1) Have a qualified trainer perform a functional movement screening. This identifies weaknesses and maladaptive movement patterns that have developed.
2) Work with your trainer through corrective exercise to retrain you to "move like a human." We are all born with proper movement patterns but they are destroyed by our sitting patterns and sedentary lifestyle.
3) Building upon proper movement patterns begin to develop strength. Strength starts with the core. It doesn't matter how strong your arms and legs are when they are attached to an unstable core.
4) Now go out and move like a human! What are we designed to do? We are built to walk long distances. We are built to sprint short distances. We are made to pick up heavy things!
The gym is about building durability! Proper movements + Strength = durability. Durability is what allows us to enjoy physical human activities like hiking, biking, climbing, gardening, swimming, playing without injury.
The gym is not where you go to lose weight. You lose weight in the kitchen. But that's a post for another day...