Generally healthy , active participants ( n = 72 ; age = 44 13 years ) were assigned randomly to control ( n = 10 ) or one of five 13-week exercise programs : ( 1 ) 10-min brisk walking 1/week ( n = 10 ) , ( 2 ) 10-min brisk walking 3/week ( n = 10 ) , ( 3 ) 30-min brisk walking 3/week ( n = 18 ) , ( 4 ) 60-min brisk walking 3/week ( n = 10 ) , and ( 5 ) 30-min running 3/week ( n = 14 ) , in addition to their regular physical activity .