Gait Mechanics Depend Upon Quadriceps Central Activation Ratio in an Anterior Knee Pain Cohort

Gait Mechanics Depend Upon Quadriceps Central Activation Ratio in an Anterior Knee Pain Cohort Son SJ*, Kim HS†, Wiseman B‡, Seeley MK*, Hopkins JT*: *Brigham Young University, Provo, UT, †West Chester University, West Chester, PA, ‡West Virginia University, Morgantown, WV. Context: Quadriceps deficits are often present in an anterior knee pain (AKP) population. However, common self-reported classification tools including Visual Analog Scale (VAS), Kujala Anterior Knee Pain (KAKP), Tampa Scale for Kinesiophobia (TSK), Tegner Activity Level (TAL) scores, and/or other subject inclusion criteria may not be sensitive enough to identify specific movement characteristics in patients with AKP. Quadriceps central activation ratio (CAR) may help to discriminate movement characteristics in patients with AKP. Objective: To examine gait mechanics between two subdivisions of AKP patients, separated by quadriceps function (CAR < 0.95 and CAR > 0.95). AKP patients were defined by VAS, KAKP, TSK, and TAL scores. Design: Cohort. Setting: Controlled laboratory. Patients or Other Participants: 30 (M=16, F=14; 22.3±3 yrs, 175±9 cm, 72.5±14 kg) AKP patients participated: 15 Quadriceps Deficit (QD: CAR = 0.91±0.04, VAS = 3.87±1.3, KAKP = 82.9±6.6, TSK = 37.9±4.7, TAL = 6.3±1.2) and 15 Quadriceps Functional (QF: CAR = 0.97±0.01, VAS = 3.93±0.7, KAKP = 79.3±7.9, TSK = 36.9±5.2, TAL = 6.8±1.4). Interventions: Subjects performed three quadriceps maximum voluntary contractions (MVC) for 3 sec on a Biodex dynamometer (100 Hz). When MVC torque plateaued 1.5-2 sec later, a superimposed burst was transmitted to two electrodes placed on their quadriceps to measure CAR. Two successful trials were averaged for data analysis. Subjects performed five gait trials at a self-selected walking speed. Gait data were collected using high-speed video (240 Hz) and a force plate (1200 Hz). A functional analysis was used to detect mean between-group differences in gait mechanics during the entire stance phase (0-17% = loading response, 18-50% = mid-stance, 51-83% = terminal stance, and 84-100% = pre-swing). This analysis allowed us to compare variables as polynomial functions rather than discrete values. If 95% confidence intervals did not overlap zero, significant differences existed between groups (p < 0.05). Main Outcome Measures: Sagittal-plane knee joint angle (˚), internal knee joint torque (N∙m), and vertical ground reaction force (VGRF; N/kg). Results: Relative to QF patients, QD patients demonstrated (i) decreased knee flexion angle at 4-90% of stance, (ii) reduced internal knee extension torque at 14-32% of stance, and (iii) reduced VGRF at 19-37% of stance and increased VGRF at 46-70% of stance (p < 0.05). Conclusions: The present data suggest that relative to QF patients, QD patients adopt quadriceps weakness gait mechanics that have been reported in individuals with knee osteoarthritis, ACL reconstruction, and effused knee joints. These alterations may create long-term compensatory gait patterns at the knee and adjacent ankle and hip joints, which may lead to mechanical and biological changes in knee articular cartilage. Future research is needed to examine a potential relationship between these gait alterations and articular cartilage health over the long-term.
Listed In: Biomechanics, Gait

&#039;Moving Forward&#039;: Gait, Cognition and Associated Risk Factors: Insights from SHARE and TILDA

The established pathway of cognitive decline identifies Mild Cognitive Impairment (MCI) as a common pre-dementia syndrome. As MCI can represent the endpoint of cognitive decline or a transient state, more predictive diagnostic tools are required. A new pre-dementia syndrome, Motoric Cognitive Risk (MCR) syndrome, has been proposed. It is defined by slow gait and cognitive complaints but absence of dementia and mobility disability. MCR aims to improve on the predictive power of MCI, this study aims to explore it’s claim. Associations have been uncovered between differing cognitive domains and specific characteristics of gait. Leveraging the gait-cognitive function relationship is a novel approach to potentially highlighting those experiencing cognitive decline. However, the diagnostic tool of MCR is a new construct and currently imperfect, its efficacy not fully validated and sensitivity for dementia prediction relatively unknown. Reliable data on prevalence and risk factors help contribute to this validation process. In this presentation prevalence data for a multi-country aging study and a nationally representative community dwelling aging study will be presented. The variables available in both datasets which will be of interest in this study include; Gait Speed, Global Cognition (Mini-Mental State Exam (MMSE) score), Presence of Cognitive Complaints, Age, Body Mass Index (BMI), Dementia diagnosis (reported or imputed) and Waist Circumference. This study will inform the following research project, which will aim to assess whether specific gait components or combinations alone are better than the MCR construct in their association to cognitive decline.
Listed In: Gait, Neuroscience


Introduction and Objectives: It has previously been reported that deterioration in contractile strength and tendon stiffness in the elderly is associated with altered motor task execution and reduced performance while walking [1,2], and that resistance training improves muscle function, resulting in more effective and safer gait characteristics in the older population [3]. In particular, triceps surae (TS) muscle-tendon unit (MTU) properties seem to be an important determinant for walk-to-run transition speed [4], emphasizing the relevant role intrinsic MTU properties play in gait performance. The objective of this empirical study was to examine the hypothesis that maximal walking velocity is related to TS MTU mechanical and morphological properties and their enhanced capacities would improve gait velocity in the elderly. Methods: Thirty four older female adults (66±7 yrs.) took part in the study. Nineteen of them were recruited for the experimental group, who underwent a 14-week TS MTU physical exercise intervention which has been previously established to increase muscle strength and tendon stiffness [5]. The remaining 15 subjects formed the control group (no physical exercise intervention). The experimental group performed three times per week five sets of four repetitive (3·s loading, 3·s relaxation) isometric plantar flexion contractions in order to induce high cyclic strain magnitudes on the TS tendon and aponeurosis. Maximal walking velocity, defined as walking with a double support phase, was determined by using two force plates (60 x 40 cm, 1080 Hz; Kistler, Winterthur, CH) and a motion capture system (Vicon Motion Systems, Oxford, UK) with 12 infrared cameras operating at a frequency of 120 Hz. TS MTU properties were assessed using simultaneous dynamometry and ultrasonography (Esaote MyLab Five; Esaote Biomedica, Genoa, IT). Results: A significant correlation was found between the TS MTU mechanical and morphological properties and maximal gait velocity (0.40 < r < 0.64; P < 0.05; n = 34). The experimental group showed higher TS contractile strength, tendon stiffness, and higher gastrocnemius medialis muscle thickness post- compared to pre-intervention (P < 0.05). However, calculated maximal gait velocity did not differ between pre and post-intervention measurements (2.39 ± 0.41 vs. 2.44 ± 0.45 m·s-1). Control subjects showed no statistically significant differences in maximal gait velocity or TS MTU mechanical and morphological properties. Conclusion: This empirical study confirms previous forward simulation models [4] proposing that intrinsic TS MTU properties are significant determinants of gait performance. However, older adults may not be capable of fully utilizing improvements of the MTU capacities while walking at maximal velocities following a 14 week physical exercise intervention. Therefore, the benefits of a long term physical exercise intervention (1.5 years) will be discussed.
Listed In: Biomechanics, Gait, Other

Effects of Transcutaneous Electrical Nerve Stimulation on Gait Kinetics in Individuals with Experimentally Induced Knee Joint Pain

Background: Knee joint pain (KJP) independently alters motor function and gait mechanics, and these alterations may accelerate chronic knee joint disease. While TENS restores motor function deficits, it is unclear whether TENS restores compensatory gait mechanics. The purpose was to examine the effects of KJP on lower-extremity joint moments, and the effects of TENS on the aforementioned variables. We hypothesized that KJP will result in altered gait patterns, and TENS will help restore these mechanical alterations. Methods: We randomly selected 15 subjects for the TENS group, after which subjects were matched for the placebo group. Subjects underwent 3 sessions (hypertonic, isotonic, control). A 20-gauge flexible catheter was inserted into the right infrapatellar fat pad, and an infusion pump infused a saline of 0.154 mL•min¯¹ for 50 min (total = 7.7 mL). A TENS protocol was set at a biphasic mode with 120 µs and 180 Hz for 20 min. To blind placebo treatment, subjects in the placebo group was told that an electrical stimulation had been set to sub-sensory level. High-speed video (240 Hz) and an instrumented treadmill (1200 Hz) were used for gait analysis. Functional analysis of variance were used to evaluate differences between groups over time for joint moments. The mean curve with 95% CIs is represented by polynomial functions, showing us the entire stance, rather than identifying discrete peak points. If 95% CIs did not cross zero, significant difference existed (P < 0.05). Discussion: KJP independently increase internal knee varus moments, which were consistent with previous finding using patients with osteoarthritic knee pain. These compensatory gait patterns may be a result of a pain-avoidance motor deficits strategies. Since observed patterns can create altered mechanical and biological stress patterns on articular surface, it may increase the risk of degenerative knee disease. However, attempting to reduce perceived pain and increase neuron activation through TENS can help overcome deficits in knee and hip joint moments.
Listed In: Biomechanics, Gait, Sports Science

Perception of Self-Motion Impacts the Variability of Plantar Propulsion Force in Diabetes

People with diabetes mellitus (DM) have been reported of increased ground reaction force (GRF) and plantar propulsion force (PPF) that will worsen the formation of plantar ulcer. The reliance of perception of self-motion has been previously addressed for maintaining stability during locomotion in DM. Therefore, we speculate that perception of self-motion will affect DM’s plantar force adjustment by decreasing GRF/PPF along with reducing of variability (CV). We recruited five DMs and three healthy controls to walk on an instrumented treadmill with their self-selected pace. All subjects went through three no self-motion and three self-motion walking trials (120s/trial). The self-motion was generated by presenting a virtual corridor that moved toward subjects with their matched velocity. Three-axis force data were recorded at 300 Hz. Two-factor ANOVA with repeated measures were conducted to examine the role of visual cue impacts GRF/PPF in DM and age-matched healthy. The visual cue and group factors show significant interaction on PPFPeak and PPFCV. The following comparisons showed significant visual effect on reducing: (1) PPFPeak in healthy controls; (2) PPFCV in DM patients. Generally, the decreased PPFPeak and PPFCV founded in this study were in line with previous study and can be explained as the optimization of neuromuscular locomotor system in the anteroposterior direction. Furthermore, visual perception of self-motion shows its effect on reducing PPFPeak during toe-off in healthy controls. Lastly, the significant decreased PPFCV of DM versus healthy stands for the reduced human movement variability observed in DM’s neuromuscular locomotor system when perception of self-motion is provided.
Listed In: Biomechanics, Gait, Physical Therapy

Static postural control does not strongly predict dynamic gait stability recovery following a trip in adults with and without vestibular dysfunction

Unilateral peripheral vestibular disorder (UPVD) negatively affects upper and lower body motor performance, but postural control during quiet stance in UPVD patients has not been directly compared with dynamic stability control after an unexpected perturbation during locomotion. We analysed centre of pressure (COP) characteristics during static posturography in UPVD patients and healthy controls and compared this with performance of a trip recovery task. 17 UPVD patients and 17 healthy controls were unexpectedly tripped while walking on a treadmill. The margin of stability (MoS) was calculated at touchdown (TD) of the perturbed step and the first six recovery steps. Posturography was used to assess postural stability during 30 seconds of standing with eyes open and closed using a force plate. The trip reduced the MoS of the perturbed leg (p<0.05) with no significant differences in MoS between the groups. Controls returned to MoS baseline level in five steps and patients did not return within the six steps. UPVD patients showed a greater total COP sway path excursion (closed eyes only), anterior-posterior range of COP distance and a more posterior COP position in relation to the posterior boundary of the base of support. There were no significant correlations between COP sway path excursion and MoS values. We concluded that UPVD patients have a diminished ability to control and recover dynamic gait stability after an unexpected trip and lower static postural stability control compared to healthy matched controls, but that trip recovery and static postural control rely on different control mechanisms.
Listed In: Biomechanics, Gait, Neuroscience, Physical Therapy, Posturography


A popular method for measuring initial contact (foot-strike) during running is the force platform. It has been proposed that the foot contact events can be estimated using peak impact related accelerations of the leg using accelerometers. Various studies have been conducted to compare force platform and accelerometer methods in walking and running. The aim of this study was to develop a method for identifying peak impact accelerations in the anterior- posterior axis using the Delsys Trigno System during running and compare this with initial contact via force plates. Seven national and international sprinters completed runs across a force platform with an accelerometer fixed to their shin. The results showed the acceleration of the anterior-posterior axis approximated foot-strike within ±0.017 s of the foot-strike event detected by the force plate.
Listed In: Biomechanics, Gait

Comparison of accelerometry stride time calculation methods

The purpose of this study was to investigate how a newly proposed method of stride time calculation, utilising data filtered at 2 Hz, compared to previous methods. Tibial accelerometry data for 6 participants completing half marathon running training were collected. One run was selected for each participant at random, from which five consecutive running strides were ascertained. Four calculation methods were employed to derive each stride time and results were compared. No significant difference was found between methods (p=1.00). The absolute difference in stride time, when comparing the proposed method to previous methods, ranged from 0.000 seconds to 0.039 seconds. Filtered data could offer a simplified technique for stride time output during running gait analysis, particularly when applied during automated data processing for large data sets.
Listed In: Biomechanics, Gait, Sports Science

Quantifying varus and valgus thrust in individuals with severe knee osteoarthritis

Background: Gait abnormalities can influence surgical outcomes in people with severe knee osteoarthritis (OA) and thus a thorough understanding of gait abnormalities in these people prior to arthroplasty is important. Varus-valgus thrust is a characteristic linked to OA disease progression that has not yet been investigated in a cohort with severe knee OA awaiting knee arthroplasty. The aims of this study were to determine i) prevalence of varus and valgus thrust in a cohort with severe knee OA compared to an asymptomatic group, ii) whether the thrust magnitude differed between these groups iii) differences between varus and valgus thrusters within the OA cohort and iv) whether certain measures could predict thrust in the OA cohort. Methods: 40 patients with severe knee OA scheduled for primary TKR and 40 asymptomatic participants were recruited. Three-dimensional gait analysis was performed on all participants, with the primary biomechanical measures of interest being: varus and valgus thrust, knee adduction angle, peak KAM, and KAM impulse. Additionally, static knee alignment and quadriceps strength were assessed in the subgroup with knee OA. Findings: No difference was found in the prevalence of varus and valgus thrust between the severe OA and control groups (Pearson chi-square = 3.735, p value = 0.151). The OA varus thrust group had a significantly higher peak KAM (p=0.000), KAM impulse (p=0.001), static alignment (p=0.021), and lower quadriceps strength (p=0.041) than the valgus thrust group. Peak KAM and quadriceps strength were found to explain 34.9% of the variation in maximum thrust, such that an increase in KAM and a decrease in quadriceps strength were associated with an increase in maximum (varus) thrust. Interpretation: Few differences between the severe OA and control groups were seen, however dichotomizing the groups into varus and valgus cohorts revealed a number of biomechanical differences. Patients with severe OA are often treated as a homogenous cohort; however, by classifying which individuals have a varus or valgus thrust, we have identified a subset of patients with poorer biomechanics who could potentially be at a higher risk of a worse outcome after surgery.
Listed In: Biomechanics, Gait, Orthopedic Research

Marathon Stride Rate Dynamics: A Case Study

The purpose of this study was to investigate stride rate (SR) dynamics of a recreational runner participating in his debut marathon. Tibial accelerometry data obtained during a half marathon (R1) and marathon (R2) were utilised. SR data were extracted utilising novel computational methods and descriptive statistics were utilised for analysis of R2, and comparison of the first half of the marathon (R2half) to R1. Results indicate that the participant employed comparable SR strategy in R1 and R2half. For R2 a combined decreasing trend in SR and increased variance in SR from 30 km (R2 =0.0238) was observed. Results indicate that the participant had the ability to maintain SR strategy for the first half of the marathon, however as fatigue onset occurred this ability decreased. Running strategies on SR during fatigue may be of future use to recreational runners.
Listed In: Biomechanics, Gait, Sports Science