Limitations imposed by wearing armour on Medieval soldiers' locomotor performance

In Medieval Europe, soldiers wore steel plate armour for protection during warfare. Armour design reflected a trade-off between protection and mobility it offered the wearer. By the fifteenth century, a typical suit of field armour weighed between 30 and 50 kg and was distributed over the entire body. How much wearing armour affected Medieval soldiers' locomotor energetics and biomechanics is unknown. We investigated the mechanics and the energetic cost of locomotion in armour, and determined the effects on physical performance. We found that the net cost of locomotion (C(met)) during armoured walking and running is much more energetically expensive than unloaded locomotion. C(met) for locomotion in armour was 2.1-2.3 times higher for walking, and 1.9 times higher for running when compared with C(met) for unloaded locomotion at the same speed. An important component of the increased energy use results from the extra force that must be generated to support the additional mass. However, the energetic cost of locomotion in armour was also much higher than equivalent trunk loading. This additional cost is mostly explained by the increased energy required to swing the limbs and impaired breathing. Our findings can predict age-associated decline in Medieval soldiers' physical performance, and have potential implications in understanding the outcomes of past European military battles.     

The effects of substratum on locomotor performance in lacertid lizards

Locomotion is important to animals because it has direct implications for fitness through its role in predator escape, prey capture, and territory defence. Despite significant advances in our understanding of animal locomotion, studies exploring how substrate properties affect locomotor performance remain scant. In the present study, we explore how variation in substrate (sand, slate, cork) affects locomotor performance in lacertid lizards that differ in morphology. Moreover, we explore whether substrate effects are the same for different types of locomotor performance (speed, acceleration, and stamina). Our results show that the substrate affected most types of locomotor performance studied but not always in the same way. Although substrate effects were species‐dependent for the maximal speed over 50 cm and the distance run to exhaustion, this was not the case for acceleration capacity. These results suggest that substrate texture differentially affects burst performance vs. longer duration measures of locomotor performance. Finally, straightforward relationships between habitat use and the substrate on which performance was maximized were not observed. This suggests that the evolution of locomotor capacity is complex and that animals may show compromise phenotypes allowing them to deal with a variety of substrates in their natural environment. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●●, ●●–●●.     

Morphological correlates of locomotor performance in hatchling Amblyrhynchus cristatus

Previous studies of locomotor performance from a variety of perspectives often assumed that speed and limb length were strongly correlated. Despite support of this assumption from biomechanical models, few empirical studies have demonstrated a significant relationship between measures of locomotor capacity, such as maximum velocity, and length of the hindlimb at either the inter- or intra-specific level. We examined whether one measure of locomotor performance, maximum velocity, correlates with body size and elements of the hindlimb in hatchling marine iguanas (Amblyrhynchus cristatus). Larger hatchlings ran faster. Removing the effects of body size revealed that relative lengths of the tibia and hindfoot correlated with size-adjusted maximum velocity. Individuals with relatively long tibia and short pes were relatively faster than individuals with short tibia and long pes. Functional morphological analyses predict that femur length should correlate with maximum velocity. However, our analyses failed to support this prediction. Because hatchling marine iguanas exploit relatively open habitats, the relationship between maximum velocity and limb morphology may be interpreted as an adaptation enhancing escape from predators.     

Thermal dependence of locomotor performance in two cool-temperate lizards

Temperate-zone ectotherms experience varying or very low ambient temperatures and may have difficulty in attaining preferred body temperatures. Thus, adaptations to reduce the thermal dependence of physiological processes may be present. We measured the optimal temperature range for sprint speed and compared it with the selected body temperatures (T _sel) of two sympatric, cool-temperate lizards: the diurnal skink Oligosoma maccanni and the primarily nocturnal gecko Woodworthia (previously Hoplodactylus) “Otago/Southland”. We also investigated whether time-of-day influenced sprint speed. Contrary to results for other reptiles, we found that time-of-day did not influence speed in either species. For each species, the optimal temperature range for sprinting and T _sel overlapped, supporting the ‘thermal coadaptation’ hypothesis. However, the optimal range of temperatures for speed is not always attainable during activity by either species, which have limited opportunities to attain T _sel in the field. The thermal sensitivity of sprint speed in these two species does not appear to have evolved to fully match their current thermal environment. More data on cold-adapted species are needed to fully understand physiological adaptation in ectotherms.     

Comparative locomotor performance of marsupial and placental mammals

Marsupials are often considered inferior to placental mammals in a number of physiological characters. Because locomotor performance is presumed to be an important component of fitness, we compared marsupials and placentals with regard to both maximal running speeds and maximal aerobic speeds (=speed at which the maximal rate of oxygen consumption, VOlmax, is attained). Maximal aerobic speed is related to an animal's maximal sustainable speed, and hence is a useful comparative index of stamina.
Maximal running speeds of 11 species of Australian marsupials, eight species of Australian murid rodents, two species of American didelphid marsupials, and two species of American rodents were measured in the laboratory and compared with data compiled from the literature. Our values are greater than, or equivalent to, those reported previously. Marsupials and placentals do not differ in maximal running speeds (nor do Australian rodents differ from non-Australian rodents). Within these groups, however, species and families may differ considerably. Some of the interspecific variation in maximal running speeds is related to differences in habitat: species inhabiting open habitats (e.g. deserts) tend to be faster than are species from habitats with more cover, or arboreal species.
Maximal aerobic speeds (compiled from the literature) were higher in large species than in small species. However, marsupials and placentals show no general difference with regard to maximal aerobic speeds.
Maximal running speeds and maximal aerobic speeds for 18 species of mammals were not correlated, after correcting for correlations with body size. Thus, the fastest sprinters do not necessarily have high maximal aerobic speeds.     

Effects of pregnancy on locomotor performance: an experimental study on lizards

Pregnancy is associated with reduced locomotor performance in many types of animals, but we do not know to what degree this correlation is caused by simple physical burdening, versus physiological changes associated with pregnancy, or to confounding variables (such as season or female body size) that simultaneously influence both reproductive investment and locomotor speeds. To identify causal effects of burden on locomotion, we need to experimentally manipulate the size of the load being carried. Injection of sterile fluid into the peritoneal cavities of 84 garden skinks (Lampropholis guichenoti) showed that speeds decreased with increasing burdens. Lizards with a burden equivalent to 25% of their body mass ran about 15% slower, mirroring the situation seen in gravid lizards of this population. Thus, simple physical burdening appears to be the primary causal component of the locomotor cost of reproduction within these animals. A lizard's sex, body size and shape had little effect on its running ability either before or after treatment, but faster lizards showed a greater performance decrement after burdening than did their slower conspecifics.     

Effects of pregnancy on body temperature and locomotor performance of velvet geckos

Pregnancy is a challenging period for egg laying squamates. Carrying eggs can encumber females and decrease their locomotor performance, potentially increasing their risk of predation. Pregnant females can potentially reduce this handicap by selecting higher temperatures to increase their sprint speed and ability to escape from predators, or to speed up embryonic development and reduce the period during which they are burdened with eggs (‘selfish mother’ hypothesis). Alternatively, females might select more stable body temperatures during pregnancy to enhance offspring fitness (‘maternal manipulation hypothesis’), even if the maintenance of such temperatures compromises a female's locomotor performance. We investigated whether pregnancy affects the preferred body temperatures and locomotor performance of female velvet geckos Amalosia lesueurii. We measured running speed of females during late pregnancy, and one week after they laid eggs at four temperatures (20°, 25°, 30° and 35 °C). Preferred body temperatures of females were measured in a cost-free thermal gradient during late pregnancy and one week after egg-laying. Females selected higher and more stable set-point temperatures when they were pregnant (mean =29.0 °C, T_set =27.8–30.5 °C) than when they were non-pregnant (mean =26.2 °C, T_set =23.7–28.7 °C). Pregnancy was also associated with impaired performance; females sprinted more slowly at all four test temperatures when burdened with eggs. Although females selected higher body temperatures during late pregnancy, this increase in temperature did not compensate for their impaired running performance. Hence, our results suggest that females select higher temperatures during pregnancy to speed up embryogenesis and reduce the period during which they have reduced performance. This strategy may decrease a female's probability of encountering predatory snakes that use the same microhabitats for thermoregulation. Selection of stable temperatures by pregnant females may also benefit embryos, but manipulative experiments are necessary to test this hypothesis.     

Overcoming obstacles: the effect of obstacles on locomotor performance and behaviour

Sprinting and jumping ability are key performance measures that have been widely studied in vertebrates. The vast majority of these studies, however, use methodologies that lack an ecological context by failing to consider the complex habitats in which many animals live. Because successfully navigating obstacles within complex habitats is critical for predator escape, running, climbing, and/or jumping performance are each likely to be exposed to selection. In the present study, we quantify how behavioural strategies and locomotor performance change with increasing obstacle height. Obstacle size had a significant influence on behaviour (e.g. obstacle crossing strategy, intermittent locomotion) and performance (e.g. sprint speed, jump distance). Jump frequency and distance increased with obstacle size, suggesting that it likely evolved because it is more efficient (i.e. it reduces the time and distance required to reach a target position). Jump angle, jump velocity, and approach velocity accounted for 58% of the variation in jump distance on the large obstacle, and 33% on the small obstacle. Although these variables have been shown to significantly influence jump distance in static jumps, they do not appear to be influential in running (dynamic) jumps onto a small obstacle. Because selection operates in simple and complex habitats, future studies should consider quantifying additional measures such as jumping or climbing with respect to the evolution of locomotion performance. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Environmental maternal effects on locomotor performance in the common lizard (Lacerta vivipara)

Environmental (i.e. non-genetic) maternal effects have the potential to associate the environmental conditions faced by mothers during gestation or before egg laying with the phenotype of their offspring. For this reason, maternal effects may play a major role in determining offspring phenotype independently of the genotype of the individuals, and can thus be considered a mechanistic basis of phenotypic plasticity. Despite the ecological and evolutionary implications of environmental maternal effects, few studies have experimentally investigated this phenomenon in reptiles. Here we report the results of an experimental laboratory study on the effects of maternal feeding rate and density on offspring locomotor performance in the common lizard (Lacerta vivipara). Lacerta vivipara is a viviparous lizard, and viviparity enhances the probability of a maternal influence on offspring phenotype. We focused on a particular phenotypic trait, maximal sprint running speed, because this trait is thought to be selectively important in squamates. Sprint speed was a repeatable trait, and it varied significantly among families. Maternal feeding rate significantly affected sprint speed, whereas density had no effect on this trait. The effect of maternal feeding rate differed according to the sex of the offspring and their body size, resulting in significant two-way and three-way interactions among these factors. In other words, the maternal feeding rate changed the shape of the allometric relationship between speed and size, but differently for males and females. The complexity of such effects makes it extremely difficult to offer an adaptive interpretation, but emphasizes the role played by the environment in shaping phenotypes among generations.     

The effect of hypoxia on locomotor performance and behaviour during escape in Liza aurata

Escape performance was investigated in the golden grey mullet Liza aurata exposed to various levels of oxygen: >85 ( i.e. normoxia), 50, 20 and 10 % air saturation. Since the golden grey mullet performed aquatic surface respiration when air saturation approached 15–10 %, escape performance was tested at 10 % air saturation with and without access to the surface (10 % S and 10 % C, respectively). Various locomotor and behavioural variables were measured, such as cumulative distance, maximum swimming speed, acceleration, responsiveness (per cent of responding fish), response latency and directionality. Golden grey mullet showed a decrease in responsiveness when the oxygen level was reduced to 10 % air saturation, whether the surface access was obstructed or not. Hypoxia did not have any effect on the response latency. Cumulative distance and maximum swimming speed over a fixed time were significantly different between normoxic conditions and 10 % C, while no differences were found in maximum acceleration. While the fish's 'C‐bend' was mainly directed away from the stimulus in normoxia, the proportion of away and towards 'C‐bend' was random when the oxygen was ≤20 % air saturation. This suggested an impairment of the left‐right discrimination at the initiation of the fast start. Hypoxia affected golden grey mullet escape performance mainly through an impairment of responsiveness and directionality, while locomotor performance was affected only in severe hypoxia when the surface was obstructed. The study showed that, in addition to forcing the fish to the surface as shown by previous studies, hypoxia may also reduce fish elusiveness facing a predator by directly impairing its escape performance.     

Convergent evolution of locomotor morphology but not performance in gymnotiform swimmers

Convergent evolution of a novel locomotor strategy implies that a fitness benefit may be associated with the new gait. Opportunities to study this phenomenon are often constrained by a lack of transitional taxa, but teleost fishes offer examples of extant species across such evolutionary shifts in gait. For instance, one species from Osteoglossiformes and the entire order of Gymnotiformes independently evolved a novel gait, gymnotiform locomotion, where thrust is produced by the undulation of an elongate anal fin. Here, we investigate whether this convergence in gait is also associated with similarities in shape, burst swimming abilities, and/or steady‐swimming energetics. Specifically, we measured body and fin morphology of fish within Gymnotiformes and Osteoglossiformes, along with closely related Siluriformes and Cypriniformes, to examine the link between gymnotiform locomotion and morphology in a phylogenetic context. Second, we tested the burst swimming capabilities and oxygen consumption during endurance swimming of a subset of the same gymnotiform, osteoglossiform, and cypriniform species, including “transitional” Osteoglossiformes that exhibit intermediate gaits, to determine whether the evolution of this specialized gait is associated with a change in either of these performance metrics. Our results suggest that convergence on the gymnotiform gait is associated with morphological convergence, but does not constrain a fish's maximum sprinting speeds or their energetic demands during steady swimming.     

Time of testing affects locomotor performance in nocturnal versus diurnal snakes

Studies of the thermal dependence of locomotor performance in ectotherms have provided extensive data on species differences, but often have neglected the time of day at which the test organism is usually active. To compare performance abilities among species that are active at different times of day, do we need to measure performance at the time of day that each species is normally active, or can we adopt the (logistically more convenient) alternative of testing all taxa at the same time (i.e. during daylight hours)? We scored swimming speeds of six species of Australian elapid snakes, incorporating both diurnal and nocturnal species, at a range of temperatures encompassing the usual conditions experienced during activity, and at night as well as by day. Nocturnal species swam faster by night than by day, whereas the reverse was true for diurnal taxa. The magnitude of species differences in speed depended on test temperatures as well as time of day. Thus, interspecific comparisons of locomotor abilities need to consider not only the differing activity temperatures normally experienced by species active at different times of day, but also circadian rhythms in performance.     

Hindlimb morphology and locomotor performance in waders: an evolutionary approach

Locomotion performance (measured as stride frequency and stride length) was studied in 16 species of waders. Differences in hindlimb morphology (osteology and myology) were analysed among species. Evolutionary changes in both locomotion and morphological variables were analysed using comparative methods revealing the existence of some ecomorphological patterns relating these two sets of characters. Evolutionary changes in stride frequency were correlated with changes in the muscles M. iliotibialis cranialis, M. iliotibiales lateralis and M. gastrocnemius, whereas changes in stride length showed correlated evolution with changes in the length of distal segments of the leg. We identify two different evolutionary strategies in locomotion of waders. One is a change in distal leg segments (skeletal system), an adaptive modification that increases stride length; the second is a change in the skeletal-muscular system, providing an increase in muscular performance (force or speed of contraction) in several muscles, and is an adaptation that increases stride frequency.     

Cool running: locomotor performance at low body temperature in mammals

Mammalian torpor saves enormous amounts of energy, but a widely assumed cost of torpor is immobility and therefore vulnerability to predators. Contrary to this assumption, some small marsupial mammals in the wild move while torpid at low body temperatures to basking sites, thereby minimizing energy expenditure during arousal. Hence, we quantified how mammalian locomotor performance is affected by body temperature. The three small marsupial species tested, known to use torpor and basking in the wild, could move while torpid at body temperatures as low as 14.8-17.9°C. Speed was a sigmoid function of body temperature, but body temperature effects on running speed were greater than those in an ectothermic lizard used for comparison. We provide the first quantitative data of movement at low body temperature in mammals, which have survival implications for wild heterothermic mammals, as directional movement at low body temperature permits both basking and predator avoidance.     

Thermal acclimation of locomotor performance in tadpoles of the frog Limnodynastes peronii

Previous analyses of thermal acclimation of locomotor performance in amphibians have only examined the adult life history stage and indicate that the locomotor system is unable to undergo acclimatory changes to temperature. In this study, we examined the ability of tadpoles of the striped marsh frog (Limnodynastes peronii) to acclimate their locomotor system by exposing them to either 10 °C or 24 °C for 6 weeks and testing their burst swimming performance at 10, 24, and 34 °C. At the test temperature of 10 °C, maximum velocity (U_max) of the 10 °C-acclimated tadpoles was 47% greater and maximum acceleration (A_max) 53% greater than the 24 °C-acclimated animals. At 24 °C, U_max was 16% greater in the 10 °C-acclimation group, while there was no significant difference in A_max or the time taken to reach U_max (T-U_max). At 34 °C, there was no difference between the acclimation groups in either U_max or A_max, however T-U_max was 36% faster in the 24 °C-acclimation group. This is the first study to report an amphibian (larva or adult) possessing the capacity to compensate for cool temperatures by thermal acclimation of locomotor performance. To determine whether acclimation period affected the magnitude of the acclimatory response, we also acclimated tadpoles of L. peronii to 10 °C for 8 months and compared their swimming performance with tadpoles acclimated to 10 °C for 6 weeks. At the test temperatures of 24 °C and 34 °C, U_max and A_max were significantly slower in the tadpoles acclimated to 10 °C for 8 months. At 10 °C, T-U_max was 40% faster in the 8-month group, while there were no differences in either U_max or A_max. Although locomotor performance was enhanced at 10 °C by a longer acclimation period, this was at the expense of performance at higher temperatures. Accepted: 25 June 1999     

Early experience influences both habitat choice and locomotor performance in tiger snakes

Through adaptive developmental plasticity, individuals may function most effectively in the type of environment in which they have spent most of their time. Such habitat-specific modifications may favor active selection of that habitat type later in life, further reinforcing developmentally plastic phenotypic modifications. The interaction between these processes may have profound evolutionary implications. In nature, Australian tiger snakes (Notechis scutatus) use a complex mosaic of terrestrial, arboreal, and aquatic habitats. We raised juvenile tiger snakes for the first 11 months of life in enclosures mimicking one of these habitats and then tested their habitat selection when offered a choice of habitat types. Snakes consistently selected the habitat types in which they had been reared, and they were more effective at locomotion in those habitats than in the others. This attachment to a familiar habitat and phenotypically flexible adjustments in order to function effectively in that habitat constitute a positive feedback loop. That is, animals benefit by choosing a familiar habitat because they can fine-tune behaviors in ways that enable them to function better in that habitat, and, by consistently selecting that kind of habitat, they not only reinforce those phenotypically plastic adjustments but also are placed under continuing selection to cope with the challenges (of foraging, predator evasion, etc.) imposed by that habitat type. The end result may be to create ecomorphs, whereby different individuals within a population become specialized for different types of habitats even in the absence of genetic differentiation.     

多疣壁虎的体温调节及运动能力热依赖性

本文测定了多疣壁虎(Gekko japonicus)的野外活动体温、喜好体温以及运动能力热依赖性,探讨夜行性蜥蜴的体温调节及其对动物功能表达的作用。在自然条件下,多疣壁虎的活动体温存在明显的月份间差异,但无性别和年龄间的差异。在实验室条件下,怀卵雌体(29.8℃)和幼体(29.9℃)的喜好体温显著高于非怀卵雌体(28.5℃)和雄体(28.2℃)。体温能显著影响多疣壁虎的运动能力,在15℃-34℃范围内,其平均跑速随体温上升而加快,超过34℃后则随体温升高而减慢。多疣壁虎的平均跑速及其热敏感性无显著的年龄组间差异。在夜间活动期,雄体、非怀卵雌体和幼体的体温调节有效度低,而怀卵雌体的体温调节有效度则较高。结果显示怀卵雌体的体温调节较非怀卵雌体和雄体更精确     

Limitations and mechanisms influencing the migratory performance of soaring birds

Migration is costly in terms of time, energy and safety. Optimal migration theory suggests that individual migratory birds will choose between these three costs depending on their motivation and available resources. To test hypotheses about use of migratory strategies by large soaring birds, we used GPS telemetry to track 18 adult, 13 sub‐adult and 15 juvenile Golden Eagles Aquila chrysaetos in eastern North America. Each age‐class had potentially different motivations during migration. During spring, the migratory performance (defined here as the directness of migratory flight) of adults was higher than that of any other age‐classes. Adults also departed earlier and spent less time migrating. Together, these patterns suggest that adults were primarily time‐limited and the other two age‐classes were energy‐limited. However, adults that migrated the longest distances during spring also appeared to take advantage of energy‐conservation strategies such as decreasing their compensation for wind drift. During autumn, birds of all age‐classes were primarily energy‐minimizers; they increased the length of stopovers, flew less direct routes and migrated at a slower pace than during spring. Nonetheless, birds that departed later in autumn flew more directly, indicating that time limitations may have affected their decision‐making. During both seasons, juveniles had the lowest performance, sub‐adults intermediate performance and adults the highest performance. Our results show age‐ and seasonal variation in time and energy‐minimization strategies that are not necessarily exclusive of one another. Beyond time and energy, a complex suite of factors, including weather, experience and navigation ability, influences migratory performance and decision‐making.