Skeletal transients on heel strike in normal walking with different footwear
Abstract
Simultaneous measurements during normal walking of the transient acceleration on heel strike in the tibia and skull show peaks of ∼ 5 g and 0.5 g respectively when hard heels were worn. Resilient heels halved the amplitudes, while rebound could be avoided by a construction including a viscoelastic polymer insert. The transient is propagated as travelling waves up (and outwards from) the skeleton, its inconspicuous appearance in force plate studies being due to the non-uniform and non-synchronous acceleration of various parts of the body.
Implications of these findings are noted, including the potential contribution of heel strike transients to osteoarthritic degeneration. Aggravation of symptoms in sufferers from back troubles may well be due to shear induced by them in para-osteal tissue. Possible physiological roles for the transients, which may account for their existence, are also mentioned.
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Feasibility assessment of transfer functions describing biomechanics of the human lower limb during the gait cycle
2021, Biomedical Signal Processing and ControlTransfer functions could model biomechanical parameters to conveniently analyze the system dynamics of the lower limb during daily activities, e.g., walking. The current study evaluates the feasibility of transfer functions as a means of predicting surface electromyography (sEMG) of lower limb muscles based on axial tibial (ATA) and femoral (FA) accelerations. Since the transfer functions are comparable in accuracy to commonly used long short-term memory models (LSTM), the transfer function-based methodology can assist in the design of novel prostheses while being competitive with mainstream models.
Data were collected from eight participants with no medical history that would alter their gait cycles. The data included the sEMG of four primary muscle groups, ATA and FA, and heel-strike triggering signal, while the subjects walked at 5.28 km/h on a treadmill. A fast Fourier transform (FFT) was performed on the filtered ensemble averages of the ATA, FA and normalized average rectified sEMG signals, which were used to approximate the time domain Fourier series. Transfer functions relating ATA-to-sEMG and FA-to-sEMG were derived from the Fourier series equations to generate time-domain intra-subject predictions of sEMG signals. With respect to predictive accuracy, these transfer functions were compared with sEMG-to-sEMG LSTM models trained on sEMG data from some of the participants. It was hypothesized that the transfer functions would be at least comparable to the LSTM models.
The results indicate that the predicted sEMG signals were able to capture the temporal characteristics of the measured sEMG signal based on either ATA or FA. The muscle activities and acceleration were in good agreement with the walking gait cycle events. Only 13 Fourier terms were needed to effectively predict the sEMG from the acceleration signals, indicating the computational efficiency of the investigated analysis framework. For the ATA-to-sEMG transfer functions, the mean square difference (MSD) between the predicted and measured sEMG signals was low and comparable to the LSTM models.
Overall, the feasibility and competitiveness of the transfer functions with LSTM models was confirmed with respect to predictive accuracy. Potential applications of the transfer functions include the control of powered prosthetics and the detection of gait pathologies.
Surface acceleration transmission during drop landings in humans
2021, Journal of BiomechanicsThe purpose of this study was to quantify the magnitude and frequency content of surface-measured accelerations at each major human body segment from foot to head during impact landings. Twelve males performed two single leg drop landings from each of 0.15 m, 0.30 m, and 0.45 m. Triaxial accelerometers (2000 Hz) were positioned over the: first metatarsophalangeal joint; distal anteromedial tibia; superior to the medial femoral condyle; L5 vertebra; and C6 vertebra. Analysis of acceleration signal power spectral densities revealed two distinct components, 2–14 Hz and 14–58 Hz, which were assumed to correspond to time domain signal joint rotations and elastic wave tissue deformation, respectively. Between each accelerometer position from the metatarsophalangeal joint to the L5 vertebra, signals exhibited decreased peak acceleration, increased time to peak acceleration, and decreased power spectral density integral of both the 2–14 Hz and 14–58 Hz components, with no further attenuation beyond the L5 vertebra. This resulted in peak accelerations close to vital organs of less than 10% of those at the foot. Following landings from greater heights, peak accelerations measured distally were greater, as was attenuation prior to the L5 position. Active and passive mechanisms within the lower limb therefore contribute to progressive attenuation of accelerations, preventing excessive accelerations from reaching the torso and head, even when distal accelerations are large.
Using the loading response peak for defining gait cycle timing: A novel solution for the double-belt problem
2020, Journal of BiomechanicsSplit-belt treadmills (SBTM) contain force plates under each belt that measure ground reaction force (GRF). Initial contact (IC) detection for each gait cycle obtained from the GRF is used for calculating temporal gait parameters (e.g., gait variability, step time, stride time). Occasionally, the participant steps with one leg on the contralateral belt (i.e., crossing) making the IC undetectable and the calculation of temporal gait parameters are compromised. We term this the double-belt problem (DBP). Objective: here we developed a complementary detection method using the loading response peak (LRP), anchor point for calculating gait parameters. Methods: we used GRF gait data from twenty adults (age 56.45 ± 4.81 y; 6 males) who walked on an SBTM. First, we used no-crossing gait periods free of the DBP to calculate stride time, step time, and stride time to stride time coefficient of variation and evaluated the true error and the normalized true error of the LRP detection method. Then, we used multiple comparisons between no-crossing data and crossing data. Results: we found that normalized errors (in comparison to the IC method) are ≤5.1%. Strong correlations were found between gait parameters computed based on the two detection methods (Intraclass correlation coefficient ≥0.97; p ≤ 0.001). Conclusion: detecting gait cycle timing based on the LRP detection method is reliable for estimating temporal gait parameters, demonstrating high correspondence with the gold standard IC detection method.
Effect of improvement in quadriceps strength asymmetry on trunk movement asymmetry after total knee arthroplasty
2020, Gait and PosturePatients with knee osteoarthritis (OA) demonstrate trunk movement asymmetry during walking; this asymmetry is associated with disability and quadriceps strength asymmetry.
What are the differences between trunk movement asymmetries before and after total knee arthroplasty (TKA) and associations between the changes in trunk movement asymmetry and quadriceps strength asymmetry?
In this prospective cohort study, 27 patients (mean age, 71.0 years; women, 85.2%) were assessed at 1 month before and 6 months after surgery. Trunk movement asymmetry (harmonic ratio) was assessed at their preferred pace using a triaxial accelerometer. The isometric quadriceps strength was evaluated using a hand-held dynamometer, and the quadriceps strength inter-limb absolute difference was calculated. Multivariate analyses were performed to compare the trunk movement asymmetries before and after surgery with covariate adjustment (gait pain, gait velocity, and non-operated-limb Kellgren and Lawrence [K&L] grade) and to investigate the association between the changes in trunk movement asymmetry and quadriceps strength inter-limb difference with covariate adjustment (age, sex, and non-operated-limb K&L grade).
The trunk movement asymmetry in the medio-lateral (mean difference, 0.61; 95% confidence interval [CI], 0.22 to 1.00) and antero-posterior (mean difference, 1.15; 95% CI, 0.48 to 1.83) directions significantly decreased postoperatively compared with the preoperative results. A decreased quadriceps strength inter-limb difference was significantly associated with a decreased medio-lateral trunk movement asymmetry (β = 0.68; 95% CI, 0.30 to 1.06).
TKA plays an important role in the improvement of trunk stability during walking in patients with knee OA. Decreasing quadriceps strength asymmetry may be a key to improving trunk movement asymmetry.
Trunk movement asymmetry associated with pain, disability, and quadriceps strength asymmetry in individuals with knee osteoarthritis: a cross-sectional study
2019, Osteoarthritis and CartilageThis study examined 1) the clinical relevance of trunk movement asymmetry, which was evaluated using a trunk-mounted inertial measurement unit (IMU), and 2) the relationship between trunk movement asymmetry and lower limb muscle strength asymmetry in individuals with knee osteoarthritis (OA).
One-hundred-thirty-one participants (mean age, 74.2 years; 71.8% female; Kellgren and Lawrence [K&L] grade ≥1) underwent gait analysis at their preferred pace for IMU-based measurement of trunk movement asymmetry (harmonic ratio [HR] and improved HR). The isometric strength of quadriceps and hip abductors was evaluated using a hand-held dynamometer. Pain and disability level were evaluated using a validated self-reported questionnaire. Multiple regression analyses with covariate adjustment were performed to examine the relationship between trunk movement asymmetry (independent variable) and pain, disability level, or muscle strength asymmetry (dependent variables).
Individuals with severe knee OA (K&L grade ≥3) had increased trunk movement asymmetry in the medio-lateral axis compared to those with a K&L grade of 1. Increased trunk movement asymmetry was associated with a greater knee pain and disability. The increased trunk movement asymmetry was significantly associated with an increase in the asymmetry of quadriceps strength, but not with asymmetry in the strength of hip abductor.
Our findings indicate that increased medio-lateral trunk movement asymmetry may be an indicator of impairment, rather than adaptation, in individuals with knee OA. This preliminary finding warrants validation by future study. Paying close attention to medio-lateral trunk movement asymmetry may be key to our understanding of OA-related pain and disability.
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2018, Clinical BiomechanicsFollowing anterior cruciate ligament reconstruction, individuals exhibit sagittal plane knee loading deficits as they underload their injured limb during running. These between-limb biomechanical differences are difficult to clinically detect. Wearable accelerometers may aid in the development of early rehabilitation programs to improve symmetrical loading. This study aimed to identify whether segment accelerations from wearable accelerometers can predict knee loading asymmetry in an anterior cruciate ligament reconstructed population.
14 individuals 5-months post-anterior cruciate ligament reconstruction performed self-selected speed running. Data were collected concurrently using a marker-based motion system and accelerometers positioned on participants' shanks and thighs. Stepwise linear regression was used to determine predictive value of accelerometer data on biomechanical variables.
Shank acceleration was not predictive of any biomechanical variable. Between-limb differences in thigh axial acceleration explained 30% of the variance in between-limb differences in knee power absorption (p = 0.045), suggesting that accelerometers placed on proximal joint segments may provide information regarding knee loading asymmetry. Between-limb differences in thigh axial acceleration also explained 38% of the variance in between-limb differences in ground reaction force (p = 0.002).
These relationships indicate that accelerations from wearable accelerometers may provide some useful information regarding knee loading during running in individuals following anterior cruciate ligament reconstruction.