You can find this exercise on page 221 of the book Synergistic Golf.
Exercise Type: STRENGTH
Exercise Category: CHEST, SHOULDERS, STRENGTH
Start in basic pushup position. Whether knees remain down or up, there should be a straight line between head, shoulders, spine, hips, and knees. Place hands directly under chest with index fingers and thumbs touching in the shape of a diamond. Keeping spine and abdominals tight, lower body straight down to the floor by bending at elbows and return to straight arms. Repeat 10x for 3 sets. Inhale as you lower down, exhale on the return push back up.