 This paper proposes a new method for estimating the innervation zone, IZ, of a muscle using monopolar high-density surface electromyrography, SEM, signals. The IZ is the region where the nerve fibers are closest to the muscle fiber, and it is important for understanding how the muscles contract. The proposed method uses principal component analysis, PCA, to identify the channels which are closest to the IZ, as these channels will have shorter time delays between them compared to other channels. The method was tested using simulations and experiments, and the results showed that the PCA-based method outperformed the cross-correlation method, CCM, which is commonly used for IZ estimation. This article was authored by Qin Jun Huang, Ma Qi Chen, Ying Chen Zhang, and others.