Presumably a 42 year old who can meet the fitness tests will be a better candidate than a 25 year old who cannot. Less 42 year olds will be able to meet the requirements, but the ones that do are what they’re after.

Note that fitness standards are bracketed by age, so the standards themselves get more lenient as age increases. The standards in question: https://www.goarmy.com/content/dam/goarmy/files/HQDA_EXORD_2...