11.   Only people taking vigorous exercise outdoors would be affected by high levels, the group decided.

12.   As always, check with your doctor before you stop taking any medication and before beginning a vigorous exercise program.

13.   Aside from the occasional desultory shuffle to the office vending machine for some stale pretzels, there are few opportunities for vigorous exercise in the average office.

14.   As they age, the study showed, those who regularly engage in vigorous aerobic exercise like running are much less likely to develop life-inhibiting disabilities.

15.   A resting body uses far less oxygen than one doing vigorous exercise.

16.   A stroll on this walkway, called Scales of the Universe, is vigorous algebraic exercise.

17.   After rising early each morning, Perez spends an hour or so in vigorous exercise aboard his stair and treadmill machines.

18.   Both of these group travel sponsors provide time for children to be with children, particularly at the end of the day, and to get vigorous exercise.

19.   But for the ultimate benefit -- substantially longer life -- only vigorous regular exercise will do, according to a Harvard University study published Wednesday.

20.   But there is something to be said for a machine that allows you to engage in vigorous physical exercise in the sitting position.