When loading heavy passenger luggage into a taxi trunk, what is the ergonomically correct lifting technique a driver should use to prevent back injury?

1. Keep legs straight and bend at the waist to lift
2. Bend at the knees, keep the back straight, and lift using the leg muscles while keeping the load close to the body
3. Twist your torso quickly while lifting to swing the bag into the trunk
4. Lift with one arm while leaning backward