Static lifting strength and maximal isometric voluntary contractions of back, arm and shoulder muscles

Abstract

Young adult men and women (nine of each) performed maximal voluntary contractions (isometric) of the back extensors, shoulder flexors (45^° and 135^°), elbow flexorsand grip. Each subject also exerted maximal voluntary isometric lift on a tray in a 12 point positional matrix consisting of three horizontal distances (18, 36 and 51 cm from the ankles) and four vertical heights (33, 81, 134 and 190cm from the floor). Additionally, seven anthropometric measures were made on each subject. The results revealed women to men strength ratios from 0-46 to 0-73 for the five muscle group tests. In maximal isometric tray lifting women were able to exert approximately 50% of the force applied by men in the lower six test positions (below waist height) and 33% in the upper six test positions (above waist height). Regression analysis, using maximal isometric tray lifting strength as the dependent variable and the five muscle group strengths and anthropometric data as independent variables, revealed the insufficiency of a single multivariate predictor. Arm and shoulder strengths were suggested as limiting factors in lifting by their appearance in 19 of the 24 regression equations (12 each for men and women). Isometric back extension strength appeared in ten of the equations. Height seemed to be an important factor for men in lifts above waist level (134 cm or above).