What is the safest way to lift a heavy box?

Heavy is relative, it depends with your weight and the weight of the object. Mostly you have to use the lifting equipment for lifting heavy things in order to avoid ergonomics issues.

Incase you want to lift something that you think you can lift, do not use your back: squat down, bending at the hips and knees, lift using your kness and not your back. 

Bend the knee and lift the box close to your body and straight 

Do not attempt to lift by bending forward. Bend your hips and knees to squat down to your load, keep it close to your body, and straighten your legs to lift.

Whenever you are lifting anything manually it is recomended that you use your leg muscles and not your back to avoid back aches and/or permanent disability.Assist each other where possible and if available use Lifting equipment that has been inspected and Colour Coded.

Using the proper technique when moving boxes, heavy furniture, or other objects will greatly reduce the risk of injury and soreness. Jobs that require you to consistently move heavy objects especially require that you learn and consistently use the proper technique to keep yourself safe, each and every time.

Manual lifting if the heavy box weighs 25kg and below. Bend the knees and lift up.

Lift by the help of mechanical lifting device if the heavy box is more than 25kg. 

Basically i will outline ways to carry an heavy box;

1. Bring the object you're lifting as close to your body as possible. Hug the load.
2. Make sure your feet, knees and torso are pointed toward the load when you're ready to lift.
3. Keep your back upright as you prepare to lift.
4. If the box weight is beyond the carrieers limit, it is then advisable to use the forklift machine.

Heavy box Must stack on pallets and lift with lifter

Hug the load & Bring the object you're lifting as close to your body as possible.

Avoid turning your body while lifting or holding a heavy object.