​The thing about Fitness is that you need to fined an area that interests you, this can be running, swimming, cycling, doing a sport, or training in the gym. It needs to be an activity that will motivate you to keep going.

Exercise doesn't need to take long, it can be done in a short space of time, especially as we all tend to lead busy lives. 30 mins a day of a variety of exercise including high intensity intervals will be effective, this can be done in various locations.

Half and full marathon or Triathlon training will require longer training sessions, but here it is not just about running as far as you can every time, it's about training smart so you build your ability up not just wear yourself out. so shorter more intense sessions here are needed as well as the long, but remember the body needs to recover, and the longer the session the longer the body needs so don't kill yourself on the longer sessins every weekend. 

Resistance training is also important here as the posture must be strengthened to cope with the extra effort to the system, especially core muscles, and joint support, to cut down on injury.