A method for analyzing muscle signals, wherein the method comprises: - receiving a signal, the signal having been measured from a muscle in a resting state by a muscle signal apparatus comprising an electrode arrangement comprising at least two pairs of electrodes of conducting material arranged to make contact with skin when the electrode arrangement is operated for picking up the muscle signal, the at least two pairs of electrodes having a different distance between the electrodes in the pair for creating a different depth sensitivity for the at least two pairs of electrodes; an electrical insulator surrounding at least one of said electrodes; a passive earth body of conducting material arranged to make contact with the skin when the electrode arrangement is operated, the earth body surrounding the at least two pairs of electrodes to limit the at least two pairs from picking up a signal from outside of the extent of the earth body; the method further comprising: - determining, by a processor, a measure indicative of frequency content of the signal, the determining comprising - determining a moment value of a spectrum of said signal, wherein said moment is indicative of a measure determined by multiplying a frequency value of a frequency bin with an amplitude value of the same bin to form a bin product and summing bin products for different frequencies, and wherein said moment value corresponds to frequency content of said signal, - determining whether said moment has a normal value, a low value or a high value, corresponding to a normal, low and high frequency content of said signal, - determining that the muscle is in a non-tired state if said moment has a normal value, - determining that the muscle is in a tired state if said moment has a low value, and - determining that the muscle is in a passive involuntary tension state if said moment has a high value. - receiving a signal, the signal having been measured from a muscle in a resting state by a muscle signal apparatus comprising an electrode arrangement comprising at least two pairs of electrodes of conducting material arranged to make contact with skin when the electrode arrangement is operated for picking up the muscle signal, the at least two pairs of electrodes having a different distance between the electrodes in the pair for creating a different depth sensitivity for the at least two pairs of electrodes; an electrical insulator surrounding at least one of said electrodes; a passive earth body of conducting material arranged to make contact with the skin when the electrode arrangement is operated, the earth body surrounding the at least two pairs of electrodes to limit the at least two pairs from picking up a signal from outside of the extent of the earth body; the method further comprising: at least two pairs of electrodes of conducting material arranged to make contact with skin when the electrode arrangement is operated for picking up the muscle signal, the at least two pairs of electrodes having a different distance between the electrodes in the pair for creating a different depth sensitivity for the at least two pairs of electrodes; an electrical insulator surrounding at least one of said electrodes; a passive earth body of conducting material arranged to make contact with the skin when the electrode arrangement is operated, the earth body surrounding the at least two pairs of electrodes to limit the at least two pairs from picking up a signal from outside of the extent of the earth body; the method further comprising: - determining, by a processor, a measure indicative of frequency content of the signal, the determining comprising - determining a moment value of a spectrum of said signal, wherein said moment is indicative of a measure determined by multiplying a frequency value of a frequency bin with an amplitude value of the same bin to form a bin product and summing bin products for different frequencies, and wherein said moment value corresponds to frequency content of said signal, - determining whether said moment has a normal value, a low value or a high value, corresponding to a normal, low and high frequency content of said signal, - determining that the muscle is in a non-tired state if said moment has a normal value, - determining that the muscle is in a tired state if said moment has a low value, and - determining that the muscle is in a passive involuntary tension state if said moment has a high value.