Strategies for enhancing proprioception and neuromuscular control of the knee

The effect of a novel movement strategy in decreasing ACL risk factors in female adolescent soccer players

There is a need to investigate the effect of specific movement strategies in reducing biomechanical risk factors for anterior cruciate ligament injury in young female athletes. The purpose of this study was (a) to determine the feasibility of implementing a novel movement strategy (Core-PAC) into a team warm-up before soccer training based on subject compliance and integration of the Core-PAC into the warm-up and (b) to determine whether the Core-PAC would improve peak knee flexion angles and peak abduction moments at the knee during a side cut (SC) and an unanticipated side cut (USC) before kicking a soccer ball, and a side hop (SH) task after immediate instruction and after a 4-week training program. A convenience sample of ten 14- to 16-year-old female soccer players were instructed in the Core-PAC immediately after baseline testing and during a training program consisting of a 20-minute warm-up, 2 times per week. The Core-PAC was understood and accepted by the subjects and incorporated into their warm-up activities with good compliance. After the immediate instruction, there were significant increases in peak knee flexion angles of a mean 6.4° during the SC (p = 0.001), 3.5° during the USC (p = 0.007), and 5.8° during the SH (p < 0.001) tasks. Peak knee abduction moments decreased by a mean of 0.25 N·m·kg(-1) during the SC (p < 0.03), 0.17 N·m·kg(-1) during the USC (p = 0.05), and 0.27 N·m·kg(-1) during the SH (p = 0.04) tasks. After the 4-week training program, some individuals showed improvement. The results of this study suggest that the Core-PAC may be 1 method of modifying high-risk movements for ACL injury such as side cutting and single-leg landing.

Altered postural sway persists after anterior cruciate ligament reconstruction and return to sport

Postural sway is defined as the movement of a body's center of mass within the base of support to maintain postural equilibrium. Deficits in postural sway are present after ACL injury; however, current evidence linking it to future injury risk is unclear. The purpose of this study was to determine if postural sway deficits persist after ACL reconstruction (ACLR). The hypothesis tested was that after ACLR, patients who return to sport (RTS) would demonstrate differences in postural sway compared to control (CTRL) subjects. Fifty-six subjects with unilateral ACLR released to RTS, and 42 uninjured CTRL subjects participated. Dynamic postural sway was assessed and 3-way (2×2×2) ANOVA was used to analyze the variables. A side×group×sex (p=0.044) interaction in postural sway was observed. A side×group analysis also revealed an interaction (p=0.04) however, no effect of sex was observed (p=0.23). Analysis within the ACLR cohort showed less (p=0.001) postural sway on the involved side (1.82±0.84°) versus the uninvolved side (2.07±0.96°). No side-to-side differences (p=0.73) were observed in the CTRL group. The involved limb of subjects after ACLR demonstrated the least postural sway. In conclusion, these findings indicate that dynamic postural sway may be significantly altered in a population of athletes after ACLR and RTS compared to CTRL subjects. Further investigation is needed to determine if deficits in postural sway can be used as an effective criterion to assist in the decision to safely RTS after ACLR.

Inter-segmental postural coordination measures differentiate athletes with ACL reconstruction from uninjured athletes

Athletes who sustain non-contact anterior cruciate ligament (ACL) injuries and undergo surgical reconstruction exhibit deficits in sensorimotor control, which often impairs lower-limb movement coordination. The purpose of this experiment was to measure the influence of sensorimotor deficits on the ankle-hip coordination of a postural coordination task in athletes following ACL reconstruction. Twenty-two female athletes who were cleared to return to sports participation following ACL reconstruction and 22 uninjured female athletes performed a unilateral dynamic postural rhythmic coordination task at two movement frequencies (0.2 and 0.7 Hz). Athletes with ACL-reconstruction exhibited greater ankle-hip relative phase variability and reduced regularity of coupling than uninjured athletes, especially during the 0.2 Hz condition. The results of this study show altered lower extremity coordination patterns in athletes following ACL reconstruction and return to sports participation. The results also indicate that dynamical coordination measures may provide objective measures of sensorimotor deficits following ACL reconstruction and can potentially guide rehabilitation interventions following reconstruction.

The effect of sex and age on isokinetic hip-abduction torques

CONTEXT

As high school female athletes demonstrate a rate of noncontact anterior cruciate ligament (ACL) injury 3-6 times higher than their male counterparts, research suggests that sagittal-plane hip strength plays a role in factors associated with ACL injuries.

OBJECTIVE

To determine if gender or age affect hip-abductor strength in a functional standing position in young female and male athletes.

DESIGN

Prospective cohort design.

SETTING

Biomechanical laboratory.

PARTICIPANTS

Over a 3-y time period, 852 isokinetic hip-abduction evaluations were conducted on 351 (272 female, 79 male) adolescent soccer and basketball players.

INTERVENTION

Before testing, athletes were secured in a standing position, facing the dynamometer head, with a strap secured from the uninvolved side and extending around the waist just above the iliac crest. The dynamometer head was positioned in line with the body in the coronal plane by aligning the axis of rotation of the dynamometer with the center of hip rotation. Subjects performed 5 maximum-effort repetitions at a speed of 120°/s. The peak torque was recorded and normalized to body mass. All test trials were conducted by a single tester to limit potential interrater test error.

MAIN OUTCOME MEASURE

Standing isokinetic hip-abduction torque.

RESULTS

Hip-abduction torque increased in both males and females with age (P < .001) on both the dominant and nondominant sides. A significant interaction of gender and age was observed (P < .001), which indicated that males experienced greater increases in peak torque relative to body weight than did females as they matured.

CONCLUSIONS

Males exhibit a significant increase in normative hip-abduction strength, while females do not. Future study may determine if the absence of similar increased relative hip-abduction strength in adolescent females, as they age, may be related to their increased risk of ACL injury compared with males.

An integrated approach to change the outcome part II: targeted neuromuscular training techniques to reduce identified ACL injury risk factors

Prior reports indicate that female athletes who demonstrate high knee abduction moments (KAMs) during landing are more responsive to neuromuscular training designed to reduce KAM. Identification of female athletes who demonstrate high KAM, which accurately identifies those at risk for noncontact anterior cruciate ligament (ACL) injury, may be ideal for targeted neuromuscular training. Specific neuromuscular training targeted to the underlying biomechanical components that increase KAM may provide the most efficient and effective training strategy to reduce noncontact ACL injury risk. The purpose of the current commentary is to provide an integrative approach to identify and target mechanistic underpinnings to increased ACL injury in female athletes. Specific neuromuscular training techniques will be presented that address individual algorithm components related to high knee load landing patterns. If these integrated techniques are employed on a widespread basis, prevention strategies for noncontact ACL injury among young female athletes may prove both more effective and efficient.

Effects of task-specific augmented feedback on deficit modification during performance of the tuck-jump exercise

CONTEXT

Anterior cruciate ligament (ACL) injuries are prevalent in female athletes. Specific factors have possible links to increasing a female athlete's chances of suffering an ACL injury. However, it is unclear if augmented feedback may be able to decrease possible risk factors.

OBJECTIVE

To compare the effects of task-specific feedback on a repeated tuck-jump maneuver.

DESIGN

Double-blind randomized controlled trial.

SETTING

Sports-medicine biodynamics center.

PATIENTS

37 female subjects (14.7 ± 1.5 y, 160.9 ± 6.8 cm, 54.5 ± 7.2 kg).

INTERVENTION

All athletes received standard off-season training consisting of strength training, plyometrics, and conditioning. They were also videotaped during each session while running on a treadmill at a standardized speed (8 miles/h) and while performing a repeated tuck-jump maneuver for 10 s. The augmented feedback group (AF) received feedback on deficiencies present in a 10-s tuck jump, while the control group (CTRL) received feedback on 10-s treadmill running.

MAIN OUTCOME MEASURES

Outcome measurements of tuck-jump deficits were scored by a blinded rater to determine the effects of group (CTRL vs AF) and time (pre- vs posttesting) on changes in measured deficits.

RESULTS

A significant interaction of time by group was noted with the task-specific feedback training (P = .03). The AF group reduced deficits measured during the tuck-jump assessment by 23.6%, while the CTRL training reduced deficits by 10.6%.

CONCLUSIONS

The results of the current study indicate that task-specific feedback is effective for reducing biomechanical risk factors associated with ACL injury. The data also indicate that specific components of the tuck-jump assessment are potentially more modifiable than others.

The 2012 ABJS Nicolas Andry Award: The sequence of prevention: a systematic approach to prevent anterior cruciate ligament injury

BACKGROUND

ACL injuries are common, often devastating injuries that lead to short-term disability and long-term sequelae, many of which lack effective treatment, such as osteoarthritis. Therefore, prevention of ACL injury is currently the only effective intervention for these life-altering sequelae, while much of the literature has a rehabilitative focus.

QUESTIONS/PURPOSES

The primary long-term purpose of our multidisciplinary collaborative research team has been to develop ACL injury prevention programs by determining which factors related to ACL injury should be altered, followed by how and when they should be altered.

METHODS

Our primary study objectives were to determine: (1) modifiable risk factors; (2) how these factors can best be modified; and (3) when is the best time to diminish these risk factors. Throughout the course of various studies, we determined the modifiable factors related to increased ACL injury risk. Our research team then focused on exploring numerous ways to augment these factors to maximize prevention efforts. We developed a sequence of prevention models that provide a framework to monitor progress toward the ultimate goal of preventing ACL injuries.

RESULTS

The modifiable factors shown in our work include biomechanical and neuromuscular functionality. When targeted in physical training, we have determined that these factors can be enhanced to effectively aid in the prevention of ACL injuries. Preliminary data have shown that childhood and early adolescence may be valuable periods to implement such training.

CONCLUSIONS

Current evidence has led to the evolution of clinical assessment tools for high-risk athletes and interventions for large populations and specific high-risk individuals. Targeted intervention implemented at the specified developmental stage of highest risk may be the final step toward the maximal reduction of ACL injury risk in young athletes.

A musculoskeletal modeling approach for estimating anterior cruciate ligament strains and knee anterior-posterior shear forces in stop-jumps performed by young recreational female athletes

The central goal of this study was to contribute to the advancements being made in determining the underlying causes of anterior cruciate ligament (ACL) injuries. ACL injuries are frequently incurred by recreational and professional young female athletes during non-contact impact activities in sports like volleyball and basketball. This musculoskeletal-neuromuscular study investigated stop-jumps and factors related to ACL injury like knee valgus and internal-external moment loads, knee anterior-posterior (AP) shear forces, ACL strains and internal forces. Motion capture data was obtained from the landing phase of stop-jumps performed by eleven young recreational female athletes and electromyography (EMG) data collected from quadriceps, hamstring and gastrocnimius muscles which were then compared to numerically estimated activations. Numerical simulation tools used were Inverse Kinematics, Computed Muscle Control and Forward Dynamics and the knee modeled as a six degree of freedom joint. Results showed averaged peak strains of 12.2 ± 4.1% in the right and 11.9 ± 3.0% in the left ACL. Averaged peak knee AP shear forces were 482.3 ± 65.7 N for the right and 430.0 ± 52.4 N for the left knees, approximately equal to 0.7-0.8 times body weight across both knees. A lack of symmetry was observed between the knees for valgus angles (p < 0.04), valgus moments (p < 0.001) and muscle activations (p < 0.001), all of which can be detrimental to ACL stability during impact activities. Comparisons between recorded EMG data and estimated muscle activations show the relation between electrical signal and muscle depolarization. In summary, this study outlines a musculoskeletal simulation approach that provides numerical estimations for a number of variables associated with ACL injuries in female athletes performing stop-jumps.

Balance and agility training does not always decrease lower limb injury risks: a cluster-randomised controlled trial

The objective of this study was to examine the effects on lower limb injury rates of adding structured balance and agility exercises to the 80-day basic training programme of army recruits. A blocked (stratified), cluster-randomised controlled trial was employed, with one intervention group (IG) and one control group (CG), in which 732 male and 47 female army recruits from the Australian Army Recruit Training Centre participated through to analysis. The IG performed specified balance and agility exercises in addition to normal physical training. The incidence of lower limb injury during basic training was used to measure effect. Analysis, which adhered to recommendations for this type of trial, used a weighted paired t-test based on the empirical logistic transform of the crude event rates. The intervention had no statistically significant effect on lower limb injury incidence (RR = 1.25, 95% CI 0.97-1.53, 90% CI 1.04-1.47), on knee and ankle injury incidence (RR = 1.08, 95% CI 0.83-1.38), and on knee and ankle ligament injury incidence (RR = 0.98, 95% CI 0.64-1.47). We conclude that the intervention, implemented in this fashion, is possibly harmful, with our best estimate of effect being a 25% increase in lower limb injury incidence rates. This type of structured balance and agility training added to normal military recruit physical training did not significantly reduce lower limb, knee and ankle, or knee and ankle ligament injury rates. Caution needs to be used when adding elements to training programmes with the aim of reducing injury, as fatigue associated with the addition may actually raise injury risk.

Distance reached in the Anteromedial Reach Test as a function of learning and leg length

The anteromedial reach test (ART) is a new outcome measure for assessing dynamic knee stability in anterior cruciate ligament-injured patients. The effect of learning and leg length on distance reached in the ART was examined. Thirty-two healthy volunteers performed 15 trials of the ART on each leg. There was a moderate correlation (r = .44-.50) between reach distance and leg length, therefore reach distances were normalized for leg length. Normalized reach distance increased significantly over the 15 trials (p < .01), reaching a plateau after 8 trials, identified by a moving average graph. It is recommended that participants be afforded eight practice trials and that reach distances be normalized by expressing them as a percentage of leg length.

Real-time intersession and interrater reliability of the functional movement screen

The purpose of this study was to examine the real-time intersession and interrater reliability of the functional movement screen (FMS). The overall study consisted of 19 volunteer civilians (12 male, 7 female). The intersession reliability consisted of 12 men and 7 women, whereas 10 men and 6 women participated in the interrater reliability test session. Two raters (A and B) were involved in the interrater reliability aspect of this study. The FMS includes 7 tests: deep squat (DS), hurdle step (HS), in-line lunge (IL), shoulder mobility (SM), active straight leg raise (ASLR), trunk stability push-up (TSPU), and rotary stability (RS). Researchers analyzed the data via intraclass correlation (ICC). To determine the reliability of the intersession scoring of the FMS and the intrasession interrater scoring of the FMS a 2-way mixed effects model intraclass correlation coefficient (ICC(3,1)) was used for the continuous data, whereas a weighted Cohen's kappa (κ) was used for the categorical data. The dependent variables were FMS total score (0-21 scale) and associated tests were DS, HS, IL, SM, ASLR, TSPU, and RS. Intersession reliability (ICC, SEM) and κ were as follows: FMS total score (0.92, 0.51), DS (κ = 0.69), HS (κ = 0.16), IL (κ = 0.69), SM (κ = 0.84), ASLR (κ = 0.69), TSPU (κ = 0.77), and RS (no covariance). Interrater reliability (ICC, SEM) and κ were as follows: FMS total score (0.98, 0.25), DS (κ = 1.0), HS (κ = 0.33), IL (κ = 0.88), SM (κ = 0.90), ASLR (κ = 0.88), TSPU (κ = 0.75), and RS (no covariance). The FMS total scores displayed high intersession and interrater reliabilities. Finally, with the exception of HS, all tasks displayed moderate to high intersession reliability and good to high interrater reliability.

Knee rotational laxity and proprioceptive function 2 years after partial ACL reconstruction

PURPOSE

The aim of our study was to evaluate knee rotational laxity and proprioceptive function 2 years after partial anterior cruciate ligament (ACL) reconstruction. According to our hypothesis, partial ACL reconstruction could restore knee laxity and function to the intact level.

METHODS

We conducted a study in fifteen consecutive patients undergoing partial ACL reconstruction. Fifteen anteromedial bundle tears were identified intraoperatively. Partial ACL reconstructions were performed by the same senior surgeon using a single-incision technique. A bone-patellar tendon-bone graft was used in 13 cases and a double-stranded semitendinosus graft in 2 cases of chronic patellar tendonitis. The mean age at surgery was 29 years. The time between ACL tear and surgery averaged 7.8 months (range 2.5-29.5 months). We developed an original device designed to assess knee proprioception (passive and active) and measure weight-bearing rotational laxity in full extension and at 30°, 60° and 90° of knee flexion. All measurements were taken on both the reconstructed and healthy knee.

RESULTS

The mean follow-up of the study was 3.4 years (range 2.6-4.4). No statistically significant difference in rotational laxity, active or passive proprioception could be observed between the reconstructed and healthy knee. External rotation was significantly greater than internal rotation in full extension and at 30° of flexion in the reconstructed and the healthy knee (P < 0.05). For each knee, active proprioception was found to be significantly different (higher) than passive proprioception (P < 0.05).

CONCLUSION

Our study did not detect any difference in rotational laxity and proprioception between the reconstructed and the healthy knee. Therefore, partial ACL reconstruction appears to restore satisfactory knee laxity and function in case of partial ACL tear.

LEVEL OF EVIDENCE

IV.

Anterior cruciate ligament strain and tensile forces for weight-bearing and non-weight-bearing exercises: a guide to exercise selection

There is a growing body of evidence documenting loads applied to the anterior cruciate ligament (ACL) for weight-bearing and non-weight-bearing exercises. ACL loading has been quantified by inverse dynamics techniques that measure anterior shear force at the tibiofemoral joint (net force primarily restrained by the ACL), ACL strain (defined as change in ACL length with respect to original length and expressed as a percentage) measured directly in vivo, and ACL tensile force estimated through mathematical modeling and computer optimization techniques. A review of the biomechanical literature indicates the following: ACL loading is generally greater with non-weight-bearing compared to weight-bearing exercises; with both types of exercises, the ACL is loaded to a greater extent between 10° to 50° of knee flexion (generally peaking between 10° and 30°) compared to 50° to 100° of knee flexion; and loads on the ACL change according to exercise technique (such as trunk position). Squatting with excessive forward movement of the knees beyond the toes and with the heels off the ground tends to increase ACL loading. Squatting and lunging with a forward trunk tilt tend to decrease ACL loading, likely due to increased hamstrings activity. During seated knee extension, ACL force decreases when the resistance pad is positioned more proximal on the anterior aspect of the lower leg, away from the ankle. The evidence reviewed as part of this manuscript provides objective data by which to rank exercises based on loading applied to the ACL. The biggest challenge in exercise selection post-ACL reconstruction is the limited knowledge of the optimal amount of stress that should be applied to the ACL graft as it goes through its initial incorporation and eventual maturation process. Clinicians may utilize this review as a guide to exercise selection and rehabilitation progression for patients post-ACL reconstruction.

Incidence of contralateral and ipsilateral anterior cruciate ligament (ACL) injury after primary ACL reconstruction and return to sport

OBJECTIVE

Incidence rate (IR) of an ipsilateral or contralateral injury after anterior cruciate ligament reconstruction (ACLR) is unknown. The hypotheses were that the IR of anterior cruciate ligament (ACL) injury after ACLR would be greater than the IR in an uninjured cohort of athletes and would be greater in female athletes after ACLR than male athletes.

DESIGN

Prospective case-control study.

SETTING

Regional sports community.

PARTICIPANTS

Sixty-three subjects who had ACLR and were ready to return to sport (RTS) and 39 control subjects.

INDEPENDENT VARIABLES

Second ACL injury and sex.

MAIN OUTCOME MEASURES

Second ACL injury and athletic exposure (AE) was tracked for 12 months after RTS. Sixteen subjects after ACLR and 1 control subject suffered a second ACL injury. Between- and within-group comparisons of second ACL injury rates (per 1000 AEs) were conducted.

RESULTS

The IR of ACL injury after ACLR (1.82/1000 AE) was 15 times greater [risk ratio (RR) = 15.24; P = 0.0002) than that of control subjects (0.12/1000 AE). Female ACLR athletes demonstrated 16 times greater rate of injury (RR = 16.02; P = 0.0002) than female control subjects. Female athletes were 4 (RR = 3.65; P = 0.05) times more likely to suffer a second ACL injury and 6 times (RR = 6.21; P = 0.04) more likely to suffer a contralateral injury than male athletes.

CONCLUSIONS

An increased rate of second ACL injury after ACLR exists in athletes when compared with a healthy population. Female athletes suffer contralateral ACL injuries at a higher rate than male athletes and seem to suffer contralateral ACL injuries more frequently than graft re-tears. The identification of a high-risk group within a population of ACLR athletes is a critical step to improve outcome after ACLR and RTS.

Current concepts for rehabilitation and return to sport after knee articular cartilage repair in the athlete

Articular cartilage injury is observed with increasing frequency in both elite and amateur athletes and results from the significant acute and chronic joint stress associated with impact sports. Left untreated, articular cartilage defects can lead to chronic joint degeneration and athletic and functional disability. Treatment of articular cartilage defects in the athletic population presents a therapeutic challenge due to the high mechanical demands of athletic activity. Several articular cartilage repair techniques have been shown to successfully restore articular cartilage surfaces and allow athletes to return to high-impact sports. Postoperative rehabilitation is a critical component of the treatment process for athletic articular cartilage injury and should take into consideration the biology of the cartilage repair technique, cartilage defect characteristics, and each athlete's sport-specific demands to optimize functional outcome. Systematic, stepwise rehabilitation with criteria-based progression is recommended for an individualized rehabilitation of each athlete not only to achieve initial return to sport at the preinjury level but also to continue sports participation and reduce risk for reinjury or joint degeneration under the high mechanical demands of athletic activity.

The mechanistic connection between the trunk, hip, knee, and anterior cruciate ligament injury

Neuromuscular control of the trunk and knee predicts anterior cruciate ligament injury risk with high sensitivity and specificity. These predictors are linked, as lateral trunk positioning creates high knee abduction torque (load). The hypotheses explored are that lateral trunk motion increases load and that neuromuscular training that enhance trunk control will decrease load.

Effects of sex on compensatory landing strategies upon return to sport after anterior cruciate ligament reconstruction

STUDY DESIGN

Controlled laboratory, cross-sectional, cohort design.

OBJECTIVE

To determine if a sex-specific pattern of lower limb asymmetries is present during a drop vertical jump (DVJ) maneuver at the time of return to sport after anterior cruciate ligament (ACL) reconstruction.

BACKGROUND

A high incidence of second ACL injury is reported after reconstruction; however, the underlying mechanisms of this injury are unclear. While asymmetrical dynamic loading patterns predictive of primary ACL injury in healthy female athletes were observed in female athletes 2 years after ACL reconstruction, it is unknown if similar asymmetries are present in male athletes after ACL reconstruction at the time of return to sport.

METHODS

A total of 98 participants were included in the study, 56 of whom had unilateral ACL reconstruction (35 female, 21 male) and had been released to return to unrestricted level 1 and 2 sports, and 42 of whom were uninjured, activity-matched control participants (29 female, 13 male). Lower extremity kinetic data were analyzed during a bilateral drop vertical jump maneuver from a 31-cm box. Peak vertical ground reaction force (VGRF) was calculated during the landing phase of the drop vertical jump and normalized to body weight (BW). A 2-by-2-by-2 analysis of variance was used to determine differences between side (involved versus uninvolved), group (ACL reconstruction versus control), and sex (female versus male) for the peak VGRF.

RESULTS

A significant side-by-group interaction for peak VGRF (P = .002) was observed during the landing phase of the drop vertical jump in the entire cohort. The involved limb of the ACL reconstructed group displayed significantly lower VGRF (mean ± SD, 1.77 ± 0.35 BW) than the uninvolved limb (2.2 ± 0.4 BW, P<.001) and both the preferred limb (2.0 ± 0.4 BW, P = .002) and nonpreferred limb (2.09 ± 0.42 BW, P<.001) in the control group. No effect of sex was noted.

CONCLUSION

After ACL reconstruction, both male and female participants at the time of return to sport demonstrated involved limb asymmetries in peak VGRF during landing from a bipedal task. These deficits, which persist at the time of return to sport, may increase the risk of future injury and indicate that rehabilitation after ACL reconstruction may require more targeted interventions to address involved limb biomechanical deficits in athletes of both sexes prior to return to sport participation.

Biomechanics laboratory-based prediction algorithm to identify female athletes with high knee loads that increase risk of ACL injury

OBJECTIVE

Knee abduction moment (KAM) during landing predicts non-contact anterior cruciate ligament (ACL) injury risk with high sensitivity and specificity in female athletes. The purpose of this study was to employ sensitive laboratory (lab-based) tools to determine predictive mechanisms that underlie increased KAM during landing.

METHODS

Female basketball and soccer players (N=744) from a single county public school district were recruited to participate in testing of anthropometrics, maturation, laxity/flexibility, strength and landing biomechanics. Linear regression was used to model KAM, and logistic regression was used to examine high (>25.25 Nm of KAM) versus low KAM as surrogate for ACL injury risk.

RESULTS

The most parsimonious model included independent predictors (β±1 SE) (1) peak knee abduction angle (1.78±0.05; p<0.001), (2) peak knee extensor moment (0.17±0.01; p<0.001), (3) knee flexion range of motion (0.15±0.03; p<0.01), (4) body mass index (BMI) Z-score (-1.67±0.36; p<0.001) and (5) tibia length (-0.50±0.14; p<0.001) and accounted for 78% of the variance in KAM during landing. The logistic regression model that employed these same variables predicted high KAM status with 85% sensitivity and 93% specificity and a C-statistic of 0.96.

CONCLUSIONS

Increased knee abduction angle, quadriceps recruitment, tibia length and BMI with decreased knee flexion account for 80% of the measured variance in KAM during a drop vertical jump.

CLINICAL RELEVANCE

Females who demonstrate increased KAM are more responsive and more likely to benefit from neuromuscular training. These findings should significantly enhance the identification of those at increased risk and facilitate neuromuscular training targeted to this important risk factor (high KAM) for ACL injury.

Balance training for neuromuscular control and performance enhancement: a systematic review

OBJECTIVE

As a result of inconsistencies in reported findings, controversy exists regarding the effectiveness of balance training for improving functional performance and neuromuscular control. Thus, its practical benefit in athletic training remains inconclusive. Our objective was to evaluate the effectiveness of training interventions in enhancing neuromuscular control and functional performance.

DATA SOURCES

Two independent reviewers performed a literature search in Cochrane Bone, Joint and Muscle Trauma Group Register and Cochrane Controlled Trials Register, MEDLINE, EMBASE, PEDro (Physiotherapy Evidence Database), and SCOPUS.

STUDY SELECTION

Randomized controlled trials and controlled trials without randomization with healthy and physically active participants aged up to 40 years old were considered for inclusion. Outcomes of interest were postural control, muscle strength, agility, jump performance, sprint performance, muscle reflex activity, rate of force development, reaction time, and electromyography.

DATA EXTRACTION

Data of interest were methodologic assessment, training intervention, outcome, timing of the outcome assessment, and results. Standardized mean differences and 95% confidence intervals were calculated when data were sufficient.

DATA SYNTHESIS

In total, 20 randomized clinical trials met the inclusion criteria. Balance training was effective in improving postural sway and functional balance when compared with untrained control participants. Larger effect sizes were shown for training programs of longer duration. Although controversial findings were reported for jumping performance, agility, and neuromuscular control, there are indications for the effectiveness of balance training in these outcomes. When compared with plyometric or strength training, conflicting results or no effects of balance training were reported for strength improvements and changes in sprint performance.

CONCLUSIONS

We conclude that balance training can be effective for postural and neuromuscular control improvements. However, as a result of the low methodologic quality and training differences, further research is strongly recommended.

Postoperative rehabilitation of the posterior cruciate ligament

Diagnosis and management of posterior cruciate ligament injuries has evolved, and now the treatment often includes surgical intervention. The purpose of this paper is to define the current approach to postsurgical management after the posterior cruciate ligament reconstruction, review conservative management, and discuss surgical outcomes using a specified program.

Knee proprioception following ACL reconstruction; a prospective trial comparing hamstrings with bone-patellar tendon-bone autograft

We prospectively studied knee proprioception following ACL reconstruction in 40 patients (34 men and six women; mean age 31 years). The patients were allocated into two equal groups; group A underwent reconstruction using hamstrings autograft, and group B underwent reconstruction using bone-patellar tendon-bone autograft. Proprioception was assessed in flexion and extension by the joint position sense (JPS) at 15°, 45° and 75°, and time threshold to detection of passive motion (TTDPM) at 15° and 45°, preoperatively and at 3, 6 and 12 months postoperatively. The contralateral healthy knee was used as internal control. No statistical difference was found between the ACL-operated and the contralateral knees in JPS 15°, 45° and 75° at 6 and 12 months, in both study groups. No statistical difference was found between the ACL-operated and the contralateral knees in TTDPM 15° at 6 and 12 months, nor regarding TTDPM 45° at 3, 6 and 12 months, in group A. No statistical difference was found in JPS and TTDPM between the two grafts, at any time period. Knee proprioception returned to normal with ACL reconstruction at 6 months postoperatively, without any statistically significant difference between the autografts used.

Proprioception following partial meniscectomy in stable knees

PURPOSE

to investigate the proprioceptive function of patients with isolated meniscal tears of the knee before and after arthroscopic partial meniscectomy.

METHODS

one hundred subjects (50 patients who underwent a knee arthroscopy and 50 normal controls) were evaluated using single-leg dynamic postural stabilometry. All participants were assessed clinically and radiologically. Knee outcome scores were obtained for all subjects.

RESULTS

of the 50 patients arthroscoped, 34 were found to have meniscal tears. Twenty-nine of these patients were reassessed 3 months post-operatively. There was a significant proprioceptive deficit in subjects with meniscal tears when compared to their normal contra-lateral knee (P < 0.001) and the control group (P < 0.001). Partial meniscectomy resulted in a significant improvement in knee outcome scores but not proprioception measurements (n.s.).

CONCLUSION

patients with isolated meniscal tears were found to have a significant proprioceptive deficit which persisted following arthroscopic partial meniscectomy despite an otherwise successful clinical outcome.

Proprioceptive acuity in the frontal and sagittal planes of the knee: a preliminary study

Though the knee experiences three-dimensional loading during everyday tasks, assessment of proprioceptive acuity has typically been limited to the primary direction of movement, knee flexion and extension. While loading in the constrained directions (varus/valgus and internal/external rotation) may contribute to injury and joint disease, little information is available regarding proprioceptive acuity in these planes of movement. The primary aim of this study was to characterize proprioceptive acuity in the frontal plane (varus/valgus) and to compare it with sagittal plane (flexion/extension) proprioceptive acuity in healthy subjects. Proprioception was assessed in 17 young, healthy subjects (11 females, 6 males, ages 21-33 years) using the threshold to detection of passive movement (TDPM). TDPM was found to be significantly (P < 0.001) lower in the frontal plane [valgus: mean (SD) 0.60 (0.20)° and varus: 0.58 (0.23)°] compared with the sagittal plane [extension: 0.78 (0.34)°, flexion: 0.82 (0.48)°]; however, no significant differences were noted within the same plane of movement. Results from this preliminary study may suggest more accurate proprioceptive acuity in the frontal plane compared with the sagittal plane. While further examination is necessary to confirm this relationship, more accurate frontal plane acuity may reflect a protective neural mechanism which enables more precise neuromuscular control of the joint in this constrained plane of movement.

Controle postural em pacientes com lesão do ligamento cruzado anterior

A lesão do ligamento cruzado anterior (LCA) do joelho acarreta alterações somatosensoriais em função da perda de informações provenientes dos mecanorreceptores presentes no LCA. Esses receptores constituem importante fonte de informação sensorial, afetando o desempenho de vários atos motores, dentre os quais o controle postural. O estudo objetivou analisar o controle postural de indivíduos com joelhos normais e com lesão unilateral do LCA. Participaram 15 voluntários com lesão do LCA (grupo lesado) e 15 voluntários com joelhos normais (grupo controle). O controle postural foi analisado por plataforma de força, sendo o voluntário instruído a assumir a situação experimental em apoio unipodal direito e esquerdo, posicionado no centro da plataforma de modo estático e com os olhos fechados. A plataforma de força forneceu informações de forças e momentos no eixo vertical e horizontal, a partir das quais foi obtida a área de deslocamento do centro de pressão nas direções ântero-posterior e médio-lateral. Os resultados mostram que indivíduos com lesão do LCA apresentaram maior amplitude média de oscilação comparados aos do grupo controle, sugerindo que o deficit no controle postural seja devido à perda de informações proprioceptivas nos indivíduos com LCA. Esses resultados têm implicações para a abordagem clínica de indivíduos com lesão do LCA.

The association between lower extremity energy absorption and biomechanical factors related to anterior cruciate ligament injury

BACKGROUND

Greater total energy absorption by the lower extremity musculature during landing may reduce stresses placed on capsuloligamentous tissues with differences in joint contributions to energy absorption potentially affecting anterior cruciate ligament injury risk. However, the relationships between energy absorption and prospectively identified biomechanical factors associated with non-contact anterior cruciate ligament injury have yet to be demonstrated.

METHODS

Sagittal plane total, hip, knee and ankle energy absorption, and peak vertical ground reaction force, anterior tibial shear force, knee flexion and knee valgus angles, and internal hip extension and knee varus moments were measured in 27 individuals (14 females, 13 males) performing double leg jump landings. Correlation coefficients assessed the relationships between energy absorption during three time intervals (initial impact phase, terminal phase, and total landing) and biomechanical factors related to anterior cruciate ligament injury.

FINDINGS

More favorable values of biomechanical factors related to non-contact anterior cruciate ligament injury were associated with: 1) Lesser total (R(2)=0.178-0.558), hip (R(2)=0.229-0.651) and ankle (R(2)=0.280), but greater knee (R(2)=0.147) energy absorption during the initial impact phase; 2) Greater total (R(2)=0.170-0.845), hip (R(2)=0.599), knee (R(2)=0.236-0.834), and ankle (R(2)=0.276) energy absorption during the terminal phase of landing; and 3) Greater knee (R(2)=0.158-0.709), but lesser hip (R(2)=0.309) and ankle (R(2)=0.210-0.319) energy absorption during the total landing period.

INTERPRETATION

These results suggest that biomechanical factors related to anterior cruciate ligament injury are influenced by both the magnitude and timing of lower extremity energy absorption during landing.

Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport

BACKGROUND

Athletes who return to sport participation after anterior cruciate ligament reconstruction (ACLR) have a higher risk of a second anterior cruciate ligament injury (either reinjury or contralateral injury) compared with non-anterior cruciate ligament-injured athletes.

HYPOTHESES

Prospective measures of neuromuscular control and postural stability after ACLR will predict relative increased risk for a second anterior cruciate ligament injury.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

Fifty-six athletes underwent a prospective biomechanical screening after ACLR using 3-dimensional motion analysis during a drop vertical jump maneuver and postural stability assessment before return to pivoting and cutting sports. After the initial test session, each subject was followed for 12 months for occurrence of a second anterior cruciate ligament injury. Lower extremity joint kinematics, kinetics, and postural stability were assessed and analyzed. Analysis of variance and logistic regression were used to identify predictors of a second anterior cruciate ligament injury.

RESULTS

Thirteen athletes suffered a subsequent second anterior cruciate ligament injury. Transverse plane hip kinetics and frontal plane knee kinematics during landing, sagittal plane knee moments at landing, and deficits in postural stability predicted a second injury in this population (C statistic = 0.94) with excellent sensitivity (0.92) and specificity (0.88). Specific predictive parameters included an increase in total frontal plane (valgus) movement, greater asymmetry in internal knee extensor moment at initial contact, and a deficit in single-leg postural stability of the involved limb, as measured by the Biodex stability system. Hip rotation moment independently predicted second anterior cruciate ligament injury (C = 0.81) with high sensitivity (0.77) and specificity (0.81).

CONCLUSION

Altered neuromuscular control of the hip and knee during a dynamic landing task and postural stability deficits after ACLR are predictors of a second anterior cruciate ligament injury after an athlete is released to return to sport.

Evidence of gender-specific motor templates to resist valgus loading at the knee

Gender differences in neuromuscular control of the lower extremity may contribute to increased injury risk in females, but the neurophysiological mechanisms underlying these differences remain unclear. In this study, we sought to explore the effect of gender on volitional and reflex neuromuscular responses to a rapid valgus perturbation at the knee applied under "intervene" and "do not intervene" conditions. Multiple 7 degrees ramp-and-hold valgus perturbations were applied at the neutrally extended knee of 12 male and 12 female healthy subjects, while surface electromyography over the quadriceps and hamstrings recorded the neuromuscular response. Volitional responses did not vary between groups, perhaps reflecting the relative novelty of the loading direction. However, reflex responses observed under the "do not intervene" paradigm did vary by gender. Males demonstrated much more frequent and consistent reflex muscle activation than females. Moreover, muscle activation patterns were gender-specific. Diminished responses in female subjects may indicate that the position-based valgus perturbation did not produce the necessary mechanical stimulus to elicit reflexes. These gender differences in reflex control of the knee provide new insight into the control of frontal-plane knee joint movement and loading and may elucidate the neuromechanical underpinnings associated with neuromuscular control.

Proprioception of the wrist joint: a review of current concepts and possible implications on the rehabilitation of the wrist

STUDY DESIGN

Narrative review. Recent years have brought new research findings on the subject of wrist joint proprioception, which entails an understanding of the wrist as part of a sensorimotor system where afferent information from nerve endings in the wrist joint affects the neuromuscular control of the joint. An understanding of proprioception is also essential to adequately rehabilitate patients after wrist injuries. The aim of this narrative review was to give the reader a background of proprioception as it relates to neuromuscular control and joint stability, what is presently known in relation to the wrist joint and how these findings may be applied to the field of wrist rehabilitation.

LEVEL OF EVIDENCE

5.

A 5° medial wedge reduces frontal but not saggital plane motion during jump landing in highly trained women athletes

Lower extremity mechanics during landing have been linked to traumatic and nontraumatic knee injuries, particularly in women’s athletics. The effects of efforts to mitigate these risks have not been fully elucidated. We previously reported that a 5° medial wedge reduced ankle eversion and knee valgus. In the present report we further investigated the effect of a 5° medial wedge inserted in the shoes of female athletes on frontal plane hip motion, as well as ankle, knee, hip, and trunk saggital plane motion during a jump landing task. Kinematic data were obtained from 10 intercollegiate female athletes during jump landings from a 31 cm platform with and without a 5° medial wedge. Hip adduction was reduced 1.98° (95% CI 0.97–2.99°) by the medial wedge but saggital plane motions were unaffected. A 5° medial wedge reduces frontal plane motion and takes the knee away from a position associated with anterior cruciate ligament injury and patellofemoral pain syndrome. Although frontal plane motion was not captured it is unlikely to have increased in a bilateral landing task. Thus, it is likely that greater muscle forces were generated in these highly trained athletes to dissipate ground reaction forces when a medial wedge was in place. Additional investigation in younger and lesser trained athletes is warranted to assess the impact of orthotic devices on knee joint mechanics.

Methodological report: dynamic field tests used in an NFL combine setting to identify lower-extremity functional asymmetries

Side-to-side differences in lower-extremity biomechanics may be predictive of increased risk of lower-extremity injuries in athletes. The purpose of this report is to provide field testing methodology for tests designed to isolate lower-extremity asymmetry and to demonstrate the potential for these tests to provide reliable measures. Six athletes (3 females, 3 males) were tested on 2 consecutive days for activities incorporated into a replicated National Football League (NFL) combine setting. Vertical hop power (VHP) and jump height were measured on a portable force platform as athletes performed maximum effort hops for 10 seconds. The modified agility T-test (MAT) incorporates two 90-degree single-leg cuts during the trial and was measured as total time for completion. Intraclass correlations (within ICC [3,k], between ICC [3,1]) were calculated. The VHP test had good to excellent within-session reliability for peak power of both the right (ICC = 0.942) and left (ICC = 0.895) sides. Jump height showed excellent within-session reliability for both the right (ICC = 0.963) and left (ICC = 0.940) sides. The between-session reliability for peak power between jumps was good for the right (ICC = 0.748) and left (ICC = 0.834) sides. Jump height showed good to excellent between-session reliability on the right (ICC = 0.794) and left (ICC = 0.909) sides. The MAT also showed good reliability between days (ICC = 0.825).The results indicate that the VHP test provides reliable assessment of both within- and between-session jump height and power production. The MAT also provides good reliability between testing days. Both the VHP and the MAT may be useful for clinicians to identify the presence of lower-limb asymmetry and potential injury risk factors in athletic populations.

Limited hip and knee flexion during landing is associated with increased frontal plane knee motion and moments

BACKGROUND

It has been proposed that female athletes who limit knee and hip flexion during athletic tasks rely more on the passive restraints in the frontal plane to deceleration their body center of mass. This biomechanical pattern is thought to increase the risk for anterior cruciate ligament injury. To date, the relationship between sagittal plane kinematics and frontal plane knee motion and moments has not been explored.

METHODS

Subjects consisted of 58 female club soccer players (age range: 11-20 years) with no history of knee injury. Kinematics, ground reaction forces, and surface electromyography were collected while each subject performed a drop landing task. Subjects were divided into two groups based on combined sagittal plane knee and hip flexion angles during the deceleration phase of landing (high flexion and low flexion).

FINDINGS

Subjects in the low flexion group demonstrated increased knee valgus angles (P=0.02, effect size 0.27), increased knee adductor moments (P=0.03, effect size 0.24), decreased energy absorption at the knee and hip (P=0.02, effect size 0.25; and P<0.001, effect size 0.59), and increased vastus lateralis EMG when compared to subjects in the high flexion group (P=0.005, effect size 0.35).

INTERPRETATION

Female athletes with limited sagittal plane motion during landing exhibit a biomechanical profile that may put these individuals at greater risk for anterior cruciate ligament injury.

Sex differences in "weightlifting" injuries presenting to United States emergency rooms

Benefits of resistance training include improved muscle strength and sports performance and may include reduced injuries. However, few studies have examined sex differences in resistance training-related injuries. The objective of this investigation was to evaluate sex differences in injuries associated with strength training in adolescents and young adults by type (sprains and strains, fractures), mechanism (accidental, nonaccidental), and location (head, trunk, arm, hand, leg, foot) of injury. We hypothesized that there would be sex differences in type, mechanism, and location of strength training injuries. The U.S. Consumer Product Safety Commission (CPSC) National Electronic Injury Surveillance System (NEISS) was queried from 2002 to 2005 using the CPSC code for "Weightlifting." Subjects between the ages of 14 and 30 years were included in the study. CPSC sampling weights were used to calculate national estimates from the sample of 3,713 patients (men = 3,102; women = 611). Weighted Chi-square analyses were used to compare differences in mechanism, type, and location of injury for men versus women. Men had significantly more sprains and strains (p = 0.004), whereas women demonstrated increased accidental injuries compared to men (p < 0.001). The trunk was the most commonly injured body part for both men (36.9%) and women (27.4%). Men had more trunk injuries than women (p < 0.001), whereas women had more foot (p < 0.001) and leg (p = 0.03) injuries than men (p < 0.001). The findings indicate that men may suffer more exertional-type resistance injuries during strength training (sprains and strains) compared to women, especially at the trunk. Conversely, women may be more susceptible to lower-extremity injuries resulting from accidents during resistance training.

Influence of age on neuromuscular control during a dynamic weight-bearing task

Neuromuscular control strategies might change with age and predispose the elderly to knee-joint injury. The purposes of this study were to determine whether long latency responses (LLRs), muscle-activation patterns, and movement accuracy differ between the young and elderly during a novel single-limb-squat (SLS) task. Ten young and 10 elderly participants performed a series of resistive SLSs (approximately 0-30 degrees) while matching a computer-generated sinusoidal target. The SLS device provided a 16% body-weight resistance to knee movement. Both young and elderly showed significant overshoot error when the knee was perturbed (p < .05). Accuracy ofthe tracking taskwas similar between the young and elderly (p = .34), but the elderly required more muscle activity than the younger participants (p < .05). The elderly group had larger LLRs than the younger group (p < .05). These results support the hypothesis that neuromuscular control of the knee changes with age and might contribute to injury.

Video analysis of trunk and knee motion during non-contact anterior cruciate ligament injury in female athletes: lateral trunk and knee abduction motion are combined components of the injury mechanism

BACKGROUND

The combined positioning of the trunk and knee in the coronal and sagittal planes during non-contact anterior cruciate ligament (ACL) injury has not been previously reported.

HYPOTHESIS

During ACL injury female athletes demonstrate greater lateral trunk and knee abduction angles than ACL-injured male athletes and uninjured female athletes.

DESIGN

Cross-section control-cohort design.

METHODS

Analyses of still captures from 23 coronal (10 female and 7 male ACL-injured players and 6 female controls) or 28 sagittal plane videos performing similar landing and cutting tasks. Significance was set at p < or = 0.05.

RESULTS

Lateral trunk and knee abduction angles were higher in female compared to male athletes during ACL injury (p < or = 0.05) and trended toward being greater than female controls (p = 0.16, 0.13, respectively). Female ACL-injured athletes showed less forward trunk lean than female controls (mean (SD) initial contact (IC): 1.6 (9.3) degrees vs 14.0 (7.3) degrees, p < or = 0.01).

CONCLUSION

Female athletes landed with greater lateral trunk motion and knee abduction during ACL injury than did male athletes or control females during similar landing and cutting tasks.

CLINICAL RELEVANCE

Lateral trunk and knee abduction motion are important components of the ACL injury mechanism in female athletes as observed from video evidence of ACL injury.

Rehabilitation after anterior cruciate ligament injury influences joint loading during walking but not hopping

OBJECTIVE

The purpose of this study was to identify changes in clinical outcome and lower extremity biomechanics during walking and hopping in ACL-injured subjects before and after a 20-session neuromuscular and strength training programme.

STUDY DESIGN

Pre and post experimental design.

SETTING

Outpatient clinic, primary care.

PATIENTS

32 subjects with unilateral ACL injury, mean 60 (SD 35) days after injury, with a mean age of 26.2 (5.4) years.

INTERVENTION

The rehabilitation programme consisted of neuromuscular and strength exercises.

MAIN OUTCOME MEASUREMENTS

Outcome measurements assessed before and after a 20-session rehabilitation programme were: self-assessment questionnaires (KOS-ADL, IKDC2000, Global function), four single-leg hop tests, and isokinetic muscle strength tests. Lower extremity kinematics and kinetics were captured during the stance phase of gait and landing after a single leg hop, synchronised with three force plates.

RESULTS

These ACL-injured individuals significantly improved their clinical outcome after rehabilitation. Gait analysis disclosed a significantly improved knee extension moment after rehabilitation, but no change in hip or knee excursions. During landing after hop no change in knee excursion or knee moment was recorded.

CONCLUSION

After rehabilitation the ACL-injured subjects showed a significantly improved clinical outcome, but lower extremity biomechanics were still significantly impaired during both walking and hopping. The rehabilitation programme influenced knee joint loading during walking, but not during hopping. Longer rehabilitation should be considered before ACL-injured individuals return to jumping activities.

The importance of sensory-motor control in providing core stability: implications for measurement and training

Although the hip musculature is found to be very important in connecting the core to the lower extremities and in transferring forces from and to the core, it is proposed to leave the hip musculature out of consideration when talking about the concept of core stability. A low level of co-contraction of the trunk muscles is important for core stability. It provides a level of stiffness, which gives sufficient stability against minor perturbations. Next to this stiffness, direction-specific muscle reflex responses are also important in providing core stability, particularly when encountering sudden perturbations. It appears that most trunk muscles, both the local and global stabilization system, must work coherently to achieve core stability. The contributions of the various trunk muscles depend on the task being performed. In the search for a precise balance between the amount of stability and mobility, the role of sensory-motor control is much more important than the role of strength or endurance of the trunk muscles. The CNS creates a stable foundation for movement of the extremities through co-contraction of particular muscles. Appropriate muscle recruitment and timing is extremely important in providing core stability. No clear evidence has been found for a positive relationship between core stability and physical performance and more research in this area is needed. On the other hand, with respect to the relationship between core stability and injury, several studies have found an association between a decreased stability and a higher risk of sustaining a low back or knee injury. Subjects with such injuries have been shown to demonstrate impaired postural control, delayed muscle reflex responses following sudden trunk unloading and abnormal trunk muscle recruitment patterns. In addition, various relationships have been demonstrated between core stability, balance performance and activation characteristics of the trunk muscles. Most importantly, a significant correlation was found between poor balance performance in a sitting balance task and delayed firing of the trunk muscles during sudden perturbation. It was suggested that both phenomena are caused by proprioceptive deficits. The importance of sensory-motor control has implications for the development of measurement and training protocols. It has been shown that challenging propriocepsis during training activities, for example, by making use of unstable surfaces, leads to increased demands on trunk muscles, thereby improving core stability and balance. Various tests to directly or indirectly measure neuromuscular control and coordination have been developed and are discussed in the present article. Sitting balance performance and trunk muscle response times may be good indicators of core stability. In light of this, it would be interesting to quantify core stability using a sitting balance task, for example by making use of accelerometry. Further research is required to develop training programmes and evaluation methods that are suitable for various target groups.

Validation of a method to measure the proprioception of the knee

INTRODUCTION

Proprioception is an important mechanism in knee stability and function. After an injury like an anterior cruciate ligament (ACL) rupture changes appear in knee proprioception which play a major role in rehabilitation. There are several methods to measure proprioception; the threshold to detect passive motion (TTDPM) is often used to quantify proprioception. In this study the reliability and validity were tested of an apparatus, which measures the TTDPM based on the Lund technique of Fridén and Roberts (Sweden).

MATERIALS AND METHODS

Sixteen healthy participants were tested on both legs, from start position 20 degrees and 40 degrees, towards extension (TE) and flexion (TF). The same measurement was repeated 12 (6-21) days later.

RESULTS

An overall mean TTDPM of 0.58 degrees (95% confidence interval CI=0.53-0.62 degrees ) was found. Thresholds were different depending on direction of motion and start position. TTDPM in 20 degrees TE (0.51 degrees, CI=0.48-0.56 degrees) and in 40 degrees TF (0.54 degrees, CI=0.50-0.58 degrees ) were significantly lower than TTDPM in 40 degrees TE (0.68 degrees , CI=0.63-0.74 degrees) and in 20 degrees TF (0.58 degrees, CI=0.54-0.63 degrees). Thresholds were rising with age. Women had higher thresholds than men.

CONCLUSION

The method is a reliable and valid way to measure proprioception. The next step is to use this method on patients with an ACL-rupture and compare these results with healthy subjects.

Neuromuscular training techniques to target deficits before return to sport after anterior cruciate ligament reconstruction

Surgical intervention and early-phase rehabilitation after anterior cruciate ligament (ACL) reconstruction have undergone a relatively rapid and global evolution over the past 25 years. Despite the advances that have significantly improved outcomes, decreases in healthcare coverage (limited visits allowed for physical therapy) have increased the role of the strength and conditioning specialist in the rehabilitation of athletes returning to sport after ACL reconstruction. In addition, there is an absence of standardized, objective criteria to accurately assess an athlete's ability to progress through the end stages of rehabilitation and safely return to sport. The purpose of this Scientific Commentary is to present an example of a progressive, end-stage return to sport protocol that is targeted to measured deficits of neuromuscular control, strength, power, and functional symmetry that are rehabilitative landmarks after ACL reconstruction. The proposed return to sport training protocol incorporates quantitative measurement tools that will provide the athlete with objective feedback and targeted goal setting. Objective feedback and targeted goal setting may aid the strength and conditioning specialist with exercise selection and progression. In addition, a rationale for exercise selection is outlined to provide the strength and conditioning specialist with a flexible decision-making approach that will aid in the modification of return to sport training to meet the individual athlete's abilities and to target objectively measured deficits. This algorithmic approach may improve the potential for athletes to return to sport after ACL reconstruction at the optimal performance level and with minimized risk of reinjury.

Timing of neuromuscular activation of the quadriceps and hamstrings prior to landing in high school male athletes, female athletes, and female non-athletes

There is a discrepancy between males and females in regards to lower extremity injury rates, particularly at the knee [Agel, J., Arendt, E.A., Bershadsky, B., 2005. Anterior cruciate ligament injury in National Collegiate Athletic Association basketball and soccer: a 13-year review. American Journal of Sports Medicine 33, (4) 524-530]. Gender differences in neuromuscular recruitment characteristics of the muscles that stabilize the knee are often implicated as a factor in this discrepancy. There is considerable research in the area of gender differences in regards to neuromuscular characteristics of the lower extremity in response to perturbation; however, most studies have been performed on the adult population only. Additionally, there is no consensus as to the gender differences that have been demonstrated. The purpose of this study was to compare muscular preactivation of selected lower extremity muscles (vastus medialis, rectus femoris, and medial/lateral hamstrings) in adolescent female basketball athletes, male basketball athletes, and female non-athletes in response to a drop landing. Subjects in the female non-athlete group recruited rectus femoris significantly slower than both the female athlete and male athlete groups (619.9=588.5>200.1ms prior to ground contact). The female non-athlete group also demonstrated a significantly slower vastus medialis compared to the female athlete group (127.1 vs 408.1ms), but not significantly slower than the male athlete group (127.1 vs 275.7ms). There were no differences between female athletes and male athletes for time to initial contraction of any muscle groups. No differences were found among the groups for medial or lateral hamstring activation. This study demonstrates that physical conditioning due to basketball participation appears to affect neuromuscular recruitment in adolescents and reveals a necessity to find alternate methods of training the hamstrings for improved neuromuscular capabilities to prevent injury.

Effect of a neuromuscular training program on the kinetics and kinematics of jumping tasks

BACKGROUND

Altered motor control strategies are a proposed cause of the female athlete's increased risk for noncontact anterior cruciate ligament injury. Injury prevention programs have shown promising results in decreasing the incidence of anterior cruciate ligament injury.

PURPOSE

To evaluate the effect of the Kerlan-Jobe Orthopaedic Clinic Modified Neuromuscular Training Program on the biomechanics of select jumping tasks in the female collegiate athlete.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty female National Collegiate Athletic Association Division I soccer and basketball players performed vertical jump, hopping tests, and 2 jumping tasks (drop jump and stop jump). All subjects completed a 6-week neuromuscular training program with core strengthening and plyometric training. Three-dimensional motion analysis and force plate data were used to compare the kinetics and kinematics of jumping tasks before and after training.

RESULTS

Dynamic knee valgus moment during the stance phase of stop jump tasks decreased after completion of the neuromuscular training program (P = .04), but differences were not observed for the drop jump. Initial knee flexion (P = .003) and maximum knee flexion (P = .006) angles increased during the stance phase of drop jumps after training, but differences were not observed for the stop jump. The athletes showed improved performance in vertical jump (P < .001), right 1-legged hop (P < .001), and left 1-legged hop (P < .001).

CONCLUSION

Completion of a 6-week neuromuscular training program improved select athletic performance measures and changed movement patterns during jumping tasks in the subject population.

CLINICAL RELEVANCE

The use of this neuromuscular training program could potentially modify the collegiate athlete's motion strategies, improve performance, and lower the athlete's risk for injury.