ANALYSIS OF NORMAL AND SHEAR FORCES DURING STRAIGHTAWAY AND TURN RUNNING

Abstract

The purpose of this study was to compare the normal and shear forces aqd impulses exhibited by track runners during indoor straightaway running and turn running simulating an 18-meter radius inside curve and an outer 23.48-meter radius curve 0f.a -. 200-meter track. Average force and impulse of force during foot impact were examined for differences between the track condition as well as differences between the inside and outside legs. Ten male (Mean hgt =175.9 cm. and Mean wgt = 70.8 kg) and four female (Mean hgt =168.1 cm. and Mean wgt = 57.7 kg) college track athletes made up the subject group. Volunteers for the study were screened on the basis of their primary event(s), i.e., only sprinters and runners of distances 400 meters or less and jumpers were used. Data were recorded ,with a ICstler Instrument force measurement platform system interfaced to a microcomputer. Relatively similar average vertical impact forces of 11 18.05 N, 1029.73 N, and 1044.60 N were found for straightaway, inside curve, and outside curve, respectively, and only slight differences appeared for corresponding vertical impulses, i.e.,. 152.04 N-sec,158.02 N-sec, and 155.46 N-sec. Two-factor ANOVA confirmed a lack of significant difference for the main effect, track condition, as well as for leg, i.e., inside or outside leg (p > 0.05). However, for shear force, differences between track condition--but not leg-were revealed (p < 0.001). Shear impulse of force was significant for both main effects, i.e., track condition (p < 0.001) and leg condition (p < 0.05). Post-hoc analysis revealed the source of differences for both shear force and shear impulse to be between the straightaway running condition and both types of turn running. Values for shear force and impulse for the inner curve exceeded those for the outer curve, but the differences were insignificant (p > ,051. Although a middle lane assignment for curve running is generally viewed by track athletes and coaches as critical to successful performance, these findings for moderate speed running do not support that from a biomechanical standpoint.