“Bone Insufficiency

Conditions that decrease bone strength and density...”

“Poor Conditioning

Doing too much too soon is a common cause of stress fractures.” 

“Improper Technique

Anything that alters the mechanics of how your foot absorbs impact as it strikes the ground may increase your risk for a stress fracture.”

“Change in Surface 

A change in training or playing surface, such as a tennis player going from a grass court to a hard court...”

“Improper Equipment

Wearing worn or flimsy shoes that have lost their shock-absorbing ability may contribute to stress fractures.”

Ref: http://orthoinfo.aaos.org/topic.cfm?topic=a00379

Picture: Active.com