A suitcase lift involves lifting with only one side of your body. The suitcase deadlift is a good example. But the suitcase method can also be used with other exercises, like the lunge.
With weight on only one side of your body, a suitcase lunge makes the structures of the knees, hips and trunk work hard to remain neutral. Your initial tendency will be to twist and lean to counter the load and fight for a position of better leverage – don't do this! The benefits come from staying neutral.
How to Do It
Grab one dumbbell or kettlebell. Hold it to your side like a suitcase.
Perform alternating lunges as you stay neutral. Now, it's common for this exercise to be done using only contralateral loading. Alternating your reps is a simple way to ensure the body is subjected to ipsilateral loading as well.
Switch the weight to the other hand and do the same number of alternating reps.
Tips
Don't allow your torso to lean or twist (toward or away) from the weight as you lunge.
Don't allow your hips to sway or twist from the weight.
Your shoulders should stay stacked on top of your hips. Your shoulders and hips should also stay level with the ground and squared with a wall in front of you.
This loading method can be used for any lunge variation: walking lunge, forward lunge, reverse lunge, etc.