Force steadiness during a co-contraction task can be improved with practice, but only by young adults and not by middle-aged or old adults.
Holmes MR, Gould JR, Pe?a-Gonz?lez I, Enoka RM. Force steadiness during a co-contraction task can be improved with practice, but only by young adults and not by middle-aged or old adults. Exp Physiol. 2015 Feb 01; 100(2):182-92.