True - no one is going to use a treadmill to fully compensate for too high a food intake for the rate of energy use by the body. But it has a function in keeping joints moving and we are talking here about an increase in weight due to less activity. I use a treadmill to compensate for the fact I don't walk much as it's too hot.
For those who are interested, Forest Camp in Valencia is hosting karate sessions every Sunday afternoon. They are now JKA (Japan Karate Association) accredited. Rates are Php600 a month or Php500 if you pay the whole year.