When Dad is working out on the elliptical trainer, Grafton comes running down and joins in by running laps around the staircase in the basement. Not just 2 or 3 times. More like 90. Seriously. He has run laps for 15 minutes straight, at about 10 seconds per lap. Without stopping once. I couldn't believe it the first time I saw him do this. He kept telling me we weren't going to stop until the "race was over."
When Dad is not working out, Grafton will have me time him with a stopwatch. He can hold 6-7 seconds per lap for 10 or so laps.
If Dad can get him to exert this level of effort on a hiking trail, we could start working out together on a regular basis.