INFLUENCE OF STAIR DIMENSIONS AND SUBJECT HEIGHT ON ANGULAR DISPLACEMENT OF THE TRUNK DURING STAIRCLIMBING

Abstract

For more than a decade, stairclimbing has been touted (e.g., Edwards, 1983) as an easy and effective way to build physical activity into one's daily routine, for staircases are both readily available and they require the climber to move against a natural resistance force (i.e., gravity). Yet gravity may destabilize the climber and lead to a potentially injurious fall if the line of gravity (i.e., centre of mass)falls outside the climber’s base of support. It has been suggested that stabilitymay be accomplished by varying the orientation of the trunk segment (Krebs etal., 1992) yet systematic investigations of the relationship between trunk orientation, the internal constraints (e.g., subject height), and external constraints(e.g., stair dimensions) imposed when stairclimbing have yet to be reported. The purpose of this study, therefore, was to examine the angular displacement of the trunk while climbing over stairs of differing dimensions. Six healthy, physically active young-adult females with a mean age of 21.8 years (SD = 2.6), grouped by height, completed 10 trials each of free-speed stair ascent and descent over three staircases classified as steep (45º), moderate (33 º), or shallow (16 º) in slope. Results of a mixed between-within repeated measures MANOVA yielded several significant results. While ascending stairs, those subjects classified as short in height demonstrated significantly (F(2,9)=5.32, pc<03) greater trunk range of motion values (X=9.97 º, SD=0.43) than did their medium (X=8.96 º, SD=0.79) ortall (X=7.49 º, SD=1.74) counterparts. Similarly for the task of stair descent, significant differences between groups (F(2,9)=22.8, p<.01) and between stepping conditions (F(2,9)=9.61, p<.01) were observed as was an interaction effect(F(4,9)=5.61, p<.02) for trunk range of motion. Although trends were apparent, differences in the maximum or minimum trunk angles observed between groups or by stepping condition, during stair ascent or stair descent, were not significant. The results of this study support the premise that trunk segment orientation is varied depending upon the dimensions of the stair being climbed and the stature of the climber. Future studies of stairclimbing should acknowledge the effects of these constraints on the movement behaviour of the climber and, in particular, explore the relationship between trunk orientation and climber stability.