Standard warm-up to be done before all workouts:

Warm-up
Pick One: Run 1/4 mile / Row 500m / Airdyne 20 calories

Then,

3 rounds:
10 Overhead PVC squats (Example)
10 Hand Release Push-ups (Example)

10 Back extensions (Example), GHD Sit-ups (Example), or 20 Standard sit-ups