The rear deltoid shoulder exercise will provide the shoulder strength when trying to pull soothing. It will also boost your energy when you will do back exercises. The movements for the rear deltoid exercise passively will activate the back muscles; so in a way you get two exercises for one. There is no need for a workout machine, all you have to do is get a hold of a pair of dumbbells, but try not to over react with its weight.; here is how to do it.
Grab a pair of dumbbells, preferably smaller in weight and bend forward so that your upper body will be parallel to the floor. This bended position will require straightening your back and moving the chest a bit forward; also bending the knees a little bid. This body position is to protect the waist.
In that bend position; hold the dumbbells in front of you and then move the dumbbells to the side with elbows slightly bend. The exercise will look like trying to simulate flying in reverse. You can look at the floor or forward while doing this exercise.
For starters make 3 sets of 12, 10 and 8 repetitions starting with a pair of dumbbells 2 kg each.
This exercise can also be performed while sitting down. Instead of bending forward, sit on a bench with the upper body the same way as in the standing version; place your legs in together with your feet forward. Do the same repetitions as in the standing position and make sure the dumbbells move below your knees.