[watwut]

Around 40, if you are not exercising, you will become noticeably weaker. After a while you start loosing muscle. Your back hurts. It is not possible to ignore it anymore, be it walking up stairs, during holiday or when outside with kids or just when walking to work. Exercising works. And it feels more pleasant then I remember it from younger age. Moreover things like running are not boring anymore (because you did not done those really fun things for years, so you cant compare.)

When your back or whatever hurts and when you have high blood pressure and what not, doctor tells you to do move more. Many people started those runs after healths problems started and sport really helps. The competitions and trying limits is really treating it the way the same people approached school, work, hobbies and pretty much everything in their life before.

Those 10k, 20k and marathons are achievements available to middle aged people. (5k easily reachable) We can run, we cant lift as much we cant effectively start sports that require flexibility or agility. In a lot of senses, these people are not doing anything different then their done whole their life wherever it was possible, except that they adjusted choice of activity to aging bodies needs.