A biomechanical analysis of male and female athletes during preplanned change of direction (COD) tasks

Abstract

With rising female participation in multidirectional sports, this thesis examined cutting biomechanics to better understand how sex, cutting angle (45° vs 90°) and limb preference influence both performance and non-contact ACL injury risk. Using a combination of Discrete Point Analysis (DPA) and Statistical Parametric Mapping (SPM), this work utilised systematic review, meta-analysis, and empirical studies to establish the biomechanical determinants of multiplanar knee joint loads (KJLs) and their influence on cutting performance and ACL injury risk. The systematic review developed a technical framework linking lower limb and trunk orientation, foot placement, braking strategy and ground reaction force (GRF) profiles to KJLs, highlighting high risk profiles such as wide foot-plants, knee abduction, hip internal rotation, rearfoot landings, and trunk lean towards the cutting leg.

Meta-analysis revealed that females demonstrated greater knee abduction angles at initial contact (SMD = 0.687, 95% CI 12 0.299-1.076, p = 0.001) and smaller peak knee flexion angles (SMD = 0.374, 95% CI 0.098 - 0.649, p = 0.008) yet pooled analyses of multiplanar KJLs revealed no significant sex differences (internal knee adduction moment, p = 0.107). Time specific sex differences in KJLs were identified in the empirical chapter whereby females generated greater knee abduction moments during left 90° cuts at 44-48% of stance (p = 0.040), greater velocity normalised knee abduction moments during left cuts (p = 0.008) and knee abduction angles during stance and initial contact (p = 0.016-0.032). Clear sex differences in penultimate foot contact (PFC) braking strategies were observed, with females producing significantly greater vertical ground reaction forces during right and left cuts (p = < 0.001, p = 0.002) and ankle dominant braking through greater PFC ankle dorsiflexion moments (p= 0.032, p = 0.048). Conversely, males cut faster than females (p = < 0.001), with greater approach velocities (p < 0.001), wider foot plants (p = < 0.001), greater hip abduction (p = 0.008-0.029) and increased lateral trunk flexion (p = 0.006 – 0.022). Cutting angle strongly influenced injury risk with 90° cuts producing greater knee abduction moments and internal rotation moments than 45° cuts (p = < 0.001 – 0.001 and p = < 0.001). SPM identified between angle differences in all variables examined. Skill training history were negatively associated with knee abduction moments (-0.034 Nm.kg per year) suggesting a protective effect.

Chapter 5 identified the non-preferred limb to generate greater knee abduction moments (p = 0.030). Asymmetry in knee abduction moments was characterised by greater lateral trunk flexion (p = 0.018), hip abduction (p = 0.022), and hip external rotation (p = 0.031). Chapter 7 confirmed the performance injury conflict during 45° and 90° cuts with performance associated with greater approach velocity, wide foot plants and higher knee flexion, abduction and internal rotation moments, concurrently increasing injury risk (p = 0.001- 0.045). Knee abduction moments and internal rotation moments were strongly correlated (p = <0.001) indicating greater ACL loading. Performance determinants were also angle dependent, with sagittal plane mechanics underpinning 45° cuts (p = <0.001-0.048), with braking and multiplanar mechanics such as hip abduction, lateral trunk lean, and wider foot plant distances (p = <0.001 – 0.035) during 90° cuts.

This thesis provides several novel contributions to COD biomechanics research by integrating discrete and continuous analyses to identify phase specific, sex, angle, and limb dependent determinants of knee joint loading. To mitigate the
higher non-contact ACL risk in females, findings support increasing skill training provision, promoting hip and knee dominant braking, reducing knee abduction at IC and during stance, and maintaining neutral foot and trunk alignment Practitioners should apply integrated angle-specific training that develops braking strength and neuromuscular control to enhance performance while mitigating knee joint loading.

Date of Award	2024
Original language	English
Awarding Institution	Canterbury Christ Church University