The Effect of Exertion and Sex on Vertical Ground Reaction Force Variables and Landing Mechanics.

The purpose of this investigation was to determine how exertion and sex affected a variety of vertical ground reaction force (VGRF) parameters during a jump-landing task, including peak VGRF, peak VGRF asymmetry, loading rate, and loading rate asymmetry. Additionally, we wanted to determine whether landing mechanics changed after exertion as measured by the Landing Error Scoring System (LESS). Forty recreationally active participants (20 men and 20 women) completed jump landings from a 30-cm-high box onto force plates before and after repeated bouts of an exercise circuit until a specific rating of perceived exertion was achieved. Three-way (sex × time × limb) analyses of variance were used to analyze variables pre-exertion to postexertion. No significant 3-way interactions were observed for peak VGRF (p = 0.31) or loading rate (p = 0.14). Time by sex interactions were observed for peak VGRF (p = 0.02) and loading rate (p = 0.008). Post hoc analysis revealed that men increased landing force and loading rate after exertion while women did not. Landing mechanics, as assessed by total LESS score, were worse after exertion (p < 0.001) with increased frequency of errors for knee flexion <30° at initial contact, lateral trunk flexion, and not flexing the hip during landing. Women may be more resistant to exertion compared with men and use different joint controls' strategies to cope with VGRF after exertion. However, VGRF asymmetry is not affected by sex and exertion. Limiting peak VGRF and addressing landing postures, especially after exertion, should be components of injury prevention strategies.

Range of motion, postural alignment, and LESS score differences of those with and without excessive medial knee displacement.

OBJECTIVE: To determine range of motion (ROM), postural alignment, and dynamic motion differences between those with and without medial knee displacement (MKD) during the overhead squat (OHS). We hypothesized those with MKD would have restricted ROM, differing postural alignment, and poorer quality dynamic motion than those without MKD. DESIGN: Observational. SETTING: University Research Laboratory. PARTICIPANTS: Ninety-seven healthy recreationally active college-aged individuals. INDEPENDENT VARIABLES: Groups were determined by the presence (MKD group) or absence (control group) of MKD during an OHS. MAIN OUTCOME MEASURES: Range of motion measures were active and passive ankle dorsiflexion with the knee straight and bent, hip internal and external rotation, and hip abduction. Postural alignment measures were Q angle, navicular drop, and genu recurvatum. Quality of dynamic motion was measured using total Landing Error Scoring System (LESS) score. RESULTS: The MKD group had significantly less active (P = 0.017) and passive (P = 0.045) ankle dorsiflexion with the knee straight, as well as significantly increased Q angle (P = 0.004) and decreased navicular drop (P = 0.009). There were no significant differences in total LESS score or the other outcome measures. CONCLUSIONS: There is select ROM, such as ankle dorsiflexion, and postural measures clinicians can screen for that may be related to increased MKD and theoretically elevated risk of injury.

Jump-landing mechanics after anterior cruciate ligament reconstruction: a landing error scoring system study.

CONTEXT: The Landing Error Scoring System (LESS) is a clinical evaluation of jump-landing mechanics and may provide useful information in assisting with return-to-sport decisions in patients after anterior cruciate ligament reconstruction (ACLR). However, it is currently unknown how patients with ACLR perform on the LESS compared with healthy controls. OBJECTIVE: To determine if the total LESS score differed between individuals with ACLR and healthy controls and to determine the types of errors that differ between groups. DESIGN: Cross-sectional study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 27 individuals with unilateral ACLR (age = 19.8 ± 1.8 years, height = 170 ± 5.5 cm, mass = 68.8 ± 11.9 kg) and 27 controls (age = 20.5 ± 1.7 years, height = 169 ± 8.4 cm, mass = 66.6 ± 9.0 kg) with no history of ACLR. INTERVENTION(S): Each participant completed 3 trials of a standardized jump-landing task. MAIN OUTCOME MEASURE(S): Each jump landing was assessed for specific postures using standardized LESS criteria by a blinded evaluator. Individual LESS items were summed to create a total LESS score. The dominant limb was assessed in the control group, and the reconstructed limb was assessed in the ACLR group. RESULTS: The ACLR group had higher LESS scores compared with controls (ACLR: 6.7 ± 2.1 errors, control: 5.6 ± 1.5 errors, P = .04). Additionally, the ACLR group was more likely to err when landing with lateral trunk flexion (Fisher exact test, P = .002). CONCLUSIONS: Individuals with ACLR had worse landing mechanics as measured by the LESS. Lateral trunk deviation may be related to quadriceps avoidance in the reconstructed limb or poor trunk neuromuscular control. The LESS is useful for evaluating landing errors in patients with ACLR and may help to identify areas of focus during rehabilitation and before return to sport.