Effects of fatigue on lower limb, pelvis and trunk kinematics and lower limb muscle activity during single-leg landing after anterior cruciate ligament reconstruction

Fatigue-induced Landing Alterations in ACL Reconstructed Athletes after Return-to-Sport

At the time of return-to-sport, anterior cruciate ligament reconstructed athletes still show altered neuromechanics in their injured leg during single leg hopping tasks. Part of these alterations can be magnified when these athletes are fatigued. So far, little is known whether fatigue-induced landing alterations persist after return-to-sport. Therefore, the aim of this study was to evaluate whether these alterations persist in the six months following return-to-sport. Sixteen anterior cruciate ligament reconstructed athletes performed five unilateral hop tasks before and after a fatigue protocol. The hop tasks were executed at three different time points (return-to-sport, 3 and 6 months post-return-to-sport). A 2-by-3 repeated measures ANOVA was performed to evaluate whether fatigue-induced landing alterations persisted 3 and 6 months following return-to-sport. At 6 months following return-to-sport, fatigue still induces a reduction in hamstring medialis activation and an increase in the knee abduction moment during a vertical hop with 90-degree inward rotation. Most fatigue-induced landing alterations present at the time of return-to-sport normalize after resumption of sports activities. However, a larger knee abduction moment in the injured leg after resumption of sports activities can still be observed.

Hip Strength Recovery After Anterior Cruciate Ligament Reconstruction

Background

Return-to-play (RTP) assessment after anterior cruciate ligament reconstruction (ACLR) rarely includes hip strength.

Hypothesis

It was hypothesized that (1) patients after ACLR will have weaker hip abduction (AB) and adduction (AD) strength compared with the contralateral limb, with larger deficits in women, (2) there will be a correlation between hip and thigh strength ratios and patient-reported outcomes (PROs), and (3) hip AB and AD strength will improve over time.

Study Design

Descriptive laboratory study.

Methods

Included were 140 patients (74 male, 66 female; mean age, 24.16 ± 10.82 years) who underwent RTP assessment at 6.1 ± 1.6 months after ACLR; 86 patients underwent a second assessment at 8.2 ± 2.2 months. Hip AB/AD and knee extension/flexion isometric strength were measured and normalized to body mass, and PRO scores were collected. Strength ratios (hip vs thigh), limb differences (injured vs uninjured), sex-based differences, and relationships between strength ratios and PROs were determined.

Results

Hip AB strength was weaker on the ACLR limb (ACLR vs contralateral: 1.85 ± 0.49 vs 1.89 ± 0.48 N·m/kg; P < .001) and hip AD torque was stronger (ACLR vs contralateral: 1.80 ± 0.51 vs 1.76 ± 0.52 N·m/kg; P = .004), with no sex-by-limb interaction found. Lower hip-to-thigh strength ratios of the ACLR limb were correlated with higher PRO scores (r = -0.17 to -0.25). Over time, hip AB strength increased in the ACLR limb more than in the contralateral limb (P = .01); however, the ACLR limb remained weaker in hip AB at visit 2 (ACLR vs contralateral: 1.88 ± 0.46 vs 1.91 ± 0.45 N·m/kg; P = .04). In both limbs, hip AD strength was greater at visit 2 than visit 1 (ACLR: 1.82 ± 0.48 vs 1.70 ± 0.48 N·m/kg; contralateral: 1.76 ± 0.47 vs 1.67 ± 0.47 N·m/kg; P < .01 for both).

Conclusion

The ACLR limb had weaker hip AB and stronger AD compared with the contralateral limb at initial assessment. Hip muscle strength recovery was not influenced by sex. Hip strength and symmetry improved over the course of rehabilitation. Although strength differences across limbs were minor, the clinical importance of these differences is still unknown.

Clinical Relevance

The evidence provided highlights the need to integrate hip strength into RTP assessments to identify hip strength deficits that may increase reinjury or lead to poor long-term outcomes.

Subsequent Jumping Increases the Knee and Hip Abduction Moment, Trunk Lateral Tilt, and Trunk Rotation Motion During Single-Leg Landing in Female Individuals

Single-leg landings with or without subsequent jumping are frequently used to evaluate landing biomechanics. The purpose of this study was to investigate the effects of subsequent jumping on the external knee abduction moment and trunk and hip biomechanics during single-leg landing. Thirty young adult female participants performed a single-leg drop vertical jumping (SDVJ; landing with subsequent jumping) and single-leg drop landing (SDL; landing without subsequent jumping). Trunk, hip, and knee biomechanics were evaluated using a 3-dimensional motion analysis system. The peak knee abduction moment was significantly larger during SDVJ than during SDL (SDVJ 0.08 [0.10] N·m·kg-1·m-1, SDL 0.05 [0.10] N·m·kg-1·m-1, P = .002). The trunk lateral tilt and rotation angles toward the support-leg side and external hip abduction moment were significantly larger during SDVJ than during SDL (P < .05). The difference in the peak hip abduction moment between SDVJ and SDL predicted the difference in the peak knee abduction moment (P = .003, R2 = .252). Landing tasks with subsequent jumping would have advantages for evaluating trunk and hip control as well as knee abduction moment. In particular, evaluating hip abduction moment may be important because of its association with the knee abduction moment.

Neuromuscular activity of the lower-extremities during running, landing and changing-of-direction movements in individuals with anterior cruciate ligament reconstruction: a review of electromyographic studies

PURPOSE

Running, jumping/landing and cutting/change of direction (CoD) are critical components of return to sport (RTS) following anterior cruciate ligament reconstruction (ACLR), however the electromyographic (EMG) activity patterns of the operated leg during the execution of these tasks are not clear.

METHODS

A systematic review was conducted to retrieve EMG studies during running, jumping/landing and cutting/(CoD) in ACLR patients. MEDLINE, PubMed, SPORTDiscus and Web of Science databases were searched from 2000 to May, 2022 using a combination of keywords and their variations: "anterior cruciate ligament reconstruction" OR "ACLR", "electromyography" OR "EMG", "running", "jumping" OR "landing", "cutting" OR "change-of-direction" OR "CoD". The search identified studies comparing EMG data during running, landing and cutting/(CoD) between the involved limb and contralateral or control limbs. Risk of bias was assessed and quantitative analyses using effect sizes were performed.

RESULTS

Thirty two studies met the inclusion criteria. Seventy five percent (24/32) of the studies reported altered EMG activity pattern of the ACLR leg during running, jumping/landing and cutting/(CoD) when compared with either the healthy control leg or the contra-lateral leg. Twelve studies showed decreased, delayed or earlier onset and delayed peak in quadriceps EMG activity with small to large effect sizes and 9 studies showed increased, delayed or earlier onset and delayed peak in hamstrings EMG activity with small to large effect sizes. Four studies showed a "hamstrings-dominant" strategy i.e. decreased quadriceps coupled with increased hamstrings EMG activity in both running and jumping/landing irrespective of graft type. One study reported that on the grounds of decreased quadriceps activity, lower hamstrings EMG activity was predictive of ipsilateral re-injury in ACLR patients.

CONCLUSION

This systematic review of Level III evidence showed that the ACLR leg displays decreased quadriceps or increased hamstrings EMG activity or both despite RTS. Simultaneous decreased quadriceps and increased hamstrings EMG activity was shown for both running and jumping/landing. From a clinical perspective this "hamstrings dominant" strategy can serve as a protective mechanism against graft re-injury.

LEVEL OF EVIDENCE

III.

The Effect of Fatigue on Trunk and Pelvic Jump-Landing Biomechanics in View of Lower Extremity Loading: A Systematic Review

Fatigue has often been considered a risk factor for developing sports injuries, modulating lower extremity jump-landing biomechanics. The impact of fatigue on proximal trunk and pelvic biomechanics has been suggested to play an important role in lower extremity loading and injury risk, yet the available evidence remains ambiguous as the trunk and pelvis were often not the primary focus of research. Therefore, the purpose of this systematic review was to determine how fatigue affects trunk and pelvic three-dimensional jump-landing biomechanics. PubMed (MEDLINE), Web of Science, Embase, CINAHL and SPORTDiscus were consulted up to and including April 2022 for potential studies investigating the effect of fatigue on trunk and pelvic kinematics, kinetics and/or muscular activity during jump-landing tasks in healthy, physically active populations. Methodological quality of the studies was assessed by the modified Downs and Black checklist. Twenty-one studies were included and methodological quality was moderate to high among these studies. The results indicate prevailing evidence for more trunk flexion during standardized jump-landing tasks after lower extremity muscle fatigue. Otherwise, lumbo-pelvic-hip muscle fatigue does not seem to elicit major detrimental changes to these jump-landing biomechanics. Although a wide variability of trunk and pelvic jump-landing strategies was observed, the results provide evidence for increased trunk flexion after lower extremity muscle fatigue. This proximal strategy is suggested to help unload fatigued lower extremity structures and lack of this compensation might increase knee injury risk.

A facile inverse dynamics method to study the impacts of fatigue on the lower limb biomechanics

Fatigue can significantly affect the biomechanics of the anterior cruciate ligament (ACL) during single-legged jumping, and these changes are closely related to ACL injuries. Unfortunately, there is no convenient way to accurately and quickly track these changes. This present study aimed to develop such a method based on video capture and inverse dynamics simulation.Are our method's results accurate and reliable? Fifteen participants performed sing-legged jumping before and after the fatigue protocol, and their actions were videotaped. The videos were processed and converted to marked motion data, used to drive the mannequin model in AnyBody Modelling System (AMS) for the inverse dynamics simulations. The ACL segment was also constructed based on one participant's MRI data and added the mannequin model.Our results were similar to the findings from previous studies. Neuromuscular fatigue decreased the peak flexion angles and increased the low-the-limb muscle strength and activation. These alterations might contribute to ACL tears and ruptures. In addition, the simulation showed that the ACL force significantly (p < 0.05) increased as a result of fatigue during single-legged jumping. Our study provides a facile and reliable method to study the effects of neuromuscular fatigue on lower-the-limb biomechanics. Such a method can be applied to investigate other risk factors on ACL injuries and assist in developing workable plans for athlete training in the future.

Trunk Biomechanics in Individuals with Knee Disorders: A Systematic Review with Evidence Gap Map and Meta-analysis

BACKGROUND

The trunk is the foundation for transfer and dissipation of forces throughout the lower extremity kinetic chain. Individuals with knee disorders may employ trunk biomechanical adaptations to accommodate forces at the knee or compensate for muscle weakness. This systematic review aimed to synthesize the literature comparing trunk biomechanics between individuals with knee disorders and injury-free controls.

METHODS

Five databases were searched from inception to January 2022. Observational studies comparing trunk kinematics or kinetics during weight-bearing tasks (e.g., stair negotiation, walking, running, landings) between individuals with knee disorders and controls were included. Meta-analyses for each knee disorder were performed. Outcome-level certainty was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE), and evidence gap maps were created.

RESULTS

A total of 81 studies investigating trunk biomechanics across six different knee disorders were included (i.e., knee osteoarthritis [OA], total knee arthroplasty [TKA], patellofemoral pain [PFP], patellar tendinopathy [PT], anterior cruciate ligament deficiency [ACLD], and anterior cruciate ligament reconstruction [ACLR]). Individuals with knee OA presented greater trunk flexion during squatting (SMD 0.88, 95% CI 0.58-1.18) and stepping tasks (SMD 0.56, 95% CI 0.13-.99); ipsilateral and contralateral trunk lean during walking (SMD 1.36; 95% CI 0.60-2.11) and sit-to-stand (SMD 1.49; 95% CI 0.90-2.08), respectively. Greater trunk flexion during landing tasks in individuals with PFP (SMD 0.56; 95% CI 0.01-1.12) or ACLR (SMD 0.48; 95% CI 0.21-.75) and greater ipsilateral trunk lean during single-leg squat in individuals with PFP (SMD 1.01; 95% CI 0.33-1.70) were also identified. No alterations in trunk kinematics of individuals with TKA were identified. Evidence gap maps outlined the lack of investigations for individuals with PT or ACLD, as well as for trunk kinetics across knee disorders.

CONCLUSION

Individuals with knee OA, PFP, or ACLR present with altered trunk kinematics in the sagittal and frontal planes. The findings of this review support the assessment of trunk biomechanics in these individuals in order to identify possible targets for rehabilitation and avoidance strategies.

TRIAL REGISTRATION

PROSPERO registration number: CRD42019129257.

The influence of gluteal muscle strength deficits on dynamic knee valgus: a scoping review

Anterior cruciate ligament (ACL) injuries are caused by both contact and non-contact injuries. However, it can be claimed that non-contact ones account approximately for 70% of all cases. Thus, several authors have emphasized the role of reduction of muscle strength as a modifiable risk factor referred to non-contact ACL injury, with the latter being targeted by specific training interventions.The present paper wants to review the available literature specifically on the relationship between dynamic knee valgus, gluteal muscles (GM) strength, apart from the potential correlation regarding ACL injury.After a research based on MEDLINE via PubMed, Google scholar, and Web of Science, a total of 29 articles were collected and thus included.Additionally, this review highlights the crucial role of gluteal muscles in maintaining a correct knee position in the coronal plane during different exercises, namely walking, running, jumping and landing.

Which assessments are used to analyze neuromuscular control by electromyography after an anterior cruciate ligament injury to determine readiness to return to sports? A systematic review

BACKGROUND

Adequate neuromuscular control of the knee could be one element to prevent secondary injuries after an anterior cruciate ligament (ACL) injury. To assess neuromuscular control in terms of time, amplitude and activity, electromyography (EMG) is used. However, it is unclear which assessments using EMG could be used for a safe return to sports (RTS). Therefore, we aimed to summarize EMG-related assessments for neuromuscular control of the knee in adult patients after an ACL injury to decide upon readiness for RTS.

METHODS

This systematic review followed guidelines of Preferred Reporting of Items for Systematic Reviews and Meta-Analyses (PRISMA) and Cochrane recommendations. MEDLINE/PubMed, EMBASE, CINAHL, Cochrane Library, Physiotherapy Evidence Database (PEDro), SPORTDiscus and the Web of Science were searched from inception to March 2019 and updated in November 2020. Studies identifying electromyographic assessments for neuromuscular control during dynamic tasks in adult, physically active patients with an anterior cruciate ligament injury were eligible and qualitatively synthesized. Two independent reviewers used a modified Downs and Black checklist to assess risk of bias of included studies.

RESULTS

From initially 1388 hits, 38 mainly cross-sectional, case-controlled studies were included for qualitative analysis. Most studies provided EMG outcomes of thigh muscles during jumping, running or squatting. Outcomes measures described neuromuscular control of the knee in domains of time, amplitude or activity. Risk of bias was medium to high due to an unclear description of participants and prior interventions, confounding factors and incompletely reported results.

CONCLUSIONS

Despite a wide range of EMG outcome measures for neuromuscular control, none was used to decide upon return to sports in these patients. Additional studies are needed to define readiness towards RTS by assessing neuromuscular control in adult ACL patients with EMG. Further research should aim at finding reliable and valid, EMG-related variables to be used as diagnostic tool for neuromuscular control. Moreover, future studies should aim at more homogenous groups including adequately matched healthy subjects, evaluate gender separately and use sport-specific tasks. Registration The protocol for this systematic review was indexed beforehand in the International Prospective Register of Systematic Reviews (PROSPERO) and registered as CRD42019122188.

Comparing myofascial meridian activation during single leg vertical drop jump in patients with anterior cruciate ligament reconstruction and healthy participants

BACKGROUND

Muscles work synergistically to support the body during landing. Myofascial meridians have been described to classify muscles into functional synergies. The role that these functional lines plays in positioning the trunk and lower extremity of patients with anterior cruciate ligament reconstruction (ACLR) and healthy athletes during drop landing tasks remains unclear.

RESEARCH QUESTION

The purpose of this study was to compare the front and back functional lines (FFL and BFL) muscle activation in patients with ACLR and healthy participants during single leg vertical drop jump (SLVDJ).

METHODS

Thirty-two male athletes (post-ACLR = 16, healthy = 16) participated (age = 23.3 ± 2.3 years). Superficial electromyography of FFL (adductor longus [AL], rectus abdominis [RA], pectoralis major) and BFL (vastus lateralis [VL], gluteus maximus [GMax], latissimus dorsi [LD]) was collected during the SLVDJ and compared at initial contact and maximum knee flexion between groups using t-tests and limbs using paired-samples t-tests.

RESULTS

In the FFL, the AL (p < 0.05) and RA (p < 0.05) muscles were more active in the healthy group compared to the ACLR group at initial contact and maximum knee flexion. PM demonstrated greater activation in the healthy group only at maximum knee flexion (p < 0.05). In the BFL, the VL (p < 0.05) and GMax (p < 0.05) muscles were more active in the ACLR group, whereas the LD (p < 0.05) muscles demonstrated greater activation in the healthy group at initial contact and maximum knee flexion. There were no healthy group inter-limb differences in FFL and BFL activation. ACLR participants demonstrated greater non-injured limb VL, AL, GMax and LD activation (p < 0.05) and greater injured limb PM and RA activation (p < 0.05).

SIGNIFICANCE

Based on the present data, patients after ACLR may present with an alteration in BFL and FFL muscles activation during a drop jump task. Functional line muscles during dynamic activities may change lower extremity positioning and lead to increase ACL injury risk.

Influence of Fatigue on Some Kinematic Parameters of Basketball Passing

Kinematic analysis is an objective method for examining basketball technique. However, there are just a few studies featuring a kinematic analysis of passing. The purpose of this study was to determine whether the kinematic parameters and accuracy of passing changed when players were under the influence of fatigue. Eleven Croatian basketball players who are members of the youth national program (age: 18.36 ± 0.67 years; height: 192.32 ± 9.98 cm; weight: 83.35 ± 11.19 kg; body fat: 15.00 ± 4.40%, arm span: 194.34 ± 10.39 cm) participated in fatigue and non-fatigue repetitive tests. A Xsens suit was used to analyze the kinematic parameters of push passing; a radar gun was used to determine ball speed; heart rate and blood lactate were used to identify fatigue and non-fatigue state. There was a significant difference in angular velocities of shoulder (p = 0.01), elbow (p = 0.04), and wrist (p = 0.01), accuracy (p = 0.01), ball speed (p = 0.00), pelvis position (p = 0.00), and velocity of the pelvis in X-axis (p = 0.00) between fatigue and non-fatigue state. Fatigue influences some kinematic parameters and accuracy of passing. The findings of this study suggest that coaches conduct as many drills as possible in situational conditions that are similar to the conditions during the basketball game itself.

Effects of Toe Direction on Biomechanics of Trunk, Pelvis, and Lower-Extremity During Single-Leg Drop Landing

CONTEXT

Toe direction is an important factor affecting knee biomechanics during various movements. However, it is still unknown whether toe direction will affect trunk and pelvic movements.

OBJECTIVE

To examine and clarify the effects of toe directions on biomechanics of trunk and pelvis as well as lower-extremities during single-leg drop landing (SLDL).

DESIGN

Descriptive laboratory study.

SETTING

Research laboratory.

PARTICIPANTS

A total of 27 male recreational-level athletes.

INTERVENTION(S)

Subjects performed SLDL under 3 different toe directions, including 0° (toe neutral), 20° (toe-in [TI]), and -20° (toe-out). SLDL was captured using a motion analysis system. Nondominant leg (27 left) was chosen for the analysis.

MAIN OUTCOME MEASURES

Peak values of kinematic and kinetic parameters during landing phase were assessed. In addition, those parameters at the timing of peak vertical ground reaction force were also assessed. The data were statistically compared among 3 different toe directions using 1-way repeated measures of analysis of variance or Friedman χ2 r test.

RESULTS

Peak knee abduction angle and moment in TI were significantly larger than in toe neutral and toe-out (P < .001). Moreover, peak greater anterior inclination, greater inclination, and rotation of trunk and pelvis toward the nonlanding side were seen in TI (P < .001). At the timing of peak vertical ground reaction force, trunk inclined to the landing side with larger knee abduction angle in TI (P < .001).

CONCLUSIONS

Several previous studies suggested that larger knee abduction angle and moment on landing side as well as trunk and pelvic inclinations during landing tasks were correlated with knee ligament injury. However, it is still unknown concerning the relationship between toe direction and trunk/pelvis movements during landing tasks. From the present study, TI during SLDL would strongly affect biomechanics of trunk and pelvis as well as knee joint, compared with toe neutral and toe-out.

Altered Neuromuscular Activity of the Lower-Extremities During Landing Tasks in Patients With Anterior Cruciate Ligament Reconstruction: A Systematic Review of Electromyographic Studies

CONTEXT

Altered lower-limb biomechanics have been observed during landing task in patients with anterior cruciate ligament reconstruction (ACLR), which increases the risk of secondary anterior cruciate ligament injury. However, the alteration in neuromuscular activity of the lower-extremity during landing task is not clear.

OBJECTIVE

To compare the muscle activity pattern assessed by electromyography between the involved limb of patients with ACLR and the contralateral limb or control limb of matched healthy subjects during landing task.

EVIDENCE ACQUISITION

Database of PubMed, Ovid, Scopus, and Web of Science from the inception of the databases until July 2019, using a combination of keywords and their variations: (anterior cruciate ligament OR ACL) AND (electromyography OR EMG) AND (landing OR land). Studies that assessed lower-extremity muscle activity patterns during landing task in patients with ACLR and compared them either with the contralateral side or healthy controls were included.

EVIDENCE SYNTHESIS

Of the 21 studies, 16 studies reported altered muscle activity pattern during landing tasks when compared with either the healthy controls or the contralateral side. For the specific muscle activity patterns, the majority of the studies showed no significant difference in reactive muscle activity, and comparisons across studies revealed a possible trend toward the early onset of quadriceps and hamstring activity and increased cocontraction of the involved limb. There are inconsistent findings regarding the alteration in muscle timing and preparatory muscle activity.

CONCLUSIONS

Patients with ACLR displayed an altered muscle activity pattern during landing tasks, even though they were considered to be capable for sport return. Nevertheless, a firm conclusion could not be drawn due to great heterogeneity in the subject selection and study methods.

Are Anterior Cruciate Ligament-reconstructed Athletes More Vulnerable to Fatigue than Uninjured Athletes?

INTRODUCTION

Fatigue has a negative impact on lower extremity neuromuscular and biomechanical control. Because anterior cruciate ligament reconstruction (ACLR) athletes show already neuromuscular/biomechanical deficits in an unfatigued state, the negative impact of fatigue may magnify these deficits or help expose other deficits. So far, this has only scarcely been assessed warranting further research.

METHODS

Twenty-one athletes who had an ACLR and 21 uninjured controls performed five unilateral landing tasks before and after a match simulation protocol, whereas muscle activation (vastus medialis, vastus lateralis, hamstrings medialis, hamstrings lateralis, gastrocnemius medialis, gastrocnemius lateralis, gluteus medius) and landing kinematics and kinetics of the hip, knee, and ankle joint were recorded. A two-way ANOVA with a mixed-model design (main effects for group and fatigue) was used to compare landing kinematics, kinetics, and muscle activation between groups, and prefatigue and postfatigue. To avoid unjustified reduction of the data to discrete values, we used one-dimensional Statistical Parametric Mapping.

RESULTS

Only two interaction effects were found: an increased postfatigue knee abduction moment and an increased postfatigue thorax flexion angle was found in the ACL injured legs but not in the uninjured legs of the ACL group or in the control group, during the lateral hop and the vertical hop with 90° medial rotation, respectively.

CONCLUSIONS

This study showed that overall ACLR athletes and uninjured athletes have similar biomechanical and neuromuscular responses to fatigue. For two biomechanical parameters, however, we did find an interaction effect, suggesting that landing deficits in ACLR athletes may become clearer in certain tasks when fatigued.

Match Play-induced Changes in Landing Biomechanics with Special Focus on Fatigability

INTRODUCTION

Growing evidence exists that match-related fatigue induces biomechanical alterations that might increase lower extremity injury risk. Fatigue studies often use match simulation protocols that expose all subjects to a standardized demand (e.g., a fixed distance/time). In those studies, the induced level of fatigue depends then on subjects' fatigability. If between-subject variability in fatigability is high, this might confound overall fatigue effects. Therefore, the first aim was to investigate whether a fatigue protocol with fixed demand causes alterations in landing patterns. Second, we assessed the relationship between fatigability and landing patterns as we hypothesized that athletes with high fatigability would show movement patterns that involve greater injury risk.

METHODS

Eighteen athletes performed three different unilateral landing tasks before and after a match simulation protocol while muscle activation (vastus medialis, vastus lateralis, hamstrings medialis, hamstrings lateralis, gastrocnemius medialis, gastrocnemius lateralis, and gluteus medius) and landing kinematics and kinetics of the hip, knee, and ankle joint were recorded. Furthermore, RPE was administered to measure fatigability. ANOVA analyses were conducted to investigate fatigue effects on landing patterns. Correlation analyses assessed the relationship between fatigability (postfatigue RPE) and landing patterns.

RESULTS

The ANOVA analyses did not show any overall postfatigue alterations in landing patterns. However, correlation analyses showed an association between fatigability and landing patterns. Athletes who had higher RPE scores showed smaller postfatigue knee flexion angles and smaller pre- and postfatigue knee abduction angles across different landing tasks.

CONCLUSION

The fixed demand protocol did not cause overall alterations in landing patterns. When fatigability was taken into account, high fatigability was related with less optimal landing patterns.

Fatigue Increases Dynamic Knee Valgus in Youth Athletes: Results From a Field-Based Drop-Jump Test

PURPOSE

To determine whether fatigue increases dynamic knee valgus in adolescent athletes, as measured after a standardized exercise protocol and video-based drop-jump test. A secondary aim was to determine whether individual risk factors place certain athletes at increased risk for dynamic knee valgus.

METHODS

Athletes aged 14 to 18 years were recruited for this video analysis study. Athletes were recorded performing a standard drop-jump to assess dynamic valgus. Participants then completed a standardized exercise protocol. Fatigue was quantified using a maximum vertical jump, which was compared with pre-exercise values. The drop-jump was repeated postexercise. All drop-jump recordings were randomized and scored for dynamic valgus by 11 blinded reviewers. Univariate analysis was performed to identify characteristics that predisposed athletes to increased dynamic valgus.

RESULTS

Eighty-five (47 female, 38 male) athletes with an average age of 15.4 years were included in this study. Forty-nine percent of athletes demonstrated an increase in dynamic valgus determined by drop-jump assessment after exercise. A significantly greater percentage of athletes were graded "medium or high risk" in jumps recorded after the exercise protocol (68%) as compared with before the exercise protocol (44%; P < .01). Female athletes (P < .01) and those older than 15 years of age (P < .01) were the most affected by fatigue.

CONCLUSIONS

In conclusion, our study found that exercise increases dynamic knee valgus in youth athletes. Female athletes and those older than 15 years of age were most significantly affected by exercise. Greater fatigue levels were found to correlate with an increase in dynamic knee valgus, which may place athletes at greater anterior cruciate ligament injury risk. The field-based exercise drop-jump test is a low-cost and reproducible screening tool to identify at-risk athletes who could possibly benefit from anterior cruciate ligament injury-prevention strategies.

LEVEL OF EVIDENCE

III, Comparative trial.

Females with patellofemoral pain have impaired impact absorption during a single-legged drop vertical jump

BACKGROUND

Females with patellofemoral pain (PFP) have been reported to land with altered biomechanics in some, but not all studies. Kinematic alterations previously reported may indicate, and relate to potential impairments in absorbing impact.

RESEARCH QUESTION

To compare vertical ground reaction force (vGRF) and lower limb kinematics during single-legged drop vertical jumps in females with and without PFP; and establish the relationship between vGRF and kinematics during this task.

METHODS

Fifty-two physically active females (26 with PFP and 26 controls) participated in the present cross-sectional study. Peak of vGRF was evaluated during landing; and lower limb kinematics in the sagittal and frontal planes during deceleration (landing) and acceleration (take-off) phases were evaluated.

RESULTS

The PFP group had 11% greater vGRF (p < 0.01); and 13-24% lower hip, knee and ankle excursion in the sagittal plane during acceleration and deceleration phases (p ≤ 0.02) compared to the control group. No significant between group differences (p > 0.05) for hip, knee and ankle excursion in the frontal plane were identified. Greater impact was significantly correlated with reduced knee (r = -0.56), hip (r = -0.50) and ankle (r = -0.41) excursion in the sagittal plane during the acceleration phase in the control group, but not in the PFP group. No significant correlations were found between vGRF and kinematics variables during the deceleration phase in either group.

SIGNIFICANCE

Impaired ability to absorb load and reduced lower limb movement in the sagittal plane during landing in females with PFP may provide separate treatment targets during rehabilitation.

Association of Hip and Trunk Strength With Three-Dimensional Trunk, Hip, and Knee Kinematics During a Single-Leg Drop Vertical Jump

Martinez, AF, Lessi, GC, Carvalho, C, and Serrao, FV. Association of hip and trunk strength with three-dimensional trunk, hip, and knee kinematics during a single-leg drop vertical jump. J Strength Cond Res 32(7): 1902-1908, 2018-Kinematic changes have been correlated with different lower-limb injuries. Movement is influenced by multiple factors and strength is one of the contributors that can influence it. Thus, the aim of this study was to evaluate the correlation among trunk and hip isometric strength with trunk and lower-limb kinematics during a single-leg drop vertical jump. Twenty-three healthy recreational female athletes aged between 18 and 35 years underwent isometric evaluation of hip abductor, hip extensor, and lateral trunk muscle strength and 3-dimensional trunk and lower-limb kinematics during a single-leg drop vertical jump. Pearson's correlation coefficients (r) were calculated to establish the association among hip and trunk strength and trunk, hip, and knee kinematics. As result, no significant correlations were found between the peak and movement excursion values of kinematic and hip and trunk isometric strength data. The lack of correlation between isometric strength and kinematics in healthy female athletes indicates that intervention programs should not be focused solely on strength exercises to influence the movement pattern during single-landing activities.

Comparison of the effects of fatigue on kinematics and muscle activation between men and women after anterior cruciate ligament reconstruction

OBJECTIVES

Studies comparing the effects of fatigue between men and women after anterior cruciate ligament (ACL) reconstruction are lacking. The purpose of this study was to compare the effects of muscle fatigue on trunk, pelvis and lower limb kinematics and on lower limb muscle activation between male and female athletes who underwent ACL reconstruction.

DESIGN

Cross-sectional study.

SETTING

Laboratory setting.

PARTICIPANTS

Fourteen recreational athletes (7 males and 7 females) with unilateral ACL reconstruction participated of this study.

MAIN OUTCOME MEASURES

Trunk, pelvis and lower limb kinematics and muscle activation of the vastus lateralis, gluteus medius and gluteus maximus were evaluated during a single-leg drop vertical jump landing before and after a fatigue protocol.

RESULTS

Females had greater peak knee abduction after fatigue in relation to before fatigue (P = 0.008), and in relation to men after fatigue (P = 0.011). Also, in females, peak knee abduction was greater in the reconstructed limb in relation to the non-reconstructed limb after fatigue (P = 0.029). Males showed a greater mean amplitude of activation of the vastus lateralis muscle after fatigue in relation to before fatigue (P < 0.001).

CONCLUSIONS

Muscle fatigue produced kinematic alterations that have been shown to increase the risk for a second ACL injury in female athletes.