Jump Landings Research Articles

Frontal and Sagittal Plane Biomechanics During Drop Jump Landing in Boys Who Are Obese

To investigate the frontal and sagittal plane lower extremity biomechanics during drop jump landings in boys who were obese and boys who were of healthy weight. Twelve boys participated, 6 were considered as healthy weight (body mass index for age <85%, age 11.0 +/- 0.8 years), and 6 were considered as obese (body mass index for age >95%, age 12.1 +/- 0.7 years). Three-dimensional data were collected during landing from a drop jump. Group means were compared using Student t tests (alpha = 0.05). Significant differences were found in peak hip adduction moment, timing of peak dorsiflexion and knee flexion angles, and timing of peak knee extension and abduction moments. Boys who were obese exhibited significant differences in frontal and sagittal plane biomechanics when landing from a jump compared with healthy weight peers. These differences could place boys who are obese at greater risk for lower extremity injuries when they engage in jump-landing activities.

A Gender Comparison of Lower Extremity Landing Biomechanics Utilizing Different Tasks

Jump landings are routinely used to study gender differences in landing. Standardizing the jump height to a fixed vertical distance may bias results as women are forced to land from heights that are a greater percentage of their own maximum vertical jump (MVJ). PURPOSE: To compare lower extremity mechanics between genders from a fixed height and from a self initiated jump. METHODS: Nine male (21.50±1.20 years, 173.25±2.82cm, 75.58±7.92kg, 60.97±5.81cm MVJ) and 8 female (20.56±1.24 years, 161.11±6.01cm, 57.58±11.65kg, 33.13±9.76cm MVJ) subjects participated in this study. Subjects were given standard footwear. Maximum vertical jump heights were obtained. Subjects performed 6 successful trials of a drop landing (DL) from a 61cm height and a self initiated vertical jump landing (VJ) at their 80% MVJ height in random order. A 6-camera, EVa 3-D motion capture system (Motion Analysis, Santa Rosa, CA) captured (120 Hz) and analyzed (EVa version 5.11 and KinTrak 6.0 software) dominant lower extremity joint kinematics based on an 11 marker, 3 segment (thigh, shank, foot) model. Joint centers for the hip, knee and ankle were created according to Euler angle calculations. A synchronized force plate (AMTI, Watertown, MA) recorded time of initial contact and maximal vertical force. Dependent variables included: knee flexion angles at initial contact (KFIC), at maximal vertical ground reaction force, (KFMZ) and maximum knee flexion angle (MaxKF). Data were exported into spreadsheet and means for all trials in both conditions were created and imported to SPSS 13.0. Two 1-way ANOVAs tested for differences (P = 0.05) between groups in each condition. RESULTS: No significant differences were found between males and females for KFIC or KFMZ in either the VJ or DL. No significant difference was found in MaxKF between males (75.55± 8.46) and females (67.52± 6.31) in the DL. However, males had greater MaxKF angles (83.38± 18.90) than females in the VJ (66.22±15.01) (P=.001). CONCLUSIONS: Contrary to other published reports, our results showed no difference in knee flexion angles between genders in a DL task. Males exhibited greater absolute knee flexion in the VJ, which is not surprising given their MVJ heights. Future research investigating lower extremity motion during landing should incorporate appropriately comparable tasks.

The Effects of Temporal Changes in Unanticipated Stimuli on Lower Limb Mechanics during Jump Landings

The Effects of Temporal Changes in Unanticipated Stimuli on Lower Limb Mechanics during Jump Landings

The Relationship between Quadriceps Muscle Force, Knee Flexion, and Anterior Cruciate Ligament Strain in an in Vitro Simulated Jump Landing

Background An instrumented cadaveric knee construct was used to quantify the association between impact force, quadriceps force, knee flexion angle, and anterior cruciate ligament relative strain in simulated unipedal jump landings. Hypothesis Anterior cruciate ligament strain will correlate with impact force, quadriceps force, and knee flexion angle. Study Design Descriptive laboratory study. Methods Eleven cadaveric knees (age, 70.8 [19.3] years; 5 male; 6 female) were mounted in a custom fixture with the tibia and femur secured to a triaxial load cell. Quadriceps, hamstring, and gastrocnemius muscle forces were simulated using pretensioned steel cables (stiffness, 7 kN/cm), and the quadriceps tendon force was measured using a load cell. Mean strain on the anteromedial bundle of the anterior cruciate ligament was measured using a DVRT. With the knee in 25° of flexion, the construct was vertically loaded by an impact force initially directed 4 cm posterior to the knee joint center. Tibiofemoral kinematics was measured using a 3D optoelectronic tracking system. Results The increase in anterior cruciate ligament relative strain was proportional to the increase in quadriceps force (r2 = 0.74; P <. 00001) and knee flexion angle (r2 = 0.88; P <. 00001) but was not correlated with the impact force (r2 = 0.009; P =. 08). Conclusion The increase in knee flexion and quadriceps force during this simulated 1-footed landing strongly influenced the relative strain on the anteromedial bundle of the anterior cruciate ligament. Clinical Relevance These results suggest that even in the presence of knee flexor muscle forces, the increase in quadriceps force required to prevent the knee from flexing during landing can place the anterior cruciate ligament at risk for large strains.

Functional Stability During Jumps And Jump Landings

The notion that lower extremity function is symmetrical is common in the scienfitic literature. In addition, health care professionals often use the uninjured lower extremity as a benchmark for the injured limb during rehabilitation. However, the unilateral nature of injuries may indicate that the assumption of functional symmetry may be false. In addition, differences in injury rates between males and females dictates the need for a gender comparison. PURPOSE To evaluate ground reaction forces and measures of dynamic stability for right and left legs during drop landings and countermovement jumps and subsequent landings. METHODS Eleven healthy males females (age: 22.3±4.0 y, 180.3±7.3 cm, 78.4±9.3kg) and10 healthy females (age: 21.1±1.2 y, 164.6±5.3 cm, 61.0±5.6kg) with no history of lower extremity injury or vestibular disorders participated. Subjects performed two drop jumps from a height of 40cm and two maximum vertical jumps (in random order). Each activity concluded by executing two-footed landings with each foot striking separate force plates (200 Hz). During each landing, subjects were instructed to stabilize as quickly as possible, place their hands on their hips, and hold that position for three seconds. Maximum vertical ground reaction forces during each phase of the jumps and landings, as well as, times to stabilization during landings were calculated for right and left legs. RESULTS Separate two-way ANOVA (side × gender) revealed females took significantly longer to stabilize during drop landings than males [F(1,38)=11.676, p = .002] based on vertical ground reaction forces. More specifically, females required an additional 500ms to become stable. No main effects for side (p > 0.05). No interactions were detected (p > 0.05). CONCLUSION The results indicate that healthy individuals achieve stability with their right and left legs similarly while performing jump tasks. The increased time to stabilization required by females may help explain the increased rate of injury commonly observed in the athletic female population and provides justification for future studies involving dynamic stability and gender differences. Posters Displayed One and one-half hour author presentation times are staggered among authors from 9:30–11:00 a.m. and 11:00 a.m.–12:30 p.m.

Functional Stability During Jumps And Jump Landings

Functional Stability During Jumps And Jump Landings

Lower Extremity Biomechanics Differ in Prepubescent and Postpubescent Female Athletes during Stride Jump Landings

Epidemiological evidence suggests the incidence of injury in female athletes is greater after the onset of puberty and that landing from a jump is a common mechanism of knee injury. This investigation compared lower extremity joint kinematics and joint resultant forces and moments during three types of stride jump (stride jump followed by a static landing; a ballistic vertical jump; and a ballistic lateral jump) between pre- and postpubescent recreational athletes to provide some insight into the increased incidence of injury. Sixteen recreationally active postpubescent women (ages 18–25 years) and 16 recreationally active prepubescent girls (ages 8–11 years) participated in this study. High speed 3D videography and force plate data were used to record each jumper’s performance of the stride jumps, and an inverse dynamic procedure was used to estimate lower extremity joint resultant forces and moments and power. These dependent variables were submitted to a 2 × 3 (Maturation Level × Landing Sequence) MANOVA with repeated measures on the last factor. The findings indicated that postpubescents landed with the knee more extended (4.4°) and had greater extension moments (approximately 30% greater hip and knee extension moments) and powers (40% greater knee power). Further, the post-pubescent athletes had greater knee anterior/posterior forces as well as medio-lateral resultant forces. The differences found between the two groups suggest there may be anatomical and physiological changes with puberty that lead to differences in strength or neuromuscular control which influence the dynamic restraint system in these recreational athletes. A combination of these factors likely plays a role in the increased risk of injury in postpubescent females.