Yeah all this lift with your legs not with your back? It's bullshit.
That's health and safety advice from the 80's and those guys all have demolished their knees.
Use your whole body to lift, make your feet into a stable base, lift the object with your arms and core muscles to bring it close to your body then stand with your legs. If you try to lift with only your legs for long periods of time (months to years) you will annihilate your knees. This is current advice from actual industry, not just dudebros on the internet.