The team of researchers from Australia, the US, Canada and South Korea demonstrated motors that could spin at nearly 600 revolutions per minute, turning a weight 2, 000 times heavier than the yarn itself.

BBC: Nanotube yarns twist like muscles

And that two days a week means a couple of 15- to 20-minute sessions on weight-training machines in the gym.

CNN: Weights plus walking equals more fit in less time

At 6-feet-4, the 46-year-old Mr. Rhodes isn't concerned about losing weight but rather keeping it on, and maintaining his stamina requires a 50-minute workout with a personal trainer three times a week.

WSJ: Opera Singer Builds Up Stamina for 'Carmen'

My version of your weight to strength is how many calories can I burn in a given 10, 20, or 30 minute time period on my exercise machines.

FORBES: Wealth and Fitness Secret - Ratios

Walking at a pace of 20-minute miles burns about 240-300 calories per hour depending on weight.

FORBES: How To Stay Healthy