"Hij heeft meer oefening nodig."
Translation:He needs more practice.
"Oefening" can mean loads of things.
While maybe not the most common it can refer to "physical exercise". For example: "Military exercise" = "Militaire oefening" "The exercise makes me run faster" = "De oefening laat me sneller rennen" "Those exercises load my legs" = "Die oefeningen belasten mijn benen"
All examples in which 'oefening(en)' refer to physical exercise.
Please consider: the phrase "he needs more exercise" (uncountable noun) specifically means "he needs to do more of an activity requiring physical effort". It necessarily refers to physical exercise.
In contrast, the phrase "he needs more exercises" (countable noun) could refer to physical exercise, or to some other type of activity. So this latter expression appears to be a better translation for "Hij heeft meer oefening nodig."
"Oefening" is synonymous with "excercitie" and "lichaamsbeweging", which both are physical activity. In other words "Hij heeft meer oefening nodig" is synonymous with "Hij heeft meer lichaamsbeweging nodig", hence "He needs more exercise" is a possible translation in my opinion. Maybe it is not the most common translation but that does not matter.
@El2theK: I fully agree.
@nzcanadian's: "he needs more exercise" can be translated to hij heeft meer oefening nodig but as El2theK already mentioned, this may not be the most common one (that would be hij heeft meer lichaamsbeweging nodig). But a remark the Dutch sentence with oefening doesn't have the fixed meaning the English one has. It is not clear what kind of oefening is meant, so it can be physical as well as mental. You could also translate it to hij heeft meer training nodig, in this case as well, it could be either physical or mental training.
So the Dutch sentence hij heeft meer oefening nodig regarding undefinedness, is closer related to: "he needs more exercises"…however that English sentence (with countable noun) would normally translate to hij heeft meer oefeningen nodig again in this Dutch sentence it's not clear what kind of oefeningen are meant, but in this case that's similar to the English sentence.