International Biomechanics最新文献

Maximal voluntary isometric contractions (MVIC) are a common method to normalize electromyographic amplitude into standardized units of %MVIC. However, in 60% of drop jump research using an MVIC in 2018-2023, supramaximal activation or activation greater than 100% MVIC occurred. Therefore, MVICs may not be representative of peak muscle activation, leading to erroneous interpretation of muscle activation. The purpose of this study is to quantify EMG normalization difference in drop jump landings. Sixteen (10 M, 6F) participants were recruited for the study. MVICs were recorded from nine lower extremity muscles and this activation compared to the maximal activation recorded from 10 drop jump trials. The MVIC significantly underestimated maximum activation by 71%-140% in one-sample t-tests, for the rectus femoris (p = 0.002), vastus medialis (p < 0.001), medial gastrocnemius (p = 0.002), lateral gastrocnemius (p = 0.002), tibialis anterior (p = 0.02), and gluteus maximus (p = 0.03). The one-sample t-tests were not statistically significant for the remaining muscles with the data containing significant variability. Our data quantifies EMG normalization underestimate and supports the status in the literature where normalization with MVICs will underestimate maximal muscle activation in drop jump movements.

This study evaluates the accuracy of single camera markerless motion capture (SCMoCap) using Microsoft's Azure Kinect, enhanced with inverse kinematics (IK) via OpenSim, for upper limb movement analysis. Twelve healthy adults performed ten upper-limb tasks, recorded simultaneously by OptiTrack (marker-based) and Azure Kinect (markerless) from frontal and sagittal views. Joint angles were calculated using two methods: (1) direct kinematics based on body coordinate frames and (2) inverse kinematics using OpenSim's IK tool with anatomical keypoints. Accuracy was evaluated using root mean square error (RMSE) and Bland-Altman analysis. Results indicated that the IK method slightly improved joint angle agreement with OptiTrack for simpler movements, with an average RMSE of 8° for shoulder elevation in the sagittal plane compared to 9° with the coordinate frame method. However, both methods had higher RMSEs for rotational measurements, with IK and coordinate frame methods at 21° for shoulder rotation in the sagittal plane. Forearm pronation-supination measurements were unreliable due to tracking limitations. These findings suggest that Kinect with IK improves accuracy for simpler movements but struggles with rotational joint mechanics. Future research should focus on enhancing markerless tracking algorithms to fully realise the benefits of IK.

People with Parkinson disease (PwPD) often face challenges with maintaining balance while walking, which can stem from sensory dysfunction. Studies have identified different biomechanical strategies that aid in preserving upright balance control. Stochastic resonance (SR) stimulation delivers sub-threshold electrical noise to enhance the detection capabilities of dysfunctional sensory systems. Yet, the effectiveness of SR in enhancing gait stability in PwPD is undetermined. The purpose of this study was to investigate the effects of SR on balance control during visually perturbed walking in PwPD (NCT06829342).Fourteen individuals with PD completed the study. We established individualized sensory thresholds for SR stimulation and identified the optimal SR intensity. Following this, the participants walked within a virtually perturbed environment. Center of mass (CoM) excursion, foot placement, and ankle roll responses were assessed bilaterally.Peak CoM excursion showed a significant increase, indicating reduced stability, with the SR condition compared to no-SR at the more affected side. Outcome measures related to balance control mechanisms were insignificant.With SR, PwPD were driven by the induced fall with more sway and without significant alterations in balance strategies, which might be due to adding more noise to sensory processing and misidentifying the more affected side.

This article explores the characterization of sports injuries among young athletes participating in the 2023 Paralympic School Games. Injuries during the physiological growth phase can not only compromise the development of sports skills but also harm the physical development expected for their age group. Adaptive mechanisms to training are the main determinants of the location of injuries, traumas and musculoskeletal complaints. This paper aimed to identify occurrence of sports injuries in para athletes during the 2023 School Paralympics. The study population consisted of students who participated in the national stage of the 2023 School Paralympics, held at the Paralympic Training Center in the state of São Paulo. The sample consisted of 640 para-athletes, 253 (60.5%) females and 387 (60.5%) males, with an average age of 14.06 years. Overall, 14.9% of the participants reported injuries/illness. The team with the highest percentage of injured members was from the state of Tocantins (14.8%). Most of the injured athletes had intellectual disabilities (41.46%), practiced athletics (56.9%) and were in the final years of elementary school (21.95%), with an average age of 14.56 years, and the majority were male (56.86%).

Patients with low back pain caused by sacroiliac joint (SIJ) dysfunction have an impaired quality of life, due to reported pain, disability and activity limitations. There is increasing evidence that minimally invasive sacroiliac joint fusion (MISJF) results in improvement in pain, disability and quality of life in these patients. Some studies have reported improvements in daily physical activity following MISJF but based on bias-prone self-reports. Our aim was to provide objective data on daily physical activity in patients with SIJ dysfunction. Daily physical activity in daily life of participants was measured using a triaxial accelerometer for seven consecutive days, before surgery and 3 months after surgery. Recorded daily activities were the daily number of events and total time spent sitting or lying, standing, walking, cycling, high-activity and number of steps and sit-to-stand transfers. The quality of life was assessed by the validated Dutch EQ-5D-5 L-questionnaire. No statistical differences were observed between daily physical activity in patients with SIJ dysfunction before and 3 months after MISJF. As compared to matched controls, high-intensity physical activity was lower in both the pre- and postoperative period (p = 0.007) for patients with SIJ dysfunction. The quality of life improved significantly in patients after MSIJF, from 0.418 to 0.797 (p = 0.021) but did not reach the level of controls (1.000). Daily physical activity in patients with postpartum SIJ dysfunction does not improve 3 months following MISJF, while quality of life does improve significantly. The discrepancy between these two observations is food for new research.

Altered scapular kinematics is associated with shoulder pain. Resistance exercise is a common treatment; however, the effects of lifting an external load on scapular kinematics is limited. Understanding whether an external handheld load affects scapular kinematics in a healthy population can provide normal values utilized for comparison to individuals with shoulder pain. Currently, no studies have examined the effect of incrementally increased handheld loads. We defined the effects of varying external handheld loads on scapular kinematics during a shoulder elevation task. Healthy participants (n = 50) elevated their shoulder in the scapular plane over 4 trials. One trial of no loading (control) and 3 trials with incrementally increased external handheld loads. Scapular kinematic rotations and translations were measured during ascent and descent phases using 3D motion capture. Compared to no load, the highest external load during ascent increased scapular elevation [mean difference = 3.2 degrees (95%CI: 0.9, 5.4), p = 0.006], and during descent increased scapular elevation [mean difference = 3.9 degrees (95%CI: 2.8, 5.1), p < 0.001] and increased scapular upward rotation [mean difference = 4.5 degrees (95%CI: 2.4, 6.6), p < 0.001]. External handheld loads result in small increases in scapular elevation and scapular upward rotation. These results should be utilized as normal values to compare to individuals with shoulder pain.

Clinicians seek an accurate method to assess muscle contractility during activities to better guide treatment. We investigated application of a conductive electroactive polymer sensor as a novel wearable surface mechanomyography (sMMG) sensor for quantifying muscle contractility. The radial displacement of a muscle during a contraction is detected by the physically stretched dielectric elastomer component of the sMMG sensor which quantifies the changes in capacitance. The duration of muscle activation times for quadriceps, hamstrings, and gastrocnemius muscles demonstrated strong correlation between sMMG and EMG during a parallel squat activity and isometric contractions. A moderate to strong correlation was demonstrated between the sMMG isometric muscle activation times and force output times from a dynamometer. The potential wearable application of an electroactive polymer sensor to measure muscle contraction time is supported.