First time I did To the Mat was a month ago while visiting my mother in the UK. I had no stability ball, just resistance bands and firewalker bands so I modified those ball moves and still killed the hips, glutes, quads and hamstrings. Here's how ...
1. Stability ball roll ins while lying on your back: primarily work the hamstrings, a little glutes. What I did was, lie on the floor, butt close to a chair, put on foot on the chair, heel digging into the chair, leg bent at knee, obviously. Other leg goes straight up in the air, with resistance band around foot, pull tight on it and hold hands at your sides on the floor. Then, raise your hips up, into hip and glute bridge, and start pushing the free leg straight up in the air, repeatedly. The smaller and higher the move, i.e., like low ends, pulses, the more of a burn you will feel in that hamstring. So, do one set for each leg, of small, high pulses while Cathe and crew do 2 sets of 16 roll ins. The small, high pulses will help you mirrir the intensity of the ball roll-ins more than slow, single reps where you let the hips drop down between each rep, so keep hips as high as you can. Keep pushing the foot against that band and feel it in the hamstring and butt of the leg that is bent at the knee, because that is the one that is actually working. I believe Cathe does this move like this in GS Legs floorwork section?
2. Side leg lifts while lying against stability ball. Simply perform these while lying on your side. Easy. Use ankle weight if you want more resistance. After all, when you do these lying against the ball, the set of lifts for the second leg can be excrutiating because that leg was used to stabilize your body while you worked the other side.
3. Front leg raises while lying against ball. As suggested above, you can do these standing up or sitting close to the edge of a chair. Again, ankle weight optional.
4. Inner thigh squeezes with stability ball. This one is hard to substitute. I used a firewalker band. Put the loop around a table leg, sofa leg, something heavy that you can pull against. Stick your right ankle inside the loop, keeping the sofa/chair leg to your right and stand up. Take a step or two away from the sofa/chair leg so the band is getting more taut. Now, sweep that right leg away from the chair/sofa leg across your body towards your left side. You should feel this in the inner thigh muscle.
Does that take care of everything?
Clare