You should always do warm-up like cycling, running, skipping for at least 5-10 minutes before any workout or sports. Warm up before workout prevents you from injuries and recovery of muscle injury takes longer time, you may not be able to do workout of that particular muscle in future. Therefore, warm up is very crucial for everyone.There are several advantages of warm-up before workout:
1) Prevents you from muscle injuries because it heat up your muscles and ligaments to prepare your body for more vigorous activity.
2) Increases availability of oxygen and nutrients to your muscles.
3) Make blood flow faster which make your body more flexible and results in better workout.
4) Avoid sudden increase of blood pressure as it prepares heart for increase in activities gradually.
5) Lubricate joints and make its movement easier.
6) Increases blood temperature and prepare your body for longer workout.
If you are doing strength workout then warm-up should not exceeds 10 minutes because you need more energy for such workout and more warm up can lower down energy.
Put your one leg at back side and sit on another knee, keep your back straight. Swipe this postures with another leg. This will stretch your hips and hamstring.
Keep your hands straight up and then touch your feet without bending your hands. This will stretch lower back, hamstring and calf.
This will help in side obliques and lower let.Checkout below video for other warm up exercises :