But there is plenty of evidence of fractures without the necessity of battery or outside trauma, one I'm sure anyone that served in the military can attest to. Shin splints, heel splints, knee fractures, condyle fractures- all due to marching on a hard surface. These involve young men in their physical prime and did not suffer from osteoporosis. Unless somehow you believe that they were "worked over pretty good". They may not be "worked over pretty good", but they are "worked out pretty good". In the infantry, they are often carrying about 80 to 100 pounds of gear, supplies, and fire power for many miles over rough terrain. It's not surprising they are pushed over the amount the human body can support without causing problems.
These stress fractures are almost exclusively reported within the first 12 weeks of military service- long before they are
"carrying about 80 to 100 pounds of gear, supplies, and fire power for many miles over rough terrain". Female recruits suffer stress fractures at 10 times the rate of their male counterparts.
Actually, the activity you refer to doesn't appear to be implicated with the development of stress fractures.