Playing Catch-Up

Outdoor activities with 2 active, growing up boys are weekly affairs in our family since they were very young. Not only do outdoor activities force me to work out, they help us to bond as a family. However, with passing time, things have become less rosy for me.
The stamina of these boys, now aged 10 and 8, is unbelievably great, and will become greater, in years to come. As for my husband and I, the reverse is certainly true. As we can't defy aging (both of us in our mid-forties), our stamina has become poorer with time. Running is certainly out for both of us. So I prefer walking, especially long distance walk in parks, enjoying the beauty of nature and breeze. But walks are not attractive to the boys. They prefer to run around,zoom about with their skate-scooters, to play ball and to cycle.
We spent the Saturday 2 weeks ago cycling in East Coast Park as a family. It was only 2 years ago that both boys learnt to ride a 2-wheeler bicycle. They have now grown very comfortable with cycling, despite some minor injuries from time to time. We cycled for about an hour, covering a total distance of about 9km that day. The up slopes proved to be a real challenge for me, and towards the end of the ride, I was struggling to catch up with them. This time, the boys did something I didn't expect of them. They stopped frequently to wait for me to catch up with them. While I was pleased with their kind gesture, I urged them to keep going.
Later, it dawned on me that our roles have reversed! Not so long ago, I had to wait for them to catch up when we brought them outdoor, or I had to walk slowly alongside them. Now, they are the ones waiting for me to catch up!