This Ph.D. thesis is based on three studies performed at the Center for Sensory- Motor Interaction (SMI), Pain and Motor Control Laboratory, Department of Health Science and Technology, Aalborg University, Denmark, from 2009 to 2012.

Study I
Salomoni S.E., Graven-Nielsen T., Muscle fatigue increases the amplitude of fluctuations of tangential forces during isometric contractions, Human Movement Science (2012), In Press.

Study II
Salomoni S.E., Graven-Nielsen T., Experimental muscle pain increases variability of multidirectional forces during isometric contractions, European Journal of Applied Physiology (2012), In Press.

Study III
Salomoni S.E., Ejaz A., Laursen A.C., Graven-Nielsen T., Experimental knee pain increases variability of three-dimensional force components during isometric contractions, Submitted.