Sagittal plane walking biomechanics in individuals with knee osteoarthritis after quadriceps strengthening.

OBJECTIVE: To compare sagittal walking gait biomechanics between participants with knee osteoarthritis (KOA) who increased quadriceps strength following a lower-extremity strengthening intervention (responders) and those who did not increase strength following the same strengthening protocol (non-responders) both at baseline and following the lower extremity strengthening protocol. DESIGN: Fifty-three participants with radiographic KOA (47% female, 62.3 ± 7.1 years, BMI = 28.5 ± 3.9 kg/m2) were enrolled in 10 sessions of lower extremity strengthening over a 28-day period. Maximum isometric quadriceps strength and walking gait biomechanics were collected on the involved limb at baseline and 4-weeks following the strengthening intervention. Responders were classified as individuals who increased quadriceps strength greater than the upper limit of the 95% confidence interval (CI) for the minimal detectable change (MDC) in quadriceps strength (29 Nm) determined in a previous study. 2 × 2 functional analyses of variance were used to evaluate the effects of group (responders and non-responders) and time (baseline and 4-weeks) on time-normalized waveforms for knee flexion angle (KFA), vertical ground reaction force (vGRF), and internal knee extension moment (KEM). RESULTS: A significant group x time interaction for KFA demonstrated greater KFA in the first half of stance at baseline and greater knee extension in the second half of stance at 4-weeks in responders compared to non-responders. There was no significant group x time interaction for vGRF or internal KEM. CONCLUSIONS: Quadriceps strengthening may be used to stimulate small changes in KFA in individuals with KOA.

Aberrant gait biomechanics in individuals with ACL reconstruction are magnified during treadmill walking.

Aberrant gait biomechanics following anterior cruciate ligament reconstruction (ACLR) likely contribute to post-traumatic osteoarthritis (PTOA) development. Gait biomechanics are typically assessed overground, but the use of instrumented/force-measuring treadmills is increasingly common. The purpose of this study was to compare gait biomechanics overground and on an instrumented treadmill in individuals with ACLR and healthy controls. Twenty-four individuals with ACLR and 24 healthy controls completed overground and gait biomechanics assessments. Biomechanical outcomes included peak vertical ground reaction force (vGRF), internal knee extension (KEM) and abduction (KAM) moments, and knee flexion (KFA) and adduction angles; KFA at heel strike; knee flexion displacement; and inter-limb symmetry for each outcome. Peak KEM (P < 0.001, 95%CI [-0.016, -0.007 xBW*Ht]) and vGRF (P < 0.001, 95%CI [-0.09. -0.03 xBW]) were significantly less symmetrical in the ACLR group compared to the control group on the treadmill but not overground. Additionally, peak KEM was smaller in the ACLR limb compared to the contralateral limb both overground (P = 0.005, 95%CI [-0.010, -0.001 xBW*Ht]) and on the treadmill (P < 0.001, 95%CI [-0.015, -0.007 xBW*Ht]), but this difference was 1.8x larger on the treadmill compared to overground. Peak KFA (P = 0.001, 95%CI [-4.2, -1.2°]) and vGRF (P < 0.001, 95%CI [-0.07, -0.03 xBW]) were smaller in the ACLR limb on the treadmill but not overground. These findings suggest aberrant gait biomechanics are exacerbated during treadmill walking post-ACLR and that evaluating kinematics and kinetics on instrumented treadmills may be valuable for assessing risk factors of PTOA development.

Time course of the effects of vibration on quadriceps function in individuals with anterior cruciate ligament reconstruction.

Quadriceps dysfunction is a common, chronic complication following anterior cruciate ligament reconstruction (ACLR) that contributes to aberrant gait biomechanics and poor joint health. Vibration enhances quadriceps function in individuals with ACLR, but the duration of these effects is unknown. This study evaluated the time course of the effects of whole body vibration (WBV) and local muscle vibration (LMV) on quadriceps function. Twenty-four volunteers with ACLR completed 3 testing sessions during which quadriceps isometric peak torque, rate of torque development, and EMG amplitude were assessed prior to and immediately, 10, 20, 30, 45, and 60 min following a WBV, LMV, or control intervention. WBV and LMV (30 Hz, 2g) were applied during six one-minute bouts. WBV increased peak torque 5-11% relative to baseline and control at all post-intervention time points. LMV increased peak torque 6% relative to baseline at 10 min post-intervention and 4-6% relative to control immediately, 10 min, and 20 min post-intervention. The interventions did not influence EMG amplitudes or rate of torque development. The sustained improvements in quadriceps following vibration, especially WBV, suggest that it could be applied at the beginning of rehabilitation sessions to "prime" the central nervous system, potentially improving the efficacy of ACLR rehabilitative exercise.

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 (TimeInjury-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 TimeInjury-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. TimeInjury-ACLR ranged from nine to 67days (31.0 [14.4days]). Greater TimeInjury-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 TimeInjury-ACLR at the six-month follow-up exam. TimeInjury-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 TimeInjury-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.

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.

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.

Balance and cognitive performance during a dual-task: preliminary implications for use in concussion assessment.

OBJECTIVES: To determine the reliability and effects of a dual-task paradigm on balance and cognitive function compared to a single-task paradigm. DESIGN: Repeated measures. METHODS: Healthy participants (n=23) completed a variation of the Sensory Organization Test and the incongruent Stroop test individually (single-task) and concurrently (dual-task) during two testing sessions. RESULTS: The Sensory Organization Test and incongruent Stroop test had moderate to high reliability (1.00>ICC2,k>0.60) under the dual-task conditions. Reaction time was significantly longer (t21=-2.54, p=0.019) under the dual-task conditions, while balance scores under one of the four conditions of the Sensory Organization Test (sway floor/fixed wall) were statistically better (t22=-3.03, p=0.006) under the dual-task conditions. However, this difference in balance scores may not be clinically meaningful. CONCLUSIONS: These findings illustrate that the Sensory Organization Test and incongruent Stroop task can be reliably incorporated into a dual-task assessment paradigm. The slowed reaction time under the dual-task paradigm indicates that the dual-task provided an additional cost to cognitive function. Dual-task concussion assessment paradigms involving these two tasks are psychometrically appropriate as well as more representative of actual sporting situations. However, more research should be conducted in a concussed population to further validate this claim.

Muscle activation during side-step cutting maneuvers in male and female soccer athletes.

CONTEXT: Female soccer athletes are at greater risk of anterior cruciate ligament (ACL) injury than males. Sex differences in muscle activation may contribute to the increased incidence of ACL injuries in female soccer athletes. OBJECTIVE: To examine sex differences in lower extremity muscle activation between male and female soccer athletes at the National Collegiate Athletic Association Division I level during 2 side-step cutting maneuvers. DESIGN: Cross-sectional with 1 between-subjects factor (sex) and 2 within-subjects factors (cutting task and phase of contact). SETTING: Sports medicine research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty males (age = 19.4 +/- 1.4 years, height = 176.5 +/- 5.5 cm, mass = 74.6 +/- 6.0 kg) and 20 females (age = 19.8 +/- 1.1 years, height = 165.7 +/- 4.3 cm, mass = 62.2 +/- 7.2 kg). INTERVENTION(S): In a single testing session, participants performed the running-approach side-step cut and the box-jump side-step cut tasks. MAIN OUTCOME MEASURE(S): Surface electromyographic activity of the rectus femoris, vastus lateralis, medial hamstrings, lateral hamstrings, gluteus medius, and gluteus maximus was recorded for each subject. Separate mixed-model, repeated-measures analysis of variance tests were used to compare the dependent variables across sex during the preparatory and loading contact phases of each cutting task. RESULTS: Females displayed greater vastus lateralis activity and quadriceps to hamstrings coactivation ratios during the preparatory and loading phases, as well as greater gluteus medius activation during the preparatory phase only. No significant differences were noted between the sexes for muscle activation in the other muscles analyzed during each task. CONCLUSIONS: The quadriceps-dominant muscle activation pattern observed in recreationally active females is also present in female soccer athletes at the Division I level when compared with similarly trained male soccer athletes. The relationship between increased quadriceps activation and greater incidence of noncontact ACL injury in female soccer athletes versus males requires further study.

Exercise Sandals Increase Lower Extremity Electromyographic Activity During Functional Activities.

OBJECTIVE: Anecdotal evidence suggests that use of Exercise Sandals results in a number of positive clinical outcomes. However, little research has been conducted to determine their efficacy objectively. Our purposes were to determine the effect of Exercise Sandals on lower leg electromyography (EMG) during activities in the Exercise Sandals and to compare EMG associated with Exercise Sandals with traditional lower extremity rehabilitation exercises. DESIGN AND SETTING: Two within-subjects, repeated-measures designs were used to identify differences in lower extremity EMG: (1) between activities with and without Exercise Sandals and (2) between Exercise Sandals activities and traditional rehabilitation activities. All data were collected in the Sports Medicine Research Laboratory. SUBJECTS: Eighteen subjects involved in rehabilitation using Exercise Sandals for at least 2 weeks within the year before data collection. MEASUREMENTS: Mean EMG amplitudes from the tibialis anterior, peroneus longus, soleus, and lateral gastrocnemius muscles were measured during single-leg stance, side stepping, and "high knees," all performed with and without the Exercise Sandals, as well as single-leg stance on a foam surface and T-band kicks in the sagittal and frontal planes. RESULTS: Exercise Sandals increased lower leg EMG activity, particularly in the ankle invertors and evertors. Also, activities involving the Exercise Sandals resulted in EMG activity similar to or exceeding that associated with traditional ankle-rehabilitation exercises. CONCLUSIONS: These results, coupled with the fact that Exercise Sandals are used in a functional closed kinetic chain manner, suggest that they are an effective means of increasing lower extremity muscle activity.