Date of Award

2021

Degree Name

Exercise Science

College

College of Health Professions

Type of Degree

M.S.

Document Type

Thesis

First Advisor

Dr. Steven Leigh, Committee Chairperson

Second Advisor

Dr. Mark Timmons

Third Advisor

Dr. Kumika Toma

Abstract

Non-contact knee injuries are prevalent in dancers and have great financial and social costs. These injuries may be prevented with training that modifies jump landing movement patterns and improves lower body strength and cardiorespiratory fitness. Identifying the movement-based risk factors that are most strongly related to injury mechanisms allows healthcare providers to create effective training interventions. The purpose of this study was to determine the relationship between multivariate risk factors and injurious knee forces as a dancer lands from a jump. Twenty female dance students with at least eight years of experience were recruited. These dancers were injury-free and actively rehearsing, volunteered to participate, and signed informed consent. Participants took part in two testing sessions. On day one participants completed a dance history questionnaire, had their height and weight measured, tested their knee flexion/extension muscular endurance using an isokinetic dynamometer, and their cardiorespiratory fitness using a submaximal, graded step test. On a second day, participants completed switch leap jump landings before and after performing a Dance Aerobic Fitness Test at an increasing tempo. Threedimensional lower extremity kinematics of their landings were measured using a retro-reflective motion analysis system. Landing forces were measured using two force plates. Joint angles during the leap and at landing, and knee joint anterior shear force and external valgus moment at landing were calculated from the biomechanical data. Stepwise multiple regressions showed that when landing while fatigued, increased knee anterior shear force was predicted by a combination of greater knee valgus angle at landing and greater knee flexion angle at landing. Increased external knee valgus moment was predicted by a combination of decreased knee valgus angle at landing and decreased knee flexion angle at landing. These results indicate that a more extended landing position is possible when a dancer is fatigued, and this position can generate a greater knee valgus moment, which stresses the MCL. These results also indicate that a knee flexed and valgus landing position in combination with lower fitness levels may generate high knee anterior shear force, which stresses the ACL. A statistically significant interaction term was identified for the regression analyses, indicating that fitness level may function as a moderator of the relationships between knee angles at landing and knee joint anterior shear force, as well as knee angles at landing and external knee valgus moment. These findings can be used to direct training interventions to improve jump landing movement patterns and help to guide future research for a better understanding of fitness and its impact on fatigued landings.

Subject(s)

Kinesiology -- Research.

Dancers -- Health and hygiene -- Research.

Download

Share

COinS