Stress Fracture to the Foot. Gah!

OK.  Ordered a walking boot for my foot.  And what is not so great is that its effectively put a stop to my HIIT - which I can take but need to figure out how best to get my heart rate up.  What is disappointing is that I was on a good run, then the move, now this.  So, for those interested:

A stress fracture is generally an overuse injury. It occurs when muscles become fatigued or overloaded and can not absorb the stress and shock and repeated impact. Fatigued muscles transfer that stress to the nearby bone and the result is a small crack or fracture, in the bone.

What Causes a Foot Stress Fracture

Stress fractures in the bones of the foot are usually caused by over training or overuse. They can also be caused by repeated pounding or impact on a hard surface, such as running of concrete. Increasing the time, type or intensity of exercise too rapidly is another cause of stress fractures to the feet, as is wearing improper footwear.