Fitness guru Jack LaLanne knows push-ups. During his 30-plus years on television, he regularly demonstrated the proper push-up technique and wowed us with feats of strength like finger-tip push-ups and one-armed push-ups.

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Mr. LaLanne, 93, still does push-ups during his daily 90-minute workout. “I hate it,” he said of working out. “But I like the results. Exercise is something you’ve got to do the rest of your life.”

I was fortunate to speak with Mr. LaLanne for my Well column in this week’s Science Times, which explores why the push-up remains an enduring symbol of fitness. The article also explains why your ability to do a push-up is linked to how well you age. Here’s a calculator to tell you how many push-ups you should be doing if you are in good shape.

Read the full column here, and be sure to check out our new Well video segment, “Drop and Give Me Twenty!,” above.

How’s your push-up performance? Post your comments here.