Blinded grading showed optimal improvement at 67 C and 3 seconds and decreased efficacy below 67 C , with mean rhytide reductions of 40 , 29 , and 25 % and mean laxity reductions of 34 , 36 , and 25 % in Arms 3 ( 67 C ) , 2 ( 62 C ) , and 1 ( 52 C-57 C ) , respectively .