Search

Powerful digital grasping is essential for primates navigating arboreal environments and is often regarded as a defining characteristic of the order. However, in vivo data on primate grip strength are limited. In this study, we collected grasping data from the hands and feet of eleven strepsirrhine species to assess how ecomorphological variables—such as autopodial shape, laterality, body mass and locomotor mode—influence grasping performance. Additionally, we derived anatomical estimates of grip force from cadaveric material to determine whether in vivo and ex vivo grip strength measurements follow similar scaling relationships and how they correlate. Results show that both in vivo and anatomical grip strength scale positively with body mass, though anatomical measures may overestimate in vivo performance. Species with wider autopodia tend to exhibit higher grip forces, and forelimb grip forces exceed those of the hindlimbs. No lateralization in grip strength was observed. While strepsirrhine grip forces relative to their body weight are comparable to those of other primates and slightly exceed those of humans, they are not exceptional compared to other arboreal mammals or birds, suggesting that claims of extraordinary primate grasping abilities require further investigation. [ABSTRACT FROM AUTHOR]

Body size has an impact on all biological functions and analyzing how body size impacts functional traits such as locomotion is critical. Body size does not only vary across species but also during ontogeny. Indeed, juvenile animals are often at a competitive disadvantage due to their smaller absolute size. Consequently, understanding size‐ and age‐related changes in the locomotor system is critical for our understanding of adult phenotypes. Here, we address this question by exploring growth of the hind limb muscles in two species of closely related baboons that differ in their ecology, the olive baboon, Papio Anubis, the Guinea baboon, and Papio papio. To do so, we dissected 40 P. anubis and 10 P. papio and measured the mass and physiological cross‐sectional area (PCSA) of the hind limb muscles. Our results showed no sexual differences in size‐ or age‐related growth patterns, but did show differences between species. Whereas the scaling of muscle mass and PCSA was largely isometric in P. anubis, allometric scaling was more common in P. papio. Despite these differences between species, the knee extensors and external rotators at the knee scaled with positive allometry in both species highlighting their important role during adult locomotion. Although life‐history data for P. papio are scarce, we suggest that differences between species may be associated with differences in adult body size and age of locomotor independence between species. [ABSTRACT FROM AUTHOR]

Abstract Both resistance training (RT) and long‐duration, high‐intensity stretching induce muscular adaptations; however, it is unknown whether the modalities are complementary or redundant, particularly in well‐trained individuals. A case‐study was conducted on a competitive bodybuilder implementing long‐duration, high‐intensity stretching of the plantar flexors (60 min 6x/week for 12 weeks) in conjunction with their habitual RT. Ultrasound muscle architecture (muscle thickness [MT], fascicle length [FL], and pennation angle [PA]) measurements were collected at multiple sites at four weekly baseline sessions, six (mid) and 12 (post1) weeks following the commencement of the intervention, and a week after the intervention (post2) while isometric strength and range of motion (RoM) were obtained once at baseline, mid, post1, and post2. 2SD band plots were constructed to determine meaningful changes in MT, FL, and PA from the four baseline measures while percentage and absolute change across each timepoint were calculated for all variables. From baseline to post 1, RoM, strength, and MT increased 25.9%, 11.4%, and 7.4%–23.4%, respectively, while four MT and two PA sites exceeded the threshold for meaningful change. The combined stretching and RT protocols resulted in flexibility, strength, and MT adaptations; however, findings should be generalized with caution given the case‐study nature of our investigation.

Background Brightness-mode (B-mode) ultrasound is a valuable tool to non-invasively image skeletal muscle architectural changes during movement, but automatically tracking muscle fascicles 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 with low noise across a range of experimental conditions and image acquisition settings. Methods We 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, four 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 algorithm’s tracking accuracy, noise, and drift as the respective mean, cycle-to-cycle variability, and accumulated between-contraction variability in fascicle length and fascicle angle. We expected UltraTimTrack’s estimates to be less noisy than TimTrack’s estimates and to drift less than UltraTrack’s estimates across a range of conditions and image acquisition settings. Results The proposed algorithm yielded low-noise estimates like UltraTrack and was drift-free like TimTrack across the broad range of conditions we tested. Over 120 cyclical contractions, fascicle length and fascicle angle deviations of UltraTimTrack accumulated to 2.1 ± 1.3 mm (mean ± sd) and 0.8 ± 0.7 deg, respectively. This was considerably less than UltraTrack (67.0 ± 59.3 mm, 9.3 ± 8.6 deg) and similar to TimTrack (1.9 ± 2.2 mm, 0.9 ± 1.0 deg). Average cycle-to-cycle variability of UltraTimTrack was 1.4 ± 0.4 mm and 0.6 ± 0.3 deg, which was similar to UltraTrack (1.1 ± 0.3 mm, 0.5 ± 0.1 deg) and less than TimTrack (3.5 ± 1.0 mm, 1.4 ± 0.5 deg). UltraTimTrack was less affected by experimental conditions and image acquisition settings than its parent algorithms. It also yielded similar or lower root-mean-square deviations from manual tracking for previously published image sequences (fascicle length: 2.3–2.6 mm, fascicle angle: 0.8–0.9 deg) compared with a recently-proposed hybrid algorithm (4.7 mm, 0.9 deg), and the recently-proposed DL_Track algorithm (3.8 mm, 3.9 deg). Furthermore, UltraTimTrack’s processing time (0.2 s per image) was at least five times shorter than that of these recently-proposed algorithms. Conclusion We developed a Kalman-filter-based algorithm 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.

It is challenging to obtain in vivo or in situ experimental data from human muscles due to the invasive nature of such measurements. As a result, many investigations of human performance, surgery, or skeletal adaptation are necessarily based on musculoskeletal models. The utility of such models will depend on the question being asked and the extent to which the model is sufficiently accurate to address that question. In this perspective article, we take advantage of unique intraoperative access to the human gracilis muscle and make direct comparisons between commonly modeled parameters and those measured from the human gracilis. We directly compare muscle–tendon unit (MTU) length, optimal fiber length, and tendon slack length. Our results demonstrate that measured and modeled length parameters differ greatly. This is primarily due to the fact that slack muscle length and optimal muscle length differ greatly for the human gracilis and that models assume they are the same length. [ABSTRACT FROM AUTHOR]