Footnote

a For those interested in burning calories, going from a 20-minute mile [12-minute km] to a 15-minute mile [9-minute km] will use up 30 percent more calories per minute. Increasing the pace from a 15-minute mile [9-minute km] to a 12-minute mile [7-minute km] will burn up 50 percent more calories per minute. Most fitness walkers cover a mile in about 12 to 15 [a kilometer in about 7 to 9] minutes.