The plank exercise is an isometric fitness core exercise that involves maintaining a position similar to a push-up for the maximum possible time. Out fitness app Plank Workout helps to achieve high result, lose weight and gain a steel abs.
Demo: https://codecanyon.net/item/plank-workout-ios-workout-application/28535116
source http://www.codelist.cc/mobile/241542-plank-workout-v10-ios-workout-application.html