The best three exercises to produce a flat chest are the barbell bench press, the pec deck and the bent-forward cable crossover. The American Council on Exercise commissioned a study that identified these three exercises as having the highest level of pectoral muscle activation, leading to flatter chests.
The barbell bench press involves lying down on a bench, planting the feet securely on the ground, and having the eyes positioned directly beneath the bar. The first move is to grasp the barbell, leaving the palms forward and wrapping each thumb around the bar. Next is positioning the bar over the upper chest before bringing it down to touch the chest. With the elbows bent slightly, straighten the arms, and push upward.
The pec deck requires sitting and keeping the elbows at a right angle, which makes adjusting the machine according to height necessary. Elbows rest on the machine's wings in the middle of the pad, and the primary movement involves pushing the wings together until they almost touch and then slowly returning to the starting position.
The bent-forward cable crossover requires a high pulley machine. The feet must be hip-width apart, and elbows must be bent slightly. The hands go beneath the shoulders. The primary movement involves bringing the hands together and extending the arms before slowly returning to the starting position. Widening the arc of the movement increases the resistance.