Whole-Body Vibration Improves Early Rate of Torque Development in Individuals With Anterior Cruciate Ligament Reconstruction

Pamukoff, DN, Pietrosimone, B, Ryan, ED, Lee, DR, Brown, LE, and Blackburn, JT. Whole body vibration improves early rate of torque development in individuals with anterior cruciate ligament reconstruction. J Strength Cond Res 31(11): 2992-3000, 2017-The purpose of this study was to compare the effect of whole-body vibration (WBV) and local muscle vibration (LMV) on early and late quadriceps rate of torque development (RTD), and electromechanical delay (EMD) in individuals with anterior cruciate ligament reconstruction (ACLR). Twenty individuals with ACLR were recruited for this study. Participants performed isometric squats while being exposed to WBV, LMV, or no vibration (control) in a randomized order during separate visits. Early and late quadriceps RTD and EMD were assessed during a maximal voluntary isometric knee extension before and immediately after WBV, LMV, or control. There was a significant condition by time interaction for early RTD (p = 0.045) but not for late RTD (p = 0.11) or EMD of the vastus medialis (p = 0.15), vastus lateralis (p = 0.17), or rectus femoris (p = 0.39). Post hoc analyses indicated a significant increase in early RTD after WBV (+5.59 N·m·s·kg; 95% confidence interval, 1.47-12.72; p = 0.007). No differences were observed in the LMV or control conditions, and no difference was observed between conditions at posttest. The ability to rapidly produce knee extension torque is essential to physical function, and WBV may be appropriate to aid in the restoration of RTD after ACLR.

Time between anterior cruciate ligament injury and reconstruction and cartilage metabolism six-months following reconstruction

BACKGROUND

To determine the association between time from injury to ACL reconstruction (Time^Injury-ACLR) and biochemical markers of cartilage metabolism and inflammation six months following ACL reconstruction (ACLR).

METHODS

Individuals with a unilateral ACL injury were enrolled at initial presentation in the orthopedic clinic; blood was collected six months following ACLR. Enzyme-linked immunosorbent assays were used to analyze the ratio of serum concentrations of type-II collagen breakdown (C2C) to synthesis (CPII), plasma matrix metalloproteinase-3 (MMP-3), interleukin-6 (IL-6), and serum aggrecan neoepitope (ARGS). We used separate linear regressions to assess associations between biochemical markers and Time^Injury-ACLR.

RESULTS

Twenty-two participants (50% females, mean [SD], age 21.9 [4.5] years old; BMI 23.8 [2.6] kg/m²) completed the study. Time^Injury-ACLR ranged from nine to 67days (31.0 [14.4days]). Greater Time^Injury-ACLR predicted greater serum C2C:CPII ratios six months following ACLR (C2C:CPII=0.15 [0.02], R²=0.213, P=0.030). Males (R²=0.733, P=0.001) but not females (R²=0.030, P=0.609) demonstrated a significant association between greater C2C:CPII and Time^Injury-ACLR at the six-month follow-up exam. Time^Injury-ACLR did not associate with IL-6, MMP-3, or ARGS at six months.

CONCLUSIONS

Greater time between injury and ACL reconstruction was associated with greater serum C2C:CPII six months following ACLR in males but not females, and IL-6, MMP-3, and ARGS levels were not associated with Time^Injury-ACLR in males or females. The time between ACL injury and ACLR may affect collagen metabolism in males and should be further investigated in a larger study along with other patient-relevant outcomes.

Peak knee biomechanics and limb symmetry following unilateral anterior cruciate ligament reconstruction: Associations of walking gait and jump-landing outcomes

BACKGROUND

Aberrant walking-gait and jump-landing biomechanics may influence the development of post-traumatic osteoarthritis and increase the risk of a second anterior cruciate ligament injury, respectively. It remains unknown if individuals who demonstrate altered walking-gait biomechanics demonstrate similar altered biomechanics during jump-landing. Our aim was to determine associations in peak knee biomechanics and limb-symmetry indices between walking-gait and jump-landing tasks in individuals with a unilateral anterior cruciate ligament reconstruction.

METHODS

Thirty-five individuals (74% women, 22.1 [3.4] years old, 25 [3.89] kg/m²) with an anterior cruciate ligament reconstruction performed 5-trials of self-selected walking-gait and jump-landing. Peak kinetics and kinematics were extracted from the first 50% of stance phase during walking-gait and first 100 ms following ground contact for jump-landing. Pearson product-moment (r) and Spearman's Rho (ρ) analyses were used to evaluate relationships between outcome measures. Significance was set a priori (P ≤ 0.05).

FINDINGS

All associations between walking-gait and jump-landing for the involved limb, along with the majority of associations for limb-symmetry indices and the uninvolved limb, were negligible and non-statistically significant. There were weak significant associations for instantaneous loading rate (ρ = 0.39, P = 0.02) and peak knee abduction angle (ρ = 0.36, p = 0.03) uninvolved limb, as well as peak abduction displacement limb-symmetry indices (ρ= - 0.39, p = 0.02) between walking-gait and jump-landing.

INTERPRETATION

No systematic associations were found between walking-gait and jump-landing biomechanics for either limb or limb-symmetry indices in people with unilateral anterior cruciate ligament reconstruction. Individuals with an anterior cruciate ligament reconstruction who demonstrate high-involved limb loading or asymmetries during jump-landing may not demonstrate similar biomechanics during walking-gait.

Comprehensively Assessing the Acute Femoral Cartilage Response and Recovery after Walking and Drop-Landing: An Ultrasonographic Study

We compared the acute response and recovery of ultrasonography (US) cartilage outcomes (i.e., thickness, cross-sectional area, and echo intensity) between walking, drop-landing and control conditions in 43 young adults with no history of lower extremity injury. A femoral cartilage US assessment was performed before and after each condition to determine the acute cartilage response and recovery at 15, 30 and 45 min. Percentage change scores from pre- to all post-time points were used for analysis. Acute cartilage response and recovery were analyzed with a 3 × 4 (condition × time) repeated-measures analysis of variance. Greater deformation of the medial and lateral femoral cartilage was observed immediately after both the walking and drop-landing conditions compared with the control condition. Cartilage deformation after the drop-landing condition required longer time to recover compared with the walking condition. The femoral cartilage deformation was not accompanied by concurrent alterations in cartilage echo intensity.

Quadriceps Neuromuscular Function and Jump-Landing Sagittal-Plane Knee Biomechanics After Anterior Cruciate Ligament Reconstruction

CONTEXT

  Aberrant biomechanics may affect force attenuation at the knee during dynamic activities, potentially increasing the risk of sustaining a knee injury or hastening the development of osteoarthritis after anterior cruciate ligament reconstruction (ACLR). Impaired quadriceps neuromuscular function has been hypothesized to influence the development of aberrant biomechanics.

OBJECTIVE

  To determine the association between quadriceps neuromuscular function (strength, voluntary activation, and spinal-reflex and corticomotor excitability) and sagittal-plane knee biomechanics during jump landings in individuals with ACLR.

DESIGN

  Cross-sectional study.

SETTING

  Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Twenty-eight individuals with unilateral ACLR (7 men, 21 women; age = 22.4 ± 3.7 years, height = 1.69 ± 0.10 m, mass = 69.4 ± 10.1 kg, time postsurgery = 52 ± 42 months).

MAIN OUTCOME MEASURE(S)

  We quantified quadriceps spinal-reflex excitability via the Hoffmann reflex normalized to maximal muscle response (H : M ratio), corticomotor excitability via active motor threshold, strength as knee-extension maximal voluntary isometric contraction (MVIC), and voluntary activation using the central activation ratio (CAR). In a separate session, sagittal-plane kinetics (peak vertical ground reaction force [vGRF] and peak internal knee-extension moment) and kinematics (knee-flexion angle at initial contact, peak knee-flexion angle, and knee-flexion excursion) were collected during the loading phase of a jump-landing task. Separate bivariate associations were performed between the neuromuscular and biomechanical variables.

RESULTS

  In the ACLR limb, greater MVIC was associated with greater peak knee-flexion angle ( r = 0.38, P = .045) and less peak vGRF ( r = -0.41, P = .03). Greater CAR was associated with greater peak internal knee-extension moment (ρ = -0.38, P = .045), and greater H : M ratios were associated with greater peak vGRF ( r = 0.45, P = .02).

CONCLUSIONS

  Greater quadriceps MVIC and CAR may provide better energy attenuation during a jump-landing task. Individuals with greater peak vGRF in the ACLR limb possibly require greater spinal-reflex excitability to attenuate greater loading during dynamic movements.

The association between habitual walking speed and medial femoral cartilage deformation following 30minutes of walking

Habitual walking speed is a key functional outcome that has implications for knee biomechanics that occur during gait. Lower extremity biomechanics during walking affects the loading of the femoral cartilage. Ultrasonography (US) can be used to assess resting femoral cartilage thickness and acute cartilage deformation in response to walking. The purpose of this study was to determine the association between habitual walking speed and both resting femoral cartilage thickness and deformation. Twenty-four healthy participants with no history of knee injury volunteered for this study. Habitual walking speed was assessed with a 20-m walk test. Femoral cartilage thickness was assessed with US in the medial condyle, lateral condyle, and intercondylar regions prior to and immediately following 30min of walking. Femoral cartilage deformation was calculated as the percent change in cartilage thickness acutely following the walking protocol. Separate Pearson product moment correlations were used to assess the association between habitual walking speed and each US cartilage variable. Slower habitual walking speed was significantly associated with greater medial femoral cartilage deformation (r=0.48, P=0.018), but not with lateral and intercondylar deformation. Habitual walking speed was not significantly associated with the resting cartilage thickness in any cartilage region. These findings highlight the in vivo association between walking speed and medial femoral cartilage deformation. When controlling for body mass index, the association between walking speed and medial cartilage deformation was weakened (Δr=-0.12). Future studies are needed to determine the extent to which BMI influences the association between walking speed and cartilage deformation.

Biochemical markers of cartilage metabolism are associated with walking biomechanics 6-months following anterior cruciate ligament reconstruction

The purpose of our study was to determine the association between biomechanical outcomes of walking gait (peak vertical ground reaction force [vGRF], vGRF loading rate [vGRF-LR], and knee adduction moment [KAM]) 6 months following anterior cruciate ligament reconstruction (ACLR) and biochemical markers of serum type-II collagen turnover (collagen type-II cleavage product to collagen type-II C-propeptide [C2C:CPII]), plasma degenerative enzymes (matrix metalloproteinase-3 [MMP-3]), and a pro-inflammatory cytokine (interleukin-6 [IL-6]). Biochemical markers were evaluated within the first 2 weeks (6.5 ± 3.8 days) following ACL injury and again 6 months following ACLR in eighteen participants. All peak biomechanical outcomes were extracted from the first 50% of the stance phase of walking gait during a 6-month follow-up exam. Limb symmetry indices (LSI) were used to normalize the biomechanical outcomes in the ACLR limb to that of the contralateral limb (ACLR/contralateral). Bivariate correlations were used to assess associations between biomechanical and biochemical outcomes. Greater plasma MMP-3 concentrations after ACL injury and at the 6-month follow-up exam were associated with lesser KAM LSI. Lesser KAM was associated with greater plasma IL-6 at the 6-month follow-up exam. Similarly, lesser vGRF-LR LSI was associated with greater plasma MMP-3 concentrations at the 6-month follow-up exam. Lesser peak vGRF LSI was associated with higher C2C:CPII after ACL injury, yet this association was not significant after accounting for walking speed. Therefore, lesser biomechanical loading in the ACLR limb, compared to the contralateral limb, 6 months following ACLR may be related to deleterious joint tissue metabolism that could influence future cartilage breakdown. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2288-2297, 2017.

Quadriceps Function and Gait Kinetics after Anterior Cruciate Ligament Reconstruction

PURPOSE

Chronic quadriceps dysfunction has been implicated as a contributor to knee osteoarthritis (OA) development after anterior cruciate ligament reconstruction (ACLR). This dysfunction potentially leads to impulsive/high-rate loading during gait, thus accelerating cartilage degradation. The purpose of this study was to examine relationships between several indices of quadriceps function and gait biomechanics linked to knee OA development in individuals with ACLR.

METHODS

Gait biomechanics and quadriceps function were assessed in 39 individuals with ACLR. Indices of quadriceps function included isometric peak torque and rate of torque development (RTD), isokinetic peak torque and power, and the central activation ratio. Gait biomechanics included the peak vertical ground reaction force and loading rate, and the heel strike transient (HST) magnitude and loading rate.

RESULTS

Isometric peak torque was not associated with any of the gait biomechanical variables. However, greater RTD was associated with lesser peak vertical ground reaction force linear (r = -0.490, P = 0.003) and instantaneous (r = -0.352, P = 0.031) loading rates, as well as a lesser HST magnitude (r = -0.312, P = 0.049) and instantaneous loading rate (r = -0.355, P = 0.029). Greater central activation ratio was associated with greater HST instantaneous (r = 0.311, P = 0.050) and linear (r = 0.328, P = 0.033) loading rates. Isokinetic peak torque and power were not associated with any of the biomechanical variables.

CONCLUSION

Poor quadriceps function, especially RTD, is associated with gait kinetics linked to cartilage degradation in individuals with ACLR. These results highlight the likely role of chronic quadriceps dysfunction in OA development after ACLR and the need to emphasize improving quadriceps function as a primary rehabilitation goal.

Quadriceps Strength Predicts Self-reported Function Post-ACL Reconstruction

INTRODUCTION/PURPOSE

Quadriceps strength is a useful clinical predictor of self-reported function after anterior cruciate ligament reconstruction (ACLR). However, it remains unknown if quadriceps strength normalized to body mass (QBM) or quadriceps strength limb symmetry index (QLSI) is the best predictor of self-reported function in individuals with ACLR. We sought to determine whether QBM and QLSI are able to predict individuals with ACLR who self-report high function (≥90% on the international knee documentation committee (IKDC) index).

METHODS

Ninety-six individuals with a history of a primary unilateral ACLR were recruited for a multisite cross-sectional descriptive laboratory experiment. Bilateral isometric quadriceps strength was collected at 90° of knee flexion to calculate QBM and QLSI (ratio of the ACLR limb to the contralateral limb). Area under the curve (AUC) values were calculated using receiver operating characteristic curve analyses to determine the capacity of QBM and QLSI to predict individuals with high self-reported function on the IKDC index.

RESULTS

QBM displayed high accuracy (AUC = 0.76; 95% confidence interval, 0.66-0.86) for identifying participants with an IKDC index ≥90%. A QBM cutoff score of 3.10 N·m·kg was found to maximize sensitivity (0.61) and specificity (0.84), and displayed 8.15 (3.09-21.55) times higher odds of reporting high function. QLSI displayed a moderate accuracy (AUC = 0.62, 0.50-0.73) for identifying participants with an IKDC index ≥90%. A QLSI cutoff score of 96.5% maximized sensitivity (0.55) and specificity (0.70), and represented 2.78 (1.16-6.64) times higher odds reporting high function.

CONCLUSION

QBM is a stronger predictor of high self-reported function compared with QLSI in individuals with ACLR. Rehabilitation guidelines may benefit from incorporating the use of QBM measurements for the purpose of predicting participants that may maintain high self-reported function.

Persistent Muscle Inhibition after Anterior Cruciate Ligament Reconstruction: Role of Reflex Excitability

PURPOSE

Persistent voluntary quadriceps activation deficits are common after anterior cruciate ligament reconstruction (ACLR), but the direct causes are unclear. The primary purpose of this study was to determine whether spinal reflex excitability deficits are present in individuals with a history of ACLR, and secondarily to determine whether spinal reflex excitability predicts which individuals possess full voluntary quadriceps activation.

METHODS

One hundred and forty-seven individuals (74 healthy and 73 ACLR) participated in this cross-sectional case-control study. Quadriceps spinal reflex excitability was quantified using the Hoffmann reflex normalized to the maximal muscle response (H:M ratio). Voluntary quadriceps activation was evaluated with the burst superimposition technique and calculated via the central activation ratio (CAR). Separate 2 × 2 ANCOVA tests were used to compare between-limb and between-group differences for H:M ratio and CAR. A receiver operating characteristic curve was used to determine the accuracy of H:M ratio to predict if ACLR participants present with full voluntary activation (CAR ≥ 0.95).

RESULTS

The ACLR H:M ratio was not different between limbs or compared with the healthy group (P > 0.05). Although ACLR CAR was lower bilaterally compared with the healthy group (P < 0.001), it did not differ between limbs. The H:M ratio has poor accuracy for predicting which individuals exhibit full voluntary activation (receiver operating characteristic area under the curve = 0.52, 95% CI = 0.37,0.66; odds ratio = 2.2, 95% CI = 0.8, 5.9).

CONCLUSIONS

Spinal reflex excitability did not differ between limbs in individuals with ACLR or compared with healthy participants. The level of quadriceps spinal reflex excitability has poor accuracy at predicting which ACLR individuals would demonstrate full voluntary quadriceps activation.

Walking Speed As a Potential Indicator of Cartilage Breakdown Following Anterior Cruciate Ligament Reconstruction

OBJECTIVE

To determine whether or not self-selected walking speed associates with serum biomarkers of cartilage (collagen and proteoglycan) breakdown in anterior cruciate ligament reconstructed (ACLR) individuals.

METHODS

Twenty individuals with a history of a primary unilateral ACLR participated in this cross-sectional study. Resting blood was collected from each participant prior to completing 5 walking gait trials at a self-selected comfortable speed. Walking speed was evaluated in a 3-dimensional motion capture laboratory and determined from the velocity of the pelvic center of mass. Sera were assessed for collagen type II cleavage product (C2C) and proteoglycan (aggrecan) concentrations using commercially available specific enzyme-linked immunosorbent assays. Pearson's product-moment (r) and Spearman's (ρ) correlations were used to evaluate associations between walking speed and biomarkers of cartilage breakdown metabolism. Partial correlations were used to determine whether covariates influenced associations between walking speed and biomarkers of cartilage breakdown.

RESULTS

ACLR individuals with a slower walking speed demonstrated higher concentrations of serum C2C (r = -0.52, P = 0.02), while there was no significant association between walking speed and aggrecan concentrations (ρ = -0.29, P = 0.31). After accounting for the variance associated with stance phase duration, ACLR individuals with a slower walking speed still demonstrated greater serum C2C concentrations (partial r = -0.53, P = 0.02).

CONCLUSION

ACLR individuals who habitually walk slower may experience a greater degree of collagen breakdown, suggesting that walking speed may be a future useful clinical indicator for identifying individuals with higher levels of cartilage breakdown and preradiographic osteoarthritic joint changes.

Quadriceps rate of torque development and disability in individuals with anterior cruciate ligament reconstruction

BACKGROUND

The purpose of this study was to determine associations between self-reported function (International Knee Documentation Committee Index), isometric quadriceps strength and rate of torque development in individuals with a unilateral anterior cruciate ligament reconstruction.

METHODS

Forty-one individuals [31% male, BMI mean 25 (SD 4) kg/m², months post anterior cruciate ligament reconstruction mean 49 (SD 40)] completed the self-reported function and isometric quadriceps function testing. Rate of torque development was assessed at 0-100ms (early), 100-200ms (late) ms, and peak following the onset of contraction. Associations were examined between rate of torque development, strength, and self-reported function. Linear regression was used to determine the unique amount of variance explained by the combination of rate of torque development and strength.

FINDINGS

Higher rate of torque development 100-200ms is weakly associated with higher self-reported function in individuals with a unilateral anterior cruciate ligament reconstruction (r=0.274, p=0.091); however, rate of torque development 100-200ms does not predict a significant amount of variance in self-reported function after accounting for strength (ΔR²=0.003, P=0.721).

INTERPRETATION

Quadriceps strength has a greater influence on self-reported function compared to rate of torque development in individuals with an anterior cruciate ligament reconstruction with time from surgery.

Immediate effect of vibratory stimuli on quadriceps function in healthy adults

INTRODUCTION

The purpose of this study was to compare the effect of whole body vibration (WBV) and local muscle vibration (LMV) on quadriceps function.

METHODS

Sixty adults were randomized to WBV, LMV, or control groups. Quadriceps function [Hoffmann (H)-reflex, active motor threshold (AMT), motor evoked potential (MEP) and electromyographic amplitude, peak torque (PT), rate of torque development (RTD), and central activation ratio (CAR)] was assessed before and immediately after and 10 and 20 minutes after interventions.

RESULTS

WBV improved PT, CAR, AMT, EMG, and MEP amplitude, and EMG amplitude and CAR were greater than control after application. LMV improved EMG amplitude and AMT, and EMG amplitude was greater than control after application. AMT remained lower 10 and 20 minutes after WBV and LMV. No differences were noted between LMV and WBV. Vibration did not influence H-reflex or RTD.

CONCLUSIONS

WBV and LMV increased quadriceps function and may be used to enhance the efficacy of strengthening protocols. Muscle Nerve 54: 469-478, 2016.

Visual Utilization During Postural Control in Anterior Cruciate Ligament- Deficient and -Reconstructed Patients: Systematic Reviews and Meta-Analyses

OBJECTIVE

To determine whether anterior cruciate ligament-deficient (ACL-D) individuals and individuals with a reconstructed anterior cruciate ligament (ACL-R) rely more heavily on visual information to maintain postural control.

DATA SOURCES

PubMed, CINAHL, and SPORTDiscus databases were searched from their earliest available date to May 24, 2016, using a combination of keywords.

STUDY SELECTION

Articles were included if they reported any instrumented static single-leg balance outcome in both a patient and control sample. The means and SDs of these outcomes must have been reported with both eyes open and eyes closed.

DATA EXTRACTION

Sample sizes, means, and SDs of single-leg balance measures for each group's eyes open and eyes closed testing conditions were extracted. The methodological quality of included studies was independently evaluated by multiple authors using an adapted version of the Quality Index.

DATA SYNTHESIS

Effect sizes were calculated by dividing the differences in change between eyes closed and eyes open in the ACL-D and control group and the ACL-R and control group by the pooled SD from the eyes closed trials for each analysis. Significant differences between the ACL-D and control group (effect size, -1.66; 95% confidence interval [CI], -2.90 to -.41) were noted. The ACL-R and control group were not different (effect size, -.61; 95% CI, -2.17 to .95).

CONCLUSIONS

ACL-D individuals but not individuals with ACL-R demonstrate a greater reliance on visual information during single-leg stance compared with healthy individuals.

Quadriceps Function and Hamstrings Co-Activation After Anterior Cruciate Ligament Reconstruction

CONTEXT

  Individuals with anterior cruciate ligament reconstruction (ACLR) have quadriceps dysfunction that contributes to physical disability and posttraumatic knee osteoarthritis. Quadriceps function in the ACLR limb is commonly evaluated relative to the contralateral uninjured limb. Bilateral quadriceps dysfunction is common in individuals with ACLR, potentially biasing these evaluations.

OBJECTIVE

  To compare quadriceps function between individuals with ACLR and uninjured control participants.

DESIGN

  Cross-sectional study.

SETTING

  Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Twenty individuals with unilateral ACLR (age = 21.1 ± 1.7 years, mass = 68.3 ± 14.9 kg, time since ACLR = 50.7 ± 21.3 months; females = 14; Tegner Score = 7.1 ± 0.3; 16 patellar tendon autografts, 3 hamstrings autografts, 1 allograft) matched to 20 control participants (age = 21.2 ± 1.2 years, mass = 67.9 ± 11.3 kg; females = 14; Tegner Score = 7.1 ± 0.4) on age, sex, body mass index, and Tegner Activity Scale.

MAIN OUTCOME MEASURE(S)

  Maximal voluntary isometric knee extension was performed on an isokinetic dynamometer. Peak torque (PT), rate of torque development (RTD), electromyographic (EMG) amplitude, central activation ratio (CAR), and hamstrings EMG amplitude were assessed during maximal voluntary isometric knee extension and compared between groups using independent-samples t tests. Relationships between hamstrings co-activation and quadriceps function were assessed using Pearson correlations.

RESULTS

  Participants with anterior cruciate ligament reconstruction displayed lesser quadriceps PT (1.86 ± 0.74 versus 2.56 ± 0.37 Nm/kg, P = .001), RTD (39.4 ± 18.7 versus 52.9 ± 16.4 Nm/s/kg, P = .03), EMG amplitude (0.25 ± 0.12 versus 0.37 ± 0.26 mV, P = .04), and CAR (83.3% ± 11.1% versus 93.7% ± 3.2%, P = .002) and greater hamstrings co-activation (27.2% ± 12.8% versus 14.3% ± 3.7%, P < .001) compared with control participants. Correlations were found between hamstrings co-activation and PT (r = -0.39, P = .007), RTD (r = -0.30, P = .03), and EMG amplitude (r = -0.30, P = .03).

CONCLUSIONS

  Individuals with ACLR possessed deficits in PT, RTD, and CAR compared with control participants. Peak torque is the net result of all agonist and antagonist activity, and lesser PT in individuals with ACLR is partially attributable to greater hamstrings co-activation.

Sagittal plane kinematics predict kinetics during walking gait in individuals with anterior cruciate ligament reconstruction

BACKGROUND

Alterations in mechanical loading following anterior cruciate ligament reconstruction may lead to the development of knee osteoarthritis. Feedback that cues a change in knee kinematics during walking gait may influence mechanical loading, yet it remains unknown if knee kinematics predict kinetics during walking gait. Our aim was to determine if sagittal plane knee kinematics predict kinetics during walking gait in anterior cruciate ligament reconstructed individuals.

METHODS

Forty-one individuals with a history of primary, unilateral anterior cruciate ligament reconstruction completed a motion capture walking gait analysis. Hierarchical linear regression analyses were used in order to determine the amount of variance in the kinetic variables of interest (peak vertical ground reaction force, instantaneous and linear vertical ground reaction force loading rate) that was individually predicted by the kinematic variables of interest (knee flexion angle at heelstrike, peak knee flexion angle, and knee flexion excursion).

FINDINGS

Knee flexion excursion of the injured limb significantly predicted 11% of the variance in peak vGRF of the injured limb after accounting for gait speed and peak knee flexion angle (ΔR²=0.11, P=0.004). After accounting for gait speed and knee flexion angle at heelstrike, knee flexion excursion significantly predicted 16% of the variance in the injured limb peak vertical ground reaction force (ΔR²=0.16, P=0.001). No kinematic variable predicted vertical ground reaction force loading rate.

INTERPRETATION

Altering knee flexion excursion may be useful as a future therapeutic target for modifying peak vertical ground reaction force during walking gait following anterior cruciate ligament reconstruction.

An evaluation of the heel strike transient in obese young adults during walking gait

BACKGROUND

Obesity is considered a risk factor for knee osteoarthritis (OA) in part due to its influence on gait biomechanics. The heel strike transient (HST) is a characteristic of the ground reaction force that is indicative of a high rate of loading, but has not been evaluated in obese adults.

OBJECTIVE

To compare the incidence of HST in obese compared to normal weight adults.

METHODS

15 normal-weight (males=7, age=20.4±2.1years, body mass index=21.6±1.3kg/m(2)) and 15 obese (males=7, age=21.2±1.9years, body mass index=33.5±4.3kg/m(2)) young adults completed 10 walking trials at a standardized speed and 10 trials at a self-selected speed while ground reaction force data were sampled. HST incidence was evaluated using a dichotomous method previously identified in the literature, and compared between groups using χ(2) analyses.

RESULTS

The number of individuals classified as possessing the HST differed between the obese and normal-weight groups (8/15 vs. 3/15, p=0.047). Evaluation of the standardized residuals indicated a significantly greater than expected incidence of the HST in the obese group when walking at a standardized speed.

CONCLUSION

Our findings indicate that a greater proportion of obese compared to normal weight participants displayed a HST. The HST may provide a dichotomous method for identifying individuals with aberrant gait biomechanics.