EFFECTS OF EXERCISE ON HIP RANGE OF MOTION, TRUNK MUSCLE PERFORMANCE,AND GAIT ECONOMY

Background and Purpose. The purposes of this study were (1) to examine the effects of a passive hip extension stretching exercise program on hip extension range of motion (ROM), (2) to examine the effects of a trunk flexor exercise program on trunk flexor muscle performance, and (3) to examine the effects of passive hip extension stretching or trun k flexor exercises on walking and running economy (''Gait economy'' is defined as the steady-state oxygen consumption per unit of body weigh t required to walk or nun at a specified velocity.) Subjects. Twenty-f ive healthy, athletic, male college students (XBAR age =21 years, XBAR weight = 75 kg, XBAR height = 1 72 cm) were randomly assigned to one of three groups: a control group (n = 7), a hip extension stretching g roup (n = 9), or a trunk flexor exercise group (n = 9). Methods. Befor e and after 3 weeks of intervention, the following measurements were o btained right and left hip extension ROM, trunk flexor muscle performa nce, and walking and running economy A three x two-way (groups x test sessions) analysis of variance (ANOVA) for repeated measures for unequ al subject numbers was performed on each of the five dependent measure s, with analysis of simple main effects applied when significant inter actions were found Results. The ANOVA on right and left hip extension ROM revealed a significant interaction. Analyses of simple main effect s showed that 3 weeks (six sessions) of passive hip extension stretchi ng significantly improved right hip extension ROM (pretest = -20.4-deg rees, posttest= -83) and left hip extension ROM (pretest= - 168, postt est = - 7 0-degrees). There also was a significant interaction for tru nk flexor muscle performance The analysis of simple main effects revea led that 3 weeks of daily trunk flexor exercises significantly improve d trunk flexor muscle performance (pretest 41.5-degrees, posttest = 69 .4-degrees). The 3-week intervention program of hip extension stretchi ng or trunk flexion exercises, however, did not produce significant ch anges in walking or running economy. Conclusion and Discussions. The r esults suggest that (1) six treatment sessions of passive stretching w ere sufficient to improve hip extension ROM, (2) 3 weeks of exercises performed daily improved trunk flexor muscle performance, and (3) trai ning of isolated tasks, such as hip flexibility or trunk strengthening activities, did not Produce the desired outcome in the economy of wal king or running. Possible reasons for the results are discussed.