Table 1 - uploaded by David Carrier
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The rotational inertia of an animal can be expected to influence directly its ability to execute rapid turning maneuvers. We hypothesized that a ninefold increase in rotational inertia would reduce maximum turning performance to one-ninth of control values. To test this prediction, we increased rotational inertia about the vertical axis of six huma...
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Context 1
... measured the rotational inertia about a vertical axis in erect, standing subjects (Table 1). This posture closely approximates the posture at the end of take-off and during the flight phase of a jump turn. ...
Context 2
... posture closely approximates the posture at the end of take-off and during the flight phase of a jump turn. Hence, the standing values reported in Table 1 were similar to rotational inertia at the end of take- off and during the flight phase of a jump turn. The mean rotational inertia of the unencumbered subjects was 1.12 kg m 2 . ...
Context 3
... inertia was also measured in a crouched posture resembling that of jump initiation. Mean values were 2.23 kg m 2 and 3.19 kg m 2 for unencumbered and weight- controlled stepping turns, respectively (Table 1). Hence, crouching approximately doubled standing values of rotational inertia for these two conditions. ...
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... recordings of the ground reaction torque (A) and angular power (B) applied during maximum-effort jump turns by subject 'B'. The thick lines denote the recording obtained when the subject turned with his rotational inertia elevated 9.7-fold (Table 1) above that of the weight-controlled jump (shown by the thin line). Note that subject B did more angular work (i.e. ...
Citations
... First, there is an inverse relationship between medial and lateral stability-increasing the MOS in one direction will reduce stability in the other [12,23]. Second, gait patterns that increase stability in one direction will impede manoeuvrability in that same direction by passively resisting any self-imposed forces intended to redirect one's trajectory [8] and ultimately require larger impulses to overcome the body's resistance to movements [13,24,25]. This resistance may increase the time required to perform an effective manoeuvre towards the BOS. ...
People use the mechanical interplay between stability and manoeuvrability to successfully walk. During single-limb support, body states (position and velocity) that increase in lateral stability will inherently resist lateral manoeuvres, decrease medial stability and facilitate medial manoeuvres. Although not well understood, people can make behavioural decisions exploiting this relationship in anticipation of perturbations or direction changes. To characterize the behavioural component of the stability–manoeuvrability relationship, 24 participants performed many repetitions of a discrete stepping task involving mid-trial reactive manoeuvres (medial or lateral direction) in a Baseline (no external perturbations) and Perturbed (random mediolateral perturbations applied to their pelvis) environment. We hypothesized people would make systematic changes in lateral stability dependent on both environment (increasing lateral stability in the Perturbed environment) and anticipated manoeuvre direction (reducing lateral stability to facilitate lateral manoeuvres). Participants increased lateral stability in the Perturbed environment, coinciding with an increase in manoeuvre reaction time for laterally but not medially directed manoeuvres. Moreover, we observed lower lateral stability in both environments when people anticipated making a lateral manoeuvre when compared to medial manoeuvres. These results support the hypothesis that people behaviourally exploit the mechanical relationship between lateral stability and manoeuvrability depending on walk task goals and external environment.
... Our findings suggest that is difficult for younger schoolchildren to incorporate these different and complex motor coordination movements. Another important reason for unstable performance in the jump with max-effort rotation test over time is the increasing body weight of children, because it has been shown that body weight (size) is negatively associated with performance in this task (Lee et al., 2001). These are two main reasons, in our opinion, why this test is not frequently used in the battery of basic motor skill tests intended for primary-school-aged children (Scheuer et al., 2019). ...
Background: Primary school plays a pivotal role in shaping children's motor skill competence. Recognising this critical developmental phase, our study aimed to assess the impact of a two-year after-school physical activity intervention on fundamental motor skills among young primary school children. Methods: A cohort of twenty healthy children (10 boys, 10 girls) aged 6-7 years formed a baseline engaged in IAAF Kids' Athletics training, comprising two weekly one-hour sessions. Concurrently, a control group of twenty peers (10 boys, 10 girls) adhered to conventional practices. The assessment involved measuring jumping with max-effort rotation, sit and reach test, standing long jump, ball throwing, 4 × 10 m shuttle run, and 20 m endurance running tasks at half-year intervals throughout the two-year intervention period. Data analysis employed two-way ANOVA with repeated measurements. Results: At baseline, intervention students demonstrated superior performance (p < 0.01-0.001) in the standing long jump, ball throwing, and shuttle and endurance runs compared to control subjects. After the two-year intervention, girls in the physical activity group exhibited a positive impact (p < 0.05-0.001) on three out of six motor skills-specifically, the standing long jump, ball throwing, and endurance run-compared to their counterparts in the control group. Conversely, no statistically significant improvements were observed in any motor skills for boys in the intervention group. Conclusions: Our findings suggest that a sustained, long-term physical activity intervention can significantly enhance fundamental motor skills in girls, while no such conclusive improvements were observed in boys. Potential factors contributing to these gender-related differences are discussed.
... No reuse allowed without permission. impulses are required to overcome the body's resistance to lateral movements (16,17). This resistance 92 may increase the time required to initiate a manoeuvre. ...
The interplay between stability and manoeuvrability is fundamental for human walking. Previous research finds conflicting perspectives on how these attributes interact - mechanisms for stable walking can either facilitate or impede manoeuvrability. We postulate that these views can be explained by considering manoeuvre direction. We hypothesize that adopting gait patterns that increase lateral stability will impede laterally-directed manoeuvres but not medially-directed manoeuvres due to body positioning strategies that resist lateral movements but aid in the ability to actively generate medially-directed external moments. Twenty-four participants performed many repetitions of a discrete stepping task involving mid-trial reactive manoeuvres in both a Baseline (no external perturbations) and Complex (random perturbations applied to their pelvis) environment. We found that in the Complex environment all participants increased their lateral margin of stability when compared to the Baseline environment. This resulted in an increase in manoeuvre reaction time and foot placement error for laterally-directed manoeuvres but not for medially-directed manoeuvres in the Complex environment when compared to the Baseline environment. These results support our hypothesis and provide the novel interpretation that the stability-manoeuvrability trade-off during human walking depends on manoeuvre direction.
... The concept of rotational inertia is often introduced in high school science courses such as physics, but can be difficult for students to fully understand and connect to meaningful real-world examples. Our activity was inspired by the work of Carrier et al. (4,10) on how body shape and size influence turning performance in humans and animals, including therapod dinosaurs. ...
... The answer is complex, but time spent turning represents only part of the time needed to complete the slalom course. Additionally, slowing down turning by increasing rotational inertia causes the muscles associated with turning to shorten more slowly and produce greater forces, which partially compensates for the effect of the added inertia (10). The calculation of rotational inertia emphasizes the importance of r 2 and introduces the concept of integration. ...
Developing hands-on activities that engage and excite K-12 students is critical for stimulating interest in science-based careers. We created an activity for high school students that required them to integrate biology and physics concepts to experience how humans and animals maneuver through their environments (i.e., turning). Understanding how turning works is important because it accounts for up to 50% of daily walking steps and is needed for survival when animals elude predators and capture prey. For this activity, student groups used 2 × 4 lumber, wood screws, and a power drill to build an apparatus that, when connected to the body, altered rotational inertia (object's resistance to change in angular motion, I = mass × radius2). Students navigated through a slalom course with the apparatus (increased radius and rotational inertia) and without the apparatus (mass-matched control). Times to complete the course were compared between trials to determine the influence of rotational inertia on turning performance. Students compiled their data, graphed their results, and found that increased rotational inertia decreased turning performance. Results were connected to sports, rehabilitation, and dinosaur evolution. This activity was implemented during local, regional, national, and international outreach events and adapted for use in undergraduate courses as well (total impact, 250 students). At the end of the activity, students were able to 1) describe whether their results supported their hypothesis; 2) explain how radius influences rotational inertia and turning performance; and 3) apply results to real-world examples. Students and teachers appreciated this "outside-the-box" activity with an engineering twist and found it entertaining.
... Hatchling turtles were ~25 g, juveniles were more than an order of magnitude heavier (~300 g), and adults weighed twice as much as juveniles (~600 g). These differences in mass probably had profound impacts on the hydrodynamic performance of the different age classes, because objects with smaller mass have decreased rotational inertia than larger objects, facilitating faster turns (Lee et al., 2001;Vogel, 2013). The small mass of hatchling and juvenile turtles relative to adults would result in perturbations arising from limb movements having a greater impact on smaller individuals than larger individuals, thereby increasing the ability of hatchlings and juveniles to perform unsteady behaviours, such as intentional turning. ...
... Although the selective pressures driving differences in shape throughout turtle ontogeny are unclear, there are several functional consequences of possessing a round shell. The rotational inertia of an animal is impacted both by mass, as discussed above, and by the distance of a propulsor from the axis of rotation (Lee et al., 2001). Thus, body shape can have a profound impact on turning performance, with rounder objects, such as hatchling turtles, having decreased rotational inertia (and increased turning performance) than more oblong shapes, such as adult turtles. ...
... Thus, differences in morphology might drive differences in swimming stability through ontogeny. The oblong shells of adult turtles are likely to resist destabilizing forces passively during linear swimming by increasing rotational inertia (Webb, 1984;Walker, 2000;Lee et al., 2001), and the greater similarity in propulsive areas of the fore-and hindlimbs (Fig. 2B) might help to limit differences in anterior and posterior thrust that could contribute to extraneous lateral movements of the body during aquatic propulsion. Furthermore, the larger mass of adult turtles should passively increase their stability by increasing the force required to perturb them and decrease their turning performance by increasing their moment of inertia (Lee et al., 2001). ...
Hydrodynamic stability and the ability to turn are two important components of swimming performance in aquatic animals. Stability reduces the energetic costs of swimming, and turning performance facilitates both prey capture and predator avoidance. These components of locomotor performance are typically measured in adults, but juveniles also experience high demands on locomotor performance. To test how stability and turning performance change through ontogeny, we measured the swimming kinematics and performance of hatchling, juvenile and adult pink-bellied sideneck turtles (Emydura subglobosa) as they followed a prey stimulus, and compared these performance metrics in the context of morphometric differences across age classes. We found that in E. subglobosa, adults had the highest stability and lowest turning performance. Younger, smaller turtles are likely to be more susceptible to destabilizing forces and have rounder body shapes than adults, which might enhance turning performance. In contrast , the larger size and more extensive webbing of the limbs of adults might facilitate greater stability. These differences in performance and morphology might reflect common ontogenetic changes in the ecology of aquatic turtles. Hatchlings might benefit from enhanced turning performance to escape predators, whereas the larger size of adults makes them less susceptible to predators that could consume hatchlings whole.
... Alternatively, humans are also amenable to manipulative studies, and could be subject to experiments where the COM location is altered in a controlled manner (cf. [123][124][125]). If a systematic relationship was found between force-time profile asymmetry and COM location, then an adjustment could be made to the model to facilitate its application to extinct non-avian theropods, once their COM location was estimated. ...
How extinct, non-avian theropod dinosaurs moved is a subject of considerable interest and controversy. A better understanding of non-avian theropod locomotion can be achieved by better understanding terrestrial locomotor biomechanics in their modern descendants, birds. Despite much research on the subject, avian terrestrial locomotion remains little explored in regards to how kinematic and kinetic factors vary together with speed and body size. Here, terrestrial locomotion was investigated in twelve species of ground-dwelling bird, spanning a 1,780-fold range in body mass, across almost their entire speed range. Particular attention was devoted to the ground reaction force (GRF), the force that the feet exert upon the ground. Comparable data for the only other extant obligate, striding biped, humans, were also collected and studied. In birds, all kinematic and kinetic parameters examined changed continuously with increasing speed, while in humans all but one of those same parameters changed abruptly at the walk-run transition. This result supports previous studies that show birds to have a highly continuous locomotor repertoire compared to humans, where discrete ‘walking’ and ‘running’ gaits are not easily distinguished based on kinematic patterns alone. The influences of speed and body size on kinematic and kinetic factors in birds are developed into a set of predictive relationships that may be applied to extinct, non-avian theropods. The resulting predictive model is able to explain 79–93% of the observed variation in kinematics and 69–83% of the observed variation in GRFs, and also performs well in extrapolation tests. However, this study also found that the location of the whole-body centre of mass may exert an important influence on the nature of the GRF, and hence some caution is warranted, in lieu of further investigation.
... When walking, it is important to maintain stability, particularly in the mediolateral direction [1,2]. Having greater stability means reducing the effects of perturbing forces on one's center of mass (COM), thereby resisting movement [3,4]. When navigating through crowded areas however, people often must make quick lateral transitions that require controlled, rapid movement. ...
... Thus, the ability to apply free moments to the substrate during both locomotor and non-locomotor behaviors could be important to the evolution of foot posture in multiple mammalian lineages. Free moments have previously been studied in walking, running and turning (Holden and Cavanagh, 1991;Lee et al., 2001;Li et al., 2001;Jindrich et al., 2006;Umberger, 2008;Qiao et al., 2014). However, the role free moments play in non-locomotor behaviors and the extent to which foot posture influences free moment production have not been studied in any species. ...
In contrast to most other primates, great apes have feet in which the heel supports body weight during standing, walking and running. One possible advantage of this plantigrade foot posture is that it may enhance fighting performance by increasing the ability to apply free moments (i.e. force couples) to the ground. We tested this possibility by measuring performance of human subjects when performing from plantigrade and digitigrade (standing on the ball of the foot and toes) postures. We found that plantigrade posture substantially increased the capacity to apply free moments to the ground and to perform a variety of behaviors that are likely to be important to fighting performance in great apes. As predicted, performance in maximal effort lateral striking and pushing was strongly correlated with free moment magnitude. All else being equal, these results suggest species that can adopt plantigrade posture will be able to apply larger free moments to the ground than species restricted to digitigrade or unguligrade foot posture. Additionally, these results are consistent with the suggestion that selection for physical competition may have been one of the factors that led to the evolution of the derived plantigrade foot posture of great apes.
... An animal's rotational inertia, or resistance to rotation, is a function of how its mass is distributed in relation to the location of the rotational axis of interest. Tails can add mass far from the turning body, thus increasing the body's rotational inertia and making it more difficult to turn (Carrier et al., 2001;Walter and Carrier, 2002). But tails tend to be less rigid and more mobile than those modeled in the aforementioned studies, and hence the question of whether reductions in tail length might improve turning performance as a result of reduced rotational inertia in lizards remains to be determined. ...
... The execution of rapid turns, for example, is important as animals navigate complex environments and escape from potential predators or attempt to capture evading prey. As noted above, understanding how tail length, and thus caudal autotomy, might affect turning maneuvers has been touched on in the literature (Carrier et al., 2001;Jusufi et al., 2010;Walter and Carrier, 2002). This topic is particularly intriguing because although longer tails can help in turning the body (Jusufi et al., 2010), a shorter tail (i.e. ...
Autotomy has evolved in many animal lineages as a means of predator escape, and involves the voluntary shedding of body parts. In vertebrates, caudal autotomy (or tail shedding) is the most common form, and it is particularly widespread in lizards. Here, we develop a framework for thinking about how tail loss can have fitness consequences, particularly through its impacts on locomotion. Caudal autotomy is fundamentally an alteration of morphology that affects an animal's mass and mass distribution. These morphological changes affect balance and stability, along with the performance of a range of locomotor activities, from running and climbing to jumping and swimming. These locomotor effects can impact on activities critical for survival and reproduction, including escaping predators, capturing prey and acquiring mates. In this Commentary, we first review work illustrating the (mostly) negative effects of tail loss on locomotor performance, and highlight what these consequences reveal about tail function during locomotion. We also identify important areas of future study, including the exploration of new behaviors (e.g. prey capture), increased use of biomechanical measurements and the incorporation of more field-based studies to continue to build our understanding of the tail, an ancestral and nearly ubiquitous feature of the vertebrate body plan.
... Research has shown that errors in inertia properties have significant influence on the dynamics analysis of human locomotion [1,2]. Knowing inertia properties of body segments is essential for correctly understanding and even predicting the dynamics and locomotion performance of humans [3][4][5][6]. Hence, accurate identification of inertia properties of an individual is very important for subject-specific human motion analysis in many application areas such as medical rehabilitation, prosthetics, sports training, performance arts, etc. ...
... With those rules, we can modify the identification model by combining the jointly-appeared parameters and excluding the disappeared parameters from the original identification equations (namely, Eqs. (4) and (5)). Such a modification is suggested for identifying the barycentric parameters of a human body because some of the human joints are not spherical and some regular human motion activities (e.g., walking) occur only in the sagittal plane, which causes difficulty to individually identify all the barycentric parameters. ...
Physical modeling, simulation and analysis of an individual human body require inertia properties of the body segments of the human. Such subject-specific inertia data can be obtained only by measuring the individual human body as opposed to be derived from statistically generated anthropometric database. This paper presents experimental validation of a momentum-based approach for identifying the barycentric parameters of an individual human body which fully describes the inertia properties of the human. The identification algorithm is derived from the impulse–momentum equations of the human body which is assumed to be a multibody system with tree-type topology. Since the impulse–momentum equations are linear in terms of the unknown barycentric parameters, these parameters can be solved from the equations using a least-squares method. The approach does not require measuring or estimating accelerations and joint forces/torques because they do not appear in the impulse–momentum equations, and thus, the resulting identification procedure is less demanding on measurement data than the methods derived from the equations of motion. In this paper the test results of the identification method are validated by comparing the identified inertia parameters against the statistically established anthropometric data. Additionally, the identification results are also confirmed by comparing the contact forces using inverse dynamics to those obtained by forces plates.
