Strengthen your Glutes! Walking.

Build a better butt on the beaten track with long strides, heel-to-toe walking and lunges. When you add gradual changes to your regular walking routine, such as increasing the incline of the treadmill and throwing in a few tush-targeting moves, you can build the gluteal muscles as you get fit all over. Three muscles comprise the glutes: the gluteus maximus, which sits at the surface of the buttocks; the gluteus medius located beneath the gluteus maximus; and the deepest muscle layer, the gluteus minimus, which starts at the hipbone and connects to the femur.Warm up for five to 10 minutes. Following your warm-up, add walking lunges on the trail. Lengthen your stride and lunge with your right foot forward. Step out with your right foot, keeping the foot facing forward. Bend the right knee 90 degrees and the left knee at 90 degrees, trailing behind you. Come out of the lunge with a long stride by stepping the left foot forward into a lunge. Repeat five times on each side. If you’re new to exercise, start with dips before moving into deeper 90-degree lunges. If you’re already fit, deepen the lunge and touch your knee to the ground.Target your glutes with cardio on the move. Increase the incline of the treadmill if your walking practice is indoors; find hills or stairs when you’re outdoors. The key to building the gluteals during treadmill walking is to slow your speed and increase the incline to really build power in your tush.
https://www.livestrong.com/article/526331-how-to-get-a-bigger-butt-while-walking/