Health improvements were observed among programs at least 30 min in duration , including body composition and VO2max : 30-min walking 28.8-34 .5 mL kg ( -1 ) min ( -1 ) , 60-min walking 25.1-28 .9 mL kg ( -1 ) min ( -1 ) , and 30-min running 32.4-36 .4 mL kg ( -1 ) min ( -1 ) .