Tibial Shear Force Research Articles

Comparing Anterior Cruciate Ligament Injury Risk Variables Between Unanticipated Cutting and Decelerating Tasks

To examine the relationship between anterior cruciate ligament injury risk factors in unanticipated cutting and decelerating. Three-dimensional kinematics and ground reaction forces were collected on 11 females (22 [2]y, 1.67 [0.08]m, and 68.5 [9.8]kg) during 2 unanticipated tasks. Paired samples t tests were performed to compare dependent variables between tasks. Spearman rank correlation coefficients were calculated to analyze the relationship between peak internal knee adduction moment and peak anterior tibial shear force (ASF) during 2 unanticipated tasks. Significantly greater knee abduction angles, peak knee adduction moments, and peak ASFs were observed during cutting (P ≤ .05). A strong positive correlation existed between decelerating ASF and cutting ASF (ρ = .67), while correlations between decelerating knee adduction moment and cutting knee adduction moment and decelerating ASF and cutting knee adduction moment were not significant. In situations where time management is a necessity and only one task can be evaluated, it may be more appropriate to utilize an unanticipated cutting task rather than an unanticipated deceleration task because of the increased knee adduction moment and ASF. These data can help future clinicians in better designing more effective anterior cruciate ligament injury risk screening methods.

Movement Efficiency Profile Affects Knee Loading Responses to a Controlled Acute Exposure to High Metabolic and Mechanical Training Load

Exposure to acute high training loads (HTL) induces biomechanics associated with knee joint injury. PURPOSE: Determine if individuals with high-risk (HR) and low-risk (LR) biomechanics exhibit different changes in tri-planar knee loading in response to a controlled HTL exposure. METHODS: 43 physically active, healthy, college-aged field or court sport female athletes (n=43; age=20.5±1.6 yrs, height=167.7±7.0 cm, mass=62.8±7.1 kg) were assigned to a LR (n=21) or HR (n=22) movement profile group defined by the landing error scoring system. Peak anterior tibial shear force (ATSF (N•Nbw-1)), internal knee varus (IKVRM), and internal knee external rotation (IKERM) moments (Nm•Nbw-1•m ht-1) were measured during a jump-landing task prior to and after a metabolically and mechanically controlled HTL exposure. Participants completed five sets of treadmill running at a speed (LR:11.1±1.2 km•h-1, HR:11.3±1.0 km•h-1, t =0.702, p>0.05) coincident with 110-120% of their ventilatory threshold (LR:37.1±3.6 ml•kg-1•min-1, HR:37.1±3.6 ml•kg-1•min-1, t =0.072, p>0.05) for five minutes and 10 jump-landings from a 30 cm box half their height from a landing target line. RESULTS: A significant group-by-time interaction was observed for ATSF (F1,41=5.000, p<0.05) The HR group experienced increases in ATSF (HR-Pre-HTL: 0.86±0.10[0.82, 0.90], HR-Post-HTL: 0.90±0.08[0.86,0.93]), whereas the LR group experienced decreases in ATSF (LR-Pre-HTL: 0.82±0.17[0.76,0.90], LR-Post-HTL: 0.79±0.13[0.74,0.85]) from pre-to-post HTL exposure. No significant group-by-time interactions were observed for IKVRM (F1,41=0.648, p>0.05; HR-Pre-HTL: 0.41±0.23[0.31, 0.51], HR-Post-HTL: 0.42±0.22[0.33, 0.52] & LR-Pre-HTL: 0.28±0.14[0.22, 0.34], LR-Post-HTL: 0.25±0.11[0.21, 0.30]) or IKERM (F1,41=0.083, p>0.05; HR-Pre-HTL: 0.21±0.09[0.25,0.17], HR-Post-HTL: 0.17±0.11[0.22,0.12] & LR-Pre-HTL: 0.21±0.09[0.24,0.17], LR-Post-HTL: 0.16±0.08[0.19,0.12]). CONCLUSION: Movement profile has a large effect (d=0.98) on HTL-induced sagittal plane knee loading responses linked to knee joint injury. Individuals with greater movement efficiency appear to be more biomechanically resilient to acute HTL exposure compared to individuals with high-risk biomechanics.

Effects of Magnesium Sources and Levels on Some Tissue Magnesium Concentration and Bone Mechanical Properties in Broiler

This experiment was conducted to determine the effect of inorganic and organic sources and levels of magnesium (Mg) supplementation on plasma, tibia, meat and liver Mg concentration and mechanical properties of bones in broilers. A total of one day old 450 broiler chicks were used and assigned to six experiment groups each having five replicate, randomly. There were 15 birds in each replicates. In the experiment magnesium sulphate (MgSO4) was used as inorganic Mg source and magnesium proteinate was used as organic Mg source. Experimental diets were supplemented provide 0 (control), 0.2 and 0.4 % Mg levels inorganic and organic Mg source of basal ration, experiment period was six weeks. Main effect of Mg source and source x level interaction effect had not significant on plasma, liver, breast and thigh meat Mg concentration (P&gt; 0.05). While treatments did not significant effect on liver, breast and thigh meat Mg concentration, the main effect of Mg levels was significant effect on plasma Mg concentration (P&lt; 0.05). Plasma Mg concentration which were fed with ration added 0.2 and 0.4 % Mg level was higher than the control group. Tibia Ca concentration which were fed with ration added organic*0.2 and 0.4 % Mg levels were higher than the other groups (P&lt; 0.05). Tibia P concentration of organic Mg source fed with the group were higher than the inorganic source (P&lt; 0.05). The highest tibia Mg concentration were found to fed with organic*0.4 % Mg level of group (P&lt;0.05). Tibia shear force and tibia stress which were fed with ration added 0.2 and 0.4 % Mg levels were higher than the control group (P&lt; 0.05).

Effects of dietary supplementation of inorganic, organic or nano zinc forms on performance, eggshell quality, and bone characteristics in laying hens

Abstract This study was conducted to evaluate the efficiency of dietary zinc forms and dosages on egg production performance, egg quality, and bone characteristics in laying hens. Forty-two-week-old, 144 Lohmann LSL-Lite laying hens were allocated to 12 experimental groups in a 4 (forms) × 3 (dosages) factorial arrangement. Four zinc forms including zinc-sulphate and zinc-oxide as inorganic forms, zinc-glycine as organic form and nano zinc-oxide powder as nano form at different dosages (50, 75 and 100 mg per kg diet) were tested. Compared to the inorganic (zinc-sulphate) form, the zinc-glycine supplementation significantly depressed the egg weight, egg mass and feed conversion ratio. The eggshell thickness was significantly decreased by supplementation with nano zinc-oxide. The shear force of tibia was significantly decreased by zinc-glycine or nano zinc-oxide supplemented in the diet when compared to inorganic forms of zinc. On the other hand, the dietary 50 mg/kg dosage of zinc was sufficient for optimum performance and the dietary 75 mg/kg dosage of zinc significantly improved shear force of tibia in laying hens. Tibia zinc content increased with the dietary 100 mg/kg dosage of zinc. The interactions between zinc forms and dosages had a significant effect on egg weight, feed intake, feed conversion ratio, eggshell thickness, shear force and shear stress of bone, and tibia calcium concentration. The highest egg weight and the lowest eggshell thickness were observed for the group fed with nano Zn-oxide at 100 mg/kg in the diet. These results showed that nano zinc form supplementation negatively affects the eggshell thickness and bone mechanical properties. The zinc in nano form may not be suggested for feeding laying hens, but other forms of zinc could be used safely in layer diets.

Acute Effects of Static Stretching of Hamstring on Performance and Anterior Cruciate Ligament Injury Risk During Stop-Jump and Cutting Tasks in Female Athletes.

Ruan, M, Zhang, Q, and Wu, X. Acute effects of static stretching of hamstring on performance and anterior cruciate ligament injury risk during stop-jump and cutting tasks in female athletes. J Strength Cond Res 31(5): 1241–1250, 2017—There is limited research investigating antagonist stretch. The purpose of this study was to evaluate the influence of static stretching of hamstrings (SSH) on performance and anterior cruciate ligament (ACL) injury risk during stop-jump and 180° cutting tasks. Twelve female college athletes (age 20.8 ± 0.7 years; height 1.61 ± 0.05 m; mass 54.25 ± 4.22 kg) participated in this study. Subjects performed stop-jump and 180° cutting tasks under 2 conditions: after warm-up with 4 × 30 seconds SSH or after warm-up without SSH. Three-dimensional kinematic and kinetic data as well as electromyography of biceps femoris, rectus femoris, vastus medialis, and gastrocnemius medialis were collected during testing. Static stretching of hamstrings significantly enhanced jump height by 5.1% (p = 0.009) but did not change the takeoff speed of cutting. No significant changes in peak knee adduction moment or peak anterior tibia shear force were observed with SSH regardless of the task. The peak lateral tibia shear force during cutting was significantly (p = 0.036) reduced with SSH. The co-contraction of hamstring and quadriceps during the preactivation (stop-jump: p = 0.04; cutting: p = 0.05) and downward phases (stop-jump: p = 0.04; cutting: p = 0.05) was significantly reduced after SSH regardless of the task. The results suggest that SSH enhanced the performance of stop-jump because of decreased co-contraction of hamstring and quadriceps but did not change the performance of cutting. In addition, SSH did not increase ACL injury risk during stop-jump and cutting tasks and even reduced medial-lateral knee loading during cutting.

Increasing hip and knee flexion during a drop-jump task reduces tibiofemoral shear and compressive forces: implications for ACL injury prevention training

ABSTRACTAlthough most ACL injury prevention programmes encourage greater hip and knee flexion during landing, it remains unknown how this technique influences tibiofemoral joint forces. We examined whether a landing strategy utilising greater hip and knee flexion decreases tibiofemoral anterior shear and compression. Twelve healthy women (25.9 ± 3.5 years) performed a drop-jump task before and after a training session (10–15 min) that emphasised greater hip and knee flexion. Peak tibiofemoral anterior shear and compressive forces were calculated using an electromyography (EMG)-driven knee model that incorporated joint kinematics, EMG and participant-specific muscle volumes and patella tendon orientation measured using magnetic resonance imaging (MRI). Participants demonstrated a decrease in peak anterior tibial shear forces (11.1 ± 3.3 vs. 9.6 ± 2.7 N · kg−1; P = 0.008) and peak tibiofemoral compressive forces (68.4 ± 7.6 vs. 62.0 ± 5.5 N · kg−1; P = 0.015) post-training. The decreased peak anterior tibial shear was accompanied by a decrease in the quadriceps anterior shear force, while the decreased peak compressive force was accompanied by decreased ground reaction force and hamstring forces. Our data provide justification for injury prevention programmes that encourage greater hip and knee flexion during landing to reduce tibiofemoral joint loading.

Changing Sagittal-Plane Landing Styles to Modulate Impact and Tibiofemoral Force Magnitude and Directions Relative to the Tibia.

Ground reaction force (GRF) and tibiofemoral force magnitudes and directions have been shown to affect anterior cruciate ligament loading during landing. However, the kinematic and kinetic factors modifying these 2 forces during landing are unknown. To clarify the intersegmental kinematic and kinetic links underlying the alteration of the GRF and tibiofemoral force vectors secondary to changes in the sagittal-plane body position during single-legged landing. Crossover study. Laboratory. Twenty recreationally active participants (age = 23.4 ± 3.6 years, height = 171.0 ± 9.4 cm, mass = 73.3 ± 12.7 kg). Participants performed single-legged landings using 3 landing styles: self-selected landing (SSL), body leaning forward and landing on the toes (LFL), and body upright with flat-footed landing (URL). Three-dimensional kinetics and kinematics were recorded. Sagittal-plane tibial inclination and knee-flexion angles, GRF magnitude and inclination angles relative to the tibia, and proximal tibial forces at peak tibial axial forces. The URL resulted in less time to peak tibial axial forces, smaller knee-flexion angles, and greater magnitude and a more anteriorly inclined GRF vector relative to the tibia than did the SSL. These changes led to the greatest peak tibial axial and anterior shear forces in the URL among the 3 landing styles. Conversely, the LFL resulted in longer time to peak tibial axial forces, greater knee-flexion angles, and reduced magnitude and a more posteriorly inclined GRF vector relative to the tibia than the SSL. These changes in LFL resulted in the lowest peak tibial axial and largest posterior shear forces among the 3 landing styles. Sagittal-plane intersegmental kinematic and kinetic links strongly affected the magnitude and direction of GRF and tibiofemoral forces during the impact phase of single-legged landing. Therefore, improving sagittal-plane landing mechanics is important in reducing harmful magnitudes and directions of impact forces on the anterior cruciate ligament.

Strain Response of the Anterior Cruciate Ligament to Uniplanar and Multiplanar Loads During Simulated Landings

Background: Despite basic characterization of the loading factors that strain the anterior cruciate ligament (ACL), the interrelationship(s) and additive nature of these loads that occur during noncontact ACL injuries remain incompletely characterized. Hypothesis: In the presence of an impulsive axial compression, simulating vertical ground-reaction force during landing (1) both knee abduction and internal tibial rotation moments would result in increased peak ACL strain, and (2) a combined multiplanar loading condition, including both knee abduction and internal tibial rotation moments, would increase the peak ACL strain to levels greater than those under uniplanar loading modes alone. Study Design: Controlled laboratory study. Methods: A cadaveric model of landing was used to simulate dynamic landings during a jump in 17 cadaveric lower extremities (age, 45 ± 7 years; 9 female and 8 male). Peak ACL strain was measured in situ and characterized under impulsive axial compression and simulated muscle forces (baseline) followed by addition of anterior tibial shear, knee abduction, and internal tibial rotation loads in both uni- and multiplanar modes, simulating a broad range of landing conditions. The associations between knee rotational kinematics and peak ACL strain levels were further investigated to determine the potential noncontact injury mechanism. Results: Externally applied loads, under both uni- and multiplanar conditions, resulted in consistent increases in peak ACL strain compared with the baseline during simulated landings (by up to 3.5-fold; P ≤ .032). Combined multiplanar loading resulted in the greatest increases in peak ACL strain (P < .001). Degrees of knee abduction rotation (R2 = 0.45; β = 0.42) and internal tibial rotation (R2 = 0.32; β = 0.23) were both significantly correlated with peak ACL strain (P < .001). However, changes in knee abduction rotation had a significantly greater effect size on peak ACL strain levels than did internal tibial rotation (by ~2-fold; P < .001). Conclusion: In the presence of impulsive axial compression, the combination of anterior tibial shear force, knee abduction, and internal tibial rotation moments significantly increases ACL strain, which could result in ACL failure. These findings support multiplanar knee valgus collapse as one the primary mechanisms of noncontact ACL injuries during landing. Clinical Relevance: Intervention programs that address multiple planes of loading may decrease the risk of ACL injury and the devastating consequences of posttraumatic knee osteoarthritis.

Effects of 1.25-Dihydroxycholecalciferol and Hydroalcoholic Extract of Withania Coagulans Fruit on Bone Mineralization and Mechanical and Histological Properties of Male Broiler Chickens

An experiment was conducted to investigate the effects of hydroalcoholic extract of Withania coagulans (WC) fruit and 1.25-dihydroxycholecalciferol (1.25-(OH)2 D3) on bone mineralization, mechanical and histological properties of male broiler chickens at 21 and 42 d of age. A total of six hundred male day-old Ross 308 broiler chickens were randomly distributed according to a completely randomized experimental design in a 2×3×2 factorial arrangement with 12 treatments of five replicates of 10 birds each. Treatments consisted of two basal diets (positive control with adequate Ca level and negative control with 30% less Ca), three levels of WC (0, 100, or 200 mg/kg diet), and two levels of 1.25-(OH)2 D3 (0 or 0.5 µg/kg diet). Birds were housed in floor pens. The diets were fed ad libitum from one to 42 days of age. On day 21 and 42, one bird per replicate was sacrificed and its tibiae were removed. Both Ca and P retention increased when dietary Ca level was reduced (p<0.001). The addition of 200 mg WC/kg to positive control diet increased Ca retention (p<0.01). Except for tibia diameter, no significant main effects of experimental treatments were observed on tibia physical characteristics or on bone mineralization. The diet with 30% Ca reduction decreased tibia diameter at 42 days of age (p<0.05). The dietary addition of 1.25-(OH)2 D3 increased tibia fracture energy, width of tibia mineralized zone, and serum Ca at 42 days of age (p<0.05). At 21 days of age, supplementation of 100 mg WC/kg increased cortical thickness (p<0.05). At 42 days of age, supplementation of 100 mg WC/kg increased tibia shear force (p<0.05) and fracture energy (p<0.01). The results of this experiment showed that supplementation of 100 mg/kg hydroalcoholic extract of WC fruit increased tibia cortical thickness, shear force, and fracture energy.

Lower Extremity Injuries of Volleyball Players During Moving Spike Landing

Volleyball games worldwide have developed into aggressive volleyball games involving various types of attacking techniques. Among the various attacking techniques, the moving spike is most likely to cause body imbalance. When volleyball players perform a moving spike, to acquire more time and space when hitting the ball, they typically change their attack angle, timing, and position continually. Previous studies on run-up and landing have typically focused on vertical or forward landing. However, in actual sports scenarios, the directions of an attack landing may vary according to situations. To clarify the various sports injuries of volleyball players may sustain from landing after performing a moving spike, 10 male open level volleyball players were recruited from universities to perform 72-cm moving spike landing maneuvers. In the experiment, 11 digital motion cameras were used for 3D image capture, reflective markers were applied to track the locations of the body joints, and two AMTI 3D force plates were used to collect ground reaction force generated by the landing. The results revealed that the participant with the highest risk of sustaining a cruciate ligament tear was 172-cm tall and weighed 63 kg. The negative tibial shear force and horizontal reaction force generated from performing a moving spike were deduced to cause collateral ligament injuries to the participants who had played volleyball for 9–10 yrs. Therefore, we deduced that when volleyball players continually perform moving spike landing maneuvers without appropriate cushioning maneuvers and gear protection during training or competition, their collateral ligaments may develop chronic tendinitis.

Research-Based and Clinical Considerations for Effective Neuromuscular Training to Prevent Second Anterior Cruciate Ligament Injury

The second anterior cruciate ligament (ACL) injury after ACL reconstruction occurs at reported rates, ranging from 5-20 times greater than that of the primary injury, and results in significantly poorer patient outcomes. In athletes, most of the second ACL injuries occur within the first 2 years of return to sport. Significant functional impairments and deficits in neuromuscular control are frequently reported up to 2 years postreconstruction. Neuromuscular deficit-targeted neuromuscular training (NMT) alters high-risk biomechanics and reduces rates of primary ACL injury. Its efficacy in ACL-injured subjects is currently unknown. External loads during dynamic motion, specifically knee abduction moment, internal tibial rotation moment, and proximal anterior tibial shear force, especially in the lateral compartment, increase ACL strain. These factors are reportedly influenced by modifiable and nonmodifiable factors. ACL reconstruction subjects pose a unique challenge to clinicians and researchers due to the numerous confounding factors in identifying and addressing their risk of reinjury. However, they also may provide clinicians and researchers with a great deal of accessible, highly pertinent clinical, anatomical, and biomechanical information in the forms of medical images, charts, and rehabilitation notes. Thorough determination of postoperative biomechanical impairments, modifiable and nonmodifiable risk factors, and the effects of NMT on these factors aids in eventual reduction of second ACL injury rates. A properly structured and executed large-scale, multicenter trial to evaluate the biomechanical efficacy of NMT in the context of these factors would be invaluable both clinically and academically.

Individuals with chronic ankle instability exhibit altered landing knee kinematics: Potential link with the mechanism of loading for the anterior cruciate ligament

BackgroundAlterations in sagittal plane landing biomechanics in the lower extremity have been observed within the chronic ankle instability (CAI) population. Interestingly, a potential link between the risk of anterior cruciate ligament (ACL) injury and ankle sprain history has been proposed. However, it is not known if the observed biomechanical changes associated with CAI could mimic factors related to the mechanism of ACL injury. We investigated the influence of CAI on anterior tibial shear force (ATSF), lower extremity sagittal plane kinematics, and posterior ground reaction force (GRF) in a jump landing task. MethodsNineteen participants with CAI and 19 healthy control participants performed a vertical stop jump. Peak ATSF was calculated during the first landing of the stop jump, with sagittal-plane kinematics and posterior GRF measured at peak ATSF. Independent t-tests, multiple linear regression, and Pearson bivariate correlation were used for statistical analysis. FindingsParticipants with CAI demonstrated less knee flexion at peak ATSF compared to the controls (P=.026). No group-differences were found for peak ATSF or the other biomechanical variables. Knee flexion was moderately correlated with peak ATSF (r=−0.544, P=.008); however, the contributing factor that most explained the variance in ATSF was posterior GRF (R2=0.449; P=.002) in the CAI group. InterpretationOur findings indicate that the CAI group may be exhibiting altered knee function during functional movement. Screening knee movement patterns in individuals with CAI may help develop preventative measures for future joint injury throughout the kinetic chain.

The relationship of kinematics of trunk and knee in sagittal plane with anterior tibia shear force during single leg landing

The relationship of kinematics of trunk and knee in sagittal plane with anterior tibia shear force during single leg landing

Neuromuscular fatigue alters postural control and sagittal plane hip biomechanics in active females with anterior cruciate ligament reconstruction.

Background:Females with history of anterior cruciate ligament (ACL) injury and subsequent ligament reconstruction are at high risk for future ACL injury. Fatigue may influence the increased risk of future injury in females by altering lower extremity biomechanics and postural control.Hypothesis:Fatigue will promote lower extremity biomechanics and postural control deficits associated with ACL injury.Study Design:Descriptive laboratory study.Methods:Fourteen physically active females with ACL reconstruction (mean age, 19.64 ± 1.5 years; mean height, 163.52 ± 6.18 cm; mean mass, 62.6 ± 13.97 kg) volunteered for this study. Postural control and lower extremity biomechanics were assessed in the surgical limb during single-leg balance and jump-landing tasks before and after a fatigue protocol. Main outcome measures were 3-dimensional hip and knee joint angles at initial contact, peak angles, joint angular displacements and peak net joint moments, anterior tibial shear force, and vertical ground reaction force during the first 50% of the loading phase of the jump-landing task. During the single-leg stance task, the main outcome measure was center of pressure sway speed.Results:Initial contact hip flexion angle decreased (t = −2.82, P = 0.01; prefatigue, 40.98° ± 9.79°; postfatigue, 36.75° ± 8.61°) from pre- to postfatigue. Hip flexion displacement (t = 2.23, P = 0.04; prefatigue, 45.19° ± 14.1°; postfatigue, 47.48° ± 14.21°) and center of pressure sway speed (t = 3.95, P < 0.05; prefatigue, 5.18 ± 0.96 cm/s; postfatigue, 6.20 ± 1.72 cm/s) increased from pre- to postfatigue. There was a trending increase in hip flexion moment (t = 2.14, P = 0.05; prefatigue, 1.66 ± 0.68 Nm/kg/m; postfatigue, 1.91 ± 0.62 Nm/kg/m) from pre- to postfatigue.Conclusion:Fatigue may induce lower extremity biomechanics and postural control deficits that may be associated with ACL injury in physically active females with ACL reconstruction.Clinical Relevance:Rehabilitation and maintenance programs should incorporate activities that aim to improve muscular endurance and improve the neuromuscular system’s tolerance to fatiguing exercise in efforts to maintain stability and safe landing technique during subsequent physical activity.

Anterior cruciate ligament injury alters preinjury lower extremity biomechanics in the injured and uninjured leg: the JUMP-ACL study

BackgroundInformation as to how anterior cruciate ligament (ACL) injury and reconstructive surgery (ACLR) alter lower extremity biomechanics may improve rehabilitation and return to play guidelines, reducing the risk for repeat...

The effects of dietary 1, 25-dihydroxycholecalciferol and hydroalcoholic extract of Withania somnifera root on bone mineralisation, strength and histological characteristics in broiler chickens

1. This study was carried out to investigate the effects of 1, 25-dihydroxycholecalciferol (1, 25 (OH)2 D3) and a hydroalcoholic extract of Withania somnifera (WS) root on performance, mineral retention, bone mineralisation, bone mechanical and bone histological characteristics of broiler chicks.2. A 2 × 3 × 2 factorial experiment consisted of a positive control diet with adequate Ca and a negative control diet (Ca concentration reduced by 30%), three concentrations of WS (0, 75 and 150 mg/kg diet), and two concentrations of 1, 25 (OH)2 D3 (0 and 0.5 μg/kg diet).3. A total of 600 male one-d-old Ross 308 broiler chicks were randomly distributed into 60 floor pens, with 10 birds each. Each treatment was replicated 5 times (50 birds). Diets were given ad libitum from one to 42 d of age. On d 21 and 42, one bird per replicate was killed and tibiae were removed.4. Dietary treatments did not affect feed intake and feed conversion. The maximum body weight gain (2475 g) was noted in birds fed on a diet adequate in Ca and supplemented with 75 mg/kg WS.5. The Ca and P retentions were significantly higher in birds that were given a diet with 30% less Ca. Supplementation of 150 mg/kg WS significantly improved Ca retention in birds receiving a negative control compared to those given a positive control diet (83.0% vs. 66.3%). Ca retention was significantly improved with the addition of 0.5 μg/kg 1, 25 (OH)2 D3 to the diet containing 75 mg/kg WS, regardless of dietary Ca concentration (79.5 vs. 73.3 and 77.9 vs. 68.9).6. On d 21, birds that received WS had significantly higher tibia Ca compared to those of controls. No significant effects on tibia Ca were noted at 42 d. Birds given a negative control diet supplemented with 75 mg/kg WS and 0.5 μg/kg 1, 25 (OH)2 D3 displayed a similar tibia Ca compared to those given only 150 mg/kg WS. Dietary supplementation of 1, 25 (OH)2 D3 significantly increased tibia Ca and tibial mineralised zone width in birds at 42 d of age.7. Tibia shear force and stiffness were significantly increased by supplementation of WS. Administration of 1, 25 (OH)2 D3 resulted in a significantly lower width of the proliferative zone at 21 d of age. Reduction of the Ca supply significantly reduced the mineralised zone and cortical thickness at this age.8. The present study showed that WS supplementation improved Ca retention, bone calcification and mechanical properties with no adverse effects on performance. Also, synergistic effects of WS and 1, 25 (OH)2 D3 were observed on Ca retention and bone calcification.

Hamstrings Stiffness and Landing Biomechanics Linked to Anterior Cruciate Ligament Loading

Greater hamstrings stiffness is associated with less anterior tibial translation during controlled perturbations. However, it is unclear how hamstrings stiffness influences anterior cruciate ligament (ACL) loading mechanisms during dynamic tasks. To evaluate the influence of hamstrings stiffness on landing biomechanics related to ACL injury. Cross-sectional study. Research laboratory. A total of 36 healthy, physically active volunteers (18 men, 18 women; age = 23 ± 3 years, height = 1.8 ± 0.1 m, mass = 73.1 ± 16.6 kg). Hamstrings stiffness was quantified via the damped oscillatory technique. Three-dimensional lower extremity kinematics and kinetics were captured during a double-legged jump-landing task via a 3-dimensional motion-capture system interfaced with a force plate. Landing biomechanics were compared between groups displaying high and low hamstrings stiffness via independent-samples t tests. Hamstrings stiffness was normalized to body mass (N/m·kg(-1)). Peak knee-flexion and -valgus angles, vertical and posterior ground reaction forces, anterior tibial shear force, internal knee-extension and -varus moments, and knee-flexion angles at the instants of each peak kinetic variable were identified during the landing task. Forces were normalized to body weight, whereas moments were normalized to the product of weight and height. Internal knee-varus moment was 3.6 times smaller in the high-stiffness group (t22 = 2.221, P = .02). A trend in the data also indicated that peak anterior tibial shear force was 1.1 times smaller in the high-stiffness group (t22 = 1.537, P = .07). The high-stiffness group also demonstrated greater knee flexion at the instants of peak anterior tibial shear force and internal knee-extension and -varus moments (t22 range = 1.729-2.224, P < .05). Greater hamstrings stiffness was associated with landing biomechanics consistent with less ACL loading and injury risk. Musculotendinous stiffness is a modifiable characteristic; thus exercises that enhance hamstrings stiffness may be important additions to ACL injury-prevention programs.

Preferential Loading of the ACL Compared With the MCL During Landing

Background: Strong biomechanical and epidemiological evidence associates knee valgus collapse with isolated, noncontact anterior cruciate ligament (ACL) injuries. However, a concomitant injury to the medial collateral ligament (MCL) would be expected under valgus collapse, based on the MCL’s anatomic orientation and biomechanical role in knee stability. Purpose/Hypothesis: The purpose of this study was to investigate the relative ACL to MCL strain patterns during physiological simulations of a wide range of high-risk dynamic landing scenarios. We hypothesized that both knee abduction and internal tibial rotation moments would generate a disproportionate increase in the ACL strain relative to the MCL strain. However, the physiological range of knee abduction and internal tibial rotation moments that produce ACL injuries are not of sufficient magnitude to compromise the MCL’s integrity consistently. Study Design: Controlled laboratory study. Methods: A novel in sim approach was used to test our hypothesis. Seventeen cadaveric lower extremities (mean age, 45 ± 7 years; 9 female and 8 male) were tested to simulate a broad range of landings after a jump under anterior tibial shear force, knee abduction, and internal tibial rotation at 25° of knee flexion. The ACL and MCL strains were quantified using differential variable reluctance transducers. An extensively validated, detailed finite element model of the lower extremity was used to help better interpret experimental findings. Results: Anterior cruciate ligament failure occurred in 15 of 17 specimens (88%). Increased anterior tibial shear force and knee abduction and internal tibial rotation moments resulted in significantly higher ACL:MCL strain ratios (P < .05). Under all modes of single-planar and multiplanar loading, the ACL:MCL strain ratio remained greater than 1.7, while the relative ACL strain was significantly higher than the relative MCL strain (P < .01). Relative change in the ACL strain was demonstrated to be significantly greater under combined multiplanar loading compared with anterior tibial shear force (P = .016), knee abduction (P = .018), and internal tibial rotation (P < .0005) moments alone. Conclusion: While both the ACL and the MCL resist knee valgus during landing, physiological magnitudes of the applied loads leading to high ACL strain levels and injuries were not sufficient to compromise the MCL’s integrity. Clinical Relevance: A better understanding of injury mechanisms may provide insight that improves current risk screening and injury prevention strategies. Current findings support multiplanar knee valgus collapse as a primary factor contributing to a noncontact ACL injury.

The Effects of Three Jump Landing Tasks on Kinetic and Kinematic Measures: Implications for ACL Injury Research

This study compared the biomechanics of jump landing tasks used in ACL research. Twenty-seven female subjects performed a drop landing (DL), a drop landing with a vertical jump (DVJ), and a forward jump landing with a vertical jump (FVJ). We hypothesized that as one progressed from the drop landing through the forward-vertical jump that the kinematic and kinetic demands would increase, with progressively increasing knee and hip forces, moments, and angles on landing. Separate repeated-measures ANOVAs were performed. The FVJ had the highest peak anterior tibial shear force (p < 0.001), hip flexion angle (p < 0.001), knee flexion moment (p < 0.001), and knee valgus moment (p < 0.001). The DL had the smallest knee flexion angle (p = 0.001) and hip flexion angle (p < 0.001), while the DVJ had the lowest knee valgus moment (p < 0.001). These results indicate that seemingly minor variations between jump landing tasks may influence landing biomechanics. Caution should be used when comparing studies using different tasks.

Lower Extremity Energy Absorption and Biomechanics During Landing, Part I: Sagittal-Plane Energy Absorption Analyses

Eccentric muscle actions of the lower extremity absorb kinetic energy during landing. Greater total sagittal-plane energy absorption (EA) during the initial impact phase (INI) of landing has been associated with landing biomechanics considered high risk for anterior cruciate ligament (ACL) injury. We do not know whether groups with different INI EA magnitudes exhibit meaningful differences in ACL-related landing biomechanics and whether INI EA might be useful to identify ACL injury-risk potential. To compare biomechanical factors associated with noncontact ACL injury among sagittal-plane INI EA groups and to determine whether an association exists between sex and sagittal-plane INI EA group assignment to evaluate the face validity of using sagittal-plane INI EA to identify ACL injury risk. Descriptive laboratory study. Research laboratory. A total of 82 (41 men, 41 women; age = 21.0 ± 2.4 years, height = 1.74 ± 0.10 m, mass = 70.3 ± 16.1 kg) healthy, physically active individuals volunteered. We assessed landing biomechanics using an electromagnetic motion-capture system and force plate during a double-legged jump-landing task. Total INI EA was used to group participants into high, moderate, and low tertiles. Sagittal- and frontal-plane knee kinematics; peak vertical and posterior ground reaction forces (GRFs); anterior tibial shear force; and internal hip extension, knee extension, and knee varus moments were identified and compared across groups using 1-way analyses of variance. We used a χ (2) analysis to compare male and female representation in the high and low groups. The high group exhibited greater knee-extension moment and posterior GRFs than both the moderate (P < .05) and low (P < .05) groups and greater anterior tibial shear force than the low group (P < .05). No other group differences were noted. Women were not represented more than men in the high group (χ(2) = 1.20, P = .27). Greater sagittal-plane INI EA likely indicates greater ACL loading, but it does not appear to influence frontal-plane biomechanics related to ACL injury. Women were not more likely than men to demonstrate greater INI EA, suggesting that quantification of sagittal-plane INI EA alone is not sufficient to infer ACL injury-risk potential.