This is an excerpt from Jim Stoppani's Encyclopedia of Muscle & Strength-2nd Edition by Jim Stoppani.
TRX Knee Tuck
Get on the floor in a push-up position with your feet placed in the stirrups of a TRX. Adjust the TRX handles so that they are just above the floor.
Tuck your knees in toward your chest. Hold the tucked position for a second, and then return to the starting position by extending your legs back.
Band Rising Knee
Attach a band to a stable structure as low to the floor as possible and attach the other end of the band to your left ankle with an ankle cuff. Stand in a fighting stance with your right foot in front of your left.
As quickly and as explosively as possible, drive your knee up toward your chest as high as possible and return your foot back to the start position. Complete all reps on the left leg and then perform in the same way with your right leg.