcting these errors are to 1) don't use any weight (at least at first), and 2) use a mirror - your back and lifted leg should be parallel to the ground during the "bend" portion of the exercise.
- Photos 1 - 3 are the right technique.
- The right technique is motivated by developing lateral stability and balance throughout the ankles, knees, and hips.
- Common errors: too much weight, drooping leg, letting weights rest on the ground, and putting lifted foot on the ground between reps.
- Technique Fixes: Lose the weight, use a mirror.
By thy way, my running form improved noticeably last year thanks in no small part to this exercise.