Old age and treachery will overcome youth and strength.

My dad was a superb semi-pro tennis player. It’s one of the reasons I became a skier.

The last time I tried to compete with him, he was about 50. I was 23.

I had speed and strength and endurance. He had wicked accuracy.

Dad could put his shots in the far corner from wherever I happened to be. I was forced to respond to each shot with some desperate defensive lob, aiming only roughly at the center of his court in hopes of saving the volley. Run ragged, I collapsed after the second set.

Dad, of course, didn’t have to run. His game was in his fingers and wrist. His expertise was subtle, and required relatively small movements of his forearm to guide the racquet. My game was gross, requiring that I heave 160 pounds of meat around the court.

Here’s the lesson for low-impact skiing: Use subtle moves inside the boot, and lateral gestures of the hands, to adjust the angle of the ski and thus the radius of the turn. Take advantage of terrain shape to guide your trajectory. You could waste a lot of energy lifting and throwing your body around, but why bother? The mountain will beat you after the second set.