Step back, drop down, drive up. Med ball locked at your chest.
Keep your weight in the front heel and torso upright as you lower and rise.
Stepping backwards shifts the emphasis onto the stationary front leg, where the glutes do the heavy lifting as you sink and drive, with the quads assisting at the knee. The medicine ball at your chest adds front-loaded resistance that keeps your torso honest and upright. Reverse lunges are the knee-friendliest of the lunge family, which makes this loaded version an easy recommendation for almost anyone.
Stepping back keeps your front shin more vertical and removes the braking force of catching a forward step. The front leg loads through the hip more than the knee, so people whose knees complain about forward lunges usually get on fine with these.
Both work. Alternating spreads fatigue and suits conditioning, finishing all reps on one leg builds a deeper burn and better focus on the working glute. Pick based on the goal of the session, not habit.
Take a slightly longer step back, keep your weight rooted through the front heel, and allow a slight hinge forward from the hips with a tall spine. Drive up by pushing the floor away through that heel and squeeze the glute to finish standing.
