It will. Just give it 10 years.

I have! More than :)

Carrying a heavy backpack can be practiced. It does not hurt your back.

Age my friend. Age.

I just schlepped 150 kg (in 30 kg chunks, and not 2km but some distance with lifting) and I’m entering my eighth decade on Earth. No back pain. Did have a little back pain in middle age, but a few years in the gym with a personal trainer fixed that right up. Fitness, my friend, fitness.

Some people have not inherited grade A+ genes and have conditions - fitness yes, but genetics too my friend, genetics.

Nicely said.

People complain they can't lift shit but don't do anything besides taking anti pain pill.

The secret to growing well is avoiding processed food, cardio 30 min per day minimum and weight lifting.