Lower limb muscle pre-motor time measures during a choice reaction task associate with knee abduction loads during dynamic single leg landings

The inter-laboratory equivalence for lower limb kinematics and kinetics during unplanned sidestepping

Much inter-intra-tester kinematic and kinetic repeatability research exists, with a paucity investigating inter-laboratory equivalence. The objective of this research was to evaluate the inter-laboratory equivalence between time varying unplanned kinematics and moments of unplanned sidestepping (UnSS). Eight elite female athletes completed an established UnSS procedure motion capture laboratories in the UK and Australia. Three dimensional time varying unplanned sidestepping joint kinematics and moments were compared. Discrete variables were change of direction angles and velocity. Waveform data were compared using mean differences, 1D 95%CI and RMSE. Discrete variables were compared using 0D 95% CI. The mean differences and 95%CI for UnSS kinematics broadly supported equivalence between laboratories (RMSE≤5.1°). Excluding hip flexion/extension moments (RMSE = 1.04 Nm/kg), equivalence was also supported for time varying joint moments between laboratories (RMSE≤0.40 Nm/kg). Dependent variables typically used to characterise UnSS were also equivalent. When consistent experimental and modelling procedures are employed, consistent time varying UnSS lower limb joint kinematic and moment estimates between laboratories can be obtained. We therefore interpret these results as a support of equivalence, yet highlight the challenges of establishing between-laboratory experiments or data sharing, as well as establishing appropriate ranges of acceptable uncertainty. These findings are important for data sharing and multi-centre trials.

The effectiveness of fatigue on repositioning sense of lower extremities: systematic review and meta-analysis

INTRODUCTION

An injury can significantly harm both individual and team performance. One of the most important risk factors for sports-related injuries, especially non-collision injuries, is fatigue. It seems that poor proprioception may play an essential role to impose athletes to further injuries. This systematic review and meta-analysis aimed to examine the effectiveness of fatigue on the repositioning sense of the lower extremity joints.

METHOD

The electronic databases, including PubMed, Web of Science, Scopus, and Google Scholar were systematically searched from inception to 11January 2024. The obtained records were exported to the EndNote Software version 8. Then, two investigators examined the records independently to find eligible studies based on the inclusion/exclusion criteria. In the case of disagreements, a consequence method was utilized. The quality of the eligible studies was evaluated using the Downs and Black checklist. Comprehensive Meta-Analysis (CMA) software ver. 3 software was used for statistical analysis. Q-test and I2 were employed to examine the data homogeneity. In addition, considering the risk of bias, the Funnel Plot and trim-and-fill method were used.

RESULTS

After reviewing the titles and abstracts of 3883 studies found in the selected databases, 43 articles were found to be eligible to include in meta-analyses. The results showed that fatigue led to a significant increase in the active absolute error of the knee (SDM = 0.524, 95% CI = 0.406-0.841), ankle in the horizontal plane (SDM = 0.541, 95% CI = 0.367-0.715), ankle in the sagittal plane (SDM = 0.443, 95% CI = 0.088-0.798), and hip (SDM = 0.988, 95% CI = 0.135-1.841). However, fatigue had no significant effects on the passive absolute error of the knee and ankle in horizontal plane and relative angular error of the knee.

CONCLUSION

Fatigue can diminish the active joint position sense of the lower extremities and thus may increase the risk of injury by reducing proprioception. Therefore, future research could be conducted to investigate the potential impact of integrated fatigue-mitigating exercises into athletes' training programs, with the aim of reducing the incidence of sports-related injuries.

Deceleration Profiles Between the Penultimate and Final Steps of Planned and Reactive Side-Step Cutting

CONTEXT

Noncontact anterior cruciate ligament injury often occurs during rapid deceleration and change-of-direction maneuvers. These activities require an athlete to generate braking forces to slow down the center of mass and change direction in a dynamic environment. During preplanned cutting, athletes can use the penultimate step for braking before changing direction, resulting in less braking demand during the final step. During reactive cutting, athletes use different preparatory movement strategies during the penultimate step when planning time is limited. However, possible differences in the deceleration profile between the penultimate and final steps of preplanned and reactive side-step cuts remain unknown.

OBJECTIVE

To comprehensively evaluate deceleration during the penultimate and final steps of preplanned and reactive cutting.

DESIGN

Cross-sectional study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirty-six women (age = 20.9 ± 1.7 years, height = 1.66 ± 0.07 m, mass = 62.4 ± 8.7 kg).

INTERVENTION

Participants completed 90° side-step cutting maneuvers under preplanned and reactive conditions.

MAIN OUTCOME MEASURE(S)

Approach velocity, velocity at initial contact, and cutting angle were compared between conditions. Stance time, deceleration time, and biomechanical indicators of deceleration were assessed during the penultimate and final steps of preplanned and reactive 90° cuts. Separate repeated-measures analysis-of-variance models were used to assess the influence of step, condition, and their interaction on the biomechanical indicators of deceleration.

RESULTS

Approach velocity (P = .69) and velocity at initial contact of the penultimate step (P = .33) did not differ between conditions. During reactive cutting, participants achieved a smaller cutting angle (P < .001). We identified a significant step-by-condition interaction for all biomechanical indicators of deceleration (P values < .05).

CONCLUSIONS

A lack of planning time resulted in less penultimate step braking and greater final step braking during reactive cutting. As a result, participants exhibited a decreased cutting angle and longer stance time during the final step of reactive cutting. Improving an athlete's ability to respond to an external stimulus may facilitate a more effective penultimate step braking strategy that decreases the braking demand during the final step of reactive cutting.

Cognitive Load Influences Drop Jump Landing Mechanics During Cognitive-Motor-Simulated Shooting

INTRODUCTION

Military duties require immense cognitive-motor multitasks that may predispose soldiers to musculoskeletal injury. Most cognitive challenges performed in the research laboratory are not tactical athlete specific, limiting generalizability and transferability to in-field scenarios. The purpose of this study was to determine the impact of a cognitive-motor multitask (forward drop jump landing while simultaneously performing simulated shooting) on knee kinetics and kinematics.

METHODS

Twenty-four healthy collegiate Reserve Officer's Training Corps members (18 males and 6 females, 20.42 ± 1.28 years, 174.54 ± 10.69 cm, 78.11 ± 14.96 kg) volunteered, and knee kinetics and kinematics were assessed between baseline and cognitive-loaded conditions. Repeated measures ANOVAs were conducted for each dependent variable with the within-subject factor of condition (baseline vs. cognitive load).

RESULTS

Univariate ANOVAs indicated that knee flexion angle at initial contact (IC) (decreased 6.07°; d = 3.14), knee flexion displacement (increased 6.78°; d = 1.30), knee abduction angle at IC (increased 2.3°; d = 1.46), peak knee abduction angle (increased 3.04°; d = 0.77), and peak vertical ground reaction force (increased 0.81 N/kg; d = 2.13) were significant between conditions (P < .001). Therefore, cognitive load resulted in decreased knee flexion and increased knee abduction angle at IC and greater peak vertical ground reaction force, all factors commonly associated with knee injury risk. Peak knee flexion angle and knee abduction displacement were not significant between conditions (P > .05).

CONCLUSIONS

Cognitive challenge induced knee landing biomechanics commonly associated with injury risk. Injury risk screening or return-to-training or duty assessments in military personnel might consider both baseline and cognitive conditions.

Unanticipated fake-and-cut maneuvers do not increase knee abduction moments in sport-specific tasks: Implication for ACL injury prevention and risk screening

Non-contact anterior cruciate ligament injuries typically occur during cutting maneuvers and are associated with high peak knee abduction moments (KAM) within early stance. To screen athletes for injury risk or quantify the efficacy of prevention programs, it may be necessary to design tasks that mimic game situations. Thus, this study compared KAMs and ranking consistency of female handball players in three sport-specific fake-and-cut tasks of increasing complexity. The biomechanics of female handball players (n = 51, mean ± SD: 66.9 ± 7.8 kg, 1.74 ± 0.06 m, 19.2 ± 3.4 years) were recorded with a 3D motion capture system and force plates during three standardized fake-and-cut tasks. Task 1 was designed as a simple pre-planned cut, task 2 included catching a ball before a pre-planned cut in front of a static defender, and task 3 was designed as an unanticipated cut with three dynamic defenders involved. Inverse dynamics were used to calculate peak KAM within the first 100 ms of stance. KAM was decomposed into the frontal plane knee joint moment arm and resultant ground reaction force. RANOVAs (α ≤ 0.05) were used to reveal differences in the KAM magnitudes, moment arm, and resultant ground reaction force for the three tasks. Spearman's rank correlations were calculated to test the ranking consistency of the athletes' KAMs. There was a significant task main effect on KAM (p = 0.02; ηp2 = 0.13). The KAM in the two complex tasks was significantly higher (task 2: 1.73 Nm/kg; task 3: 1.64 Nm/kg) than the KAM in the simplest task (task 1: 1.52 Nm/kg). The ranking of the peak KAM was consistent regardless of the task complexity. Comparing tasks 1 and 2, an increase in KAM resulted from an increased frontal plane moment arm. Comparing tasks 1 and 3, higher KAM in task 3 resulted from an interplay between both moment arm and the resultant ground reaction force. In contrast to previous studies, unanticipated cutting maneuvers did not produce the highest KAMs. These findings indicate that the players have developed an automated sport-specific cutting technique that is utilized in both pre-planned and unanticipated fake-and-cut tasks.

Athletes with high knee abduction moments show increased vertical center of mass excursions and knee valgus angles across sport-specific fake-and-cut tasks of different complexities

Young female handball players represent a high-risk population for anterior cruciate ligament (ACL) injuries. While the external knee abduction moment (KAM) is known to be a risk factor, it is unclear how cutting technique affects KAMs in sport-specific cutting maneuvers. Further, the effect of added game specificity (e.g., catching a ball or faking defenders) on KAMs and cutting technique remains unknown. Therefore, this study aimed: (i) to test if athletes grouped into different clusters of peak KAMs produced during three sport-specific fake-and-cut tasks of different complexities differ in cutting technique, and (ii) to test whether technique variables change with task complexity. Fifty-one female handball players (67.0 ± 7.7 kg, 1.70 ± 0.06 m, 19.2 ± 3.4 years) were recruited. Athletes performed at least five successful handball-specific sidestep cuts of three different complexities ranging from simple pre-planned fake-and-cut maneuvers to catching a ball and performing an unanticipated fake-and-cut maneuver with dynamic defenders. A k-means cluster algorithm with squared Euclidean distance metric was applied to the KAMs of all three tasks. The optimal cluster number of koptimal = 2 was calculated using the average silhouette width. Statistical differences in technique variables between the two clusters and the tasks were analyzed using repeated-measures ANOVAs (task complexity) with nested groupings (clusters). KAMs differed by 64.5%, on average, between clusters. When pooling all tasks, athletes with high KAMs showed 3.4° more knee valgus, 16.9% higher downward and 8.4% higher resultant velocity at initial ground contact, and 20.5% higher vertical ground reaction forces at peak KAM. Unlike most other variables, knee valgus angle was not affected by task complexity, likely due to it being part of inherent movement strategies and partly determined by anatomy. Since the high KAM cluster showed higher vertical center of mass excursions and knee valgus angles in all tasks, it is likely that this is part of an automated motor program developed over the players' careers. Based on these results, reducing knee valgus and downward velocity bears the potential to mitigate knee joint loading and therefore ACL injury risk.

The impact of repeated bouts of shiftwork on rapid strength and reaction time in career firefighters

The purpose of this study was to examine the influence of repeated bouts of shiftwork on lower extremity maximal and rapid strength and reaction time in career firefighters. Thirty-five firefighters (3 females; 34.3 ± 9.1 years) performed a psychomotor vigilance test (PVT) and reactive maximal isometric strength assessment prior to and following a full shift rotation (three 24-hr on-off shifts). Reaction time (RT), maximal, absolute and normalised rapid strength (50, 100, 150, 200 ms), and PVT measures were assessed on-site. Separate linear regression models were used to evaluate the POST-PRE change in variables adjusted for BMI, age, sleep, and call duration. Early (50 ms) absolute rapid strength was the only variable significantly reduced (-25.9%; p = 0.031) following the full shift rotation. Our findings indicate that early rapid strength may be a sensitive measure in detecting work-related fatigue, despite minimal changes in sleep between work and non-work nights and a low call duration. Practitioner summary: We examined the impact of repeated shiftwork on changes in reaction time and neuromuscular function. Early rapid strength was a sensitive, portable lab assessment that feasibly measured work-related fatigue in career firefighters. Interventions that mitigate work-related fatigue may be impactful at preventing falls and/or risk of musculoskeletal injury.

Predicting neuromuscular control patterns that minimize ACL forces during injury prone jump landing maneuvers in downhill skiing using a musculoskeletal simulation model

Competitive skiers encounter a high risk of sustaining an ACL injury during jump-landing in downhill ski racing. Facing an injury-prone landing manoeuvre, there is a lack of knowledge regarding optimum control strategies. So, the purpose of the present study was to investigate possible neuromuscular control patterns to avoid injury during injury-prone jump-landing manoeuvres. A computational approach was used to generate a series of 190 injury-prone jump-landing manoeuvres based on a 25-degree-of-freedom sagittal plane musculoskeletal skier model. Using a dynamic optimization framework, each injury-prone landing manoeuvre was resolved to identify muscle activation patterns of the lower limbs and corresponding kinematic changes that reduce peak ACL force. In the 190 injury-prone jump-landing simulations, ACL forces peaked during the first 50 ms after ground contact. Optimized muscle activation patterns, that reduced peak ACL forces, showed increased activation of the monoarticular hip flexors, ankle dorsi- and plantar flexors as well as hamstrings prior to or during the early impact phase (<50 ms). The corresponding kinematic changes were characterized by increased hip and knee flexion and less backward lean of the skier at initial ground contact and the following impact phase. Injury prevention strategies should focus on increased activation of the monoarticular hip flexors, ankle plantar flexors and rapid and increased activation of the hamstrings in combination with a flexed landing position and decreased backward lean to reduce ACL injury risk during the early impact phase (<50 ms) of jump landing.HighlightsFirst study investigating advantageous control strategies during injury-prone jump-landing manoeuvres in downhill skiing using a musculoskeletal simulation model and dynamic optimization framework.The simulation results predicted high injury risk during the first 50 ms after initial ground contact.Optimized neuromuscular control patterns showed adapted activation patterns (timing and amplitude) of muscles crossing the knee as well as the hip and ankle joints prior to and after initial ground contact, respectively.An optimized control strategy during an injury-prone landing manoeuvre was characterized kinematically by increasing hip and knee flexion and less backward lean of the skier at initial ground contact and the following impact phase.

Effect of unplanned athletic movement on knee mechanics: a systematic review with multilevel meta-analysis

OBJECTIVE

To compare the effects of pre-planned and unplanned movement tasks on knee biomechanics in uninjured individuals.

DESIGN

Systematic review with meta-analysis.

DATA SOURCES

Five databases (PubMed, Google Scholar, Cochrane Library, ScienceDirect and Web of Science) were searched from inception to November 2020. Cross-sectional, (randomised) controlled/non-controlled trials comparing knee angles/moments of pre-planned and unplanned single-leg landings/cuttings were included. Quality of evidence was assessed using the tool of the Grading of Recommendations Assessment, Development and Evaluation working group.

METHODS

A multilevel meta-analysis with a robust random-effects meta-regression model was used to pool the standardised mean differences (SMD) of knee mechanics between pre-planned and unplanned tasks. The influence of possible effect modifiers (eg, competitive performance level) was examined in a moderator analysis.

RESULTS

Twenty-five trials (485 participants) with good methodological quality (Downs and Black) were identified. Quality of evidence was downgraded due to potential risk of bias (eg, confounding). Moderate-quality evidence indicates that unplanned tasks evoked significantly higher external knee abduction (SMD: 0.34, 95% CI: 0.16 to 0.51, 14 studies) and tibial internal rotation moments (SMD: 0.51, 95% CI: 0.23 to 0.79, 11 studies). No significant between-condition differences were detected for sagittal plane mechanics (p>0.05). According to the moderator analysis, increased abduction moments particularly occurred in non-professional athletes (SMD: 0.55, 95% CI: 0.14 to 0.95, 5 studies).

CONCLUSION

Unplanned movement entails higher knee abduction and tibial internal rotation moments, which could predispose for knee injury. Exercise professionals designing injury-prevention protocols, especially for non-elite athletes, should consider the implementation of assessments and exercises requiring time-constrained decision-making.

PROSPERO REGISTRATION NUMBER

CRD42019140331.

The influence of decision making and divided attention on lower limb biomechanics associated with anterior cruciate ligament injury: a narrative review

Cognitive loads have been shown to influence anterior cruciate ligament (ACL) injury risk. Two main sources of cognitive loads that athletes experience are decision making and dividing attention between multiple tasks. The aim of this paper was to review previous studies examining the effects of decision making and divided attention on lower limb biomechanics during landing and cutting. Previous research has shown decision making to significantly influence a number of biomechanical variables associated with increased risk of ACL injury, such as reduced knee flexion at initial contact, increased knee valgus angles, increased knee extension moment and increased knee valgus moment in decision-making tasks compared to pre-planned tasks. Furthermore, dividing attention between multiple tasks has been shown to result in reduced knee flexion at initial contact, increased vertical ground reaction force, and reduced stability during landing/cutting. The changes in lower limb biomechanics observed as a result of both decision making and dividing attention are likely due to a reduced ability to anticipate ground contact and implement protective movement patterns associated with reduced ACL loading. Collectively, these findings emphasise the need for tasks that incorporate decision making and divided attention when investigating ACL injury mechanisms and developing ACL injury risk screening assessments.

Visuomotor reaction time difference between patellofemoral pain syndrome and healthy individuals: Cross-sectional study

OBJECTIVE

Although many studies indicated a decreased reaction time in post-traumatic complaints including ACL injury, no study has been devoted to measure reaction time in patients with patellofemoral pain syndrome (PFPS). The purpose of the present study was to compare the visuomotor reaction time between PFPS and healthy individuals.

METHODS

Twenty five patients with PFPS (20 women and 5 men, mean age 29.28 years, SD 5.59) and 25 healthy controls (19 women, 6 men, mean age 29.32, years SD 5.30) were recruited in the present study. The dependent variables were upper extremity reaction time, upper extremity error rate, knee extension reaction time in both involved and non-involved legs, plantar flexion reaction time in both involved and non-involved legs.

RESULTS

The results of one-way multiple analysis of variance showed that patients with PFPS had slower upper extremity reaction time (P=0.047, Effect size (ES)=0.39) and plantar flexion reaction time (symptomatic side) (P<0.001, ES=0.77) as compared with healthy control. The symptomatic knee extension reaction time was slower than the healthy matched leg, but this difference was not statistically significant (P=0.296, ES= 0.19).

CONCLUSION

The present study suggests that the reaction time might be considered as a factor associated with PFPS.

Single- Versus Dual-Task Functional Movement Paradigms: A Biomechanical Analysis

CONTEXT

Laboratory-based movement assessments are commonly performed without cognitive stimuli (ie, single-task) despite the simultaneous cognitive processing and movement (ie, dual task) demands required during sport. Cognitive loading may critically alter human movement and be an important consideration for truly assessing functional movement and understanding injury risk in the laboratory, but limited investigations exist.

OBJECTIVE

To comprehensively examine and compare kinematics and kinetics between single- and dual-task functional movement among healthy participants while controlling for sex.

DESIGN

Cross-sectional study.

SETTING

Laboratory. Patients (or Other Participants): Forty-one healthy, physically active participants (49% female; 22.5 ± 2.1 y; 172.5 ± 11.9 cm; 71.0 ± 13.7 kg) enrolled in and completed the study.

INTERVENTION(S)

All participants completed the functional movement protocol under single- and dual-task (subtracting by 6s or 7s) conditions in a randomized order. Participants jumped forward from a 30-cm tall box and performed (1) maximum vertical jump landings and (2) dominant and (3) nondominant leg, single-leg 45° cuts after landing.

MAIN OUTCOME MEASURES

The authors used mixed-model analysis of variances (α = .05) to compare peak hip, knee, and ankle joint angles (degrees) and moments (N·m/BW) in the sagittal and frontal planes, and peak vertical ground reaction force (N/BW) and vertical impulse (Ns/BW) between cognitive conditions and sex.

RESULTS

Dual-task resulted in greater peak vertical ground reaction force compared with single-task during jump landing (mean difference = 0.06 N/BW; 95% confidence interval [CI], 0.01 to 0.12; P = .025) but less force during dominant leg cutting (mean difference = -0.08 N/BW; 95% CI, -0.14 to -0.02; P = .015). Less hip-flexion torque occurred during dual task than single task (mean difference = -0.09 N/BW; 95% CI, -0.17 to -0.02). No other outcomes were different between single and dual task (P ≥ .053).

CONCLUSIONS

Slight, but potentially important, kinematic and kinetic differences were observed between single- and dual-task that may have implications for functional movement assessments and injury risk research. More research examining how various cognitive and movement tasks interact to alter functional movement among pathological populations is warranted before clinical implementation.

A model-based approach to predict neuromuscular control patterns that minimize ACL forces during jump landing

Jump landing is a common situation leading to knee injuries involving the anterior cruciate ligament (ACL) in sports. Although neuromuscular control is considered as a key injury risk factor, there is a lack of knowledge regarding optimum control strategies that reduce ACL forces during jump landing. In the present study, a musculoskeletal model-based computational approach is presented that allows identifying neuromuscular control patterns that minimize ACL forces during jump landing. The approach is demonstrated for a jump landing maneuver in downhill skiing, which is one out of three main injury mechanisms in competitive skiing.

Perceptual-Cognitive Function and Unplanned Athletic Movement Task Performance: A Systematic Review

The performance of choice-reaction tasks during athletic movement has been demonstrated to evoke unfavorable biomechanics in the lower limb. However, the mechanism of this observation is unknown. We conducted a systematic review examining the association between (1) the biomechanical and functional safety of unplanned sports-related movements (e.g., jumps/runs with a spontaneously indicated landing leg/cutting direction) and (2) markers of perceptual–cognitive function (PCF). A literature search in three databases (PubMed, ScienceDirect and Google Scholar) identified five relevant articles. The study quality, rated by means of a modified Downs and Black checklist, was moderate to high (average: 13/16 points). Four of five papers, in at least one parameter, found either an association of PCF with task safety or significantly reduced task safety in low vs. high PCF performers. However, as (a) the outcomes, populations and statistical methods of the included trials were highly heterogeneous and (b) only two out of five studies had an adequate control condition (pre-planned movement task), the evidence was classified as conflicting. In summary, PCF may represent a factor affecting injury risk and performance during unplanned sports-related movements, but future research strengthening the evidence for this association is warranted.

The Effects of a Cognitive Dual Task on Jump-landing Movement Quality

Investigations on movement quality deficits associated with jump landing are numerous, however, these studies are often performed in laboratories with little distraction to the participant. This is contrary to how injury typically occurs secondary to sport-specific distraction where the athlete is cognitively loaded during motor performance. Thus, the purpose of this study was to determine the effect of a cognitive load on jump-landing movement quality. A dual-task design was used to determine the effects of a dual-task on tuck jump movement quality in 20 participants. There were three cognitive conditions (no cognitive task, easy-cognitive task, and difficult-cognitive task). The dual task elicited statistically significant changes in overall tuck jump score (movement quality) across the conditions with tuck jump score increasing from 3.52±1.64 baseline to 4.37±1.25 with the easy-cognitive task to 4.67±1.24 with the difficult-cognitive task. The findings of this study may be useful to screen for individuals at risk of lower extremity injury utilizing the tuck jump when paired with a cognitive task. The screening would then identify individuals who may have poor neuromuscular control when cognitively loaded.

Running-related muscle activation patterns and tibial acceleration across puberty

This study examined whether differences exist in tibial acceleration transients and electromyography (EMG) variables during running across female pubertal development. Sixty-four girls classified as pre- (n = 19), early/mid- (n = 22) and late/post-pubertal development (n = 23) ran in a laboratory whilst EMG data were recorded from quadriceps, hamstring and calf muscle groups, and acceleration transients from a triaxial accelerometer. The late/post-pubertal girls exhibited delayed vastus lateralis onset (mean difference (MD) = 0.02, 95% CI = 0.008, 0.34 ms)) compared to pre-pubertal girls, lower vastus lateralis pre-activation (MD = 7.02, 95% CI = 12.63, 1.42%) compared to early/mid-pubertal girls, and longer time to peak (TTP) anterior/posterior (A/P) tibial acceleration compared to pre-pubertal girls (MD = 0.02, 95% CI = 0.006, 0.03 s). By contrast, late/post-pubertal girls demonstrated earlier semitendinosus onset compared to both early/mid- (MD = 0.02, 95% CI = 0.03, 0.005 ms) and pre-pubertal girls (MD = 0.02, 95% CI = 0.04, 0.007 ms). No other between-group differences were found for peak A/P, vertical and TTP vertical tibial acceleration (p > 0.05). Subsequently, regression analysis revealed that EMG variables accounted for approximately 34% (R² = 0.34) of the variance in TTP A/P tibial acceleration. These findings highlight that neuromuscular recruitment patterns and kinetics differ across female pubertal development while running and should be further explored in the context of adolescent female musculoskeletal injuries.

Neurocognitive challenged hops reduced functional performance relative to traditional hop testing

OBJECTIVE

Determine the relationship between four foundational single-leg hop tests and respective neurocognitive single-leg hop tests.

DESIGN

Cross-sectional; SETTING: University gymnasium.

PATIENTS OR OTHER PARTICIPANTS

Twenty-two participants (9 Male, 13 Female, 20.9 ± 2.5 years, 171.2 ± 11.7 cm, 70.3 ± 11.0 kg) were recruited. Maximum distance was measured for three hop tests (single-leg hop, single-leg crossover hop, single-leg triple hop) and fastest time was measured for the fourth (single-leg 6-m hop) for traditional and neurocognitive conditions.

MAIN OUTCOME MEASURES

Pearson correlations were conducted to assess the relationship between the new neurocognitive hop and the analogous traditional hop. One repeated measures MANOVA was conducted for each leg to determine the difference in hop performance between hop conditions (traditional and neurocognitive) for the dependent variables. Alpha level was set at α < 0.05.

RESULTS

Correlations ranged from 0.86 to 0.92 between traditional and neurocognitive hop tests. The repeated measures MANOVA was significant for condition for both legs (p < 0.05). Specifically, the crossover hop (average percent decrease 10.37%), triple hop (average percent decrease 7.13%), and 6-m hop (average percent decrease 81.67%) were statistically different between traditional and neurocognitive conditions (p < 0.05).

CONCLUSION

The addition of neurocognitive reactive and anticipatory components to simulate more sport specific scenarios may improve functional testing for return to sport.

Revised Approach to the Role of Fatigue in Anterior Cruciate Ligament Injury Prevention: A Systematic Review with Meta-Analyses

BACKGROUND

Causes of anterior cruciate ligament (ACL) injuries are multifactorial. Anterior cruciate ligament injury prevention should thus be approached from a multifactorial perspective as well. Training to resist fatigue is an underestimated aspect of prevention programs given that the presence of fatigue may play a crucial role in sustaining an ACL injury.

OBJECTIVES

The primary objective of this literature review was to summarize research findings relating to the kinematic and kinetic effects of fatigue on single-leg landing tasks through a systematic review and meta-analysis. Other objectives were to critically appraise current approaches to examine the effects of fatigue together with elucidating and proposing an optimized approach for measuring the role of fatigue in ACL injury prevention.

METHODS

A systematic literature search was conducted in the databases PubMed (1978-November 2017), CINAHL (1992-November 2017), and EMBASE (1973-November 2017). The inclusion criteria were: (1) full text, (2) published in English, German, or Dutch, (3) healthy subjects, (4) average age ≥ 18 years, (5) single-leg jump landing task, (6) evaluation of the kinematics and/or kinetics of the lower extremities before and after a fatigue protocol, and (7) presentation of numerical kinematic and/or kinetic data. Participants included healthy subjects who underwent a fatigue protocol and in whom the effects of pre- and post-fatigue on three-dimensional lower extremity kinematic and kinetics were compared. Methods of data collection, patient selection, blinding, prevention of verification bias, and study design were independently assessed.

RESULTS

Twenty studies were included, in which four types of single-leg tasks were examined: the single-leg drop vertical jump, the single-leg drop landing, the single-leg hop for distance, and sidestep cutting. Fatigue seemed to mostly affect initial contact (decreased angles post-fatigue) and peak (increased angles post-fatigue) hip and knee flexion. Sagittal plane variables at initial contact were mostly affected under the single-leg hop for distance and sidestep cutting conditions whilst peak angles were affected during the single-leg drop jump.

CONCLUSIONS

Training to resist fatigue is an underestimated aspect of prevention programs given that the presence of fatigue may play a crucial role in sustaining an ACL injury. Considering the small number of variables affected after fatigue, the question arises whether the same fatigue pathways are affected by the fatigue protocols used in the included laboratory studies as are experienced on the sports field.

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

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

The combined impact of a perceptual-cognitive task and neuromuscular fatigue on knee biomechanics during landing

BACKGROUND

A large majority of anterior cruciate ligament (ACL) injuries are non-contact, most often occurring during a landing or change of direction. Recent research indicates that cognitive factors may be involved in non-contact ACL injuries. The aim of this study was to determine if a game-situation perceptual-cognitive load leads to altered landing kinematics in physically fatigued female athletes.

METHODS

Nineteen female recreational athletes were recruited to perform a series of jumping and landing trials. In a first phase, eight trials were performed in an isolated condition and eight were performed while participants performed a perceptual-cognitive task. Before a second identical phase, participants underwent a muscular fatigue protocol. Knee-joint kinematics were recorded and compared between conditions using paired t-tests.

RESULTS

Muscle fatigue led to statistically significant increases in peak knee abduction and peak internal knee rotation as well as a decrease in maximum knee flexion, when comparing conditions without the perceptual-cognitive task. The perceptual-cognitive task had no statistically significant effect on any knee rotations, either pre- or post-fatigue. However, a subgroup of 12 athletes showed a significant increase in knee abduction in the presence of the perceptual-cognitive task, only in the fatigued condition.

CONCLUSION

A perceptual-cognitive task combined with muscle fatigue alters knee kinematics of landing for a subset of recreational athletes, potentially increasing the risk of ACL rupture. Further studies are necessary to confirm this finding and to identify characteristics of at-risk individuals to target them for injury prevention protocols.

The effects of instrument-assisted soft tissue mobilization on active range of motion, functional fitness, flexibility, and isokinetic strength in high school basketball players

Although many studies have focused on stretching techniques for athletes, no comprehensive studies have investigated the use of the instrument-assisted soft tissue mobilization (IASTM) technique in young basketball players. The active properties of muscle and subjective reporting of functional ability were used to identify the effects of IASTM on the calf muscle. Active range of motion (AROM), functional fitness, and isokinetic lower strength in the knees and ankles were measured in 40 healthy young basketball players. They were divided into the IASTM group (n= 20) and a control group (CG, n= 20). Twenty asymptomatic young basketball players were treated with IASTM six times per week for 8 weeks. The remaining 20 participants did not receive a treatment intervention between tests and served as the control. Ankle AROM (two knee positions of 0∘ and 45∘ flexion), functional fitness at the knee and ankle (side-step and vertical jump), and isokinetic peak torque were determined during ankle dorsiflexion (DF) and plantar flexion (PF) and knee extension (EX) and flexion (FX). The data were analyzed using repeated-measures analysis of variance. Significant differences were observed between the two groups in IASTM and control AROM 0∘ knee flexion (right: DF; p< 0.001 and PF; p< 0.001; left: DF; p< 0.001 and PF; p= 0.011), AROM 45∘ knee flexion (right: DF; p< 0.001 and PF; p= 0.009; left: DF; p< 0.001 and PF; p= 0.001), functional fitness (side step; p= 0.001, sit and reach; p= 0.025, vertical jump; p= 0.001), ankle isokinetic strength 30∘/sec (right: DF; p= 0.001 and PF; p= 0.001; left: DF; p< 0.001 and PF; p= 0.002), ankle isokinetic strength 120∘/sec (right: DF; p= 0.049 and PF; p= 0.001; left: DF; p= 0.023 and PF; p< 0.001), knee isokinetic strength 60∘/sec (right: EX; p= 0.001, FX; p= 0.001 and hamstring and quadriceps ratio [H/Q]; p= 0.001, left: EX; p= 0.001, FX; p= 0.001 and H/Q; p= 0.001), and knee isokinetic strength 180∘/sec (right: EX; p= 0.001, FX; p= 0.001 and H/Q; p= 0.001; left: EX; p= 0.001, FX; p= 0.010 and H/Q; p= 0.001). These results suggest that IASTM improves functional fitness and lower body muscle strength in young basketball players.

Neuroscience Application to Noncontact Anterior Cruciate Ligament Injury Prevention

Context:

Many factors, including anatomy, neuromuscular control, hormonal regulation, and genetics, are known to contribute to the noncontact anterior cruciate ligament (ACL) injury risk profile. The neurocognitive and neurophysiological influences on the noncontact ACL injury mechanism have received less attention despite their implications to maintain neuromuscular control. Sex-specific differences in neurocognition may also play a critical role in the elevated female ACL injury risk. This report serves to frame existing literature in a new light to consider neurocognition and its implications for movement control, visual-motor function, and injury susceptibility.

Evidence Acquisition:

Sources were obtained from PubMed, MEDLINE, Web of Science, and LISTA (EBSCO) databases from 1990 onward and ranged from diverse fields including psychological and neuroscience reviews to injury epidemiology and biomechanical reports.

Study Design:

Clinical review.

Level of Evidence:

Level 5.

Results:

Neurological factors may contribute to the multifactorial ACL injury risk paradigm and the increased female injury susceptibility.

Conclusion:

When developing ACL injury prevention programs, considering neurocognition and its role in movement, neuromuscular control, and injury risk may help improve intervention effectiveness.

Evaluating the fall risk among elderly population by choice step reaction test

Falls during daily activities are often associated with injuries and physical disabilities, thereby affecting quality of life among elder adults. Balance control, which is crucial in avoiding falls, is composed of two elements: muscle strength and central nervous system (CNS) control. A number of studies have reported that reduced muscle strength raises the risk of falling. However, to date there has been only limited research focused on the relationship between fall risk and the CNS. This study aimed to investigate the relationship between CNS and risk of falling among the elderly. A total of 140 elderly people (92 females and 48 males) were divided into faller and nonfaller groups based on questionnaire responses concerning falls in their daily life. Participants undertook a choice step reaction test in which they were required to respond to random visual stimuli using foot movements as fast as possible in the left or right directions. Response time was quantified as premotor time (PMT) and motor time (MT). In addition, the participants’ electro-myography data were recorded during the choice step reaction test. A maximal isokinetic torque test was also performed. PMT was greater in the fallers than in the nonfallers group. There was a significant difference between fall status and direction on PMT. PMT of the left limb in nonfallers was faster than the right, but in fallers there was no difference between left and right limbs. A similar phenomenon was also observed for MT. There were significant differences between fallers and nonfallers in maximum isokinetic torque at knee and ankle joints. The correct rate of PMT was higher than other variables, such as MT and maximal isokinetic torque, in evaluating elderly fall risk by using logistic regression analyses. The results suggest that PMT in the choice step reaction test could be a useful parameter to assess risk of fall among elder adults. In addition, decreased maximal isokinetic torque was related to greater PMT and disappearance of asymmetry in older adults who were at higher risk of fall, especially in the lower limb.

Mapping current research trends on neuromuscular risk factors of non-contact ACL injury

The aim of this systematic review was (i) to identify neuromuscular markers that have been predictive of a primary non-contact ACL injury, (ii) to assess whether proposed risk factors have been supported or refuted in the literature from cohort and case-control studies, and (iii) to reflect on the body of research that aims at developing field based tools to assess risk through an association with these risk factors. Electronic searches were undertaken, of PubMed, SCOPUS, Web of Science, CINAHL and SPORTDiscus examining neuromuscular risk factors associated with ACL injury published between January 1990 and July 2015. The evidence supporting neuromuscular risk factors of ACL injury is limited where only 4 prospective cohort studies were found. Three of which looked into muscular capacity and one looked into muscular activation patterns but none of the studies found strong evidence of how muscular capacity or muscular activation deficits are a risk factor for a primary non-contact ACL injury. A number of factors associated to neural control and muscular capacity have been suggested to be related to non-contact ACL injury risk but the level of evidence supporting these risk factors remains often elusive, leaving researchers and practitioners uncertain when developing evidence-based injury prevention programs.

Neuromuscular performance of Bandal Chagui: Comparison of subelite and elite taekwondo athletes

With the aim of comparing kinematic and neuromuscular parameters of Bandal Chagui kicks between 7 elite and 7 subelite taekwondo athletes, nine Bandal Chaguis were performed at maximal effort in a selective reaction time design, simulating the frequency of kicks observed in taekwondo competitions. Linear and angular leg velocities were recorded through 3D motion capture system. Ground reaction forces (GRF) were evaluated by a force platform, and surface electromyographic (sEMG) signals were evaluated in the vastus lateralis, biceps femoris, rectus femoris, tensor fasciae lata, adductor magnus, gluteus maximus, gluteus medius, and gastrocnemius lateralis muscles of the kicking leg. sEMG data were processed to obtain the cocontraction indices (CI) of antagonist vs. overall (agonist and antagonist) muscle activity. CI was measured for the hip and knee, in flexion and extension, and for hip abduction. Premotor, reaction (kinetic and kinematic), and kicking times were evaluated. Timing parameters, except kinetic reaction time, were faster in elite athletes. Furthermore, CI and angular velocity during knee extension, foot and knee linear velocity, and horizontal GRF were significantly higher in elite than in subelite athletes. In conclusion, selected biomechanical parameters of Bandal Chagui appear to be useful in controlling the training status of the kick and in orienting the training goal of black belt competitors.

Electromechanical delay of the hamstrings during eccentric muscle actions in males and females: Implications for non-contact ACL injuries

Sex differences in neuromuscular functioning has been proposed as one of the factors behind an increased relative risk of non-contact anterior cruciate ligament (ACL) injury in females. The aim of this study was to explore sex differences in electromechanical delay (EMD) of the hamstring muscles during eccentric muscle actions and during a range of movement velocities. This study recruited 110 participants (55 males, 55 females) and electromyography of the semitendinosus, semimembranosus and biceps femoris was determined during eccentric actions at 60, 120 and 240°/s. No significant sex differences were observed irrespective of muscle examined or movement velocity. Irrespective of sex EMD significantly increased with increasing movement velocity (P < 0.01). There was no significant difference in the EMD of the 3 muscles examined. Our findings suggest that during eccentric actions of the hamstrings that there are no sex differences, irrespective of movement velocity. This would suggest that other factors are probably responsible for the increased relative risk of non-contact ACL injury in females compared to males.

Effects of maturation on combined female muscle strength and ACL structural factors

OBJECTIVES

Relations between lower limb muscle strength and female ACL injury risk are well documented. How these relations combine with key ACL geometries however, is unknown. Identifying how these combined factors are impacted by maturation would benefit current risk screening and prevention efforts. This study compared hamstrings and quadriceps strength and ACL cross sectional area (CSA) indices across three maturation groups.

DESIGN

Cross-sectional human experimental.

METHODS

MRI scans of the dominant knee were collected in 35 females stratified into early (9.7±0.8yrs), middle (12.9±1.7yrs), and late (14.8±0.6yrs) maturation groups. Hamstring and quadriceps muscle volumes and ACL CSA measures were obtained. Isokinetic strength data were quantified for dominant knee flexors and extensors. Peak hamstring and quadriceps concentric and eccentric strength per unit volume magnitudes (QCSPV, HCSPV, QESPV, HESPV) were determined. Metrics and select ratios were submitted to a one way ANOVA to determine the main effect of maturation.

RESULTS

Significant decreases occurred in HESPV (N/cm(3)) and ACL CSA (cm(2)/kgm), respectively, from early (0.188±0.023N/cm(3), 0.007±0.002cm(2)/kgm) to middle (0.157±0.029N/cm(3), 0.005±0.002cm(2)/kgm, p=0.034, p=0.029), and middle to late (0.132±0.031N/cm(3), 0.003±0.001cm(2)/kgm, p=0.044, p=0.018) maturation. A significant decrease in HESPV:QCSPV occurred between early (1.795±0.496) and middle (1.362±0.277, p=0.018) maturation.

QCSPV

ACL CSA was significantly greater in late (37.26±13.35) compared to middle (25.81±9.17, p=0.021) maturation.

CONCLUSIONS

Key ratios between female knee quadriceps and hamstring strength and ACL size parameters, which may directly impact ACL injury risk, are substantially different among three maturation states. The results are potentially hazardous strength mismatches in mid-pubertal females, where a smaller (weaker) ACL may be unable to stabilize quadriceps dominated loading strategies.

Neuroplasticity following anterior cruciate ligament injury: a framework for visual-motor training approaches in rehabilitation

SYNOPSIS

The neuroplastic effects of anterior cruciate ligament injury have recently become more evident, demonstrating underlying nervous system changes in addition to the expected mechanical alterations associated with injury. Interventions to mitigate these detrimental neuroplastic effects, along with the established biomechanical changes, need to be considered in the rehabilitation process and return-to-play progressions. This commentary establishes a link between dynamic movement mechanics, neurocognition, and visual processing regarding anterior cruciate ligament injury adaptations and injury risk. The proposed framework incorporates evidence from the disciplines of neuroscience, biomechanics, motor control, and psychology to support integrating neurocognitive and visual-motor approaches with traditional neuromuscular interventions during anterior cruciate ligament injury rehabilitation. Physical therapists, athletic trainers, strength coaches, and other health care and performance professionals can capitalize on this integration of sciences to utilize visual-training technologies and techniques to improve on already-established neuromuscular training methods.

LEVEL OF EVIDENCE

Therapy, level 5.

Deconstructing the Anterior Cruciate Ligament: What We Know and Do Not Know About Function, Material Properties, and Injury Mechanics

Anterior cruciate ligament (ACL) injury is a common and potentially catastrophic knee joint injury, afflicting a large number of males and particularly females annually. Apart from the obvious acute injury events, it also presents with significant long-term morbidities, in which osteoarthritis (OA) is a frequent and debilitative outcome. With these facts in mind, a vast amount of research has been undertaken over the past five decades geared toward characterizing the structural and mechanical behaviors of the native ACL tissue under various external load applications. While these efforts have afforded important insights, both in terms of understanding treating and rehabilitating ACL injuries; injury rates, their well-established sex-based disparity, and long-term sequelae have endured. In reviewing the expanse of literature conducted to date in this area, this paper identifies important knowledge gaps that contribute directly to this long-standing clinical dilemma. In particular, the following limitations remain. First, minimal data exist that accurately describe native ACL mechanics under the extreme loading rates synonymous with actual injury. Second, current ACL mechanical data are typically derived from isolated and oversimplified strain estimates that fail to adequately capture the true 3D mechanical response of this anatomically complex structure. Third, graft tissues commonly chosen to reconstruct the ruptured ACL are mechanically suboptimal, being overdesigned for stiffness compared to the native tissue. The net result is an increased risk of rerupture and a modified and potentially hazardous habitual joint contact profile. These major limitations appear to warrant explicit research attention moving forward in order to successfully maintain/restore optimal knee joint function and long-term life quality in a large number of otherwise healthy individuals.

What is normal? Female lower limb kinematic profiles during athletic tasks used to examine anterior cruciate ligament injury risk: a systematic review

BACKGROUND

It has been proposed that the performance of athletic tasks where normal motion is exceeded has the potential to damage the anterior cruciate ligament (ACL). Determining the expected or 'normal' kinematic profile of athletic tasks commonly used to assess ACL injury risk can provide an evidence base for the identification of abnormal or anomalous task performances in a laboratory setting.

OBJECTIVE

The objective was to conduct a systematic review of studies examining lower limb kinematics of females during drop landing, drop vertical jump, and side-step cutting tasks, to determine 'normal' ranges for hip and knee joint kinematic variables.

DATA SOURCES

An electronic database search was conducted on the SPORTDiscus(TM), MEDLINE, AMED and CINAHL (January 1980-August 2013) databases using a combination of relevant keywords.

STUDY SELECTION

Studies identified as potentially relevant were independently examined by two reviewers for inclusion. Where consensus could not be reached, a third reviewer was consulted. Original research articles that examined three-dimensional hip and knee kinematics of female subjects during the athletic tasks of interest were included for review. Articles were excluded if subjects had a history of lower back or lower limb joint injury or isolated data from the female cohort could not be extracted.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two reviewers independently assessed the quality of included studies. Data on subject characteristics, the athletic task performed, and kinematic data were extracted from included studies. Studies were categorised according to the athletic task being examined and each study allocated a weight within categories based on the number of subjects assessed. Extracted data were used to calculate the weighted means and standard deviations for hip and knee kinematics (initial contact and peak values). 'Normal' motion was classified as the weighted mean plus/minus one standard deviation.

RESULTS

Of 2,920 citations, a total of 159 articles were identified as potentially relevant, with 29 meeting all inclusion/exclusion criteria. Due to the limited number of studies available examining double-leg drop landings and single-leg drop vertical jumps, insufficient data was available to include these tasks in the review. Therefore, a total of 25 articles were included. From the included studies, 'normal' ranges were calculated for the kinematic variables of interest across the athletic tasks examined.

LIMITATIONS

Joint forces and other additional elements play a role in ACL injuries, therefore, focusing solely on lower limb kinematics in classifying injury risk may not encapsulate all relevant factors. Insufficient data resulted in no normal ranges being calculated for double-leg drop land and single-leg drop vertical jump tasks. No included study examined hip internal/external rotation during single-leg drop landings, therefore ranges for this kinematic variable could not be determined. Variation in data between studies resulted in wide normal ranges being observed across certain kinematic variables.

CONCLUSIONS

The ranges calculated in this review provide evidence-based values that can be used to identify abnormal or anomalous athletic task performances on a multi-planar scale. This may be useful in identifying neuromuscular factors or specific muscular recruitment strategies that contribute to ACL injury risk.

Inter-session reliability and sex-related differences in hamstrings total reaction time, pre-motor time and motor time during eccentric isokinetic contractions in recreational athlete

The purposes were twofold: (a) to ascertain the inter-session reliability of hamstrings total reaction time, pre-motor time and motor time; and (b) to examine sex-related differences in the hamstrings reaction times profile. Twenty-four men and 24 women completed the study. Biceps femoris and semitendinosus total reaction time, pre-motor time and motor time measured during eccentric isokinetic contractions were recorded on three different occasions. Inter-session reliability was examined through typical percentage error (CVTE), percentage change in the mean (CM) and intraclass correlations (ICC). For both biceps femoris and semitendinosus, total reaction time, pre-motor time and motor time measures demonstrated moderate inter-session reliability (CVTE<10%; CM<3%; ICC>0.7). The results also indicated that, although not statistically significant, women reported consistently longer hamstrings total reaction time (23.5ms), pre-motor time (12.7ms) and motor time (7.5ms) values than men. Therefore, an observed change larger than 5%, 9% and 8% for total reaction time, pre-motor time and motor time respectively from baseline scores after performing a training program would indicate that a real change was likely. Furthermore, while not statistically significant, sex differences were noted in the hamstrings reaction time profile which may play a role in the greater incidence of ACL injuries in women.

Comparison of foot pedal reaction time among patients with right or left hemiplegia and able-bodied controls

BACKGROUND

Although inpatient stroke rehabilitation provides clinicians with the opportunity to prepare patients for continuation of prestroke activities, little is known about the patients' ability to safely resume driving at the point of discharge to the community.

OBJECTIVE

To compare foot pedal response times of 20 stroke patients with right hemiplegia (RH) or left hemiplegia (LH) and 10 controls.

METHODS

A cross-sectional design was used. Response times were measured using 3 foot pedal operation techniques: (1) right-sided accelerator with right leg operating accelerator and brake, (2) right-sided accelerator with left leg operating accelerator and brake, and (3) left-sided accelerator with left leg operating accelerator and brake. Outcomes included reaction time (RT), movement time (MT), and total response time (TRT).

RESULTS

Controls demonstrated faster RT than patients with RH (263 vs 348 ms; P < .001) or LH (316 ms; P < .05) for all conditions, as well as faster MT than patients with RH (P < .05 for all) but not LH when using the right leg (258 vs 251 ms; P = .82). Controls demonstrated faster TRT than patients with RH (P < .001 for all) but not LH when using the right leg (515 vs 553 ms; P = .44).

CONCLUSIONS

When using the nonparetic leg, patients with LH had braking response times comparable to controls, but patients with RH demonstrated significant impairment of both the paretic and nonparetic legs.

Comparison of gluteal and hamstring activation during five commonly used plyometric exercises

BACKGROUND

Anterior cruciate ligament injuries occur frequently in athletics, and anterior cruciate ligament injury prevention programs may decrease injury risk. However, previous prevention programs that include plyometrics use a variety of exercises with little justification of exercise inclusion. Because gluteal and hamstring activation is thought to be important for preventing knee injuries, the purpose of this study was to determine which commonly used plyometric exercises produce the greatest activation of the gluteals and hamstrings.

METHODS

EMG (Electromyography) amplitudes of the hamstring and gluteal muscles during preparatory and loading phases of landing were recorded in 41 subjects during 5 commonly used plyometric exercises. Repeated measures ANOVAs (Analysis of Variance) were used on 36 subjects to examine differences in muscle activation.

FINDINGS

Differences in hamstring (P<.01) and gluteal (P<.01) activities were identified across exercises during the preparatory and landing phases. The single-leg sagittal plane hurdle hops produced the greatest gluteal and hamstring activity in both phases. The 180° jumps did not produce significantly greater gluteal or hamstring activity than any other exercise.

INTERPRETATION

Single-leg sagittal plane hurdle hops may be the most effective exercise to activate the gluteals and hamstrings and may be important to include in anterior cruciate ligament injury prevention programs, given the importance of these muscles for limiting valgus loading of the knee. Because 180° jumps do not produce greater gluteal and hamstring activation than other plyometric exercises, their removal from injury prevention programs may be warranted without affecting program efficacy.

Anticipatory effects on anterior cruciate ligament loading during sidestep cutting

BACKGROUND

A key to understanding potential anterior cruciate ligament injury mechanisms is to determine joint loading characteristics associated with an injury-causing event. However, direct measurement of anterior cruciate ligament loading during athletic tasks is invasive. Thus, previous research has been unable to study the association between neuromuscular variables and anterior cruciate ligament loading. Therefore, the purpose of this study was to determine the influence of movement anticipation on anterior cruciate ligament loading using a musculoskeletal modeling approach.

METHODS

Twenty healthy recreationally active females were recruited to perform anticipated and unanticipated sidestep cutting. Three-dimensional kinematics and kinetics of the right leg were calculated. Muscle, joint and anterior cruciate ligament forces were then estimated using a musculoskeletal model. Dependent t-tests were conducted to investigate differences between the two cutting conditions.

FINDINGS

ACL loading significantly increased during unanticipated sidestep cutting (p<0.05). This increase was primarily due to a significant increase in the sagittal plane ACL loading, which contributed 62% of the total loading. Frontal plane ACL loading contributed 26% and transverse plane ACL loading contributed 12%.

INTERPRETATION

These results suggest that anterior cruciate ligament loading resulted from a multifaceted interaction of the sagittal plane shear forces (i.e., quadriceps, hamstrings, and tibiofemoral), as well as the frontal and transverse plane knee moments. Additionally, the results of this study confirm the hypothesis in the current literature that unanticipated movements such as sidestep cutting increase anterior cruciate ligament loading.

Altered Peak Knee Valgus during Jump-Landing among Various Directions in Basketball and Volleyball Athletes

Purpose

Excessive knee valgus during landing tasks is a contributing factor to knee injuries. Most studies have examined lower extremity biomechanics during the forward direction of a jump-landing task. Athletes perform many movements in the air and land in multi-directions. Therefore, the purpose of this study was to assess the peak knee valgus angle (PKVA) during one leg jump-landing in various directions.

Methods

Eighteen male basketball and volleyball athletes participated in the study. Participants performed one leg jump-landing tests from a 30 cm height platform in four directions. Knee valgus motion was measured using Vicon™ motion system. The data were analyzed with repeated measures ANOVA.

Results

Direction significantly (P<0.001) influenced the PKVA during landing. Significantly higher PKVA was observed for the lateral (8.8°±4.7°) direction as compared to forward (5.8°±4.6°) direction (P<0.05). The PKVA in 30° diagonal (7.5°±4.6°) and 60° diagonal (7.7°±5.7°) directions was higher than in the forward direction (P<0.05).

Conclusion

One leg jump-landing in lateral and diagonal directions results in a higher PKVA compared to landing in a forward direction and could lead to a higher risk of knee injury.

Two different fatigue protocols and lower extremity motion patterns during a stop-jump task

CONTEXT

Altered neuromuscular control strategies during fatigue probably contribute to the increased incidence of noncontact anterior cruciate ligament injuries in female athletes.

OBJECTIVE

To determine biomechanical differences between 2 fatigue protocols (slow linear oxidative fatigue protocol [SLO-FP] and functional agility short-term fatigue protocol [FAST-FP]) when performing a running-stop-jump task.

DESIGN

Controlled laboratory study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A convenience sample of 15 female soccer players (age = 19.2 ± 0.8 years, height = 1.67 ± 0.05 m, mass = 61.7 ± 8.1 kg) without injury participated.

INTERVENTION(S)

Five successful trials of a running-stop-jump task were obtained prefatigue and postfatigue during the 2 protocols. For the SLO-FP, a peak oxygen consumption (Vo(2)peak) test was conducted before the fatigue protocol. Five minutes after the conclusion of the Vo(2)peak test, participants started the fatigue protocol by performing a 30-minute interval run. The FAST-FP consisted of 4 sets of a functional circuit. Repeated 2 (fatigue protocol) × 2 (time) analyses of variance were conducted to assess differences between the 2 protocols and time (prefatigue, postfatigue).

MAIN OUTCOME MEASURE(S)

Kinematic and kinetic measures of the hip and knee were obtained at different times while participants performed both protocols during prefatigue and postfatigue.

RESULTS

Internal adduction moment at initial contact (IC) was greater during FAST-FP (0.064 ± 0.09 Nm/kgm) than SLO-FP (0.024 ± 0.06 Nm/kgm) (F(1,14) = 5.610, P = .03). At IC, participants had less hip flexion postfatigue (44.7° ± 8.1°) than prefatigue (50.1° ± 9.5°) (F(1,14) = 16.229, P = .001). At peak vertical ground reaction force, participants had less hip flexion postfatigue (44.7° ± 8.4°) than prefatigue (50.4° ± 10.3°) (F(1,14) = 17.026, P = .001). At peak vertical ground reaction force, participants had less knee flexion postfatigue (-35.9° ± 6.5°) than prefatigue (-38.8° ± 5.03°) (F(1,14) = 11.537, P = .001).

CONCLUSIONS

Our results demonstrated a more erect landing posture due to a decrease in hip and knee flexion angles in the postfatigue condition. The changes were similar between protocols; however, the FAST-FP was a clinically applicable 5-minute protocol, whereas the SLO-FP lasted approximately 45 minutes.

Effects of decision making on landing mechanics as a function of task and sex

BACKGROUND

Factors that contribute to sex-differences in the incidence of anterior cruciate ligament injuries among athletes are not well understood. Of interest is whether decision making during landing influences biomechanical factors associated with anterior cruciate ligament injury. This study examined the effects of decision making on the mechanics of two-footed landing tasks in women and men.

METHODS

Twenty-nine healthy young adults (13 women, 16 men) completed drop landings and drop-jumps under preplanned and decision-making conditions. Biomechanical data were collected and effects of decision making on lower extremity kinematics and kinetics were examined as a function of task and sex.

FINDINGS

Landing mechanics were influenced by decision-making condition, task, and sex. During drop-jumps, participants exhibited lesser hip flexion (-3.3°), lesser knee flexion (-5.1°), and greater knee abduction (+1.0°) at initial contact under decision-making conditions. Under decision-making conditions, no differences were observed in these variables between tasks or with respect to preplanned drop landings. Across tasks and sexes, participants exhibited greater ankle plantarflexion at initial contact (+1.6°), greater peak knee external rotation (+1.5°), lesser peak knee internal rotation (-1.0°), and smaller hip adduction moments (-0.2% body weight×height) under decision-making conditions. Women but not men exhibited smaller ankle inversion moments (-0.1% body weight×height) under decision-making conditions.

INTERPRETATION

Modifications in landing mechanics suggest a default towards the preplanned drop landing strategy under decision-making conditions. Across sexes, drop landings and drop-jumps may be no more dangerous under decision-making conditions, with respect to anterior cruciate ligament loading, than preplanned drop landings.

Complex integrative morphological and mechanical contributions to ACL injury risk

By failing to consider the integrative impact of key morphological and neuromechanical factors within the anterior cruciate ligament injury mechanism, we consider the current injury prevention model to be flawed. Critical links between these factors continue to be identified, suggesting that a successful prevention model should entrench neuromuscular control strategies that can successfully cater to individual morphological vulnerabilities.