Landing Forces Research Articles

Kinetic and Kinematic Assessment of the Band-Assisted Countermovement Jump.

Fernandes, JFT, Arede, J, Clarke, H, Garcia-Ramos, A, Perez-Castilla, A, Norris, JP, Wilkins, CA, and Dingley, AF. Kinetic and kinematic assessment of the band-assisted countermovement jump. J Strength Cond Res 37(8): 1588-1593, 2023-This study sought to elucidate kinetic and kinematic differences between unloaded and band-assisted countermovement jumps (CMJs). In a randomized order, 20 healthy subjects (mass 84.5 ± 18.6 kg) completed 3 repetitions of CMJs across 3 conditions: unloaded (at body mass), low, and moderate band (8.4 ± 1.9 and 13.3 ± 3.3 kg body mass reduction, respectively). For all repetitions, a force platform and linear position transducer were used to record and calculate kinetic and kinematic data. Body mass was significantly different between the unloaded, low, and moderate band conditions ( p < 0.05). Peak velocity, absolute peak, and mean force and movement duration displayed a trend that was mostly related to the condition (i.e., unloaded > low > moderate) ( p < 0.05). The opposing trend (i.e., moderate > low > unloaded) was generally observed for relative peak and mean force, reactive strength index modified, and flight time ( p < 0.05). No differences were observed for mean velocity, movement duration, and absolute and relative landing forces ( p > 0.05). The use of band assistance during CMJs can alter force, time, and velocity variables. Practitioners should be aware of the potential positive and negative effects of band assistance during CMJs.

Multidirectional Landing Kinetics, Stabilisation Times, and Associated Isokinetic Knee Torques of High-Level Female Netball Players

Netball is a multidirectional sport afflicted by a relatively high proportion of lower-extremity injuries. The purpose of this study was to evaluate the relationships between multidirectional landing stabilisation times, unilateral landing kinetics, and isokinetic knee joint torques in elite female netball players. A total of 15 players volunteered for the study (age: 20.80 ± 1.42 years; height: 1.75 ± 0.06 m; body mass: 71.69 ± 13.58 kg). All players completed a minimum of 25 multidirectional, unilateral landing tasks, as well as isokinetic dynamometry, to evaluate both concentric and eccentric knee flexion and extension torques. Players showed rapid stabilisation times upon landing (2.02 ± 0.69 s) coupled with moderately high landing forces (4.06 ± 0.82 BWs) and comparatively low isokinetic knee extensor (2.01 ± 0.49 N·m·kg−1) and flexor (1.33 ± 0.30 N·m·kg−1) strength. Moderate positive (r¯ = 0.61) and negative (r¯ = −0.63) correlations were observed between peak isokinetic knee joint strength and the force–time waveform during the early and late weight-acceptance phases of multidirectional jump landings prior to stabilisation. Multidirectional landing kinetics can potentially provide valuable insights related to TTS and possible associations with isolated knee joint musculature during the weight-acceptance phase of jump landings.

Evolution of gliding in squirrel-related rodents (Mammalia: Sciuromorpha) did not induce a new optimum on the cortical thickness of the scapular glenoid fossa.

Many of the squirrel-related rodents (i.e., Sciuromorpha) are tree-dwelling species known to be very agile climbers. This taxon also includes the most diverse clade of gliding (aerial) mammals that likely descended from a non-gliding arboreal ancestor and evolved a patagium (i.e., a gliding membrane) to increase gliding performance. Glides can cover distances of up to 150 m and landing is typically accomplished by stalling the patagium to reduce impact velocity. It remains unclear if this behavior suffices to keep stresses on the locomotor apparatus similar to those experienced by their arboreal relatives or whether gliding behavior increases landing forces and stresses. The sparsely available support reaction force data are ambiguous, but bone microstructure is highly adaptable to changes in loading regime and likely provides insights into this question. Using μCT scans, we compared the cortical thickness of the glenoid fossa of the shoulder joint between arboreal and aerial Sciuromorpha using evolutionary model comparison, while also accounting for regional differences of the glenoid fossa. We did not find any differences between these locomotor behaviors, irrespective of the glenoid region. These findings agree with previous analyses of the microstructure of the femur in Sciuromorpha. We discuss different aspects that could explain the similarity in cortical thickness. According to our analysis of glenoid cortical thickness the loading regime appears not to have changed after the evolution of gliding locomotion, likely due to adjustments in landing performance.

Effects of jump height on forelimb landing forces in border collies.

The objective of this study was to evaluate the effects of jump height on the landing forces of dogs. Client-owned Border Collies experienced in agility competition, n = 9. The study involved client owned border collies with the same AKC standard jump height of 20 inches and preferred height of 16 inches. Standard height is based upon the height of the dog at the withers, with preferred height referred to as reduction in jump height by one level due to injury or age. An AKC regulation bar jump was placed over a previously validated pressure sensitive walkway (PSW). The peak force (%BW) and peak contact pressure (kPa) of the leading and trailing forelimbs were evaluated for all dogs. There was no significant difference in landing force between the two jump heights for either peak force as a percentage of body weight or peak contact pressure when evaluated in both leading and trailing forelimbs. Our findings demonstrated no significant difference in active landing forces of peak contact pressure and peak force on the forelimbs of dogs when jumping at a standard jump height vs. a preferred jump height when controlling for velocity in dogs performing a single running bar jump. These results suggest that the recommendation of decreasing jump height for older animals or injured animals may not provide a significant decrease in the impact on the forelimbs. It is likely that other factors contribute to the total forelimb kinematics picture during competition. Veterinarians and trainers should consider additional ways to decrease impact for canine athletes as they recover from injury.

A comparison of protocols for measuring forces during landing on competition mats in gymnastics

During apparatus dismounts gymnasts land from up to 4 m above the landing surface. The gymnast needs to withstand high impact forces and the use of landing mats allows gymnasts to attenuate the forces with their landing strategy and interaction with the landing mats. Competition landings from various gymnastics apparatus involve the use of a 200 mm thick landing mat, with an additional 100 mm thick mat placed on top. The purpose of this research was to investigate the experimental protocols for measuring forces using force platforms during landings on competition mats. Three experimental protocols were compared, each of which used a force platform underneath landing mats in various set-ups. In Protocol 1 the mats were placed directly onto the force platform; in Protocol 2 the mats were placed on an enlarged raised extension; in Protocol 3 smaller mats were used with the extension. Differences between the vertical landing velocities calculated from kinematic data and from force platform data were used to assess how much impulse was transferred to the force platform in each of the protocols. Protocol 3 was the preferred method for collecting landing forces and resulted in a mean percentage velocity absolute difference of less than 2% for both one-mat and two-mat conditions. This study demonstrates the importance of keeping the landing mats clear of the force platform surroundings during the whole of the landing phase.

The Ecological Validity of Countermovement Jump to On-Court Asymmetry in Basketball.

Jump-based asymmetry is often used as an indicator of sport performance and may be used to discern injury susceptibility. Due to task specificity, however, countermovement jump asymmetry may not be representative of on-court asymmetry. As such, we assessed the association between countermovement jump asymmetry and on-court impact asymmetry metrics (n=3, and n=4, respectively) using linear regressions (α=0.05). Fifteen female basketball athletes completed countermovement jump and on-court sessions across a competitive season. A significant negative association was found between peak landing force asymmetry and both overall and medium acceleration on-court asymmetry (b=-0.1, R 2 =0.08, p<0.001; b=-0.1, R 2 =0.11, p<0.001, respectively), as well as between peak propulsive force asymmetry and on-court medium acceleration asymmetry (b=-0.24, R 2 =0.04, p=0.01). Alternatively, both peak landing and peak propulsive force asymmetry were significantly positively associated with on-court high acceleration asymmetry (b=0.17, R 2 =0.08, p<0.001; b=0.35, R 2 =0.02, p=0.04, respectively). While some overlap may exist, countermovement jump and on-court impact asymmetry appear to be independent. Thus, sport-specific monitoring may be necessary to adequately monitor injury susceptibility using asymmetry.

Kinetic and Kinematic Characteristics of Setting Motions in Female Volleyball Players

While being an integral part of both the offensive and defensive segments of the game, the biomechanical parameters of setting motions remain understudied in the scientific literature. Thus, the purpose of the present study was to examine differences in kinetic and kinematic characteristics between: (a) three types of setting motions (i.e., front, middle, back); (b) two types of setting approaches (i.e., stationary, step-in); and (c) proficient (PRO) and non-proficient (N-PRO) volleyball players. Twenty recreationally active females performed five stationary and five step-in setting approaches to Zone 4–2 in a randomized order. Uni-dimensional force plate sampling at 1000 Hz and high-definition camera recording at 30 fps were used to obtain kinetic and kinematic variables of interest. The total number of setting attempts performed by each subject was 30, accounting for a grand total of 600 attempts. PRO setters had less knee flexion, shoulder flexion, and ankle dorsiflexion at the initial concentric phase of the volleyball setting motion when compared to the N-PRO setters. Moreover, significantly greater peak concentric and landing forces, impulse, rate of force development, and vertical jump height were observed for PRO setters compared to N-PRO setters, while no significant differences were found between different setting targets and approaches.

Estimation of Resultant Airframe Forces for a Variable Pitch Fan Operating in Reverse Thrust Mode

AbstractThe resultant forces with a reverse thrust variable pitch fan (VPF) during the aircraft landing run are computed from the installed reverse thrust flow field obtained from an airframe-engine-VPF research model. The research model features a reverse flow capable VPF design in a future, geared, high-bypass ratio 40,000 lbf engine as installed onto a twin-engine airframe in landing configuration, complete with a rolling ground plane to mimic the runway. The reverse thrust flow field during the aircraft landing run is obtained from the three-dimensional RANS/URANS solutions of the model. The evolution of the installed dynamic reverse thrust flow field is characterized by the interaction of the VPF-induced reverse flow with the freestream. Several flow features like reverse flow wash-down by the freestream, external swirling helical flow development, pylon flow obstruction, 180 deg flow turn into the engine, subsequent separated flows, wake interactions, and multipass recirculating flows are observed. The resultant airframe forces due to the reverse thrust flow field are estimated by adaptations of momentum-based far-field and near-field methods. In the active thrust reverser engagement regime of 140 to 40 knots, the VPF generates a sufficient axial airframe decelerating force in the range of 45% to 8% of maximum takeoff thrust. A drag decomposition study and a notional “blocked-fan” analysis are described to understand the stack-up of the axial decelerating force. Additionally, the resultant force has a landing speed-dependent lateral force component because of the pylon obstruction-induced flow nonuniformity. A beneficial downforce component due to upward deflection of streamlines is also observed. The quantification of the resultant forces from the baseline installed airframe-engine-VPF reverse thrust flow field is a necessary step to explore the feasibility of the VPF reverse thrust system for future efficient turbofan architectures, understand force generation mechanisms, and to identify areas for subsequent design improvement.

FORÇA EXPLOSIVA DOS MEMBROS INFERIORES NO EXERCÍCIO DE PULAR CORDA APLICADO ÀS CRIANÇAS E ADOLESCENTES

ABSTRACT Introduction: The physical health of children and adolescents is directly related to school physical training quality. The improvement of adult sports effectiveness results from a concise protocol with standardized exercises. Rope skipping exercise lacks kinematic studies applied to children and adolescents. Objective: Provide a theoretical reference for jump rope exercise training for children and adolescents. Methods: Eight children aged six to eight years old were recruited to jump at a frequency of 80 and 120 jumps per minute controlled by a metronome. The technique was divided into three stages: impulse, suspension, and landing. Control in the knee joint exoskeleton balance was investigated by computerized baropodometry with differentiation of rotational angular velocity by rotational angular acceleration via Butterworth filter. After noise cleaning and multiplication, an adjustable amplification factor returned to the inlet with inertial compensation torque. Results: Initially, the impulsing force is about three times the individual’s gravity. This value and the center of mass acceleration decrease in time. The initial force is proportional to the velocity of its decrease during the impulse, and the opposite occurs with the landing force. Higher intensity is observed when raising the frequency. Conclusion: The fluctuation in the force curve in the landing phase after 20 jumps indicates low muscle strength in lower limbs to maintain activity. A speed of 80 jumps per minute controlled by music in a playful environment is recommended for children. Evidence Level II; Therapeutic Studies – Investigating the results.

Impact Of Limb And Total Body Composition On Drop Vertical Jump Landing Kinematics

Lower limbs containing elevated levels of adipose tissue exhibit diminished quadricep strength and power. Deficits in quadriceps function negatively influence sagittal knee mechanics during drop vertical jumping (DVJ) maneuvers. It is poorly understood how measures of limb and systemic composition impact landing performance and injury risk. PURPOSE: Determine the relationship between composition and sagittal knee kinematics during landing from a DVJ. METHODS: Thirty-six female (171.0 ± 7.6 cm; 66.5 ± 7.6 kg; 22.7 ± 1.8BMI) collegiate volleyball and soccer athletes participated in this study. Biomechanical variables of interest include sagittal knee angle (KA) obtained at two different points during landing using 3-dimensional marker-less motion capture during DVJ maneuvers. These two points were initial contact (IC) and the ending of the landing phase, defined where the center of gravity was at its lowest point (MIN). Higher negative sagittal angle values are indicative of greater knee flexion. Dual x-ray absorptiometry (DXA) was used to compute total body fat percentage (BF%) and bilateral limb lean mass (LLM). LLM was normalized to the total mass of the limb. Associations between landing biomechanics and compositional measures were analyzed via Pearson Product Moment correlations. RESULTS: KA at MIN in the left (-92.8 ± 8.9°) and right leg (-92.4 ± 9.5°) were associated with BF% (27.5 ± 4.3%) (Right: r = 0.430, p = 0.009; Left: r = 0.432, p = 0.008) and LLM (Right: 64.3 ± 4.3% limb mass; Left: 64.0 ± 4.6% limb mass) (Right: r = -0.416, p = 0.012; Left: r = -0.410, p = 0.013). At IC, right leg (-23.7 ± 8.4°) KA had a weak relationship to BF% (r = 0.390, p = 0.019) and LLM (r = -0.364, p = 0.029). Relationships between KA at IC in the left leg (-26.5 ± 8.3°) and BF% (r = 0.289, p = 0.088) and LLM (r = -0.311, p = 0.065) were not significant. CONCLUSIONS: The relationship between BF% and LLM and sagittal KA during DVJ landing indicate that greater LLM and lower BF% may be better for injury risk and performance. Lesser knee flexion range of motion during landing may be caused by inhibited capacity to attenuate landing forces during sport performance. Greater adipose tissue within the limb and systemically may negatively influence injury risk by reducing the ability to adequately absorb forces when landing during an athletic task.

Effects of lead leg selection on bilateral landing force-time characteristics: Return to sport testing implications.

We quantified the effect of lead leg selection on landing force-time characteristics during a vertical drop landing (VDL) initiated with a step-off. Plyometric-trained subjects (male: n=8; female: n=5; age =23±3.3years; body mass =74.4±11.2kg) performed 6step-off-initiated VDLs from a 45-cm box (n=3/lead leg). Pooled and lead leg stratified between-limb comparisons of limb-specific initial ground contact timing, peak vertical ground reaction force (Fzpeak ), and early landing-phase impulse (Impulse100ms ) were assessed by a two-factor, within-subject ANOVA, and limb symmetry indexes were calculated (α=0.05). Pooled data showed that the lead leg made contact prior to the trail leg and contributed a greater fraction to Fzpeak compared with the trail leg. Stratifying trials by lead leg selection led to significant between-limb differences in Fzpeak (p<0.05) and Impulse100ms (p<0.01) with the right leg leading but not with the left leg leading. Lead leg selection in step-off-initiated VDLs influenced landing performance and limb symmetry indexes of variables associated with lower limb injury risk, suggesting the need to control for lead leg selection in these tasks. A step-off may not be a suitable technique to initiate landing tasks when assessing limb symmetry.

Analysis of landing performance and ankle injury in elite British artistic gymnastics using a modified drop land task: A longitudinal observational study

ObjectivesTo determine whether differences in landing force and asymmetry of landing force exist between gymnasts at the time of data collection versus those that subsequently experienced an ankle injury 12-months later. Study designProspective longitudinal observational design with baseline measures and 12 month follow up. SettingBritish Gymnastics National Training Centre. ParticipantsThirty-two asymptomatic elite level gymnasts from three artistic gymnastic squads (n = 15 senior female, n = 10 junior female and n = 7 senior male). Main outcome measuresA modified drop land task was used to quantify measures of landing performance. Peak Vertical Ground Reaction Force (PVGRF) was used to measure landing force. The level of inter-limb asymmetry of landing force was calculated using the Limb Symmetry index (LSI). Other measures included injury incidence and percentage coefficient of variation (% CV). ResultsThere was no statistical difference for landing force (p = 0.481) and asymmetry of landing force (p = 0.698) when comparing injured and non-injured gymnasts. Most participants (69%) demonstrated inter-limb asymmetry of landing forces. ConclusionsOur findings observed inter-limb asymmetry of landing force in injured gymnasts, although uninjured gymnasts also exhibited asymmetry of landing force. Both magnitude of landing force and inter-limb asymmetries of landing force failed to identify the risk of ankle injury.

Understanding the Impact of Scale Height on the Kinetics and Kinematics of Dogs in Working Trials.

Working trials is a canine discipline that originated from police and military dog work. One aspect of working trials competition is for a dog to “scale” a 6ft high wooden wall. Concern has been raised in other canine disciplines that landing forces after traversing jumps may lead to soft tissue injuries. There is a paucity of research into the impact of scale height on peak vertical landing force (PVF) in dogs participating in working trials. The aim of this work was to determine whether an alteration in scale height impacts PVF and apparent joint angulation on landing. Twenty-one dogs who regularly competed in working trials traversed the scale at three different heights; 6ft (full height), 5.5ft and 5ft. Changes in PVF, apparent carpal and shoulder joint angulation and duration of landing were analyzed using general linear mixed models. Dogs weighing >25 kg had greater PVF at 6ft than at 5ft (p < 0.05). There was no effect of scale height on PVF in dogs <25kg. Duration of landing was longer at 5ft than 5.5ft (p < 0.001) and 6ft (p < 0.001). Apparent carpus angle on landing was smaller at 6ft than 5ft (p < 0.05) and 5.5ft (p < 0.05) for dogs <25 kg. Apparent carpus angle on landing did not differ at any height for dogs >25 kg (p > 0.05). Apparent shoulder angle was not affected by scale height for any dogs (p > 0.05). There was considerable variation in the study population, but this research indicates that when the scale height was lowered to 5.5ft dogs had reduced PVF and less compressed joint angles on landing. When the scale height was lowered to 5ft they altered their traversing style and greater compression and increased PVF was seen. Evidence-based approaches to canine working trials are important to ensure minimum impacts on physical health and welfare of participating dogs, in terms of risk of injury in both competition and training. Based on these findings it is recommended that the maximum height of the scale is reviewed for training and competitive purposes, to ensure minimal impacts on the health of competing dogs, while maintaining the level of competitive challenge.

Influence of Landing in Neuromuscular Control and Ground Reaction Force with Ankle Instability: A Narrative Review.

Ankle sprains are generally the most common injuries that are frequently experienced by competitive athletes. Ankle sprains, which are the main cause of ankle instability, can impair long-term sports performance and cause chronic ankle instability (CAI). Thus, a comprehensive understanding of the key factors involved in repeated ankle strains is necessary. During jumping and landing, adaptation to the landing force and control of neuromuscular activation is crucial in maintaining ankle stability. Ankle mobility provides a buffer during landing, and peroneus longus activation inhibits ankle inversion; together, they can effectively minimize the risk of ankle inversion injuries. Accordingly, this study recommends that ankle mobility should be enhanced through active and passive stretching and muscle recruitment training of the peroneus longus muscles for landing strategies should be performed to improve proprioception, which would in turn prevent ankle sprain and injury to neighboring joints.

The Influence of Shoe and Cleat Type on Lower Extremity Muscle Activation in Youth Baseball Pitchers

Background: Baseball pitching is a dynamic movement where the lower extremities generate and sequentially transfer energy to the upper extremities to maximize ball velocity. The need for lower body muscular strength to produce adequate push-off and landing forces has been documented; however, the influence footwear and surface inclination has on muscle activation remains unknown. Objectives: Determine how pitching in molded cleats and turf shoes from a pitching mound and flat ground affects stride-leg muscle activation in youth baseball pitchers while determining percent activation during each pitching phase. Methods: Cross – sectional study analyzing mean muscle activity and percent activation of the vastus medialis, semitendinosus, tibialis anterior, and medial gastrocnemius on the stride-leg of 11 youth baseball pitchers when pitching fastballs. Results: Footwear did not significantly alter vastus medialis or semitendinosus muscle activation (P 0.05). The turf shoe x pitching mound interaction elicited significantly (P 0.05) greater mean muscle activity in the medial gastrocnemius and tibialis anterior from stride foot contact to maximum glenohumeral internal rotation. Molded cleats produced greater activation levels in the tibialis anterior on flat ground from stride foot contact (0.374 ± 0.176 mV) to ball release (0.469 ± 0.150 mV). Conclusion: Findings suggest footwear significantly alters the activity level of the ankle stabilizing musculature. Youth baseball pitchers and coaches should be cognizant of what footwear is worn on a pitching surface. Maximal activation of the tibialis anterior and medial gastrocnemius can ensure the stride leg is adequately stabilized to absorb the momentum generated by trail leg.

Impaired Stretch-Shortening Cycle Function Persists Despite Improvements in Reactive Strength After Anterior Cruciate Ligament Reconstruction.

Read, PJ, Pedley, JS, Eirug, I, Sideris, V, and Oliver, JL. Impaired stretch-shortening cycle function persists despite improvements in reactive strength followingafter anterior cruciate ligament reconstruction. J Strength Cond Res 36(5): 1238-1244, 2022-Reactive strength index (RSI) during a single-leg drop jump (SLDJ) has been indicated to determine return-to-sport readiness after anterior cruciate ligament (ACL) reconstruction, but only cross-sectional studies are available. Ground reaction force data and characterization of stretch-shortening cycle (SSC) function also remain sparse. Single-leg drop jump performance, ground reaction force, and SSC function were examined in soccer players with ACL reconstruction (n = 26) and matched controls (n = 25). Injured players were tested at 2 time points (32 and 42 weeks postsurgery). Stretch-shortening cycle function was classified as good (no impact peak and spring like), moderate (impact peak but still spring like or no impact peak and not spring like), or poor (impact peak and not spring like). The involved limb displayed lower-jump height, poorer RSI, less spring-like behavior, earlier peak landing force, and a greater ratio of landing peak to take-off peak force compared with the uninvolved limb and controls at the initial assessment (p < 0.001). Proportionally, more involved limbs were categorized as poor or moderate at the initial assessment (69.2%) and follow-up (50%) in comparison with the control limbs (14%). The reactive strength index was the only variable to change significantly between the initial assessment and follow-up on the involved limb (p < 0.05). No changes in the proportion of ACL reconstructed individuals categorized as poor or moderate SSC function at the follow-up assessment were observed. Residual deficits are present in SLDJ performance, SSC function, and ground reaction force characteristics after ACL reconstruction. The reactive strength index should not be the sole metric, as observed increases did not correspond with changes in SSC function.

Pre-Landing Control for a Legged Robot Based on Tiptoe Proximity Sensor Feedback

The moment a legged robot touches the ground, the tip of its toe can experience a significant impact force. It is preferable to keep the landing impact force small because it causes imbalance and damage to the frame, motors, gears, and other components of the robot legs. In this paper, we propose a control method to mitigate the landing impact force by preliminary motion based on the proximity information of the tiptoe before landing. A proximity sensor is mounted on the tiptoe to detect the ground before landing, and feedback control is applied according to the sensor output to reduce the impact force. In landing experiments using a one-legged robot equipped with a proximity sensor on a tiptoe, we evaluated the effects of changing the sensor offset distance and the feedback gains on impact force mitigation. The results show that the landing impact force was mitigated by reducing the relative velocity of the tiptoe and the ground using the proposed proximity feedback control.

Multidirectional Hop Landings Exceed Osteogenic Thresholds with and with Instruction Withdrawn in Premenopausal Women

The purpose of this study was to quantify ground reaction forces across all planes of motion and determine the influence of instruction associated with vertical, forward and lateral hop landings in premenopausal women. Bilateral jump-landings have previously been the focus in this population with forces quantified primarily in the vertical direction. There is a need to understand and quantify the landing forces for different types of exercises to determine their osteogenic potential as a stimulus for bone development across the life stages, in addition to identifying at risk populations. Such exercises could help to build a better skeleton, and maintenance of that would decrease the susceptibility to fractures and osteoporosis in later years. Twenty-one women [Mean (SD): 43.3 (5.9) yr; 69.4 (9.6) kg; 167 (5.5) cm; 27.5 (8.7) % body fat] performed a testing session ‘with instruction’ followed by a testing session performed one week later with ‘instruction withdrawn’. The resultant magnitudes (4.02 to 4.93 body weights, BW’s) and rates of strain (237 to 319, body weights per second, BW/s), exceeded previously determined jump-landings thresholds (>3BW’s and >43BW/s, respectively) that have achieved bone gains in this population. Jump-type effects were observed, with larger peak vertical and resultant forces (↑10% to ↑14%; <i>p </i>≤.001, BW) produced for the vertical hop. Significant differences (<i>p </i>≤.001) were detected for hop landing ground reaction force’s across all planes of motion (19% to 93%) suggesting that each landing type provides a different type of force distribution as required to optimize bone stimulation. These multidirectional hop-landings represent a unique training stimulus for premenopausal women and exceed osteogenic thresholds thought pre-requisite for bone growth.

Association of Ankle Dorsiflexion and Landing Forces in Jumping Athletes.

Dorsiflexion range of motion restriction has been associated with patellar tendinopathy, but the mechanisms of how dorsiflexion restriction could contribute to knee overload remain unknown. Peak ankle dorsiflexion and ankle dorsiflexion excursion are negatively associated with peak vertical ground-reaction force (vGRF) and loading rate, and with peak patellar tendon force and loading rate, and positively associated with peak ankle plantar flexor moment. Cross-sectional study. Level 4. Kinematic and kinetic data of 26 healthy recreational jumping athletes were measured during a single-leg drop vertical jump. Pearson's correlation coefficients were calculated to establish the association between peak ankle dorsiflexion and ankle dorsiflexion excursion with peak vGRF and vGRF loading rate, with peak patellar tendon force and patellar tendon force loading rate, and with peak ankle plantar flexor moment. Ankle dorsiflexion excursion negatively correlated with peak vGRF loading rate (r = -0.49; P = 0.011) and positively correlated with peak ankle flexor plantar moment (r = 0.52; P = 0.006). In addition, there was a positive correlation between peak ankle dorsiflexion and peak vGRF (r = 0.39; P = 0.05). Ankle kinematics are associated with vGRF loading rate, ankle flexor plantar moment and peak vGRF influencing knee loads, but no association was observed between ankle kinematics and patellar tendon loads. These results suggest that increasing ankle dorsiflexion excursion may be an important strategy to reduce lower limb loads during landings but should not be viewed as the main factor for reducing patellar tendon force.

FIFA 11+ Kids program effects on jump kinetics in soccer players – A randomized controlled clinical trial

ABSTRACT This study aimed to analyse the effects of the FIFA 11+ Kids programme on jump kinetics in soccer players. Twenty-four athletes (aged 9–11 years) were randomly allocated to the following groups: 1) the FIFA 11+ Kids programme (FT, n = 12), and 2) control training (CT, n = 12). Kinetic assessments of vertical jump (VJ), drop landing (DL), and anterior jump + maximum vertical jump (AJ) were performed on a force platform before and after eight weeks of training. Post-intervention impulse peak force and maximum impulse force (VJ) were significantly greater than the baseline values in the FT group (P < 0.001). Post-intervention landing peak force values for the first and second landings (DL) were significantly greater than the baseline values in the FT group (P = 0.01 and P = 0.05, respectively). Post-intervention landing peak force in the first landing (AJ) was significantly greater than the baseline values in the FT group (P = 0.005). The FT was effective in improving the impulsion performance during VJ. However, it increased the landing forces during DL and VJ.