Christopher Kuenze

Persistent Neuromuscular and Corticomotor Quadriceps Asymmetry After Anterior Cruciate Ligament Reconstruction

CONTEXT Return to activity in the presence of quadriceps dysfunction may predispose individuals with anterior cruciate ligament reconstruction (ACLR) to long-term joint degeneration. Asymmetry may manifest during movement and result in altered knee-joint-loading patterns; however, the underlying neurophysiologic mechanisms remain unclear. OBJECTIVE To compare limb symmetry of quadriceps neuromuscular function between participants with ACLR and participants serving as healthy controls. DESIGN Descriptive laboratory study. SETTING Research laboratory. PATIENTS OR OTHER PARTICIPANTS A total of 22 individuals with ACLR (12 men, 10 women) and 24 individuals serving as healthy controls (12 men, 12 women). MAIN OUTCOME MEASURE(S) Normalized knee-extension maximal voluntary isometric contraction (MVIC) torque (Nm/kg), quadriceps central activation ratio (CAR) (%), quadriceps motor-neuron-pool excitability (Hoffmann reflex to motor wave ratio), and quadriceps active motor threshold (AMT) (% 2.0 T) were measured bilaterally and used to calculate limb symmetry indices for comparison between groups. We used analyses of variance to compare quadriceps Hoffmann reflex to motor wave ratio, normalized knee-extension MVIC torque, quadriceps CAR, and quadriceps AMT between groups and limbs. RESULTS The ACLR group exhibited greater asymmetry in knee-extension MVIC torque (ACLR group = 0.85 ± 0.21, healthy group = 0.97 ± 0.14; t44 = 2.26, P = .03), quadriceps CAR (ACLR group = 0.94 ± 0.11, healthy group = 1.00 ± 0.08; t44 = 2.22, P = .04), and quadriceps AMT (ACLR group = 1.13 ± 0.18, healthy group = 1.02 ± 0.11; t34 = -2.46, P = .04) than the healthy control group. CONCLUSIONS Asymmetries in measures of quadriceps function and cortical excitability were present in patients with ACLR. Asymmetry in quadriceps strength, activation, and cortical excitability persisted in individuals with ACLR beyond return to recreational activity. Measuring the magnitude of asymmetry after ACLR represents an important step in understanding long-term reductions in self-reported function and increased rate of subsequent joint injury in otherwise healthy, active individuals after ACLR.

Comparative Effect of Power Training and High-Speed Yoga on Motor Function in Older Patients With Parkinson Disease.

OBJECTIVES To compare the effects of power training (PWT) and a high-speed yoga program on physical performances in older patients with Parkinson disease (PD), and to test the hypothesis that both training interventions would attenuate PD symptoms and improve physical performance. DESIGN Randomized controlled trial. SETTING A laboratory of neuromuscular research and active aging. PARTICIPANTS Patients with PD (N=41; mean age ± SD, 72.2 ± 6.5y). INTERVENTIONS Two high-speed exercise interventions (specifically designed yoga program and PWT) were given for 12 weeks (twice a week), and 1 nonexercise control group. MAIN OUTCOME MEASURES Unified Parkinson Disease Rating Scale motor score (UPDRSMS), Berg Balance Scale (BBS), Mini-Balance Evaluation Systems Test (Mini-BESTest), Timed Up and Go, functional reach, single leg stance (SLS), postural sway test, 10-m usual and maximal walking speed tests, 1 repetition maximum (RM), and peak power (PPW) for leg press. RESULTS For the posttests, both training groups showed significant improvements (P<.05) in all physical measurements except functional reach on the more affected side, SLS, and postural sway compared with the pretests, and significantly better scores for UPDRSMS, BBS, Mini-BESTest, Timed Up and Go, functional reach on the less affected side, 10-m usual and maximal walking speed tests, 1RM, and PPW than controls, with no differences detected between the yoga program and PWT. CONCLUSIONS Both the specially designed yoga program and PWT programs can significantly improve physical performance in older persons with PD.

Jogging Biomechanics after Exercise in Individuals with ACL-Reconstructed Knees.

PURPOSE Return to recreational activity is a common goal for the clinician and patient after ACL reconstruction (ACLR) and structured rehabilitation. Decreased peak knee flexion angle and external knee flexion moment during walking and jogging have been indicated as significant contributors to cartilage degeneration over time after knee joint injury. The purpose of this investigation was to measure the effects of 30 min of exercise on knee joint kinetics and kinematics in participants with a history of ACLR. METHODS ACLR participants (n = 20, 9 females and 11 males) and healthy controls (n = 23, 11 females and 12 males) participated in an observational laboratory study. Gait analysis was performed on all subjects before and after a 30-min exercise protocol. Sagittal and frontal plane kinematics and kinetics were measured in the involved limb in the ACLR group and compared with healthy control participants across the gait cycle using 90% confidence intervals. Significant differences between groups were established as a consecutive 3% of the gait cycle in which 90% confidence interval did not overlap. RESULTS Preexercise, ACLR participants were more hip flexed with higher magnitude external hip flexion moments and lower magnitude external knee flexion moments during the stance phase compared with healthy controls. ACLR participants experienced preexercise to postexercise declines in hip flexion angle and external hip flexion moment along with increases in external knee flexion moment when compared with healthy controls. CONCLUSIONS Exercise-related adaptations in hip and knee biomechanics are different in individuals with a history ACLR when compared with healthy controls despite a return to recreational activity. The biomechanical response to fatiguing exercise observed in this investigation may provide insight into one potential source of elevated knee injury risk and reduced long-term knee joint health after ACLR.

Clinical Thresholds for Quadriceps Assessment After Anterior Cruciate Ligament Reconstruction

CONTEXT Normal, symmetrical quadriceps strength is a common clinical goal after anterior cruciate ligament reconstruction (ACLR). Currently, the clinical thresholds for acceptable unilateral quadriceps function and symmetry associated with positive outcomes after return to activity are unclear. OBJECTIVE To establish quadriceps-activation and knee-extension-torque cutoffs for clinical assessment after return to activity after ACLR. DESIGN Descriptive laboratory study. SETTING Laboratory. PATIENTS 22 (10 female, 12 male; age = 22.5 ± 5.0 y, height = 172.9 ± 7.1 cm, mass = 74.1 ± 15.5 kg, months since surgery = 31.5 ± 23.5) recreationally active persons with a history of unilateral, primary ACLR at least 6 months prior and 24 (12 female/12 male, age = 21.7 ± 3.6 y, height = 168.0 ± 8.8 cm, mass = 69.3 ± 13.6 kg) recreationally active healthy participants. MAIN OUTCOME MEASURES Patient-reported measures of pain, knee-related function, and physical activity level were recorded for all participants. Normalized knee-extension maximum-voluntary-isometric-contraction (MVIC) torque (Nm/kg) and quadriceps central-activation ratio (CAR, %) were measured bilaterally in all participants. Receiver-operator-characteristic (ROC) curves were used to establish thresholds for unilateral measures of normalized knee-extension MVIC torque and quadriceps CAR, as well as limb-symmetry indices (LSI). ROC curves then established clinical thresholds for normalized knee-extension MVIC torque and quadriceps CAR LSIs associated with healthy knee-related function. RESULTS Involved-quadriceps CAR above 89.3% was the strongest unilateral indicator of healthy-group membership, while quadriceps CAR LSI above 0.996 and knee-extension MVIC torque above 0.940 were the strongest overall indicators. Unilateral normalized knee-extension MVIC torque above 3.00 Nm/kg and quadriceps CAR LSI above 0.992 were the best indicators of good patient-reported knee-related outcomes. CONCLUSIONS Threshold values established in this study may provide a guide for clinicians when making return-to-activity decisions after ACLR. Normalized knee-extension MVIC torque (>3.00 Nm/kg) and quadriceps CAR symmetry (>99.6%) are both strong indicators of good patient-reported outcomes after ACLR.

Clinical and Functional Outcomes following Primary Repair versus Reconstruction of the Medial Patellofemoral Ligament for Recurrent Patellar Instability

Background. The purpose of this study was to compare outcomes of medial patellofemoral ligament (MPFL) repair or reconstruction. Methods. Fourteen knees that underwent MPFL repair and nine (F5, M4) knees that underwent reconstruction at our institution were evaluated for objective and subjective outcomes. The mean age at operation was 20.1 years for repair and 19.8 years for reconstruction. All patients had a minimum of 2 years of follow-up (range: 24–75 months). Patient subjective outcomes were obtained using the International Knee Documentation Committee (IKDC) and Kujala patellofemoral subjective evaluations, as well as Visual Analog (VAS) and Tegner Activity Scales. Bilateral isometric quadriceps strength and vastus medialis obliquus (VMO) and vastus lateralis (VL) surface EMG were measured during maximal isometric quadriceps contractions at 30° and 60° of flexion. Results. There were no redislocations in either group. There was no difference in IKDC (P = 0.16), Kujala (P = 0.43), Tegner (P = 0.12), or VAS (P = 0.05) scores at follow-up. There were no differences between repair and reconstruction in torque generation of the involved side at 30° (P = 0.96) and 60° (P = 0.99). In addition, there was no side to side difference in torque generation or surface EMG activation of VL or VMO. Conclusions. There were minimal differences found between patients undergoing MPFL repair and MPFL reconstruction for the objective and subjective evaluations in this study.

Quadriceps Muscle Function After Exercise in Men and Women With a History of Anterior Cruciate Ligament Reconstruction

CONTEXT Sex differences in lower extremity neuromuscular function have been reported after anterior cruciate ligament reconstruction (ACLR). Research evidence supports different levels of fatigability in men and women and between patients with ACLR and healthy controls. The influence of sex on the response to continuous exercise in patients with ACLR is not clear. OBJECTIVE To compare quadriceps neuromuscular function after exercise between men and women with ACLR. DESIGN Descriptive laboratory study. SETTING Laboratory. PATIENTS OR OTHER PARTICIPANTS Twenty-six active volunteers (13 men [50%]: age = 24.1 ± 4.4 years, height = 179.1 ± 9.8 cm, mass = 80.1 ± 9.4 kg, months since surgery = 43.5 ± 37.0; 13 women [50%]: age = 24.2 ± 5.6 years, height = 163.0 ± 5.9 cm, mass = 62.3 ± 8.3 kg, months since surgery = 45.8 ± 42.7) with a history of unilateral primary ACLR at least 6 months earlier. INTERVENTION(S) Thirty minutes of continuous exercise comprising 5 separate 6-minute cycles, including 5 minutes of uphill walking and 1 minute of body-weight squatting and step-ups. MAIN OUTCOME MEASURE(S) Normalized knee-extension maximal voluntary isometric contraction torque, quadriceps superimposed-burst torque, and quadriceps central activation ratio before and after exercise. We performed separate 2 (sex: men, women) × 2 (time: preexercise, postexercise) repeated-measures analyses of variance for the 3 variables. Separate, independent-samples t tests were calculated to compare preexercise with postexercise change in all dependent variables between sexes. RESULTS A significant group-by-time interaction was present for knee-extension torque (P = .04). The percentage reduction in knee-extension maximal voluntary isometric contraction torque (men = 1.94%, women = -10.32%; P = .02) and quadriceps central activation ratio (men = -1.45%, women = -8.69%; P = .03) experienced by men was less than that observed in women. CONCLUSIONS In the presence of quadriceps dysfunction, female participants experienced greater-magnitude reductions in quadriceps function after 30 minutes of exercise than male participants. This indicates a reduced ability to absorb knee-joint loads, which may have significant implications for reinjury and joint osteoarthritis in women after ACLR.

Knee extension torque variability after exercise in ACL reconstructed knees

The purpose of this study was to compare knee extension torque variability in patients with ACL reconstructed knees before and after exercise. Thirty two patients with an ACL reconstructed knee (ACL‐R group) and 32 healthy controls (control group) completed measures of maximal isometric knee extension torque (90° flexion) at baseline and following a 30‐min exercise protocol (post‐exercise). Exercise included 30‐min of repeated cycles of inclined treadmill walking and hopping tasks. Dependent variables were the coefficient of variation (CV) and raw‐change in CV (ΔCV): CV = (torque standard deviation/torque mean x 100), ΔCV = (post‐exercise – baseline). There was a group‐by‐time interaction (p = 0.03) on CV. The ACL‐R group demonstrated greater CV than the control group at baseline (ACL‐R = 1.07 ± 0.55, control = 0.79 ± 0.42, p = 0.03) and post‐exercise (ACL‐R = 1.60 ± 0.91, control = 0.94 ± 0.41, p = 0.001). ΔCV was greater (p = 0.03) in the ACL‐R group (0.52 ± 0.82) than control group (0.15 ± 0.46). CV significantly increased from baseline to post‐exercise (p = 0.001) in the ACL‐R group, while the control group did not (p = 0.06). The ACL‐R group demonstrated greater knee extension torque variability than the control group. Exercise increased torque variability more in the ACL‐R group than control group.

Drop-Landing Performance and Knee-Extension Strength After Anterior Cruciate Ligament Reconstruction.

CONTEXT Individuals with a history of anterior cruciate ligament reconstruction (ACLR) are at greater risk of reinjury and developing early-onset osteoarthritis due to persistent abnormal joint loading. Real-time clinical assessment tools may help identify patients experiencing abnormal movement patterns after ACLR. OBJECTIVE To compare performance on the Landing Error Scoring System (LESS) between participants with ACLR and uninjured control participants and to determine the relationship between LESS score and knee-extension strength in these participants. DESIGN Controlled laboratory study. SETTING Research laboratory. PATIENTS OR OTHER PARTICIPANTS Forty-six recreationally active participants, consisting of 22 with ACLR (12 men, 10 women; age = 22.5 ± 5.0 years, height = 172.8 ± 7.2 cm, mass = 74.2 ± 15.6 kg, body mass index = 24.6 ± 4.0) and 24 healthy control participants (12 men, 12 women; age = 21.7 ± 3.6 years, height = 168.0 ± 8.8 cm, mass = 69.2 ± 13.6 kg, body mass index = 24.3 ± 3.2) were enrolled. MAIN OUTCOME MEASURE(S) Bilateral normalized knee-extension maximal voluntary isometric contraction (MVIC) torque (Nm/kg) and LESS scores were measured during a single testing session. We compared LESS scores between groups using a Mann-Whitney U test and the relationships between LESS scores and normalized knee-extension MVIC torque using Spearman ρ bivariate correlations. RESULTS The ACLR participants had a greater number of LESS errors (6.0 ± 3.6) than healthy control participants (2.8 ± 2.2; t44 = -3.73, P = .002). In ACLR participants, lower normalized knee-extension MVIC torque in the injured limb (ρ = -0.455, P = .03) was associated with a greater number of landing errors. CONCLUSIONS Participants with ACLR displayed more errors while landing. The occurrence of landing errors was negatively correlated with knee-extension strength, suggesting that weaker participants had more landing errors. Persistent quadriceps weakness commonly associated with ACLR may be related to a reduced quality of lower extremity movement during dynamic tasks.

Objectively measured physical activity in patients after anterior cruciate ligament reconstruction

Background: Returning to a healthy level of physical activity is among the most commonly discussed clinical goals for patients recovering from anterior cruciate ligament reconstruction (ACLR). However, physical activity has not been objectively measured in this population. Purpose: To investigate differences in the mean time (min/d) spent in moderate-to-vigorous physical activity (MVPA) as well as the daily step count (steps/d) between patients who underwent ACLR and matched controls. A second purpose was to investigate relationships between MVPA and objective assessments of the daily step count and Tegner and Marx activity scales. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Physical activity was assessed using ActiGraph accelerometers in 33 participants with a history of primary unilateral or bilateral ACLR (mean time from surgery, 27.8 ± 17.5 months; range, 6-67 months) as well as in 33 healthy controls (matched on age, sex, and activity level). Participants wore the accelerometer for 7 days and completed the International Knee Documentation Committee subjective form and the Tegner and Marx activity scales. Independent t tests were used to determine differences in each dependent variable per group. Results: Patients who underwent ACLR spent less time in MVPA (ACLR: 79.37 ± 23.95 min/d; control: 93.12 ± 23.94 min/d; P = .02) and had a lower daily step count (ACLR: 8158 ± 2780 steps/d; control: 9769 ± 2785 steps/d; P = .02) compared with healthy matched controls. However, the Marx (ACLR median: 11.0 [interquartile range (IQR), 7-14]; control median: 12.0 [IQR, 8-13]; P = .85) and Tegner (ACLR median: 6.0 [IQR, 5-8]; control median: 7.0 [IQR, 6-8]; P = .12) scores did not differ between the groups, and no relationships were observed between objectively measured physical activity and scale measures (P > .05), except for a moderate relationship between the Tegner score and daily step count in the ACLR group (r = 0.36, P = .04). Only 24% of patients who underwent ACLR met the guideline of 10,000 steps per day compared with 42% of controls. Conclusion: Patients who underwent ACLR spent less time in MVPA and had a lower daily step count compared with highly matched controls (age, sex, and activity level) with no history of knee injuries. This was true despite being similar in activity levels, which brings into question the utility of the Tegner and Marx activity scales.

Validity of Torque-Data Collection at Multiple Sites: A Framework for Collaboration on Clinical-Outcomes Research in Sports Medicine.

CONTEXT Collecting torque data using a multimode dynamometer is common in sports-medicine research. The error in torque measurements across multiple sites and dynamometers has not been established. OBJECTIVE To assess the validity of 2 calibration protocols across 3 dynamometers and the error associated with torque measurement for each system. DESIGN Observational study. SETTING 3 university laboratories at separate institutions. EQUIPMENT 2 Biodex System 3 dynamometers and 1 Biodex System 4 dynamometer. INTERVENTIONS System calibration was completed using the manufacturer-recommended single-weight method and an experimental calibration method using a series of progressive weights. Both calibration methods were compared with a manually calculated theoretical torque across a range of applied weights. MAIN OUTCOME MEASURES Relative error, absolute error, and percent error were calculated at each weight. Each outcome variable was compared between systems using 95% confidence intervals across low (0-65 Nm), moderate (66-110 Nm), and high (111-165 Nm) torque categorizations. RESULTS Calibration coefficients were established for each system using both calibration protocols. However, within each system the calibration coefficients generated using the single-weight (System 4 = 2.42 [0.90], System 3a = 1.37 [1.11], System 3b = -0.96 [1.45]) and experimental calibration protocols (System 4 = 3.95 [1.08], System 3a = -0.79 [1.23], System 3b = 2.31 [1.66]) were similar and displayed acceptable mean relative error compared with calculated theoretical torque values. Overall, percent error was greatest for all 3 systems in low-torque conditions (System 4 = 11.66% [6.39], System 3a = 6.82% [11.98], System 3b = 4.35% [9.49]). The System 4 significantly overestimated torque across all 3 weight increments, and the System 3b overestimated torque over the moderate-torque increment. CONCLUSIONS Conversion of raw voltage to torque values using the single-calibration-weight method is valid and comparable to a more complex multiweight calibration process; however, it is clear that calibration must be done for each individual system to ensure accurate data collection.