Jay, a physician in his early 30s, was a healthy guy who ran 6 miles a day, loved nature and animals, and spent free time hiking and biking. One summer, he decided to start weight training. The problem started simply. He had finished a training session at the gym, doing upper and lower body exercises with barbells and finishing with sit-ups. A few days later, he felt more sore than usual. “My neck feels really stiff,” he told me. “I probably overdid it at the gym.” I ex…