Shoulder Tap
Main muscle: Abs
Other muscles: Triceps, Shoulders
Equipment: no equipment
Mechanics type: isolation
Fitness level: beginner
Category: Increase strength

  1. Get into a push-up position with your arms fully extended, your body in a straight line, and up on your toes. This will be your starting position.
  2. Quickly bring one hand up to tap the opposite-side shoulder, placing that hand back on the floor before repeating to the opposite side. Concurrently your body will slightly shift from one side to the other to better maintain balance. Move back and forth for the designated number of reps.

Source: bodybuilding.com