If I could only perform six exercises in the gym they would be:
Dumbbell Shoulder Press
All these exercises are compound/ multi-joint exercises which provide a full body workout. Squats and Deadlifts work all the leg muscles as well as the lower back and Transvers Abdominus/ TVA. Bench Press works your Chest, Shoulders and Triceps. The Barbell Row works your Upper Back, Biceps, Forearms and TVA. The Dumbbell Shoulder Press works your Shoulders and Triceps. By using Dumbbells, you get the advantage of a longer range of motion and the fact that you have equal weight in each hand means that your weaker arm must work just as hard as your stronger arm. By adding a twist to your Crunches, you bring the Obliques into the exercise so that no part of your abdominal area is missed.
It is important to remember that our muscles are designed to work together, not in isolation. Even if you wanted to follow a bodybuilding programme the above exercises would form the foundation of your workouts with some isolation exercises included at the end. There are a variety of different versions of these exercises for you to choose from. If you find that you don’t have the mobility for conventional Deadlifts you could try Rack Pulls or Sumo Deadlifts, then include mobility exercises for your hips as well as exercises such as Face-pulls to help stabilise your shoulder blades.
Whatever versions of the above exercises you incorporate into your training, keep in mind that they should be performed using a full range of motion, ensuring that you stay in control of the weight. It is weight lifting not weight throwing.