USING FACTOR-ANALYSIS TO IDENTIFY NEUROMUSCULAR SYNERGIES DURING TREADMILL WALKING

Neuroscientists are often interested in grouping variables to facilita te understanding of a particular phenomenon. Factor analysis is a powe rful statistical technique that groups variables into conceptually mea ningful clusters, but remains underutilized by neuroscience researcher s presumably due to its complicated concepts and procedures. This pape r illustrates an application of factor analysis to identify coordinate d patterns of whole-body muscle activation during treadmill walking. T en male subjects walked on a treadmill (6.4 km/h) for 20 a during whic h surface electromyographic (EMG) activity was obtained from the left side sternocleidomastoid, neck extensors, erector spinae, sind right s ide biceps femoris, rectus femoris, tibialis anterior, and medial gast rocnemius. Factor analysis revealed 65% of the variance of seven muscl es sampled aligned with two orthogonal factors, labeled 'transition co ntrol' and 'loading'. These two factors describe coordinated patterns of muscular activity across body segments that would not be evident by evaluating individual muscle patterns. The results show that factor a nalysis can be effectively used to explore relationships among muscle patterns across all body segments to increase understanding of the com plex coordination necessary for smooth and efficient locomotion. We en courage neuroscientists to consider using factor analysis to identify coordinated patterns of neuromuscular activation that would be obscure d using more traditional EMG analyses. (C) 1998 Elsevier Science B.V. All rights reserved.