Elite Alpine Ski Research Articles

Risk of Graft Rupture After Adding a Lateral Extra-articular Procedure at the Time of ACL Reconstruction: A Retrospective Comparative Study of Elite Alpine Skiers From the French National Team

Background: Elite alpine skiing is associated with a particularly high risk of anterior cruciate ligament (ACL) injuries, including graft ruptures. Despite a considerable focus on prevention, a reduction in injury rates has not been observed since the 1980s. Purpose: To determine whether elite alpine skiers undergoing ACL reconstruction (ACLR) with a lateral extra–articular procedure (LEAP) had a lower rate of ACL graft rupture when compared with those who underwent isolated ACLR. Study Design: Cohort study; Level of evidence, 3. Methods: Elite skiers from the French ski team who had undergone ACLR, with or without a LEAP, and had a minimum follow–up of 2 years were identified from the national ski team database. Rates of secondary ACL injury were determined via interrogation of the database, review of medical notes, and a final telemedicine interview. A multivariable analysis using the penalized Cox model was performed to explore the relationship among graft rupture, surgical procedure type, and any potential explanatory variables. Results: Among 81 ACLR procedures analyzed, 50 were isolated and 31 were combined with a LEAP, which was performed using modified Lemaire or anterolateral ligament reconstruction. Graft rupture rates were 34.0% in the isolated ACLR group and 6.5% in the ACLR + LEAP group. Multivariable analysis demonstrated that adding a LEAP was associated with a significant reduction in risk of ACL graft rupture when compared with isolated ACLR (hazard ratio [HR], 5.286 [95% CI, 1.068-26.149]; P = .0412). Age (HR, 1.114; P = .1157), sex (HR, 1.573; P = .3743), and ACL graft type (HR, 1.417; P = .5394) were not significant risk factors. Conclusion: Combined ACLR and LEAP were associated with a significant reduction in the rate of ACL graft rupture in elite alpine ski athletes. Those treated with isolated ACLR remain at extremely high risk of a second ACL injury.

In-Competition Severe Injury Events in Elite Alpine Ski Racing from 1997 to 2020: The Case of the Austrian Ski Team

BackgroundTo increase safety in elite alpine ski racing Injury Surveillance Systems were implemented and preventive measures introduced. However, studies analysing the change in athletes’ injury risk by controlling for their exposure are still scarce.ObjectivesThis study aimed to describe and analyse the risk of in-competition severe injury events (SIEcomp) in elite alpine ski racing.MethodsData recorded in the Austrian Ski Federation’s Injury Surveillance System were used to analyse the SIEcomp incidence. Information on athletes’ competition exposure was obtained from the official website of the International Ski Federation. In 23 seasons, 2333 skier seasons were recorded for the Austrian Ski Team. Within a total of 114,531 runs 169 SIEcomp occurred. Generalised Estimating Equation for Poisson Regressions were applied.ResultsThe SIEcomp incidence per 1000 runs was 1.48 [95% confidence interval (CI) 1.26–1.73] for elite alpine ski racers and 2.21 (95% CI 1.79–2.75) for the subgroup of World Cup racers. A significant sex difference was detected for the subgroup of junior racers with a higher risk for female athletes [risk ratio (RR): 2.97, 95% CI 1.46–6.05]. Between the seasons of 1997 and 2020, the seasonal SIEcomp incidence increased by a factor of 2.67 for elite alpine ski racers and 3.53 for World Cup racers. Downhill (2.75, 95% CI 2.18–3.47) had the highest SIEcomp incidence, followed by super-G (1.94, 95% CI 1.30–2.88), giant slalom (1.40, 95% CI 1.06–1.85), and slalom (0.64, 95% CI 0.43–0.96).ConclusionAlthough many preventive measures have been implemented in elite alpine ski racing, the risk of SIEcomp has increased over the last two decades.

L’ajout d’une plastie extra-articulaire à la reconstruction du LCA réduit significativement les taux de rupture de greffe : étude rétrospective comparative de skieurs alpins professionnels de l’équipe de France

Elite Alpine ski is associated with a particularly high risk of anterior cruciate ligament (ACL) injuries (including graft ruptures). Despite a considerable focus on prevention a reduction in injury rates has not been observed since the 1980s.

Acute on-snow severe injury events in elite alpine ski racing from 1997 to 2019: the Injury Surveillance System of the Austrian Ski Federation

ObjectivesThe study aimed to (1) determine the incidence and gender-specific risk ratio of acute on-snow severe injury events (SIE) in elite alpine ski racing, (2) examine the development of SIE...

Asymmetries in Ground Reaction Forces During Turns by Elite Slalom Alpine Skiers Are Not Related to Asymmetries in Muscular Strength.

The ground reaction forces (GRF) associated with competitive alpine skiing, which are relatively large, might be asymmetric during left and right turns due to asymmetries in the strength of the legs and torso and the present investigation was designed to evaluate this possibility. While skiing a symmetrical, 20-gate slalom course, the asymmetries of 9 elite alpine skiers were calculated on the basis of measurements provided by inertial motion units (IMU), a Global Navigation Satellite System and pressure insoles. In addition, specialized dynamometers were utilized to assess potential asymmetry in the strength of their legs and torso in the laboratory. In total, seven variables related to GRF were assessed on-snow and eight related to strength of the legs and torso in the laboratory. The asymmetries in these parameters between left and right turns on snow were expressed in terms of the symmetry (SI) and Jaccard indices (JI), while the asymmetries between the left and right sides of the body in the case of the laboratory measurements were expressed as the SIs. The three hypotheses to be tested were examined using multivariable regression models. Our findings resulted in rejection of all three hypotheses: The asymmetries in total GRF (H1), as well as in the GRF acting on the inside and outside legs (H2) and on the rear- and forefeet GRF (H3) during left and right turns were not associated with asymmetries in parameters related to muscular strength. Nevertheless, this group of elite slalom skiers exhibited significant asymmetry between their right and left legs with respect to MVC during ankle flexion (0.53 ± 0.06 versus 0.60 ± 0.07 Nm/kg, respectively) and hip extension (2.68 ± 0.39 versus 2.17 ± 0.26 Nm/kg), as well as with respect to the GRFs on the inside leg while skiing (66.8 ± 7.39 versus 76.0 ± 10.0 %BW). As indicated by the JI values, there were also large asymmetries related to GRF as measured by pressure insoles (range: 42.7–56.0%). In conclusion, inter-limb asymmetries in GRFs during elite alpine skiing are not related to corresponding asymmetries in muscular strength. Although our elite athletes exhibited relatively small inter-limb asymmetries in strength, their asymmetries in GRF on-snow were relatively large.

Muscle-tendon unit length changes in knee extensors and flexors during alpine skiing

ABSTRACT This study characterised the thigh muscle-tendon unit length variations (MTUv) in elite alpine skiing. MTUv were modelled for seven muscles from knee and hip angles in 17 national team skiers during 1602 cycles (546 Slalom (SL), 908 Giant-Slalom (GS), 136 Super-Giant (SG) and 12 Downhill (DH) cycles). The biarticular rectus femoris showed a dynamic pattern on both legs, especially in SL. On the other side, vastii displayed a stable length on the inside leg in all disciplines (37–46% of the cycle), contrasting with their dynamic behaviour on the outside leg being quasi-static for only 3% (SL) to 27% (DH) of the cycle. SL showed the largest amplitude of MTUv followed by GS, SG and DH. For vastus lateralis, MTUv was ~60%Lr.s−1 in SL but only ~12%Lr.s−1 in DH. In SL, a fine desynchronisation between both joints led to nearly constant MTUv (slow lengthening lasting ~45-51% of the cycle) for the biarticular hamstrings separated by faster variations during turn switch from outside to inside leg. In summary, biarticular MTUv were not characterised by single-joint behaviours, suggesting that extrapolating contraction regimen from knee joint only is not accurate in alpine skiing.

Nationality and sociocultural factors influence athlete development and sport outcomes: Perspectives from United States and Austrian youth alpine ski racing

ABSTRACT Geographical regions possess distinct sporting cultures that can influence athletic development from a young age. The United States (US) and Austria both produce elite alpine ski racers, yet have distinct sport structures (i.e., funding, skiing prominence). In this exploratory study, we investigated sport outcomes and psychological profiles in adolescent alpine ski racers attending skill development academies in the US (N= 169) and Austria (N= 209). Sport participation and psychological questionnaires (mental toughness, perfectionism, grit, coping, burnout) were administered to athletes. In Austria, athletes participated in fewer extracurricular sports, began competing and training younger, and accumulated less practice hours than athletes in the US. Athletes in the US reported greater burnout than athletes in Austria. Finally, in the US, women accumulated more practice hours and experienced more parental pressure than men, while men accumulated more practice hours in Austria. Austria’s skiing-centric sport culture may encourage athletes to fully immerse into the sport, contributing to positive psychological outcomes. Reduced sport opportunities in the US beyond educational institutions may pressure athletes to practice more to ensure continued competitive skiing. Stressors for sport participation will be unique to gender in each country though, given their implicit gender stigmas for sport participation.

Supramaximal Eccentric Training for Alpine Ski Racing—Strength Training with the Lifter

Eccentric muscular work plays a large role in alpine ski racing. Training with supramaximal eccentric loads (SME) is highly effective to improve eccentric strength but potentially dangerous. Most SME training devices do not allow the athlete to move a barbell freely as they would when performing conventional barbell training. The Intelligent Motion Lifter (IML) allows for safe SME training with a free barbell and no spotters. The IML can be used for free barbell training: a spotter for normal training, eccentric only, concentric only, and squat jumps. It is also a training and testing device for isokinetic and isometric exercise. This commentary addresses the necessity of eccentric training for elite alpine ski racers, the development of the IML and its use in training.

Changes in Anthropometric and Fitness Characteristics Over a Decade of Young Elite Alpine Ski Racers

The aim of this study was to evaluate whether anthropometric and fitness characteristics have changed between former and current elite male and female Austrian young ski racers (U11-U15). A battery of anthropometric, general, and skiing-specific fitness tests was conducted annually. In total, 1517 participants (846 males, 671 females) who were tested in 2005-2009 ("former athletes" n = 805) and 2015-2019 ("current athletes" n = 712) were included. Independent t tests and Cohen d were calculated to compare the two 5-y periods, separated by sex and age group. The level of significance was set at P < .05. No significant change in anthropometric characteristics was found over the decade. Current young ski racers performed significantly better in the maximal core flexion strength test in all age categories (ES = 0.88-1.50; P < .02). Core extension strength values were higher in current male U12 and female U12 and U13 athletes (ES = 0.54-0.71; P < .01) and better postural stability values in the lateral direction were found in the age categories U12 and U14 (ES = 0.36-0.68; P < .05), as well as in the forward/backward direction in the age categories U12-U14 (ES = 0.38-1.12; P < .03). Lower-leg extension strength values were apparent in the current U13-U15 age categories (ES = 0.36-1.03; P ≤ .001) and lower drop-jump reactive strength indices in the U13-U15 male athletes (ES = 0.49-0.80; P < .01). Current and former young ski racers differ significantly in some fitness parameters, which might lead to the assumption that some aspects (such as core strength) have gained more focus in athletic training during the last years compared with 15 y ago.

Validation of the alpine skiing 90 seconds box jump field test and prediction of power output.

The purpose of this study was to validate the alpine ski racing 90 s box jump field-test (BJ90) with the 90 s Wingate test (W90). Fifteen elite alpine ski racers were tested on the BJ90 (0.45 m × 0.75 m × 0.9 m) and the W90 (Ergomedic 894 E Monark; Monark AB, Varberg, Sweden) test in a random order. The number of hits on the BJ90 was written down every 15 s and for the W90 the load (7.5% of body weight) was manually dropped once the subjects reached maximum RPM without resistance. Correlations and partial correlations were calculated with a 2-tailed Pearson correlation analysis. A stepwise forward regression analysis was also performed. Results present significant (P<0.05) correlations and partial correlations adjusted for body weight between the total number of hits on the BJ90 and W90 peak W, peak W/kg, mean W and mean W/kg as well as with the number of hits and W90 Mean W and mean W/kg between each 15 s time slot. A linear regression predictive equation for mean relative power (W/kg) generated from the BJ90 was established: mean relative power (W/kg)=0.055*total hits+1.080 (r=0.79, P<0.001; total hits with mean W/kg). A stepwise forward regression equation for mean absolute power (W) generated from the BJ90 was also established: mean absolute power (W)=2.305*number of hits+5.081*body weight in kg-1 -169.8 (R=0.964, P<0.001, SEE=23.56). Practitioners could use the BJ90 to assess alpine skiers lower body power as previous research showed that both are correlated with performance and are able to discriminate skier level.

Validation Of The Alpine Ski Racing 90 Seconds Box Jump Field Test

Practitioners have utilized sport specific alpine ski racing field tests for lower limb power assessment for many years. PURPOSE: The purpose of this study was to validate the alpine ski racing 90 s box jump field test with the 90 s Wingate. METHODS: Elite alpine ski racers (n=15) were tested during their annual post-season physical testing combine. The box 90s box jump test was conducted on a foam plyo box of 0.45m x 0.75m x 0.9m (14 kg Plyosoft box from Escape Fitness). Subjects started at one side of the box and had to do a side jump and make contact with the top of the box and then jump back down to the other side back and forth. Final score being the total number of hits in 90 s. The Wingate test was conducted on a cycle ergometer (Ergomedic 894 E Monark). Subjects had to pedal with no resistance until they reached maximum RPM (about 5-10 s). The load (7.5% of bodyweight) was then manually dropped and subjects had to pedal at a maximal effort for 90 s. Wingate peak and mean power was measured in W and W/kg of bodyweight. Both tests were performed in a random order. Correlations between the different test results were calculated with a 2-tailed Pearson correlation analysis. Statistical significance was set at p<0.05. Subject characteristics are presented as means and standard deviations. RESULTS: Results present significant (p<0.05) correlations between the total number of hits on the 90 s box jump and Wingate peak W (r=0.73), peak W/kg (r=0.68), mean W (r=0.77) and mean W/kg (r=0.79). Results also present significant correlations with the number of hits between the following time slots: 0-15 s mean W (r=0.49), 0-15 s mean W/kg (r=0.72), 15-30 s mean W (r=0.66), 15-30 s mean W/kg (r=0.71), 30-45 s mean W (r=0.59), 30-45 s mean W/kg (r=0.66), 45-60 s mean W (r=0.82), 45-60 s mean W/kg (r=0.77), 60-75 s mean W (r=0.83), 60-75 s mean W/kg (r=0.65), 75-90 s mean W (r=0.75) and 75-90 s mean W/kg (r=0.71). A predictive regression equation using the total hits during the 90s Box Jump Test was established, where mean W/kg = 0.055*Total Hits + 1.080 (r=0.79, p<0.01; Total Hits with mean W/kg). CONCLUSIONS: The 90s box jump test is well correlated to the power output obtained with the Wingate test. Nonetheless, further research should include subjects at the national and international level in order to update the formula.

Monitoring the Return to Sport Transition After ACL Injury: An Alpine Ski Racing Case Study.

Alpine ski racing is an extreme sport and ski racers are at high risk for ACL injury. ACL injury impairs neuromuscular function and psychological readiness putting alpine skiers with ACL injury at high risk for ACL reinjury. Consequently, return to sport training and testing protocols are recommended to safeguard ACL injured athletes against reinjury. The aim of this paper was to present a real-world example of a return to sport training plan for a female elite alpine ski racer who sustained an ACL injury that was supported by an interdisciplinary performance team (IPT) alongside neuromuscular testing and athlete monitoring. A multi-faceted return to sport training plan was developed by the IPT shortly after the injury event that accounted for the logistics, healing, psychological readiness, functional milestones, work capacity and progression to support the return to sport/return to performance transition. Neuromuscular testing was conducted at several timepoints post-injury. Importantly, numerous pre-injury tests provided a baseline for comparison throughout the recovery process. Movement competencies and neuromuscular function were assessed, including an evaluation of muscle properties (e.g., the force-velocity and force-length relationships) to assist the IPT in pinpointing trainable deficits and managing the complexities of the return to sport transition. While the athlete returned to snow 7 months post-injury, presenting with interlimb asymmetries below 10%, functional and strength deficits persisted up to 18 months post-injury. More research is required to establish a valid return to sport protocol for alpine ski racers with ACL injury to safeguard against the high risk for ACL reinjury.

엘리트 알파인과 크로스컨트리 스키선수의 골밀도와 신체구성 및 등속성 근기능의 비교

엘리트 알파인과 크로스컨트리 스키선수의 골밀도와 신체구성 및 등속성 근기능의 비교

엘리트 알파인과 크로스컨트리 스키선수의 골밀도와 신체구성 및 등속성 근기능의 비교

엘리트 알파인과 크로스컨트리 스키선수의 골밀도와 신체구성 및 등속성 근기능의 비교

Strength deficits of the hamstrings following surgery on the anterior cruciate ligament: a case-control ­study of elite alpine ski racers

Background: Research to date clearly shows that injuries to the cruciate ligaments are a frequent occurrence in alpine ski racing. The hamstrings play an important role in protecting the anterior cruciate ligament (ACL). Here eccentric muscle activity, in particular, is of great significance as it plays a more important role in terms of duration and intensity than concentric muscle activity in alpine ski racing. The aim of this study was to establish whether the hamstrings of alpine ski racers show eccentric strength deficits following surgery on the anterior cruciate ligament. Methods: A case-control study was performed with athletes who had undergone surgery on the anterior cruciate ligament 49 ± 41 months previously and healthy ski racers. The total eccentric strength of both legs measured in the hamstrings supporting the ACL (n=18) was compared with the healthy group (n=70); the strength of the operated leg was also compared with the healthy leg and with the mean for the healthy group. Eccentric strength was measured during the Nordic hamstrings exercise performed on the NordBord hamstring testing system. Group comparisons were performed using ANOVA and Bonferroni Post-hoc analyses. Multiple linear regressions were used to assess the relevant independent variables explaining total eccentric strength and Limb Symmetry Index. Results: The relative total eccentric strength of both legs in the hamstrings of the ACL group was significantly lower than in the healthy group (p=0.031). In addition, the relative eccentric strength of the operated leg was significantly lower compared to the healthy group (p=0.024). Leg asymmetry was also significantly greater in athletes who had undergone surgery on one leg (p=0.016) than in healthy subjects and athletes who had undergone surgery on both legs. 56% of the total eccentric strength of both legs could be explained by surgery, age and gender. 18% of the leg asymmetry was explained by the variables surgery, total eccentric strength of both legs and height. Conclusion: Several years after anterior cruciate ligament surgery, ski racers still have deficits in terms of the eccentric strength of their hamstrings compared with healthy ski racers. Therefore more attention should be paid during rehabilitation to the eccentric strength of the hamstrings with a view to strengthening and testing them. Measurement using the NordBord system is suitable for routine monitoring of eccentric strength. Further studies are needed to improve understanding of the influence of hamstrings strength on cruciate ligament injuries.

A comparison of lower limb stiffness and mechanical muscle function in ACL-reconstructed, elite, and adolescent alpine ski racers/ski cross athletes

PurposeThe aim of this study was to compare mechanical muscle function in the eccentric/concentric phases of vertical bilateral jumping in anterior cruciate ligament-reconstructed (ACLR), elite (ELITE), and adolescent (ADOL) alpine ski racers and ski cross athletes. MethodsAlpine ski racers/ski crossers (ACLR: n = 12, age = 26.7 ± 3.8 years; ELITE: n = 12, age = 23.9 ± 3.0 years; ADOL: n = 12, age = 17.8 ± 0.7 years; females: n = 6 per group, males: n = 6 per group) performed 5 maximal countermovement jumps (CMJs) and 5 squat jumps. The ground reaction forces for each limb were analyzed using dual force plate recording to obtain body center of mass (BCM) velocity, displacement, and power. The eccentric deceleration (ECC) and concentric phases were determined from BCM velocity. CMJ net concentric and ECC impulses were calculated (body mass normalized) along with the peak and mean BCM power and maximal vertical jump height. CMJ lower limb stiffness (LLS) was determined by the slope of the ground reaction forces vs. the BCM displacement curve over the ECC phase. Concentric and ECC asymmetry indices were calculated for each leg, and the left vs. right LLS was compared. Outcome measures (reported as mean ± SD) calculated as a 5-jump mean were normalized to body mass and compared using an analysis of variance. ResultsNo between-group differences were found for peak and mean power or jump heights. There were no group differences for LLS or net concentric phase impulse, but the net ECC impulse was lower in the ADOL group compared with ELITE skiers (ADOL: 1.33 ± 0.32 Ns/kg; ELITE: 1.59 ± 0.16 Ns/kg; p < 0.05). Although no group differences were found for ECC asymmetry indices, a group × limb interaction was found for LLS (p < 0.01), which was systematically higher in the right vs. the left limb of ADOL skiers (right: 54.1 ± 17.9 N/m/kg; left: 48.7 ± 15.7 N/m/kg; p < 0.01). ConclusionADOL skiers demonstrated decreased ECC impulse and systematic right limb dominance in LLS compared with ACLR and ELITE skiers. The implication of these findings for injury and performance are unknown, but further investigation into these potential relationships is warranted.

An Inverse Relative Age Effect in Male Alpine Skiers at the Absolute Top Level.

The Relative Age Effect (RAE) can be described as the advantage of being born early after a certain cut-off date within a group of selection. The effect has been found across a wide range of sports and is particularly evident in pre-elite sports and team sports with a high selection pressure. At the absolute top level in team elite sports, the advantage of being relatively older has been reported to disappear, and even reverse, so that the relatively younger athletes are advantaged. In order to further examine such a reversal of the RAE, we investigated the performance of the overall top 50 skiers each year in the alpine World Cup, over a period of 20 years, among men (N = 234) and women (N = 235). The data indicated that the relatively younger male athletes at the absolute top level had accumulated, on average, more World Cup points compared to the relatively older skiers. No such effect was observed among the female skiers. This finding suggest the existence of a reversed relative age effect in male elite alpine skiing.

A Retrospective Analysis of Concurrent Pathology in ACL-Reconstructed Knees of Elite Alpine Ski Racers.

Background:Anterior cruciate ligament (ACL) tear is the most frequent injury in alpine ski racing, and there is a high prevalence of ACL reinjury. Limited data exist on the concurrent pathology with primary ACL tears in elite alpine ski racers and the magnitude of injury progression after primary ACL reconstruction (ACLR).Purpose:To evaluate (1) the involvement of intra-articular and multiligament pathologies at the time of primary ACLR, (2) the subsequent progression in meniscal/chondral injuries, and (3) the occurrence of ACL reinjury in elite alpine ski racers.Study Design:Case series; Level of evidence, 4.Methods:Primary ACLR operative reports (n = 28) were obtained for 32 elite alpine ski racers along with the reports of 20 operative procedures that occurred subsequent to primary ACLR. Operative reports were evaluated to identify the presence/location of multiligament injury, meniscal tears, and chondral lesions.Results:At the time of primary ACLR, a majority of knees (82%; 23/28) demonstrated concurrent injury compared with isolated ACL tears; 32% of knees sustained multiligament injuries (9/28), and 8 involved the ipsilateral medial collateral ligament (MCL). Of the ACL-injured knees, 54% had chondral lesions, of which 73% were sustained in the lateral knee compartment, and 82% of meniscal tears (14/17) were complex in nature. Bilateral ACL tears were seen in 22% of the participants, and 28% underwent ACL revision. In the case of ACL revision or future meniscal/chondral surgery, 60% of meniscal tears and 80% of chondral lesions had worsened since the time of primary ACLR.Conclusion:Concurrent injury was common in this group of elite ski racers. Primary ACL tears were typically accompanied by lateral compartment chondral lesions and complex meniscal tears that worsened over time. ACL/MCL tears were the most common multiligament injury pattern.

ACE and ACTN3 Genotypes with Physical Fitness and Performance in Collegiate Elite Alpine Ski Racer

ACE and ACTN3 Genotypes with Physical Fitness and Performance in Collegiate Elite Alpine Ski Racer

Asymmetry and Thigh Muscle Coactivity in Fatigued Anterior Cruciate Ligament-Reconstructed Elite Skiers.

The acute effects of fatigue on functional interlimb asymmetry and quadriceps/hamstring muscle activity levels, including preparatory coactivation during squat jump takeoff and landing, were evaluated in elite alpine ski racers with/without anterior cruciate ligament reconstruction (ACLR). Twenty-two elite ski racers (ACLR, n = 11; control, n = 11) performed an 80-s repeated squat jump test (jump test) on a dual force plate system with simultaneous EMG recordings in vastus lateralis, vastus medialis, semitendinosus, and biceps femoris. Asymmetry index (AI) and jump height of body center of mass (HBCM) were calculated from the ground reaction force. The normalized EMG amplitudes were obtained at takeoff, at the 25-ms interval prelanding, and at postlanding for the ACLR limb (affected limb), contralateral limb, and limbs of the control subjects (control limb). Jump height decreased with fatigue for both groups, and ACLR skiers demonstrated elevated AI in the late takeoff phase versus the early takeoff and landing phases (P < 0.0001). No fatigue-induced changes in AI were found. The affected limb of ACLR skiers showed lower normalized quadriceps EMG activity at takeoff, prelanding, and postlanding along with increased hamstring activity prelanding and postlanding compared with the contralateral limb and control limb (P < 0.001). The affected limb, contralateral limb, and control limb all demonstrated increased quadriceps and decreased hamstring activity with fatigue (P < 0.001). Functional AI values were not changed with fatigue, and the affected limb of ACLR skiers who successfully returned to sport demonstrated more hamstring dominant landings compared with the contralateral limb and uninjured control limbs. Skiers with/without ACLR demonstrated more quadriceps dominant landings with fatigue.