Abstract
A common method for assessing landing kinetic deficits related to dynamic postural stability (DPS) and peak vertical ground reaction force (PvGRF) dissipation is the standard anterior-facing vertical drop-landing task. However, this approach may lack validity in multidirectional, multiplanar sports like netball. Increasing task complexity by altering landing direction and adding a 180° mid-air rotation may better reveal critical biomechanical differences. This study aimed to: (1) compare the within-limb landing kinetics for dominant limb (DL), non-dominant limb (NDL), functional ankle instability (FAI) and non- FAI limb groups independently across six vertical drop landing conditions of differing extrinsic directional (forward [FW] vs. diagonal [DI] vs. lateral [LA]) and rotational (standard [STD] vs. 180˚ mid-air rotation [180°]) complexity among netball players; (2) examine differences in landing kinetics between DL vs. NDL, as well as FAI vs. non-FAI limbs under the same six landing conditions; (3) to additionally explore the associations between landing kinetics and summative FAI scores determined through an administered Identification of FAI (idFAI) questionnaire; (4) Finally, to determine whether the intrinsic characteristics (limb dominance, FAI, maximum concentric muscular power, and dynamic balance) commonly associated with landing performance can predict DPS index scores in drop-landing tasks of the aforementioned extrinsic complexities
Twenty-four high-level netball players (age: 20.68 ± 2.01 years; stature: 174.36 ± 4.72 cm; body mass: 67.17 ± 9.51 kg) completed the idFAI questionnaire and ball kick test (both limbs), followed by 36 unilateral drop-landing trials classified as STD or 180° mid-air rotation. For STD FW, DI, and LA landings, participants performed a minimal bilateral hop from a 40 cm box, landing on one leg on a 40 × 60 cm force plate. Players stabilised as quickly as possible within 10 seconds, hands akimbo, focusing on a target 3 m ahead. The 180° condition added a medial mid-air rotation from a posterior facing start. Participants also completed three maximal countermovement jumps (CMJs) and the modified Star Excursion Balance Test (mSEBT) for each limb. Landing metrics derived from force plate data included the dynamic postural stability index (DPSI) and its component stability indices—the anterior-posterior stability index (APSI), medial-lateral stability index (MLSI), and vertical stability index (VSI)—along with forefoot PvGRF (F-PvGRF), hindfoot PvGRF (H-PvGRF), time between F-PvGRF and H-PvGRF (TP), and maximum concentric dynamic power during the CMJ. These metrics were extracted at 1,000 Hz and computed from ground reaction forces (GRFs) using custom MATLAB code. Non-normal data (Shapiro-Wilk, p < .05) were analysed using Friedman’s ANOVA for within-limb comparisons (by direction and rotation), with Wilcoxon post hoc tests (Bonferroni corrected). Between-limb (DL vs. NDL) and group (FAI vs. non-FAI) differences were assessed using Wilcoxon and Mann-Whitney U tests, respectively (p ≤ .05). Spearman’s rank order correlations were used to associate kinetic variables to idFAI scores. Finally, six backward stepwise
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regressions were conducted to identify intrinsic predictors for the six landing tasks.
Significant within-limb effects of extrinsic complexity were found (objective 1). FW landings showed higher APSI (greater anterior-posterior instability) than DI and LA across all limb dominance and FAI groups (p < .001). STD LA landings had higher MLSI (medial-lateral instability), while 180° landings showed no MLSI differences across directions (p ≥ .285). Both 180° FW and DI landings had higher F- and H-PvGRFs than their STD counterparts across all groups (p ≤ .034, r ≥ .66), with the FAI group showing larger increases than non-FAI. Only the FAI group showed significantly higher F- and H-PvGRFs in 180° FW/DI vs. 180° LA landings (p ≤ .007, r ≥ .55). For Objective 2, the 180° FW mid-air rotation landing revealed significant between-limb differences in dominance, with higher H-PvGRFs in the dominant limb (p = .005, r = .47). Between-group FAI comparisons showed higher APSI in FAI limbs during STD LA landings (p = .020, r = .65) and higher F-PvGRFs in FAI limbs during 180° DI landings (p = .039, r = .59). For Objective 3, higher idFAI scores correlated with greater APSI instability (rs = .473, p = .020), regardless of FAI classification. For Objective 4, only 180° FW and DI landings showed significant models predicting DPSI from FAI, concentric power, and dynamic balance, explaining ~43%– 44.5% of the variance (R² =.433- .445, all p < .002); no other models were significant (p > .05).
The findings suggest that adding directional and rotational complexity to drop-landing tasks alters kinetic demands on DPS and PvGRF absorption, influenced by individual intrinsic factors. These multidirectional tasks enhance task validity by better replicating netball’s multiplanar demands and help uncover biomechanical deficits—especially in FAI limbs—often missed in standard landings. This approach may support injury prevention and inform return-to-play criteria, underscoring the need for dynamic, individualised landing training across all planes.