This is a key question and our advice is that it depends on how many different subjects you produce videos on.
As a general rule, if you produce videos on one subject (like 'tennis') or 2-3 related subjects (like 'yoga and pilates'), it probably makes sense to release one app.
On the other hand, if you produce videos on a number of different subjects (like a range of different sports), then it's in your interest to release a series of apps targeting each subject.
This is primarily because in order to generate installs and sales from app store search traffic for any given subject, you need to rank as highly as possible for that subject in the app stores. You're competing against hundreds of other apps (if not thousands) and you only have a small amount of information to do that. For Apple, the information they use is your app title and 15 keywords (just 100 characters), while for Android, the information used is your app title and description.
If your app's key information is very broad, then you are very unlikely to rank highly for the subjects you're trying to target. If, on the other hand, someone searches for 'wrestling drills' and your app is called 'Wrestling Drills', then you're likely to rank very highly for that search. Not only that, but the customer is very likely to install your app (because it's highly relevant to their interests) and highly likely to make a purchase once they've installed it (because again, the content is highly relevant to their interests).
So, as with all key questions, the answer is it depends! Hopefully the above provides some clarity.
Contact us to discuss the best approach for launching your apps!