A trainer says this one move will build lower-body strength, boost mobility and transform your squat technique

Trainer Gustavo Vaz Tostes performing the wall-facing squat. His knees, toes and hands are in contact with a black wall, his knees are bent and his hips are below his knees. He has turned his face to the camera, his mouth is open and he has a friendly, triumphant expression.

The bodyweight squat is a phenomenal exercise for developing lower-body strength and improving full-body mobility. It also mimics the movement of sitting down and standing up which is why it appears in every list of the best exercises for longevity.

The problem is, it's rarely done well. All too often, bad habits creep in, resulting in common squat mistakes like dropping your chest, allowing your knees to cave in or your spine to round. Fortunately, fitness expert Gustavo Vaz Tostes, also known as trainer Gus at digital fitness platform FIIT, has a simple solution.