Squats are one of the great leg toning exercise. For those who have back and knee injuries use chair while sitting. Learn correct technique here. When it comes to fitness, Usman Samir has been dubbed one of the best fitness trainers in Karachi. The young 25 year old fitness fanatic has changed the way people look at fitness with his innovative, effective workouts/circuits that promise results. He has been educated in the UK with over 300 individual clients under his belt. Usman is both the co-founder and head trainer at the infamous Fitness 360 which offers a unique, effective, modern and challenging way of training.