Sorry for the late reply I haven't been on the net for a few days! Ok if i had to recommend two exercises for your back these would be it - bodyweight lat pull downs and another dumbell exercise.

Chin ups - Depending on how strong you are you could use the counterweight machine but something tells me you'd adjust without it pretty quickly. It's hard to injure yourself doing them because you just fail and drop if it gets too hard really. If it gets too easy you can use a weight belt but to be honest I'm just aiming to get my reps up to a strong 20 before I worry about that.

My way of looking at it is if you use your chest muscles for boxing you will do a lot of reps so i'd like to be able to do the same with my back. Despite not doing low reps and high weight my back has increased in size fairly dramatically with my training anyway.

Dumbell exercise - OK I have to warn you - one of the guys in the gym was told to do this by his physio but didn't because he says it looks very gay. It probably does but it's pretty good for your back.

Get a mat and go onto your hands and knees. With a very light dumbell in one hand, back fairly straight, bodyweight kept in the centre raise it up from the floor/mat out to the side so it's about equal height with your back and lower again slowly. I have to stress here it's LOW WEIGHT. If you use a heavy weight you will not isolate the muscles right in the centre of your back you need to. You will use other muscles instead.

So that's with the dumbell moving laterally up but you can also do it with the dumbell moving diagonally up from lower under about your belly button out to the same place. I'd recommend doing both - for each side of course.

When i say low weight I mean ridiculously low weight. I use an 8 or ten pound dumbell despite being able to do chin ups with my full bodyweight reasonably well. Using the wrong muscles to shift heavier weight is the same mistake people make when they do the seated row incorrectly - they don't target the right muscles.

If you'd rather use the seated row you can still do it with lowish weight and it's safest then to use one of the supported seated row machines with the pad in front of your chest - but I prefer dumbells even if they do look gay!