Jumping Lunge

The Jumping Lunge works on developing explosiveness. 

Get into a lunge position—step forward and lower your body until your front thigh is parallel to the floor and your rear knee gently touches it. If you're unable to control the lowering knee and it bangs off of the ground, stop yourself and do not allow the knee to touch the floor, get very close but not bang the ground. 

Explosively Jump up and raise your back knee straight up toward your chest as the front leg drives back. Land in a lunge with the opposite leg forward. Stick the landing and repeat. 

Difficulty and Equipment
This is not an absolute scale, but in terms of progressing in ability here's how you should be progressing:

1. Unweighted (Novice)
2. Holding 2 single dumbbells/kettlebells in the suitcase position (Intermediate/Well Practiced)
3. Barbell in the back rack position (Well Practiced)

Progress in balance, and explosiveness then in weights before moving onto another difficulty level. How much should you be able to do before moving on? That's not a black and white answer however a good guide is 3 sets, 12 reps per leg of explosive movement at that weight before moving up in weight or difficulty level. 

With that said, typically these will be lower reps but your form and the main point of the movement, explosiveness, should be maintained throughout any difficulty level.