Lower limb kinematics during single leg landing in three directions in individuals with chronic ankle instability

ObjectivesTo compare the lower limb kinematics of participants with chronic ankle instability (CAI) and healthy participants during forward, lateral, and medial landings.DesignCross-sectional study.SettingLaboratory.ParticipantsEighteen athletes with CAI and 18 control athletes.Main outcome measuresHip, knee, and ankle joint kinematics during forward, lateral, and medial single-leg landings were compared between the groups using two-way ANOVA for discrete values and statistical parametric mapping two-sample t-tests for time-series data.ResultsThe CAI group had significantly greater ankle dorsiflexion than the control group (P ≤ 0.013), which was observed from the pre-initial contact (IC) for lateral and medial landings and post-IC for forward landing. The CAI group showed greater knee flexion than the control group from the IC for lateral landing and post-IC for forward landing (P ≤ 0.014). No significant differences in ankle inversion kinematics were found between the CAI and control groups. Lateral landing had a greater peak inversion angle and velocity than forward and medial landings (P < 0.001). Medial landing had a greater inversion velocity than forward landing (P < 0.001).ConclusionsThis study suggests that individuals with CAI show feedforward protective adaptations in the pre-landing phase for lateral and medial landings.     

Contributions of lower extremity joints to energy dissipation during landings

PURPOSE: The purpose of the study was to investigate changes in lower extremity joint energy absorption for different landing heights and landing techniques. METHODS: Nine healthy, active male subjects volunteered to perform step-off landings from three different heights (0.32 m, 2.5 m(-s); 0.62 m, 3.5 m(-s); and 1.03 m, 4.5 m(-s)) using three different landing techniques (soft, SFL; normal, NML; and stiff landing, STL). Each subject initially performed five NML trials at 0.62 m to serve as a baseline condition and subsequently executed five trials in each of the nine test conditions (3 heights x 3 techniques). RESULTS: The results demonstrated general increases in peak ground reaction forces, peak joint moments, and powers with increases in landing height and stiffness. The mean eccentric work was 0.52, 0.74, and 0.87 J x kg(-1) by the ankle muscles, and 0.94, 1.31, and 2.15 J x kg(-1) by the hip extensors, at 0.32, 0.62, and 1.03 m, respectively. The average eccentric work performed by the knee extensors was 1.21, 1.63, and 2.26 J x kg(-1) for the same three heights. CONCLUSIONS: The knee joint extensors were consistent contributors to energy dissipation. The ankle plantarflexors contributed more in the STL landings, whereas the hip extensors were greater contributors during the SFL landings. Also a shift from ankle to hip strategy was observed as landing height increased.     

Effects of passive ankle dorsiflexion stiffness on ankle mechanics during drop landings

ObjectivesVertical landing tasks strain the Achilles tendon and plantar-flexors, increasing acute and overuse strain injury risk. This study aimed to determine how passive ankle dorsiflexion stiffness affected ankle mechanics during single limb drop landings at different vertical descent velocities.DesignCross-sectional study.MethodsPassive ankle dorsiflexion stiffness and passive weight-bearing dorsiflexion range of motion (DROM) were quantified for 42 men. Participants were then grouped as having low (LPS: 0.94 ± 0.15 Nm °^?1; n = 16) or high (HPS: 2.05 ± 0.36 Nm °^?1; n = 16; p < 0.001) passive ankle dorsiflexion stiffness. Three-dimensional ankle joint kinematics was quantified while participants performed drop landings onto a force platform at two vertical descent velocities (slow: 2.25 ± 0.16 m s^?1; fast: 3.21 ± 0.17 m s^?1).ResultsAlthough affected by landing velocity, there were no significant effects of passive ankle dorsiflexion stiffness, nor any significant ankle dorsiflexion stiffness × vertical descent velocity interactions on any outcome variables characterising ankle mechanics during drop landings. Furthermore, there was no significant difference between the groups for passive weight-bearing DROM (LPS: 43.9 ± 4.1°; HPS: 42.5 ± 5.7°), indicating that the results were not confounded by between-group differences in ankle range of motion.ConclusionsNeither high nor low passive ankle dorsiflexion stiffness was found to influence ankle biomechanics during drop landings at different descent velocities. Landing strategies were moderated more by the demands of the task than by passive ankle dorsiflexion stiffness, indicating that passive ankle dorsiflexion stiffness may not affect plantar-flexor strain during a drop landing.     

Effect of landing stiffness on joint kinetics and energetics in the lower extremity.

Ground reaction forces (GRF), joint positions, joint moments, and muscle powers in the lower extremity were compared between soft and stiff landings from a vertical fall of 59 cm. Soft and stiff landings had less than and greater than 90 degrees of knee flexion after floor contact. Ten trials of sagittal plane film and GRF data, sampled at 100 and 1000 Hz, were obtained from each of eight female athletes and two landing conditions. Inverse dynamics were performed on these data to obtain the moments and powers during descent (free fall) and floor contact phases. Angular impulse and work values were calculated from these curves, and the conditions were compared with a correlated t-test. Soft and stiff landings averaged 117 and 77 degrees of knee flexion. Larger hip extensor (0.010 vs 0.019 N.m.s.kg-1; P less than 0.01) and knee flexor (-0.010 vs -0.013 N.m.s.kg-1; P less than 0.01) moments were observed during descent in the stiff landing, which produced a more erect body posture and a flexed knee position at impact. The shapes of the GRF, moment, and power curves were identical between landings. The stiff landing had larger GRFs, but only the ankle plantarflexors produced a larger moment (0.185 vs 0.232 N.m.s.kg-1; P less than 0.01) in this condition. The hip and knee muscles absorbed more energy in the soft landing (hip, -0.60 vs -0.39 W.kg-1; P less than 0.01; knee, -0.89 vs -0.61 W.kg-1; P less than 0.01), while the ankle muscles absorbed more in the stiff landing (-0.88 vs -1.00 W.kg-1; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationship between passive ankle dorsiflexion range,dynamic ankle dorsiflexion range and lower limb and trunk kinematics during the single-leg squat

BackgroundLimited passive ankle dorsiflexion range has been associated with increased knee valgus during functional tasks. Increased knee valgus is considered a contributing factor for musculoskeletal disorders in the lower limb. There is conflicting evidence supporting this association. The extent of passive ankle dorsiflexion range is associated with dynamic ankle dorsiflexion range and the way how these variables are related to lower limb or trunk kinematics is unclear.Research questionWhat is the association between passive ankle dorsiflexion range or dynamic ankle dorsiflexion range with shank, thigh, pelvis or trunk movements during the single-leg squat?MethodsThis is a cross-sectional study with a convenience sample. Thirty uninjured participants performed the single-leg squat with their dominant limb. Ankle, shank, thigh, pelvis and trunk 3D kinematics were recorded. Passive ankle dorsiflexion range was assessed through the weight-bearing lunge test and the dynamic ankle dorsiflexion range was defined as the ankle dorsiflexion range of motion in the sagittal plane during the single-leg squat.ResultsGreater passive ankle dorsiflexion range was associated with smaller thigh internal rotation (r= -0.38). Greater dynamic ankle dorsiflexion range was associated with smaller trunk flexion (r = 0.59) and pelvis anteversion (r= -0.47). Passive ankle dorsiflexion range and dynamic ankle dorsiflexion range were not associated.SignificanceGreater passive ankle dorsiflexion range seems to be associated with a better lower limb alignment during the single-leg squat, while dynamic ankle dorsiflexion range seems to reflect different lower limb and trunk kinematic strategies.     

Effects of elastic ankle support on running ankle kinematics in individuals with chronic ankle instability and healthy controls

BackgroundIndividuals with chronic ankle instability (CAI) have an increased risk for recurrent injuries. The preventive effects of external ankle supports are not fully understood. This study aimed to examine the effect of elastic ankle support on running ankle kinematics.Methods3D running gait analysis of individuals with and without CAI was conducted at three-minute-running trials at 2.78 m/s with and without elastic ankle support in a randomised order. Ankle kinematics and intra-individual standard deviations (variability) were calculated at each percent of the running gait cycle. Group and ankle support effects were calculated using statistical parameter mapping.ResultsTwenty-seven individuals were analysed (CAI: n = 14, controls: n = 13). When wearing ankle support, CAI individuals showed significantly decreased plantarflexion angles at 43–47 % (p = 0.033) and 49–51 % (p = 0.043) of the running gait cycle compared to normal running. In healthy controls, no differences in ankle angles between both conditions were found. Comparisons between CAI individuals and healthy controls showed statistically significant differences in the plantar-/dorsiflexion angles at 38–41 % (p = 0.044) with ankle support and at 34–46 % (p = 0.004) without ankle support. Significant ankle angle variability differences were found for ankle in-/eversion between CAI individuals and healthy controls (p = 0.041) at 32–33 % of the running gait cycle.ConclusionsElastic ankle support reduces the range of sagittal plane running ankle kinematics of CAI individuals but not of healthy controls. Further research is needed to evaluate the association between ankle support effects and the risk for recurrent ankle sprains.     

Directions of single-leg landing affect multi-segment foot kinematics and dynamic postural stability in male collegiate soccer athletes

BackgroundUnderstanding lower limb kinematics and postural control in different directions of single-leg landings is critical to evaluate postural control and prevent lower limb injuries. However, foot and ankle kinematics and postural control during single-leg landings in different directions are less known.Research questionDoes the difference in the direction of single-leg landing affect the foot kinematics on the frontal plane and dynamic postural stability?MethodsA cross-sectional study was conducted. Forty-nine male collegiate soccer players performed single-leg forward (FL), 45° lateral (LL), and medial (ML) direction landings. The lower limb, foot (rearfoot, midfoot, forefoot), and ankle kinematics during an impact phase were evaluated, and a curve analysis was performed using a statistical parametric mapping method to compare the three landings. The three landings were compared in terms of postural control parameters, including time to stabilization (TTS), peak of ground reaction forces (GRFs), root-mean-square of the mediolateral GRFs for 0–0.4 s (GRFML0.4), loading rate, and magnitude of horizontal GRFs from 0–0.4 s (HGRF-0.4), 0.4–2.4 s (HGRF-2.4), and 3.0–5.0 s.ResultsAnkle and rearfoot kinematics in LL exhibited smaller eversion and pronation positions than FL and ML (p < 0.01). The TTS-mediolateral (TTS-ML) was longer in the LL than in FL and ML (p < 0.001). The GRFML0.4, HGRF-0.4, and -2.4 in the LL and ML were greater than those in the FL (p < 0.001).SignificanceDirections of single-leg landing affect foot and ankle kinematics and postural stability. Specifically, the LL exhibits more inverted ankle and supinated rearfoot positions, and longer TTS-ML. Thus, the LL may induce stretching of the lateral ankle ligament. These findings can help understand foot kinematics and assess dynamic postural control.     

Altered movement strategies during jump landing/cutting in patients with chronic ankle instability

Centrally mediated changes in sensorimotor function have been reported in patients with chronic ankle instability (CAI). However, little is known regarding supraspinal/spinal adaptations during lower‐extremity dynamic movement during a multiplanar, single‐leg landing/cutting task. The purpose of this study was to investigate the effect of CAI on landing/cutting neuromechanics, including lower‐extremity kinematic, electromyography (EMG) activation, and ground reaction force (GRF) characteristics. One hundred CAI patients and 100 matched healthy controls performed five trials of a jump landing/cutting task. Sagittal‐ and frontal‐plane ankle, knee and hip kinematics, EMG activation in eight lower‐extremity muscles, and 3D GRF were collected during jump landing/cutting. Functional analyses of variance (FANOVA) were used to evaluate between‐group differences for dependent variables throughout the entire ground contact of the task. Relative to the control group, the CAI group revealed (a) reduced dorsiflexion, increased knee and hip flexion angles, (b) increased inversion and hip adduction angles, (c) increased EMG activation of medial gastrocnemius, peroneus longus, adductor longus, vastus lateralis, gluteus medius, and gluteus maximus, and (d) increased posterior and vertical GRF during initial landing, and reduced medial, posterior, and vertical GRF during mid‐landing and mid‐cutting. CAI patients demonstrated alterations in landing/cutting movement strategies as demonstrated by a higher susceptibility of foot placement for lateral ankle sprains, and more flexed positions of the knee and hip with higher EMG activation of knee and hip extensors to modulate GRF to compensate for the unstable ankle. This apparent compensation may be due to mechanical (limited dorsiflexion angle) and/or sensorimotor deficits in the ankle.     

Single-leg hop testing following fatiguing exercise: reliability and biomechanical analysis

A fatiguing exercise protocol was combined with single-leg hop testing to improve the possibilities of evaluating the effects of training or rehabilitation interventions. In the first test-retest experiment, 11 healthy male subjects performed two trials of single-leg hops under three different test conditions: non-fatigued and following fatiguing exercise, which consisted of unilateral weight machine knee extensions at 80% and 50%, respectively, of 1 repetition maximum (1 RM) strength. Intraclass correlation coefficients ranged from 0.75 to 0.98 for different hop test conditions, indicating that all tests were reliable. For the second experiment, eight healthy male subjects performed the fatiguing exercise protocol to investigate how fatigue influences lower-extremity joint kinematics and kinetics during single-leg hops. Hip, knee and ankle joint angles, moments and powers, as well as ground-reaction forces were recorded with a six-camera, motion-capture system and a force platform. Recovery of hop performance following the fatiguing exercise was also measured. During the take-off for the single-leg hops, hip and knee flexion angles, generated powers for the knee and ankle joints, and ground-reaction forces decreased for the fatigued hop conditions compared with the non-fatigued condition (P<0.05). Compared with landing during the non-fatigued condition, hip moments and ground-reaction forces were lower for the fatigued hop conditions (P<0.05). The negative joint power was two to three times greater for the knee than for the hip and five to 10 times greater for the knee than for the ankle during landing for all test conditions (P<0.05). Most measured variables had recovered three minutes post-exercise. It is concluded that the fatiguing exercise protocol combined with single-leg hop testing was a reliable method for investigating functional performance under fatigued test conditions. Further, subjects utilized an adapted hop strategy, which employed less hip and knee flexion and generated powers for the knee and ankle joints during take-off, and less hip joint moments during landing under fatigued conditions. The large negative power values observed at the knee joint during the landing phase of the single-leg hop, during which the quadriceps muscle activates eccentrically, indicate that not only hop distance but also the ability to perform successful landings should be investigated when assessing dynamic knee function.     

Functional instability of the ankle: differences in patterns of ankle and knee movement prior to and post landing in a single leg jump.

The aim of this study was to investigate motor control in subjects with functional instability of the ankle joint. This was achieved by analysing patterns of lower extremity motion prior to and immediately following landing during single leg jumping in subjects with functional instability of the ankle. Fourteen subjects with unilateral functional instability and 10 healthy control subjects performed single leg jumps from a 40 cm height whilst angular displacement of their ankle and knee joints were recorded. Subjects with functional instability demonstrated significantly greater ankle dorsiflexion over the period encompassing 10 ms pre landing to 20 ms post landing (p < 0.05). They also exhibited a significantly greater level of knee flexion than controls over the period from 20 ms pre landing to 60 ms post landing (p < 0.05). The timing of these significant differences leads us to conclude that they do not arise as a result of reflexively mediated peripheral events following landing.     

Gender differences in frontal and sagittal plane biomechanics during drop landings

PURPOSE: To determine gender differences in lower-extremity joint kinematics and kinetics between age- and skill-matched recreational athletes. METHODS: Inverse dynamic solutions estimated the lower-extremity flexion-extension and varus-valgus kinematics and kinetics for 15 females and 15 males performing a 60-cm drop landing. A mixed model, repeated measures analysis of variance (gender (*) joint) was performed on select kinematic and kinetic variables. RESULTS: Peak hip and knee flexion and ankle dorsiflexion angles were greater in females in the sagittal plane (group effect, P < 0.02). Females exhibited greater frontal plane motion (group (*) joint, P = 0.02). Differences were attributed to greater peak knee valgus and peak ankle pronation angles (post hoc tests, P = 0.00). Females exhibited a greater range of motion (ROM) in the sagittal plane (group main effect, P = 0.02) and the frontal plane (group (*) joint, P = 0.01). Differences were attributed to the greater knee varus-valgus ROM, ankle dorsiflexion, and pronation ROM (post hoc tests). Ground reaction forces were different between groups (group (*) direction, P = 0.05). Females exhibited greater peak vertical and posterior (A/P) force than males (post hoc tests). Females exhibited different knee moment profiles (Group main effect, P = 0.01). These differences were attributed to a reduced varus moment in females (post hoc tests). CONCLUSION: The majority of the differences in kinematic and kinetic variables between male and female recreational athletes during landing were observed in the frontal plane not in the sagittal plane. Specifically, females generated a smaller internal knee varus moment at the time of peak valgus knee angulation.     

Contribution of calcaneal and leg segment rotations to ankle joint dorsiflexion in a weight-bearing task

Joint angle is the relative rotation between two segments where one is a reference and assumed to be non-moving. However, rotation of the reference segment will influence the system's spatial orientation and joint angle. The purpose of this investigation was to determine the contribution of leg and calcaneal rotations to ankle rotation in a weight-bearing task. Forty-eight individuals performed partial squats recorded using a 3D motion capture system. Markers on the calcaneus and leg were used to model leg and calcaneal segment, and ankle joint rotations. Multiple linear regression was used to determine the contribution of leg and calcaneal segment rotations to ankle joint dorsiflexion. Regression models for left (R(2)=0.97) and right (R(2)=0.97) ankle dorsiflexion were significant. Sagittal plane leg rotation had a positive influence (left: β=1.411; right: β=1.418) while sagittal plane calcaneal rotation had a negative influence (left: β=-0.573; right: β=-0.650) on ankle dorsiflexion. Sagittal plane rotations of the leg and calcaneus were positively correlated (left: r=0.84, P<0.001; right: r=0.80, P<0.001). During a partial squat, the calcaneus rotates forward. Simultaneous forward calcaneal rotation with ankle dorsiflexion reduces total ankle dorsiflexion angle. Rear foot posture is reoriented during a partial squat, allowing greater leg rotation in the sagittal plane. Segment rotations may provide greater insight into movement mechanics that cannot be explained via joint rotations alone.     

Individuals with chronic ankle instability exhibit altered ankle kinematics and neuromuscular control compared to copers during inversion single-leg landing

ObjectivesThis study compares the ankle kinematics and muscle activities of the individuals with chronic ankle instability (CAI), coper, and control groups in normal and inversion single-leg landings.Designcross-sectional study;SettingBiomechanics laboratory.ParticipantsPhysically active adults with CAI (N = 12); and coper (N = 12) and control (N = 12) groups.Main outcome measuresThe participants performed normal and inversion single-leg landing. The muscle activity 200 ms before and after landing of the tibialis anterior, the medial gastrocnemius, and the fibularis longus (FL) were recorded. The FL latency, sagittal and frontal co-contraction indexes (CCI), ankle inversion angle at the initial contact, and the maximum inversion angle were recorded.ResultsSignificantly longer FL latency, decreased FL muscle activity, frontal CCI, and an increased maximum inversion angle at post-landing were discovered during inversion single-leg landing in the CAI group compared to the coper and control groups. However, no significant difference was observed among the CAI and coper groups during normal single-leg landing.ConclusionThese results suggest prolonged FL latency and altered ankle kinematics suggest an increased risk of recurrent lateral ankle sprains in CAI with inversion single-leg landing.     

Dynamic joint stiffness of the ankle in chronic ankle instability patients

BackgroundWhile Individuals with chronic ankle instability (CAI) exhibit altered ankle joint movement and moments during stance phase of gait, the interaction or dynamic joint stiffness (DJS) between these is not fully understood. Little attention has been placed on DJS during gait, limiting our understanding of how the most common dynamic task during daily life could affect cartilage loading.Research questionDo Individuals with CAI exhibit altered ankle DJS and mechanical energy exerted at the ankle joint during stance phase of gait?MethodsEighty-four physically active individuals, consisting of 42 individuals with CAI (12 M and 30 F) and 42 control (12 M and 30 F) participants were recruited in this study. Three-dimensional gait analysis was conducted. The sagittal ankle joint angle and moment during stance phase of walking gait were obtained. Stance phase was divided into three sub-phases: controlled plantarflexion, controlled dorsiflexion, and powered plantarflexion. Ankle DJS was represented by the slope of the joint moment plotted as a function of the joint angle. The coefficient of determination was calculated to determine how accurately data fit a linear model. Net work was calculated by the difference between work produced and absorbed. Further, sex specific exploratory analyses of DJS and work between individuals with and without CAI were conducted.ResultsLower DJS during the controlled plantarflexion (CPF) sub-phase, work produced, and net work was found in the CAI group. Males with CAI exhibited lower ankle moment changes during controlled dorsiflexion (CDF) sub-phase and work absorbed. Females with CAI exhibited lower ankle moment changes during CPF and CDF sub-phases, lower DJS during the CPF sub-phase, and lower net work.SignificanceIndividuals with CAI have alterations in DJS and work relative to uninjured controls. Females with CAI showed greater DJS related alterations, relative to controls, than their male CAI counterparts.     

The effects of ankle braces and taping on lower extremity running kinematics and energy expenditure in healthy,non-injured adults

Ankle braces and taping are commonly used to prevent ankle sprains and allow return to play following injury, however, it is unclear how passive restriction of joint motion may effect running gait kinematics and energy expenditure during exercise. The purpose of this study was to determine the effect of different types of ankle supports on lower extremity kinematics and energy expenditure during continuous running. Thirteen healthy physically active adults ran at self-selected speed on the treadmill for 30 min in four different ankle support conditions: semi-rigid hinged brace, lace-up brace, tape and control. Three-dimensional lower extremity kinematics and energy expenditure were recorded every five minutes. The semi-rigid hinged brace was most effective in restricting frontal plane ankle motion. The lace-up brace and tape restricted sagittal plane ankle motion, while semi-rigid hinged bracing allowed for normal sagittal plane ankle kinematics. Kinematic changes from all three ankle supports were generally persistent through 25–30 min of exercise. Only tape influenced knee kinematics, limiting flexion velocity and flexion-extension excursion. Small but significant increased in energy expenditure was found in tape and semi-rigid hinged brace conditions; however, the increases were not to any practically significant level (<0.5 kcal/min).     

Effects of hip and head position on ankle range of motion,ankle passive torque,and passive gastrocnemius tension

Ankle joint range of motion (ROM) is notably influenced by the position of the hip joint. However, this result remains unexplained. Thus, the aim of this study was to test if the ankle passive torque and gastrocnemius muscle tension are affected by the hip and the head positions. The torque and the muscle shear elastic modulus (measured by elastography to estimate muscle tension) were collected in nine participants during passive ankle dorsiflexions performed in four conditions (by combining hip flexion at 90 or 150°, and head flexed or neutral). Ankle maximum dorsiflexion angle significantly decreased by flexing the hip from 150 to 90° (P < 0.001; mean difference 17.7 ± 2.5°), but no effect of the head position was observed (P > 0.05). Maximal passive torque and shear elastic modulus were higher with the hip flexed at 90° (P < 0.001). During submaximal ROM, no effects of the head and hip positioning (P > 0.05) were found for both torque and shear elastic modulus at a given common ankle angle among conditions. Shifts in maximal ankle angle due to hip angle manipulation are not related neither to changes in passive torque nor tension of the gastrocnemius. Further studies should be addressed to better understand the functional role of peripheral nerves and fasciae in the ankle ROM limits.     

The effects of the tension of figure-8 straps of a soft ankle orthosis on the ankle joint kinematics while walking in healthy young adults: A pilot study

BackgroundFigure-8 straps are commonly used in ankle orthoses, which are provided to reduce the risks of primary and recurrent sprain by providing functional support. Functional treatment with ankle orthoses can provide better rehabilitation than immobilization for a mild ankle sprain. However, it is not known how much tension should be applied to the straps while donning the orthosis to optimize its effectiveness.Research questionThe aim of this study was to investigate the effects of figure-8 strap tension of a soft ankle orthosis on ankle joint kinematics in the sagittal, coronal, and transverse planes during gait in healthy young adults.MethodsTen healthy adults (five males and five females) were enrolled in this study. The 3-dimensional motion analysis system was used to evaluate the ankle kinematics of the participants during gait under five conditions: no soft ankle orthosis, soft ankle orthosis with no figure-8 straps tension (lace-up only), 50 N, 80 N, and 110 N tension of the figure-8 straps, respectively. All participants walked in a straight path at a comfortable speed.ResultsPlantarflexion angles were significantly reduced with 110 N of tension in the figure-8 straps when compared to the lace-up only and a moderate correlation with r = 0.34 (p = 0.03) was observed between the tensions of figure-8 straps and maximum plantarflexion angles at pre-swing of a gait cycle. No significant effects on ankle joint angles were demonstrated in the coronal and transverse planes.SignificanceThis study showed that increasing the tension of the figure-8 straps could restrict the ankle joint plantarflexion angle during pre-swing in gait. However, it might not affect inversion/eversion or internal/external rotation angles of the ankle joint in individuals without ankle pathologies.     

The influences of sex and posture on joint energetics during drop landings

Previous observations suggest that females utilize a more erect initial landing posture than males with sex differences in landing posture possibly related to sex‐specific energy absorption (EA) strategies. However, sex‐specific EA strategies have only been observed when accompanied by sex differences in initial landing posture. This study (a) investigated the potential existence of sex‐specific EA strategies; and (b) determined the influences of sex and initial landing posture on the biomechanical determinants of EA. The landing biomechanics of 80 subjects were recorded during drop landings in Preferred, Flexed, and Erect conditions. No sex differences in joint EA were identified after controlling for initial landing posture. Males and females exhibited greater ankle EA during Erect vs Flexed landings with this increase driven by 12% greater ankle velocity, but no change in ankle extensor moment. No differences in hip and knee EA were observed between conditions. However, to achieve similar knee EA, subjects used 7% greater mean knee extensor moment but 9% less knee angular velocity during Flexed landings. The results suggest that sex‐specific EA strategies do not exist, and that the magnitude of knee joint EA can be maintained by modulating the relative contributions of joint moment and angular velocity to EA.     

Retrospective comparison of taping and ankle stabilizers in preventing ankle injuries

The effectiveness of taping and the effectiveness of wearing a laced stabilizer in preventing ankle injuries and reinjuries over six seasons of collegiate football practices and games were assessed retrospectively. For 1 1/2 years the players all had taped ankles, and for the remaining 4 1/2 years the players chose their type of ankle support. Over the entire period, the players chose high-top or low-top shoes as preferred. During 51,931 exposures to injury (46,789 practice-exposures and 5,142 game-exposures), the 297 players sustained 224 ankle injuries and 24 reinjuries. Tape was worn during 38,658 exposures to injury (233 players), stabilizers during 13,273 exposures (127 players). Tape had been worn when 159 of the injuries and 23 of the reinjuries occurred; a stabilizer had been worn when 37 of the injuries (P = 0.003) and one of the reinjuries occurred. The combination allowing the fewest injuries overall was low-top shoes and laced ankle stabilizers.     

Effects of wobble board training on single‐leg landing neuromechanics

Balance training programs have been shown to reduce ankle sprain injuries in sports, but little is known about the transfer from this training modality to motor coordination and ankle joint biomechanics in sport‐specific movements. This study aimed to investigate the effects of wobble board training on motor coordination and ankle mechanics during early single‐leg landing from a lateral jump. Twenty‐two healthy men were randomly assigned to either a control or a training group, who engaged in 4 weeks of wobble board training. Full‐body kinematics, ground reaction force, and surface electromyography (EMG ) from 12 lower limb muscles were recorded during landing. Ankle joint work in the sagittal, frontal, and transverse plane was calculated from 0 to 100 ms after landing. Non‐negative matrix factorization (NMF ) was applied on the concatenated EMG Pre‐ and Post‐intervention. Wobble board training increased the ankle joint eccentric work 1.2 times in the frontal (P  <  .01) and 4.4 times in the transverse plane (P  <  .01) for trained participants. Wobble board training modified the modular organization of muscle recruitment in the early landing phase by separating the activation of plantar flexors and mediolateral ankle stabilizers. Furthermore, the activation of secondary muscles across motor modules was reduced after training, refocusing the activation on the main muscles involved in the mechanical main subfunctions for each module. These results suggest that wobble board training may modify motor coordination when landing from a lateral jump, focusing on the recruitment of specific muscles/muscle groups that optimize ankle joint stability during early ground contact in single‐leg landing.