Fig. 4.

Upper panel: Var_b(t) and Var_τ(t) are components of the index finger force variance, Var(f_I(t)). Lower panel: Examples of model fitting of force variance in different directions in the force space R⁴: In the direction of the main eigenvector of the covariance matrix, λ_max(t), in the direction of the force rate vector, Var(f(t))|_f′(t), and in directions orthogonal to it, Var(f (t))|_ort) per degree-of-freedom. Solid lines—experimental curves for a representative subject, dotted lines—model curves