A measurement unit comprising measurement electronics for measuring an EMG signal and a motion signal from a limb of a person, a wireless transceiver unit for transmitting and receiving data wirelessly, and a processing unit configured to - determine a principal component representation of the EMG signal and the motion signal in real time, wherein the principal component representation represents a projection of at least one feature of the EMG signal and at least one feature of the motion signal into at least one uncorrelated feature in a feature space formed by orthogonal basis vectors, and - transmit the principal component representation to an external system with the wireless transceiver unit, wherein the determining of the principal component representation in real time comprises - providing an initial value for a sample correlation matrix, wherein the sample correlation matrix represents correlations between features extracted from the EMG signal and the motion signal, - updating the sample correlation matrix iteratively, wherein a new value of the sample correlation is formed based on values of features extracted from a segment of the EMG signal and the motion signal and a previous value of the sample correlation matrix, and - calculating the principal component representation based on the updated sample correlation matrix, and wherein the initial value for the sample correlation matrix is based on preliminary measurement data gathered from the person or a plurality of persons. measurement electronics for measuring an EMG signal and a motion signal from a limb of a person, a wireless transceiver unit for transmitting and receiving data wirelessly, and a processing unit configured to - determine a principal component representation of the EMG signal and the motion signal in real time, wherein the principal component representation represents a projection of at least one feature of the EMG signal and at least one feature of the motion signal into at least one uncorrelated feature in a feature space formed by orthogonal basis vectors, and - transmit the principal component representation to an external system with the wireless transceiver unit, - determine a principal component representation of the EMG signal and the motion signal in real time, wherein the principal component representation represents a projection of at least one feature of the EMG signal and at least one feature of the motion signal into at least one uncorrelated feature in a feature space formed by orthogonal basis vectors, and - transmit the principal component representation to an external system with the wireless transceiver unit, wherein the determining of the principal component representation in real time comprises - providing an initial value for a sample correlation matrix, wherein the sample correlation matrix represents correlations between features extracted from the EMG signal and the motion signal, - updating the sample correlation matrix iteratively, wherein a new value of the sample correlation is formed based on values of features extracted from a segment of the EMG signal and the motion signal and a previous value of the sample correlation matrix, and - calculating the principal component representation based on the updated sample correlation matrix, and - providing an initial value for a sample correlation matrix, wherein the sample correlation matrix represents correlations between features extracted from the EMG signal and the motion signal, - updating the sample correlation matrix iteratively, wherein a new value of the sample correlation is formed based on values of features extracted from a segment of the EMG signal and the motion signal and a previous value of the sample correlation matrix, and - calculating the principal component representation based on the updated sample correlation matrix, and wherein the initial value for the sample correlation matrix is based on preliminary measurement data gathered from the person or a plurality of persons.