They had never seen a person recover so fast after major surgery. Sensei says he got well quickly because his chi was so strong. He attributes his health to a lifetime of martial arts practice. As you train you will start to notice your own internal energy. You feel good when the energy circulates freely, and not so good when the energy is blocked, such as at the site of muscle tension or injury.
Many people believe that martial arts training can remove such blockages and promote health.
When you train, you can decide for yourself whether you think this is true.