Locomotor Demands Research Articles

Exercise Intensity and Technical Involvement in U9 Team Handball: Effect of Game Format.

The purpose of this study was to quantify the exercise intensity and technical involvement of U9 boys’ and girls’ team handball during different game formats, and the differences between genders. Locomotor activity (total distance, distance in speed zones, accelerations, and decelerations), heart rate (HR), and technical involvement (shots, goals, and duels) metrics were collected during various 15 min game formats from a total of 57 Danish U9 players (37 boys and 20 girls). Game formats were a small size pitch (20 × 13 m) with 3 vs. 3 players and offensive goalkeepers (S3 + 1) and 4 vs. 4 players (S4), a medium size pitch (25.8 × 20 m) with 4 vs. 4 (M4) and 5 vs. 5 (M5) players, and a large size pitch (40 × 20 m) with 5 vs. 5 (L5) players. Boys and girls covered a higher total distance (TD) of high-speed running (HSR) and sprinting during L5 games compared to all other game formats (p < 0.05; ES = (−0.9 to −2.1), (−1.4 to −2.8), and (−0.9 to −1.3) respectively). Players covered the highest amount of sprinting distance in L5 games compared to all other game formats (p < 0.01; ES = 0.8 to 1.4). In all the game formats, players spent from 3.04 to 5.96 min in 180–200 bpm and 0.03 min to 0.85 min in >200 bpm of the total 15 min. In addition, both genders had more shots in S3 + 1 than M5 (p < 0.01; ES = 1.0 (0.4; 1.7)) and L5 (p < 0.01; ES = 1.1 (0.6; 2.2)). Team handball matches have high heart rates, total distances covered, and high-intensity running distances for U9 boys and girls irrespective of the game format. Locomotor demands appeared to be even higher when playing on larger pitches, whereas the smaller pitch size and fewer players led to elevated technical involvement.

Effects of age and locomotor demand on foot mechanics during walking

Older adults exhibit reductions in push-off power that are often attributed to deficits in plantarflexor force-generating capacity. However, growing evidence suggests that the foot may also contribute to push-off power during walking. Thus, age-related changes in foot structure and function may contribute to altered foot mechanics and ultimately reduced push-off power. The purpose of this paper was to quantify age-related differences in foot mechanical work during walking across a range of speeds and at a single fixed speed with varied demands for push-off power. 9 young and 10 older adults walked at 1.0, 1.2, and 1.4 m/s, and at 1.2 m/s with an aiding or impeding horizontal pulling force equal to 5% BW. We calculated foot work in Visual3D using a unified deformable foot model, accounting for contributions of structures distal to the hindfoot’s center-of-mass. Older adults walked while performing less positive foot work and more negative net foot work (p < 0.05). Further, we found that the effect of age on mechanical work performed by the foot and the ankle–foot complex increased with increased locomotor demand (p < 0.05). Our findings suggest that during walking, age-related differences in foot mechanics may contribute to reduced push-off intensity via greater energy loss from distal foot structures, particularly during walking tasks with a greater demand for foot power generation. These findings are the first step in understanding the role of the foot in push-off power deficits in older adults and may serve as a roadmap for developing future low-cost mobility interventions.

Neuromechanics and Energetics of Walking With an Ankle Exoskeleton Using Neuromuscular-Model Based Control: A Parameter Study.

Powered ankle exoskeletons that apply assistive torques with optimized timing and magnitude can reduce metabolic cost by ∼10% compared to normal walking. However, finding individualized optimal control parameters is time consuming and must be done independently for different walking modes (e.g., speeds, slopes). Thus, there is a need for exoskeleton controllers that are capable of continuously adapting torque assistance in concert with changing locomotor demands. One option is to use a biologically inspired, model-based control scheme that can capture the adaptive behavior of the human plantarflexors during natural gait. Here, based on previously demonstrated success in a powered ankle-foot prosthesis, we developed an ankle exoskeleton controller that uses a neuromuscular model (NMM) comprised of a Hill type musculotendon driven by a simple positive force feedback reflex loop. To examine the effects of NMM reflex parameter settings on (i) ankle exoskeleton mechanical performance and (ii) users’ physiological response, we recruited nine healthy, young adults to walk on a treadmill at a fixed speed of 1.25 m/s while donning bilateral tethered robotic ankle exoskeletons. To quantify exoskeleton mechanics, we measured exoskeleton torque and power output across a range of NMM controller Gain (0.8–2.0) and Delay (10–40 ms) settings, as well as a High Gain/High Delay (2.0/40 ms) combination. To quantify users’ physiological response, we compared joint kinematics and kinetics, ankle muscle electromyography and metabolic rate between powered and unpowered/zero-torque conditions. Increasing NMM controller reflex Gain caused increases in average ankle exoskeleton torque and net power output, while increasing NMM controller reflex Delay caused a decrease in net ankle exoskeleton power output. Despite systematic reduction in users’ average biological ankle moment with exoskeleton mechanical assistance, we found no NMM controller Gain or Delay settings that yielded changes in metabolic rate. Post hoc analyses revealed weak association at best between exoskeleton and biological mechanics and changes in users’ metabolic rate. Instead, changes in users’ summed ankle joint muscle activity with powered assistance correlated with changes in their metabolic energy use, highlighting the potential to utilize muscle electromyography as a target for on-line optimization in next generation adaptive exoskeleton controllers.

Wing Shape in Waterbirds: Morphometric Patterns Associated with Behavior, Habitat, Migration, and Phylogenetic Convergence.

Wing shape plays a critical role in flight function in birds and other powered fliers and has been shown to be correlated with flight performance, migratory distance, and the biomechanics of generating lift during flight. Avian wing shape and flight mechanics have also been shown to be associated with general foraging behavior and habitat choice. We aim to determine if wing shape in waterbirds, a functionally and ecologically diverse assemblage united by their coastal and aquatic habitats, is correlated with various functional and ecological traits. We applied geometric morphometric approaches to the spread wings of a selection of waterbirds to search for evolutionary patterns between wing shape and foraging behavior, habitat, and migratory patterns. We found strong evidence of convergent evolution of high and low aspect ratio wing shapes in multiple clades. Foraging behavior also consistently exhibits strong evolutionary correlations with wing shape. Habitat, migration, and flight style, in contrast, do not exhibit significant correlation with wing shape in waterbirds. Although wing shape is critical to aerial flight function, its relationship to habitat and periodic locomotor demands such as migration is complex.

Spectral Power in Marmoset Frontal Motor Cortex during Natural Locomotor Behavior.

During primate arboreal locomotion, substrate orientation modifies body axis orientation and biomechanical contribution of fore- and hindlimbs. To characterize the role of cortical oscillations in integrating these locomotor demands, we recorded electrocorticographic activity from left dorsal premotor, primary motor, and supplementary motor cortices of three common marmosets moving across a branch-like small-diameter pole, fixed horizontally or vertically. Animals displayed behavioral adjustments to the task, namely, the horizontal condition mainly induced quadrupedal walk with pronated/neutral forelimb postures, whereas the vertical condition induced walk and bound gaits with supinated/neutral postures. Examination of cortical activity suggests that β (16–35 Hz) and γ (75–100 Hz) oscillations could reflect different processes in locomotor adjustments. During task, modulation of γ ERS by substrate orientation (horizontal/vertical) and epoch (preparation/execution) suggests close tuning to movement dynamics and biomechanical demands. β ERD was essentially modulated by gait (walk/bound), which could illustrate contribution to movement sequence and coordination. At rest, modulation of β power by substrate orientation underlines its role in sensorimotor processes for postural maintenance.

Monitoring muscle over three orders of magnitude: Widespread positive allometry among locomotor and body support musculature in the pectoral girdle of varanid lizards (Varanidae).

There is a functional trade-off in the design of skeletal muscle. Muscle strength depends on the number of muscle fibers in parallel, while shortening velocity and operational distance depend on fascicle length, leading to a trade-off between the maximum force a muscle can produce and its ability to change length and contract rapidly. This trade-off becomes even more pronounced as animals increase in size because muscle strength scales with area (length2 ) while body mass scales with volume (length3 ). In order to understand this muscle trade-off and how animals deal with the biomechanical consequences of size, we investigated muscle properties in the pectoral girdle of varanid lizards. Varanids are an ideal group to study the scaling of muscle properties because they retain similar body proportions and posture across five orders of magnitude in body mass and are highly active, terrestrially adapted reptiles. We measured muscle mass, physiological cross-sectional area, fascicle length, proximal and distal tendon lengths, and proximal and distal moment arms for 27 pectoral girdle muscles in 13 individuals across 8 species ranging from 64g to 40kg. Standard and phylogenetically informed reduced major axis regression was used to investigate how muscle architecture properties scale with body size. Allometric growth was widespread for muscle mass (scaling exponent >1), physiological cross-sectional area (scaling exponent >0.66), but not tendon length (scaling exponent >0.33). Positive allometry for muscle mass was universal among muscles responsible for translating the trunk forward and flexing the elbow, and nearly universal among humeral protractors and wrist flexors. Positive allometry for PCSA was also common among trunk translators and humeral protractors, though less so than muscle mass. Positive scaling for fascicle length was not widespread, but common among humeral protractors. A higher proportion of pectoral girdle muscles scaled with positive allometry than our previous work showed for the pelvic girdle, suggesting that the center of mass may move cranially with body size in varanids, or that the pectoral girdle may assume a more dominant role in locomotion in larger species. Scaling exponents for physiological cross-sectional area among muscles primarily associated with propulsion or with a dual role were generally higher than those associated primarily with support against gravity, suggesting that locomotor demands have at least an equal influence on muscle architecture as body support. Overall, these results suggest that larger varanids compensate for the increased biomechanical demands of locomotion and body support at higher body sizes by developing larger pectoral muscles with higher physiological cross-sectional areas. The isometric scaling rates for fascicle length among locomotion-oriented pectoral girdle muscles suggest that larger varanids may be forced to use shorter stride lengths, but this problem may be circumvented by increases in limb excursion afforded by the sliding coracosternal joint.

Evolutionary Potential and Morphological Integration of the Shoulder Girdle Among Primates

The morphology of the shoulder girdle is highly varied among primates, possibly reflecting an array of functional demands placed through the range of locomotor and behavioral movements exercised in the upper limb. Variation in the shoulder girdle, and especially the scapula, is hypothesized to be the result of directional selection for different functional demands. Evolutionary analyses of the shoulder girdle often assess this anatomical region and its traits individually, which implicitly models the evolution of the girdle as independent of other traits. However, the primate shoulder girdle has developmental and functional covariances with the basicranium, pelvis, humerus, and vertebral column that we have recently demonstrated have potential to influence its evolution through correlated responses to directional selection. Whether these relationships are similar across primate taxa and how these relationships may affect morphological variation among primates is unknown.Here we evaluate the strength of the covariance and evolutionary potential among four anatomical regions: shoulder girdle, basicranium, pelvis, and humerus. We obtained cranial and postcranial linear dimensions from Alouatta, Colobus, Homo, Hylobates, and Papio. Measurements were mean standardized prior to analysis. We estimated morphological integration using Wagner's variance of the eigenvalues (VE), and estimated evolutionary potential using Hansen and Houle's evolutionary flexibility (EF) with 1000 simulated random selection gradients. EF captures how closely the evolutionary response in a group of traits follows the direction of the selection. We evaluated differences in VE and EF among taxa by performing a pairwise comparison of the bootstrapped values for each. Analyses were performed using the R statistical environment.Our results show that patterns of morphological integration and evolutionary flexibility among anatomical regions differ across primate taxa, with humans having the greatest evolutionary potential and Papio the lowest. Broadly, the patterns revealed among taxa do not strictly correspond to the functional demands of the upper limb experienced by each; taxa with different locomotor demands on the upper limb have the same kinds of covariance or evolutionary flexibility. Thus, evolutionary hypotheses of primate shoulder girdle morphological variation that evaluate functional demands alone may not account for the effect of these relationships. We conclude that different trait covariances among anatomical regions may manifest as morphological differences in the primate shoulder girdle, which has important implications for models of shoulder evolution.Support or Funding InformationThis research is supported by a National Science Foundation Doctoral Dissertation Improvement Grant (NSF BCS‐1825995).

Application of Individualized Speed Zones to Quantify External Training Load in Professional Soccer.

This study aimed to examine the interchangeability of two external training load (ETL) monitoring methods: arbitrary vs. individualized speed zones. Thirteen male outfield players from a professional soccer team were monitored during training sessions using 10-Hz GPS units over an 8-week competitive period (n = 302 observations). Low-speed activities (LSA), moderate-speed running (MSR), high-speed running (HSR) and sprinting were defined using arbitrary speed zones as <14.4, 14.4–19.8, 19.8–25.1 and ≥25.2 km·h-1, and using individualized speed zones based on a combination of maximal aerobic speed (MAS, derived from the Yo-yo Intermittent recovery test level 1), maximal sprinting speed (MSS, derived from the maximal speed reached during training) and anaerobic speed reserve (ASR) as <80% MAS, 80–100% MAS, 100% MAS or 29% ASR and ≥30% ASR. Distance covered in both arbitrary and individualized methods was almost certainly correlated in all speed zones (p < 0.01; r = 0.67-0.78). However, significant differences between methods were observed in all speed zones (p < 0.01). LSA was almost certainly higher when using the arbitrary method than when using the individualized method (p < 0.01; ES = 5.47 [5.18; 5.76], respectively). Conversely, MSR, HSR and sprinting speed were higher in the individualized method than in the arbitrary method (p < 0.01; ES = 5.10 [4.82; 5.37], 0.86 [0.72; 1.00] and 1.22 [1.08; 1.37], respectively). Arbitrary and individualized methods for ETL quantification based on speed zones showed similar sensitivity in depicting player locomotor demands. However, since these methods significantly differ at absolute level (based on measurement bias), arbitrary and individualized speed zones should not be used interchangeably.

Habitat transitions alter the adaptive landscape and shape phenotypic evolution in needlefishes (Belonidae).

Habitat occupancy can have a profound influence on macroevolutionary dynamics, and a switch in major habitat type may alter the evolutionary trajectory of a lineage. In this study, we investigate how evolutionary transitions between marine and freshwater habitats affect macroevolutionary adaptive landscapes, using needlefishes (Belonidae) as a model system. We examined the evolution of body shape and size in marine and freshwater needlefishes and tested for phenotypic change in response to transitions between habitats. Using micro‐computed tomographic (µCT) scanning and geometric morphometrics, we quantified body shape, size, and vertebral counts of 31 belonid species. We then examined the pattern and tempo of body shape and size evolution using phylogenetic comparative methods. Our results show that transitions from marine to freshwater habitats have altered the adaptive landscape for needlefishes and expanded morphospace relative to marine taxa. We provide further evidence that freshwater taxa attain reduced sizes either through dwarfism (as inferred from axial skeletal reduction) or through developmental truncation (as inferred from axial skeletal loss). We propose that transitions to freshwater habitats produce morphological novelty in response to novel prey resources and changes in locomotor demands. We find that repeated invasions of different habitats have prompted predictable changes in morphology.

Does the size and developmental stage of traits at fledging reflect juvenile flight ability among songbirds?

Abstract Morphological traits can influence the ability of animals to perform ecologically relevant tasks that are essential for their growth, survival and fitness. Understanding such links in juvenile animals is of particular importance, as periods of juvenile life are often associated with high rates of mortality and can be critical with respect to evolution of life histories and viability of populations. To study such links, an important first step is to assess relationships between juvenile morphologies and measures of performance. Altricial songbirds can provide novel insights into morphology–performance relationships owing to the high locomotor demand placed on juveniles after they leave the nest. Therefore, we examined the relationships between the size and developmental stage of juvenile traits and juvenile flight ability among 13 coexisting songbirds in east‐central Illinois. Among potential traits, we focused on relationships between flight ability and four measures of wing development at fledging as well as two body measures thought to reflect an individual's overall quality and musculature. Among measures of wing development, wing emergence was the strongest, most consistent predictor of ability within and among species. Relative wing length and wing emergence‐loading were often good predictors of flight ability as well, while relative wing‐loading was rarely a good predictor. Estimates of body mass and body condition were poor, inconsistent predictors of flight ability both within and among species. Our results highlight the importance of wing development for flight performance of juvenile songbirds. Furthermore, our evaluation of different wing characteristics suggests that the importance of macro‐scale transmissivity and wing/disc loading towards flight ability changes with respect to juvenile ontogeny. Though mass likely interacts with wing characteristics in determining flight ability, our results suggest that body mass and condition are likely reflective of other, non‐flight measures of fledgling performance. Few studies on altricial songbirds have examined morphology–performance relationships in juveniles. By linking wing emergence with juvenile flight ability, our research has taken a first step in assessing the adaptive significance of variation in wing development for juvenile songbirds. A free Plain Language Summary can be found within the Supporting Information of this article.

A comparison of rolling averages versus discrete time epochs for assessing the worst-case scenario locomotor demands of professional soccer match-play

ObjectivesTo compare fixed epochs (FIXED) and rolling averages (ROLL) for quantifying worst-case scenario (‘peak’) running demands during professional soccer match-play, whilst assessing contextual influences. DesignDescriptive, observational. MethodsTwenty-five outfield players from an English Championship soccer club wore 10-Hz microelectromechanical systems during 28 matches. Relative total and high-speed (>5.5ms−1) distances were averaged over fixed and rolling 60-s to 600-s epochs. Linear mixed models compared FIXED versus ROLL and assessed the influence of epoch length, playing position, starting status, match result, location, formation, and time-of-day. ResultsIrrespective of playing position or epoch duration, FIXED underestimated ROLL for total (∼7–10%) and high-speed (∼12–25%) distance. In ROLL, worst-case scenario relative total and high-speed distances reduced from 190.1±20.4mmin−1 and 59.5±23.0mmin−1 in the 60-s epoch, to 120.9±13.1mmin−1 and 14.2±6.5mmin−1 in the 600-s epoch, respectively. Worst-case scenario total distance was higher for midfielders (∼9−16mmin−1) and defenders (∼3–10mmin−1) compared with attackers. In general, starters experienced higher worst-case scenario total distance than substitutes (∼3.6–8.5mmin−1), but lower worst-case scenario high-speed running over 300-s (∼3mmin−1). Greater worst-case scenario total and high-speed distances were elicited during wins (∼7.3–11.2mmin−1 and ∼2.7–7.9mmin−1, respectively) and losses (∼2.7–5.7mmin−1 and ∼1.4–2.2mmin−1, respectively) versus draws, whilst time-of-day and playing formation influenced worst-case scenario high-speed distances only. ConclusionsThese data indicate an underestimation of worst-case scenario running demands in FIXED versus ROLL over 60-s to 600-s epochs while highlighting situational influences. Such information facilitates training specificity by enabling sessions to be targeted at the most demanding periods of competition.

Assessing the whole-match and worst-case scenario locomotor demands of international women’s rugby union match-play

ObjectivesTo profile the distances covered during international women’s rugby union match-play and assess the duration-specific worst-case scenario locomotor demands over 60-s to 600-s epochs, whilst comparing the values determined by fixed epoch (FIXED) versus rolling average (ROLL) methods of worst-case scenario estimation and assessing positional influences. DesignDescriptive, observational. MethodsTwenty-nine international women’s rugby union players wore 10Hz microelectromechanical systems during eight international matches (110 observations). Total, and per-half, distances were recorded, whilst relative total and high-speed (>4.4ms−1) distances were averaged using FIXED and ROLL methods over 60–600-s. Linear mixed models compared distances covered between match halves, assessed FIXED versus ROLL, and examined the influence of playing position. ResultsPlayers covered ∼5.8kmmatch−1, with reduced distances in the second- versus first-half (p<0.001). For worst-case scenario total (∼8–25%) and high-speed (∼10–26%) distance, FIXED underestimated ROLL. In ROLL, worst-case scenario relative total and high-speed distances reduced from ∼144−161mmin−1 and ∼30−69mmin−1 over 60-s, to ∼8089mmin−1 and ∼516mmin−1 in the 600-s epoch, respectively. Forwards performed less high-speed running over all epochs and covered less total distance during epochs of 60-s, 180-s, 420-s and 480-s, compared with backs. Front row players typically returned the lowest locomotor demands. ConclusionsThis is the first study reporting the positional and worst-case scenario demands of international women’s rugby union, and indicates an underestimation in FIXED versus ROLL over 60-s to 600-s epochs. Knowledge of the most demanding periods of women’s rugby union match-play facilitates training specificity by enabling sessions to be tailored to such demands.

Community-dwelling older adults with mild cognitive impairments show subtle visual attention costs when descending stairs

BackgroundOlder adults are at greater risk of falls while descending stairs. Cognitive deficits can further influence one's ability and mild cognitive impairments (MCI) specifically affect visual attention and dual tasking behavior. The present study aimed at comparing the attentional costs at different points during the approach to and descent of a staircase between older adults with and without MCI. MethodsEleven older adults with MCI and twenty-three healthy older individuals without cognitive impairments were recruited. Neuropsychological tests were carried out. In addition, participants approached and descended a 5-step staircase while a simultaneous visual Stroop dual-task was randomly introduced during the approach, transition or steady state descent phases across trials. Three-dimensional kinematics and accuracy on the Stroop task were analyzed and dual task costs were calculated. ResultsThe MCI group showed deficits for visuo-spatial attention, memory and multi-tasking abilities, as well as balance and decreased confidence for falls efficacy, but not for daily activity scores. Despite such changes, this group of community-dwelling individuals with MCI presented a functional capacity to descend stairs even during divided visual attention. However, there were subtle, but significant, group differences for movement fluidity and performance on the simultaneous cognitive task, particularly during the approach and transition to descent phases. The MCI group also tended to descend slower while using the handrails more than healthy older adults. ConclusionThe present cohort of community-dwelling older adults with MCI were functional, but appeared to prioritize locomotor demands over the simultaneous cognitive task in a possible “posture first” strategy to descend stairs. The present findings should be considered for developing more ecologically based clinical assessments of mobility deficits following cognitive impairments, with the approach and transition phases during stair descent as key points of focus.

Effect of locomotor demands on cognitive processing

Understanding how brain dynamics change with dual cognitive and motor tasks can improve our knowledge of human neurophysiology. The primary goals of this study were to: (1) assess the feasibility of extracting electrocortical signals from scalp EEG while performing sustained, physically demanding dual-task walking and (2) test hypotheses about how the P300 event-related potential is affected by walking physical exertion. Participants walked on a treadmill for an hour either carrying an empty rucksack or one filled with 40% of their body weight. During the walking conditions and during a seated control condition, subjects periodically performed a visual oddball task. We recorded scalp EEG and examined electrocortical dynamics time-locked to the target stimulus. Channel-level event-related potential analysis demonstrated that it is feasible to extract reliable signals during long duration loaded walking. P300 amplitude was reduced during loaded walking versus seated, but there was no effect of time on task. Source level activity and frequency analysis revealed that sensorimotor, parietal, and cingulate brain areas all contributed to the reduced P300 amplitude during dual-task walking. We interpret the results as supporting a prioritization of cortical resources for walking, leading to fewer resources being directed toward the oddball task during dual-task locomotion.

Lower extremity joints and muscle groups in the human locomotor system alter mechanical functions to meet task demand.

To facilitate movement through mechanically complex environments, terrestrial animals have evolved locomotor systems capable of flexibly altering internal mechanics to meet external demands. They do this by shifting imposed workloads between joints/muscle groups (central mechanical flexibility) and/or by altering the function of individual joints/muscle groups (local mechanical flexibility). In human locomotion research, central mechanical flexibility is well established and regularly reported. Local mechanical flexibility at major lower extremity joints and muscle groups, however, has received relatively less attention. We used an emerging biomechanical analysis known as functional indexing to test the hypothesis that lower extremity joints and muscle groups within the human locomotor system alter their mechanical function to meet altered locomotor demands. Thirteen healthy adults walked across a range of speeds (0.8, 1.2, 1.6, 2.0 m s-1) and slopes (0deg, +5deg, +10deg) to determine whether hip, knee and ankle joints and their extensors and flexors altered their mechanical function in response to increased speed and slope. As walking speed increased, the knee and its extensors altered their function to behave more like mechanical springs while the ankle and its extensors altered their function to behave more like motors. As slope increased, all three joints and their extensors decreased spring- and damper-like behavior and increased motor-like behavior. Our results indicate that humans - similarly to many other terrestrial animals - utilize local mechanical flexibility to meet the demands of the locomotor task at hand.

Functional and developmental influences on intraspecific variation in catarrhine vertebrae

We tested whether patterns of intraspecific variation in catarrhine vertebral shape are consistent with developmental or functional predictions. Intraspecific variation was compared across column regions, morphological features, and species. Transitional regions and later ossifying morphological features were predicted to exhibit increased variation. The lumbosacral region, biomechanically important morphological features, and species with high locomotor demand and/or dedicated pronogrady were predicted to exhibit decreased variation. We used a modified Levene's test to compare intraspecific variation in dimensions of the neural canal, vertebral bodies, and spinous and transverse processes in lower thoracic to proximal sacral vertebrae. The sample included all hominoid genera and one cercopithecoid (Chlorocebus). We found little difference in variation across regions of the vertebral column. In hominoids, vertebral body dimensions were the least variable, neural canal dimensions the most variable, with spinous and transverse processes generally intermediate. Among species, there was a general though not always significant pattern for Chlorocebus to exhibit the least variation, followed by Homo or Hylobates. Patterns of variation across morphological features may reflect the complex interaction of functional constraints, developmental timing, and/or variable biomechanical forces. Pongo's elevated variation in spinous process length suggests a release from functional constraint, consistent with its suspensory locomotion and reduced spinous processes. Interspecific differences in vertebral variation based on locomotor demand or posture are generally consistent with patterns previously reported for vertebral formula and other aspects of morphology. Future research would benefit from an expanded taxonomic sample and more detailed analyses of vertebral modularity and developmental timing.

Intraspecific variation in semicircular canal morphology—A missing element in adaptive scenarios?

Recent evidence suggests that the amount of intraspecific variation in semicircular canal morphology may, itself, be evidence for varying levels of selection related to locomotor demands. To determine the extent of this phenomenon across taxa, we expand upon previous work by examining intraspecific variation in canal radii and canal orthogonality in a broad sample of strepsirrhine and platyrrhine primates. Patterns of interspecific variation are re-examined in light of intraspecific variation to better understand the resolution at which locomotion can be reconstructed from single individuals. Data was collected from high-resolution CT scans of 14 size-matched, related species. Six of these taxa have existing data on rotational head speeds. The level of intraspecific variation was found to differ in strepsirrhine and in platyrrhine species pairs, with larger ranges of variation generally observed for the slower moving taxon than the faster moving one. Taxa that are classified as relatively agile can to some extent be separated from those who are slower-moving, but only when comparing similarly sized, closely related species with more extreme forms of locomotion. Our findings agree with previous research showing that canal intraspecific variation can fluctuate according to species-specific locomotor behavior and extends this further by identifying behaviors that may be under unusual selective pressure. It also demonstrates the complexity of interpreting inner ear morphology in the context of broadly applicable locomotor "categories" of the kind commonly used in behavioral studies. We suspect that simplified models predicting vestibular sensitivity may be unable to differentiate behaviors when only a single specimen is available.

The peak duration-specific locomotor demands and concurrent collision frequencies of European Super League rugby

ABSTRACTUnderstanding the most demanding passages of European Super League competition can optimise training prescription. We established positional and match half differences in peak relative distances (m·min−1) across durations, and the number of collisions, high-speed- and very-high-speed-distance completed in the peak 10 min period. Moving-averages (10 s, 30 s, 1 min, 5 min, 10 min) of instantaneous speed (m·s−1) were calculated from 25 professional rugby league players during 25 matches via microtechnology. Maximal m·min−1 was taken for each duration for each half. Concurrently, collisions (n), high-speed- (5 to 7 m·s−1; m) and very-high-speed-distance (> 7 m·s−1; m) were coded during each peak 10 min. Mixed-effects models determined differences between positions and halves. Aside from peak 10 s, trivial differences were observed in peak m·min−1 between positions or halves across durations. During peak 10 min periods, adjustables, full- and outside-backs ran more at high-speed and very-high-speed whilst middle- and edge-forwards completed more collisions. Peak m·min−1 is similar between positional groups across a range of durations and are maintained between halves of the match. Practitioners should consider that whilst the overall peak locomotor “intensity” is similar, how they achieve this differs between positions with forwards also exposed to additional collision bouts.

Post-stroke unilateral spatial neglect: virtual reality-based navigation and detection tasks reveal lateralized and non-lateralized deficits in tasks of varying perceptual and cognitive demands

BackgroundUnilateral spatial neglect (USN), a highly prevalent and disabling post-stroke impairment, has been shown to affect the recovery of locomotor and navigation skills needed for community mobility. We recently found that USN alters goal-directed locomotion in conditions of different cognitive/perceptual demands. However, sensorimotor post-stroke dysfunction (e.g. decreased walking speed) could have influenced the results.Analogous to a previously used goal-directed locomotor paradigm, a seated, joystick-driven navigation experiment, minimizing locomotor demands, was employed in individuals with and without post-stroke USN (USN+ and USN-, respectively) and healthy controls (HC).MethodsParticipants (n = 15 per group) performed a seated, joystick-driven navigation and detection time task to targets 7 m away at 0°, ±15°/30° in actual (visually-guided), remembered (memory-guided) and shifting (visually-guided with representational updating component) conditions while immersed in a 3D virtual reality environment.ResultsGreater end-point mediolateral errors to left-sided targets (remembered and shifting conditions) and overall lengthier onsets in reorientation strategy (shifting condition) were found for USN+ vs. USN- and vs. HC (p < 0.05). USN+ individuals mostly overshot left targets (− 15°/− 30°). Greater delays in detection time for target locations across the visual spectrum (left, middle and right) were found in USN+ vs. USN- and HC groups (p < 0.05).ConclusionUSN-related attentional-perceptual deficits alter navigation abilities in memory-guided and shifting conditions, independently of post-stroke locomotor deficits. Lateralized and non-lateralized deficits in object detection are found. The employed paradigm could be considered in the design and development of sensitive and functional assessment methods for neglect; thereby addressing the drawbacks of currently used traditional paper-and-pencil tools.

Prenatal kynurenine treatment in rats causes schizophrenia-like broad monitoring deficits in adulthood.

Elevated brain kynurenic acid (KYNA) levels are implicated in the pathology and neurodevelopmental pathogenesis of schizophrenia. In rats, embryonic treatment with kynurenine (EKyn) causes elevated brain KYNA levels in adulthood and cognitive deficits reminiscent of schizophrenia. Growing evidence suggests that people with schizophrenia have a narrowed attentional focus, and we aimed at establishing whether these abnormalities may be related to KYNA dysregulation. To test whether EKyn rats display broad monitoring deficits, kynurenine was added to the chow of pregnant Wistar dams on embryonic days 15-22. As adults, 20 EKyn and 20 control rats were trained to stable performance on the five-choice serial reaction time task, requiring the localization of 1-s light stimuli presented randomly across five apertures horizontally arranged along a curved wall, equating the locomotor demands of reaching each hole. EKyn rats displayed elevated omission errors and reduced anticipatory responses relative to control rats, indicative of a lower response rate, and showed reduced locomotor activity. The ability to spread attention broadly was measured by parsing performance by stimulus location. Both groups displayed poorer stimulus detection with greater target location eccentricity, but this effect was significantly more pronounced in the EKyn group. Specifically, the groups differed in the spatial distribution of correct but not incorrect responses. This pattern cannot be explained by differences in response rate and is indicative of a narrowed attentional focus. The findings suggest a potential etiology of broad monitoring deficits in schizophrenia, which may constitute a core cognitive deficit.