Biology subjects

Tecchio, P.

Publications and source records attributed to Tecchio, P..

4 recordsLinked to original sources

bioRxiv2026

3D ultrasound fascicle tractography for objective muscle architecture analysis.

Muscle architecture shapes muscle function and changes with age, growth, training and disease, yet quantifying three-dimensional (3D) muscle architecture in vivo remains challenging. We introduce a hybrid fascicle tractography approach for freehand 3D ultrasound data that accurately reconstructs 3D muscle fascicles with respect to an objective, anatomically relevant coordinate system defined by the muscle's central aponeurosis. The hybrid approach combines Hessian-based fascicle detection with wavelet-based refinement to generate volumetric fascicle orientations. In a synthetic dataset with known ground truth, fascicle orientations and lengths were estimated with errors of [≤]2{degrees} and ~1.5%, respectively. In vivo, the approach detected physiologically plausible fascicle lengthening in the human tibialis anterior following a passive plantar flexion rotation, whereas diffusion tensor imaging of the same muscle did not. The proposed method enables anatomically relevant, objective and non-invasive quantification of 3D muscle architecture in vivo, providing a practical framework for applications in clinical and applied muscle physiology.

bioengineering↗

bioRxiv2025

A passive upper-limb exoskeleton effectively reduces shoulder muscle activity over a large shoulder workspace

Industrial upper-limb exoskeletons are used to offload the upper limb during overhead tasks with the aim of preventing musculoskeletal disorders to the shoulder. Although numerous studies showed reduced shoulder muscle activity during upper-limb exoskeleton use for overhead postures, it remains unknown whether and how upper-limb exoskeletons provide support over a large shoulder workspace beyond overhead work. Therefore, this study evaluated the Ottobock Paexo Shoulder over a large shoulder workspace from overhead to hip height with shoulder abduction and adduction. Upper body kinematics, muscle activity, and subjective user feedback were obtained by three-dimensional motion capture, bipolar surface EMG and questionnaires, respectively, and captured while participants performed static and dynamic work tasks with an electric screwdriver. Participants completed these tasks while 1) not wearing the exoskeleton, 2) wearing a disengaged exoskeleton, with 3) moderate exoskeleton support, and with 4) high exoskeleton support. Exoskeleton support reduced deltoid muscle activity (-9 to -24s%, p[≤].001) in postures with an abducted shoulder or extended elbow, including non-overhead postures. Exoskeleton support modestly decreased shoulder flexion (-3 to -5{degrees}, p[≤].001) and increased shoulder abduction (2 to 5{degrees}, p[≤].032), but the movement patterns during the dynamic task were unaffected. Additionally, exoskeleton-related effects increased with increasing support, but the subjective perception of change also increased, and perceived comfort decreased. Our results indicate that the tested exoskeleton provides support beyond overhead work and that there is a trade-off between exoskeleton support and subjective perception. Accordingly, further optimization of user-exoskeleton interaction is warranted for long-term prevention of musculoskeletal disorders in overhead workers.

physiology↗

bioRxiv2024

UltraTimTrack: a Kalman-filter-based algorithm to track muscle fascicles in ultrasound image sequences

BackgroundBrightness-mode (B-mode) ultrasound is a valuable tool to non-invasively image skeletal muscle architectural changes during movement, but automatically estimating architectural features such as fascicle length remains a major challenge. Existing fascicle tracking algorithms either require time-consuming drift corrections or yield noisy estimates that require post-processing. We therefore aimed to develop an algorithm that tracks fascicles without drift and noise across a range of experimental conditions and image acquisition settings. MethodsWe applied a Kalman filter to combine fascicle length and fascicle angle estimates from existing and openly available UltraTrack and TimTrack algorithms into a hybrid algorithm called UltraTimTrack. We applied the hybrid algorithm to ultrasound image sequences collected from the human medial gastrocnemius of healthy individuals (N=8, 4 women), who performed cyclical submaximal plantar flexion contractions or remained at rest during passive ankle joint rotations at given frequencies and amplitudes whilst seated in a dynamometer chair. We quantified the algorithms tracking accuracy, noise, and drift as the respective mean, cycle-to-cycle, and accumulated between-contraction variability in fascicle length and fascicle angle. We expected UltraTimTracks estimates to be less noisy and to drift less across experimental conditions and image acquisition settings, compared with estimates from its parent algorithms. ResultsThe proposed algorithm had low-noise estimates like UltraTrack and was drift-free like TimTrack across the broad range of conditions we tested. Estimated fascicle length and fascicle angle deviations accumulated to 2.1 {+/-} 1.3 mm (mean {+/-} s.d.) and 0.8 {+/-} 0.7 deg, respectively, over 120 cyclical contractions. Average cycle-to-cycle variability was 1.4 {+/-} 0.4 mm and 0.6 {+/-} 0.3 deg, respectively. In comparison, UltraTrack had similar cycle-to-cycle variability (1.1 {+/-} 0.3 mm, 0.5 {+/-} 0.1 deg) but greater cumulative deviation (67.0 {+/-} 59.3 mm, 9.3 {+/-} 8.6 deg), whereas TimTrack had similar cumulative deviation (1.9 {+/-} 2.2 mm, 0.9 {+/-} 1.0 deg) but greater variability (3.5 {+/-} 1.0 mm, 1.4 {+/-} 0.5 deg). UltraTimTrack was significantly less affected by experimental conditions and image acquisition settings than its parent algorithms. It also performed well on a previously published image sequence from the human tibialis anterior, yielding a smaller root-mean-square deviation from manual tracking (fascicle length: 2.7 mm, fascicle angle: 0.7 deg) than a recently proposed hybrid algorithm (fascicle length: 4.5 mm, fascicle angle: 0.8 deg) and a machine-learning (DL_Track) algorithm (fascicle length: 8.2 mm, fascicle angle: 4.8 deg). ConclusionWe developed a Kalman-filter-based method to improve fascicle tracking from B-mode ultrasound image sequences. The proposed algorithm provides low-noise, drift-free estimates of muscle architectural changes that may better inform muscle function interpretations.

physiology↗

bioRxiv2023

Eccentric exercise is not equal to eccentric contraction

Whether eccentric exercise involves active fascicle stretch is unclear due to muscle-tendon unit (MTU) series elasticity. Therefore, this study investigated the impact of changing the activation timing and level (i.e., pre-activation) on muscle fascicle kinematics and kinetics of the human tibialis anterior during dynamometer-controlled maximal voluntary MTU-stretch-hold contractions. B-mode ultrasound and surface electromyography were employed to assess muscle fascicle kinematics and muscle activity levels, respectively. While joint kinematics were similar for MTU-stretch-hold contractions, increasing pre-activation increased fascicle shortening and stretch amplitudes (9.9 - 23.2 mm, p [≤] 0.015). This led to increasing positive and negative fascicle work with increasing pre-activation. Despite significantly different fascicle kinematics, similar peak fascicle forces during stretch occurred at similar fascicle lengths and joint angles regardless of pre-activation. Similarly, residual force enhancement (rFE) following MTU stretch was not significantly affected (6.5-7.6 %, p = 0.559) by pre-activation, but rFE was strongly correlated with peak fascicle force during stretch (rrm = 0.62, p = 0.003). These findings highlight that apparent eccentric exercise causes shortening-stretch contractions at the fascicle level rather than isolated eccentric contractions. The constant rFE despite different fascicle kinematics and kinetics suggests that a passive element was engaged at a common muscle length among conditions (e.g., optimal fascicle length). Although it remains unclear whether different fascicle mechanics trigger different adaptations to eccentric exercise, this study emphasizes the need to consider MTU series elasticity to better understand the mechanical drivers of adaptation to exercise. New & NoteworthyApparent eccentric exercises do not result in isolated eccentric contractions, but shortening-stretch contractions at the fascicle level. The amount of fascicle shortening and stretch depend on the pre-activation during the exercise and cannot be estimated from the muscle-tendon unit or joint kinematics. As different fascicle mechanics might trigger different adaptations to eccentric exercise, muscle-tendon unit series elasticity and muscle pre-activation need to be considered when eccentric exercise protocols and designed and evaluated.

physiology↗