On Monday I went to an aerobics class it the gym. On a whim.
I took one look at the three jolly Ladies of A Certain Age who stood there in lumpy lycra, and, in a rare macho moment, I thought "I can take 'em."
No, I couldn't.
I was fine on the arm exercises (Dumbell raises with 2kg weights, how sweet!), and the stomach work was made easier by the perfect view it gave me of a nearby blond man doing press ups.
But the 20 minutes of lunges nearly killed me. I looked around, the blood rushing in my ears, to expect to find the dear ladies all dead. No. They'd barely broken a sweat, and were grinning genially at me. "Would you like a cup of water, dear?" one asked.
Two days later, and I can still barely walk.