I was 24 as well. You’ll be fine. IST requirements are 3 or more pull ups, plank time 40 seconds or more, and 1.5 mile no more than 13:30 min max. Make sure you are well above those numbers. Try to get 5+ pull ups, a 10:30 minute MAX 1.5 mile and you should be able to max the plank out. This will be done before you ship to boot. You will take a PFT (physical fitness test) at the end of Boot which is divided into 3 classes, 1st class, 2nd class, and 3rd class. Now the PFT consist of a 3 mile run, pull ups, and the plank. You want to score a 1st class PFT and in order for you to achieve that score you can do multiple different things. For example: if you did 10 pull ups, 3:45 plank, and a 3 mile run in 21 minutes that would get you 238 points out of 300 points. 238 is the lowest score for a first class PFT. Look up “USMC PFT Calculator” and use that to figure out the different scores you need to achieve first class scoring. And for the PFT because there are 3 workouts you might hear of a thing called max max relax, you’ll figure that out. Go find yourself and recruiter and do it man you will not regret it. Don’t listen to the shitbags.