I don't think so, machines should always be the secondary option.
One of the rare machines that I rate is leg press, but IMO there's simply no need to do both squads and that, while squats is a loooot better exercise.
As for your back, I don't think any machine can hit your muscles as hard as t-bar rows, barbell rows and pull ups can.
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Weather is getting warmer and warmer, I feel like exercising outside on bars only. Like pull ups, dips and other stuff.
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Meh. I think 4 sets of flat and 4 sets of incline is more than enough. It's like any other muscle. Nobody is gonna do that much for legs or abs