Am I 80 yet?

Yesterday I scooped up the leaves that were piled up in front of the house. It was only about one cubic meter of stuff, but boy was I tired when I finished. My cardiovascular health is still good, so I don't feel winded or sweaty when I finish a job like that. But my muscles are wobbly and weak. And it's easy to misjudge recovery time. I walked down the stairs about an hour later and almost fell.

Left grip is 40 pounds (40, 39, 40), right grip is 97 pounds (97, 95, 92), left leg balance is 13.7 seconds, and inhale volume is TK mL.