Can be made harder by attaching a weight, however aim for strength not size. Cable Bicep curls, work this is exercise for 3 sets of 10-12 reps at the same time as the cable tricep machine. Concentrate on keeping your elbows tucked in by your side, and your shoulders back. Cable Tricep pulldown, work in a superset with the bicep exercise for 3 sets of 10-12 reps. Do one set of both bicep and tricep exercises, have 30 seconds rest then repeat again for two more sets.
Back extensions work in a slow motion, avoiding go back too far.
Aim for 2 sets of as many reps that is comfortable. Aim to take the shoulder upwards for 2 sets of 10-12 reps. Cable deltoid pull, Shoulder . You can either work one arm at a time or both together. 2 sets of 10-12 reps keeping the exercise smooth throughout.