Mobility drills, also know as dynamic stretching are wonderful. Research has found them to be superior to static stretching for increasing range of motion, raising resting heart to prepare for activity, and increasing coordination. Common versions include dynamic leg swings, using the foam roller to push the thoracic spine (i.e. ribcage) into extension, and the tea-cup drill for shoulder mobility. I have, and will discuss these at length because they are one of the most valuable things you can do for yourself to stay flexible and resilient.
So when might these actually be a bad idea? To answer that question, we need to review the "joint-by-joint approach", pioneered by Gray Cook and Mike Boyle. This theory proposes that the body is comprised of joints which alternate an emphasis on mobility, such as the ball and socket joints of the hip or shoulder, and those which emphasize stability, such as the knee or elbow. One of the stable joints is found in the pelvis, between the ilium (where you "put your hands on your hips"), and the sacrum (what most folks think of as their tailbone. This is known as the sacroiliac joint, and is a common source of low back pain.
Osteopaths, chiropractors, and physical therapists have all developed various home exercises to mobilize this joint. The problem is, however, that it's very easy to make any of the stable joints too mobile, aka "unstable". The sad truth is that this instability is the source of most of the pain which comes from these joint; conditions like plantar fasciitis, tennis elbow, AC separations, and runner's knee. While someone may, in fact, need mobilization at one of these locations, it's almost impossible to determine that for yourself. For this, see a chiropractor, or an osteopath or physical therapist with a specialty in manipulation.
