Concomitantly , light muscle activity time increased by @ @ min , from @ % @ % to @ % @ % ( whole day , P < @ ; work , P < @ ; leisure , P < @ ) , and during work time , average EMG amplitude ( percentage of EMG during maximal voluntary isometric contraction ( MVC ) ( % EMG MVC ) ) increased from @ % @ % to @ % @ % ( P < @ ) in the intervention group compared with that in the controls .