Squats, lunges, scissors (are amazing!), and really any work out for your abs or legs.
Walking on the treadmill at a high incline! It will really get your heart rate up and will be harder than running at 0 incline. Sprinting at an incline is great as well. For posting trot another great thing to do is work out your legs and abs, so I recommend squats, lunges, sit ups, crunches, planks and other workouts like that. Weightlifting in general is also very useful. Good luck!