I have done "Freeletics" for 1,5 years now and can highly recomend it. You can describe it as a "high intensity body wight only" workout. There are different workouts and most of the time, you have to do 4 of them each week (the program gives you your workout each week). Every workout contains a given number of excersises, repititions and sets and you are supposed to stop the time it takes you to complete the workout, as this is your performance measurment. You should take no break during the workout unless you absolutly have to(there is no way to do it without breaks in the beginning) Most of the workouts take 30mins to 1hour only, even though that doesn´t sound very much, it totaly!! crushed me and my friends, especialy in the beginning. You can look up some nice transformation videos on youtube. If you have any questions, feel free to ask