The starter phase of a fitness program is important because

Because if people could last the starter phase, their chance to finish the rest of program increases greatly

The hardest thing about starting a new fitness program is adjusting your body to a new routine. Study shows that ,In order for your body to recognize a new habit , it need to experienced for about 3 - 4 weeks. That's why the starter phase is really important

Well if you pick a machine to work on and that's gonna be your exercise if you don't stick to that machine your muscle strength your muscle mass rather will change because you haven't been doing it you change something in your exercise routine which changes your body's form of dealing with things for example you might become weaker or stronger depending on what kind of exercises you do in whether or not the machine you picked actually your muscles grow.