Concomitantly , light muscle activity time increased by 20.6 52.6 min , from 22.2 % 7.9 % to 25.0 % 9.7 % ( whole day , P < 0.05 ; work , P < 0.01 ; leisure , P < 0.05 ) , and during work time , average EMG amplitude ( percentage of EMG during maximal voluntary isometric contraction ( MVC ) ( % EMG MVC ) ) increased from 1.6 % 0.9 % to 1.8 % 1.0 % ( P < 0.05 ) in the intervention group compared with that in the controls .