The head-mounted laser is commonly used in clinical proprioceptive tests, but its ability to measure movement across three planes of motion has not been investigated. Therefore, this study evaluated the head-mounted laser against a validated gold standard multi-sensor inertial measurement unit (IMU) (XsensTM) in measuring cervicocephalic movement across three planes. Fourteen healthy adults (seven males and seven females) performed six repetitions each of active cervical flexion, extension, lateral flexion and rotation, whilst instructed to maintain the laser beam within a bullseye corresponding to 4.5° of movement. Primary plane means XsensTM range of motion (ROM) was used to evaluate if movement remained less than 4.5°. During flexion, extension and rotation movements, mean ROM in the primary plane using XsensTM remained within the 4.5° threshold (2.97°-3.57°), indicating that the head-mounted laser corresponded with the IMU (p ≤ 0.01). However, XsensTM mean lateral flexion movement reached 11.34° and 12.10° for left and right lateral flexion, indicating poor correspondence (p = 0.95 and 0.97). The head-mounted laser is appropriate for clinical movement assessment in the sagittal and transverse planes but not recommended for the coronal plane. Other devices should be considered for complete clinical assessment of cervical position sense.
Achilles tendinopathy (AT) is common among runners and typically presents with Achilles tendon pain. Neuromotor alterations have been reported in AT during demanding tasks such as running; however, alterations during functional tasks such as walking remain poorly understood. Such information may be relevant and inform rehabilitation targets. Therefore, this exploratory study investigated lower limb neuromotor control during walking and running in people with AT compared with healthy controls (CO). Twenty-four male runners participated (AT = 12, CO = 12) and completed walking (WALK), perturbed walking (PERTWALK), running (RUN), and perturbed running (PERTRUN) on a custom split-belt treadmill. Lower limb muscle activity was recorded using electromyography to assess activity onset, offset, and duration during unperturbed tasks, and reflex latency and amplitude during perturbed tasks. A MANOVA (α = 0.05) examined group effects (AT/CO). During WALK, AT showed delayed onset of tibialis anterior, peroneus longus, and vastus medialis (p < 0.05). During RUN, gastrocnemius medialis duration was longer, while gluteus maximus onset was delayed and shorter in AT (p < 0.05). During PERTWALK, tibialis anterior reflex latency was delayed in AT (p < 0.05), whereas reflex amplitudes and all PERTRUN outcomes were not significant. These findings indicate potential neuromotor differences in AT.
In this pilot randomized controlled trial, we assessed the effects of a core-lower limb coordinated Pilates exercise on gait and postural balance in women with bilateral flexible pes planus. Twenty-two women aged 34.64 ± 9.59 years with bilateral navicular drop ≥10 mm assessed by the navicular drop test (NDT) were randomly assigned to either a Pilates training group or a control group. Gait parameters - including foot off, step time, stride time, walking speed, and cadence - were assessed using a validated three-dimensional motion analysis system. Postural balance was quantified as center of pressure (COP) sway in both anterior - posterior (AP) and mediolateral (ML) directions, including range, velocity, and root mean square (RMS), using a force plate. Gait and balance were evaluated at baseline and after the 8-week intervention. Significant improvements were observed in step-time (p = .014), stride-time (p = .045), and cadence (p = .033), as well as postural balance variables, particularly in ML-RMS (p = .003), for the Pilates group compared to the control group. These results suggest that Pilates exercise may benefit gait and postural balance in individuals with flexible pes planus.
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.
Intervertebral disc (IVD) degeneration is a potential contributor to low-back pain. While experimental IVD injury models have demonstrated IVD structural changes, the early mechanical consequences remain unclear. This study aims to assess and compare the effects of two IVD injury models on lumbar spine instability and assess back musculature adaptations to IVD injury. Thirty-one adult male Wistar rats were assigned to three groups: IVD knife stab lesion (knife), IVD needle puncture (needle), and sham surgery control (control). In the knife and needle groups, L4/L5 IVDs were injured at 14 weeks of age. One to two weeks post-intervention, lumbar multifidus (MF) and medial longissimus (ML) muscles were excised, L4-L5 spinal segments were harvested for mechanical testing, and IVDs were collected for histology. The needle group exhibited lower peak stiffness, peak moment and hysteresis than controls in flexion, with no difference in lateral bending. IVD height and area did not differ between groups, but the needle group had a smaller nucleus relative to the annulus area compared to controls. Morphological changes were observed in both injury groups. The needle group showed a higher normalized ML mass, while the normalized MF mass was unchanged. In conclusion, lumbar spine instability was successfully established via IVD needle injury in the rat.
Patella fractures are relatively rare, though effective treatment of these fractures is essential. Screws and cerclage cable have been proposed to treat displaced patellar fractures to overcome the disadvantages of the modified tension band technique. The aim of the present study was to compare the in vitro biomechanical behaviour of a surgical construct consisting of screws and cable cerclage figure-of-eight tension band against the classic tension band technique using a specifically designed 3-D printed model of patella fracture. The patellar-fracture fixation systems tested in the current study consisted of screws and cerclage cable tension band compared to a conventional modified AO (Association of Osteosynthesis) tension band. Each system was tested in ten 3D- printed patella - fracture models. Two trials were designed to reproduce the forces the patella withstands throughout the range of knee motion. Differences between forces and displacement were explored with the Student t test. In the extension test, the between-group difference of the force required for failure was 1455,9 N greater in the screw cerclage cable setup in the flexion test, the screw cerclage group showed lower fracture displacement (1,42 mm less displacement) at higher forces (more than 244,9 N) compared to the Modified AO tension band. Differences were found to be statistically significant. Screws and cerclage cable are an alternative to conventional surgical procedures for transverse patellar fractures. Further research must establish if this setup and new non metallic materials should become the surgical treatment gold standard.
Traumatic brain injuries frequently occur in the construction industry when workers are struck with their heads in a forward-flexed position. Hard hats, the primary form of protection against such events, may not be optimized for these forward-flexed impacts since certification testing is performed with a head form in an upright configuration. In response, this study assesses the impact mitigation of six commercially available hard hats when subjected to impacts in different head orientations - upright and with 30° of forward flexion. Impactors with a mass of 3.6 kg were dropped vertically onto a Hybrid III 50th percentile head/neck form. Kinematic outcomes related to TBI (e.g. accelerations) were compared across impact conditions. Results indicated that impacts to the forward-flexed head resulted in the largest angular accelerations, and hard hats were the least effective at mitigating angular accelerations in this head position. Furthermore, correlation analysis indicated that hard hats that performed well in upright testing often performed poorly in forward-flexed conditions (or vice versa). Taken together, these results suggest consumers/employers are not equipped with the necessary information to select the safest products for all impact conditions based on safety certification results using upright testing alone.
The purpose of the present study was to examine differences in inter-limb asymmetries between countermovement vertical jump (CMJ) and single-leg jump (SLJ) performed on an innovative portable force plate system. Seventy professional athletes competing in top-tier international leagues (e.g. NBA, Super League) participated in this investigation. Following the completion of a standardized warm-up, athletes stepped on a uni-axial dual-force plate system and performed three CMJs and six SLJs without an arm swing in randomized order. Peak takeoff and landing forces were recorded for each limb, from which asymmetry percentages were derived. Wilcoxon signed-rank test was used to make statistical comparisons (p < 0.05). Significant differences were found in all asymmetry-related metrics, overall (CMJ vs. SLJ; takeoff: 7.2 vs. 1.0%; landing: 3.3 vs. 6.8%) and within each sport. Peak takeoff force asymmetry was considerably greater in CMJ than in SLJ, while peak landing force asymmetry displayed a reverse trend, with notably greater inter-limb asymmetries being detected within SLJ than CMJ. While both tests can offer useful information to sports practitioners, these results suggest that CMJ and SLJ should not be used interchangeably but rather in conjunction with one another to obtain a better insight into athletes' performance capabilities and inter-limb asymmetry magnitudes.
Maximum voluntary contractions (MVCs) are the standard normalization method for muscle activity, but can be hindered by pain and injury. Submaximal normalization may be a viable option. The study objective was to compare muscle activation between symptomatic and asymptomatic groups with MVC and submaximal normalization to determine if similar relative between-groups differences could be detected. Eighteen participants, divided into symptomatic and asymptomatic groups, performed isometric MVCs and six dynamic functional tasks. EMG data were normalized using MVC and submaximal values from a weighted overhead lift. MVCs achieved higher activation levels for most muscles, but submaximal normalization provided comparable values for serratus anterior. Significant between-group differences were observed during the Comb Hair, with higher activation in the symptomatic group for the upper trapezius, middle trapezius, and supraspinatus across both normalizations. The serratus anterior during the Overhead Reach and lower trapezius in the Tie Apron were also different between groups with both normalizations. There were some significant findings that emerged from only one normalization method. Submaximal normalization may be a viable alternative to MVC normalization for select muscles and upper limb pathological populations. Submaximal normalization allowed for meaningful comparisons of muscle activation patterns during functional tasks without the need for maximum force exertion.
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%).
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.
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.
This exploratory study examines the relationship between the eccentric utilization ratio (EUR) and the rate of force development (RFD) in squat jumps (SJ). EUR, a key metric in sports science, compares performance in countermovement jumps (CMJ) and squat jumps (SJ). The study hypothesizes that a higher EUR is associated with a poorer RFD in SJ. Basketball and soccer players, long-distance runners, alongside physical education students (209 men; age: 23.2 ± 4.95 years and 104 women; age: 22.7 ± 4.42 years) participated. The EUR was calculated from jump height, peak force and peak power. The results indicated a small to moderate but significant negative correlation between EUR based on peak force or peak power and RFD in SJ (r = -.41 and -.27), suggesting that a higher EUR might be linked to a diminished ability to rapidly develop force in SJ. Thus, a higher EUR may not indicate superior athletic performance.
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.
The purpose of this study was to study the effect of crown thickness on the fatigue life of CAD/CAM ceramic materials. CAD/CAM ceramic materials for the crown were virtually designed with three thickness designs of (a) ultra-thin occlusal crown average 0.7 mm thick (group A), (b) thin occlusal crown 1.1 mm average thick (group B), (c) thick occlusal crown 1.5 mm thick. The materials are: zirconia Cercon ZC and IPS e.max CAD (LD). Finite Element Analysis (FEA) simulations were carried out to estimate the fatigue lives of restorative materials. The lives for groups B and C under fatigue load were not significantly different from each other for Zirconia. The predicted lives for group A zirconia crowns, under fatigue load 50 N, 100 N, 120 N is 24 years, 4.3 years, 1.9 years, respectively. Results for crowns made of LD can be summarized as follows: under load 50 N, all groups have survived longer than 5 respectively, while under the load of 100 N, only group C survived longer than 5 years. 0.7 mm thick full contour Zirconia crowns possessed adequate endurance strength to survive under physiologic conditions. On the other hand, the crown made of LD should have at least 1.5 mm thickness to survive longer than 5 years.
There is a lack of knowledge in the literature concerning Body Segment Inertial Parameters (BSIP) for children aged 4 to 15 years. Nevertheless, these data are fundamental for studying the dynamics of the healthy and pathological musculoskeletal system. One common method for obtaining BSIP is to use regression equations derived from anthropometric tables. However, the majority of these equations are based on adult data. In this study, we compared certain BSIP (segment mass, center of mass position, and transverse moment of inertia) derived from adult anthropometric tables with the corresponding BSIP extracted from a pediatric anthropometric table. The goal of this study was to determine the accuracy of using adult anthropometric tables to calculate pediatric BSIP. For this comparison, we assessed the proximity of several adult anthropometric tables to a pediatric anthropometric table by Jensen (1986) for each BSIP. Our results revealed differences between the BSIP obtained using adult tables and the BSIP obtained with the pediatric table used as a reference. When considering all the tables, the mean relative difference was 12% for segment mass, 12% for center of mass position, and 25% for transverse moment of inertia. Notably, the greatest relative differences were observed for the head, hand, and foot segments. Additionally, the relative difference in female data was higher compared to males. This result could be attributed to the predominant use of male subjects in the adult tables considered in this study. Finally, the adult anthropometric tables by Dumas and Wojtsuch (2018) and De Leva (1996) provided results that were closer in comparison to Jensen (1986).
Walking in high-heel shoes (HHS) decreases the push-off power and little research has examined the specific muscle groups that compensate for it. The purpose was to examine the effects of walking in HHS compared to barefoot on lower extremity net joint work and power. Fourteen young women walked in HHS and barefoot at a fixed speed of 1.3 m·s-1. Marker position and ground reaction force data were synchronously measured at 100 and 1000 Hz, respectively. Peak power and joint work variables were computed over the power phases of the gait cycle using an inverse dynamic approach. When walking in HHS was compared to barefoot, participants exerted a diminished push-off characterized by lesser peak power and lesser work by the ankle plantar flexors in late stance (A2 phase; p < 0.001). To compensate for the reduced ankle plantar flexor power, greater peak power was generated and work was performed in early stance by hip extensors (H1 phase; p ≤ 0.001), in mid-stance by knee extensors (K2 phase; p < 0.001) and in late stance and early swing phase by hip flexor muscles (H3 phase; p ≤ 0.001). Walking in HHS induces biomechanical plasticity and causes distal-to-proximal redistribution of net joint power and work during walking.
This study explored effects of using isometric versus isokinetic maximal voluntary contractions (MVCs) to normalize EMG data from supraspinatus and infraspinatus subregions during isokinetic tasks. Participants performed submaximal isokinetic external rotation (ER) and scaption tasks at two speeds. Three isometric MVCs were used: seated ER; side-lying scaption; side-lying abduction. Isokinetic MVCs were performed in the same position and speeds as the experimental tasks. Data were normalized using peak EMG from reference tasks: MVC which produced the greatest amplitude overall (MEA), isometric MVC with greatest amplitude (isometric best), isokinetic MVC with greatest amplitude (isokinetic best), and the greatest amplitude from the isokinetic MVC that matched the experimental task (isokinetic matched). Mean %MVC from each experimental task/ sub-region were compared by normalization method. The isokinetic matched method versus the MEA method was significantly different in all comparisons with isokinetic matched resulting in relative normalized task values up to 162% greater. The isometric best method resulted in significantly greater %MVC 37% of the time compared to the MEA method, whereas there were no differences when using isokinetic best compared to MEA. Isokinetic MVCs are less likely to overestimate %MVC than isometric and their use should be considered when normalizing data from dynamic tasks.
