Does metatarsal/femur ratio predict maximal running speed in cursorial mammals?

We tested the hypothesis that hind limb proportions may be used to predict locomotor performance in a sample of 49 species of primarily cursorial mamals. Data on maximal sprint running speeds taken from published sources were related to measurements of hind limb lengths. To control for statistical complications due to the hierarchical nature of phylogenetic relationships, we used Felsenstein's (1985) independent contrasts method for analysing comparative data, and a composite phylogeny for all 49 species, based on a variety of published sources. The independent contrasts method indicates that maximal running speed does not covary significantly with body mass for this sample of mammals (mass range= 2.5–2,000 kg). Even though quality of the available speed data is highly variable, both metatarsal/femur ratio—the traditional index of 'cursoriality' in mammals—and hind limb length (corrected for body size) are significant predictors of maximal running speed. When only fully curorial species are included in the analyses (n = 32), hind limb length still significantly predicts speed (r²= 16%), but MT/F ratio does not. Although ungulates tend to have larger MT/F ratios than do Carnivora, they are not generally faster; relatonships between speed and limb proportions within the two clades show no significant differences. These and previous results suggest that hind limb proportions and maximal running speed may not have evolved in a tightly coupled fashion. Prediction of locomotor performance of extinct forms, based solely on their limb proportions, should be undertaken with caution.     

Ontogenetic and individual variation in size, shape and speed in the Australian agamid lizard Amphibolurus nuchalis

The present study investigates relationships among size, shape and speed in the Australian agamid lizard Amphibolurus nuchalis . Maximal running speed, body mass, snout-vent length, tail length, fore- and hind limb spans and thigh muscle mass were measured in 68 field-fresh individuals spanning the entire ontogenetic size range (1.3 48 g). Relative lengths of both foreand hind limbs decrease with increasing body mass (= negative allometry), whereas relative tail length and thigh muscle mass increase with body mass (= positive allometry). Repeatable and significant differences in maximal running speed exist among individuals. Maximal running speed scales as (body mass)^0.161, and 59% of the variation in maximal speed was related to body mass. Based on the results of the present and previous studies, data on scaling of body proportions alone appear inadequate to infer scaling relationships of functional characters such as top speed.
Surprisingly, individual variation in maximal speed is not related to individual variation in shape (relative limb, tail and body lengths). These components of overall shape are not independent; individuals tended to have either relatively long or relatively short limbs, tails and bodies for their body mass. Even the significant difference in multivariate shape between adult males and females has no measurable consequences for maximal speed. Speeds of field-fresh animals did not vary on a seasonal basis, and eight weeks of captivity had no effect on maximal running speeds. Gravid females and long-term (obese) captive lizards were both approximately 12% slower than field-fresh lizards.     

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.     

Running energetics of the North American river otter: do short legs necessarily reduce efficiency on land?

Semi-aquatic mammals move between two very different media (air and water), and are subject to a greater range of physical forces (gravity, buoyancy, drag) than obligate swimmers or runners. This versatility is associated with morphological compromises that often lead to elevated locomotor energetic costs when compared to fully aquatic or terrestrial species. To understand the basis of these differences in energy expenditure, this study examined the interrelationships between limb morphology, cost of transport and biomechanics of running in a semi-aquatic mammal, the North American river otter. Oxygen consumption, preferred locomotor speeds, and stride characteristics were measured for river otters (body mass=11.1 kg, appendicular/axial length=29%) trained to run on a treadmill. To assess the effects of limb length on performance parameters, kinematic measurements were also made for a terrestrial specialist of comparable stature, the Welsh corgi dog (body mass=12.0 kg, appendicular/axial length=37%). The results were compared to predicted values for long legged terrestrial specialists. As found for other semi-aquatic mammals, the net cost of transport of running river otters (6.63 J kg(-1)min(-1) at 1.43 ms(-1)) was greater than predicted for primarily terrestrial mammals. The otters also showed a marked reduction in gait transition speed and in the range of preferred running speeds in comparison to short dogs and semi-aquatic mammals. As evident from the corgi dogs, short legs did not necessarily compromise running performance. Rather, the ability to incorporate a period of suspension during high speed running was an important compensatory mechanism for short limbs in the dogs. Such an aerial period was not observed in river otters with the result that energetic costs during running were higher and gait transition speeds slower for this versatile mammal compared to locomotor specialists.     

A biomechanical constraint on body mass in terrestrial mammalian predators

Observations on extant mammals suggest that large body mass is selectively advantageous for a terrestrial predator on large herbivores. Yet, throughout the Cenozoic, some lineages of terrestrial mammalian predators attained greater maximal body masses than others. In order to explain this evolutionary pattern, the following biomechanical constraint on body mass is hypothesized. The stress, set up in the humerus by the bending moment of the peak ground reaction force at maximal running speed, increased with increasing body mass within a given lineage of terrestrial mammalian predators, resulting in a decreasing safety factor for the bone, until a predator could no longer attain the maximal running speed of its smaller relatives. The selective disadvantage of reduced maximal running speed prevented further increase of body mass within the lineage. This hypothesis is tested by examining the scaling of humeral dimensions and estimating maximal body masses in several lineages of terrestrial mammalian predators. Among lineages with otherwise similar postcranial skeletons, those with the more robust humeri at a given body mass attained the greater maximal body masses. Lineages with the longer deltoid ridges/deltopectoral crests of the humeri and/or the more distally located deltoid scars (suggesting the more distal insertions of the humeral flexors) at a given body mass also attained the greater maximal body masses. These results support the existence of the proposed biomechanical constraint, although paleoecological data suggest that some lineages of terrestrial mammalian predators failed to reach the limits, imposed by this constraint, because of the small size of available prey.     

Shaking a leg and hot to trot: the effects of body size and temperature on running speed in ants

Abstract.  1. Data were compiled from the literature and our own studies on 24 ant species to characterise the effects of body size and temperature on forager running speed.
2. Running speed increases with temperature in a manner consistent with the effects of temperature on metabolic rate and the kinetic properties of muscles.
3. The exponent of the body mass-running speed allometry ranged from 0.14 to 0.34 with a central tendency of approximately 0.25. This body mass scaling is consistent with both the model of elastic similarity, and a model combining dynamic similarity with available metabolic power.
4. Even after controlling for body size or temperature, a substantial amount of inter-specific variation in running speed remains. Species with certain lifestyles [e.g. nomadic group predators, species which forage at extreme (>60 °C) temperatures] may have been selected for faster running speeds.
5. Although ants have a similar scaling exponent to mammals for the running speed allometry, they run slower than predicted compared with a hypothetical mammal of similar size. This may in part reflect physiological differences between invertebrates and vertebrates.     

The Effect of Body Pitching on Leg-Spring Behavior in Quadruped Running

<正> In this paper we investigated how the running speed would affect the dynamics of body pitching, and whether body inertiais important for animals. Passive trotting of spring-mass model and passive bounding of spring-beam model were studied atdifferent speeds for different sets of body parameters respectively. Furthermore, different body inertias were used in bounding.We found that running speed exerts effect on leg performance by means of centrifugal force. The centrifugal force can be understoodas an enhancement to the natural frequency of the spring-mass system. The disadvantage of body pitching may beoffset by the great increase in centrifugal force at high speed. The results also reveal that body mass distribution might not be themain reason for the difference in maximal running speeds of different animals.     

Locomotor mode, maximum running speed, and basal metabolic rate in placental mammals

The locomotor performance (absolute maximum running speed [MRS]) of 120 mammals was analyzed for four different locomotor modes (plantigrade, digitigrade, unguligrade, and lagomorph-like) in terms of body size and basal metabolic rate (BMR). Analyses of conventional species data showed that the MRS of plantigrade and digitigrade mammals and lagomorphs increases with body mass, whereas that of unguligrade mammals decreases with body mass. These trends were confirmed in plantigrade mammals and lagomorphs using phylogenetically independent contrasts. Multiple regression analyses of MRS contrasts (dependent variable) as a function of body mass and BMR contrasts (predictor variables) revealed that BMR was a significant predictor of MRS in the complete data set, as well as in plantigrade and nonplantigrade mammals. However, there was severe multicollinearity in the nonplantigrade model that may influence the interpretation of these models. Although these data show mass-independent correlation between BMR and MRS, they are not necessarily indicative of a cause-effect relationship. However, the analyses do identify a negligible role of body size associated with MRS once phylogenetic and BMR effects are controlled, suggesting that the body size increase in large mammals over time (i.e., Cope's rule) can probably rule out MRS as a driving variable.     

Maximum running speed limitations on terrestrial mammals: a theoretical approach

Here we study maximum running speed (MRS) limitations on a previously proposed model of energetic and muscle-tendon unit functions on running mammals. In the present work the MRS and some anatomical or physiological limitations are estimated for mammals with body mass between 1.5 and 300 kg. The MRS variations with body mass are discussed and compared with results of previous experimental and observational studies. The tendon strength seems to be the most relevant limitation, but leg extensor muscle mass and metabolic costs could be relevant also. The physiological maximum muscle speed seems to be less important in the body mass range studied here.     

Effects of Limb Length,Body Mass,Gender, Gravidity,and Elevation on Escape Speed in the Lizard Psammodromus algirus

Most animals rely on their escape speed to flee from predators. Here, we test several hypotheses on the evolution of escape speed in the lizard Psammodromus algirus. We test that: (1) Longer limbs should improve speed sprint. (2) Heavier lizards should be impaired regarding their sprint speed ability, suggesting a trade-off between fat storage and escape capability. (3) Males should achieve faster speeds due to their higher exposure to predators. (4) Gravid females, with increased body mass, should perform lower speed than non-gravid females. And (5) there are inter-population differences in sprint speed across an elevational gradient. We measured lizards sprint speed in a lineal raceway in the laboratory, filming races in standardized conditions and then calculating their maximal speed. We found that hind limb length greatly determined maximal sprint speed, lizards with longer limbs being faster. In parallel, higher body masses reduced maximal speed, which points to a trade-off between fat storage and escaping capability. Sexual differences also arose, as males were faster than females, as a consequence of males having longer limbs. Regarding females, gravidity did not impair maximal sprint speed, suggesting adaptations which compensate for the increased body mass. Finally, we found no elevational trend in both limbs length and sprint speed. In any case, this study suggests that selection on escape capacity may cast morphological evolution, and affect other life-history traits, such as fat storage and reproduction.     

Sex, Reproductive Status, and Cost of Tail Autotomy via Decreased Running Speed in Lizards

Autotomy, voluntary shedding of body parts to permit escape, is a theoretically interesting defense because escape benefit is offset by numerous costs, including impaired future escape ability. Reduced sprint speed is a major escape cost in some lizards. We predicted that tail loss causes decreased speed in males and previtellogenic females, but not vitellogenic females already slowed by mass gain. In the striped plateau lizard, Sceloporus virgatus , adults of both sexes are subject to autotomy, and females undergo large increases in body condition (mass/length) during vitellogenesis. Time required for running 1 m was similar in intact autotomized males and previtellogenic females, but increased by nearly half after autotomy. Vitellogenic females were slower than other lizards when intact, but their speed was unaffected by autotomy. Following autotomy, speeds of all groups were similar. Thus, speed costs of autotomy vary with sex and reproductive condition: decreased running speed is not a cost of autotomy in vitellogenic females or presumably gravid females. Costs of autotomy are more complex than previously known. Speed and other costs might interact in unforseen ways, making it difficult to predict whether strategies to compensate for diminished escape ability differ with reproductive condition in females.     

Effects of size on vervet (Cercopithecus aethiops) gait parameters: a longitudinal approach

Changes in the values of certain locomotor parameters were analyzed over a range of speeds for five immature vervet monkeys sampled at 6 month intervals over approximately a 3 year period. Lateral and diagonal sequence walking gaits and transverse and rotary gallops were commonly used. The monkeys switched from walking to galloping at long cycle durations for their mass, although, as a group, their transition speeds were in agreement with data from other mammals. However, for individual monkeys, transition speed was not consistently dependent on body mass. Cycle and stance durations generally increased with increasing size at each speed for each animal, with the greatest increases occurring at slower speeds. Swing durations increased slightly with size. For any particular individual, speed was highly predictable from cycle (or stance) duration and body mass (or age). However, the multiple regression equations for each animal were significantly different from each other, suggesting that no single equation is satisfactory for all of the individuals within a species.     

Effects of obesity and sex on the energetic cost and preferred speed of walking.

The metabolic energy cost of walking is determined, to a large degree, by body mass, but it is not clear how body composition and mass distribution influence this cost. We tested the hypothesis that walking would be most expensive for obese women compared with obese men and normal-weight women and men. Furthermore, we hypothesized that for all groups, preferred walking speed would correspond to the speed that minimized the gross energy cost per distance. We measured body composition, maximal oxygen consumption, and preferred walking speed of 39 (19 class II obese, 20 normal weight) women and men. We also measured oxygen consumption and carbon dioxide production while the subjects walked on a level treadmill at six speeds (0.50-1.75 m/s). Both obesity and sex affected the net metabolic rate (W/kg) of walking. Net metabolic rates of obese subjects were only approximately 10% greater (per kg) than for normal-weight subjects, and net metabolic rates for women were approximately 10% greater than for men. The increase in net metabolic rate at faster walking speeds was greatest in obese women compared with the other groups. Preferred walking speed was not different across groups (1.42 m/s) and was near the speed that minimized gross energy cost per distance. Surprisingly, mass distribution (thigh mass/body mass) was not related to net metabolic rate, but body composition (% fat) was (r2= 0.43). Detailed biomechanical studies of walking are needed to investigate whether obese individuals adopt novel energy saving mechanisms during walking.     

Control of lateral weight transfer is associated with walking speed in individuals post-stroke

Restoring functional gait speed is an important goal for rehabilitation post-stroke. During walking, transferring of one’s body weight between the limbs and maintaining balance stability are necessary for independent functional gait. Although it is documented that individuals post-stroke commonly have difficulties with performing weight transfer onto their paretic limbs, it remains to be determined if these deficits contributed to slower walking speeds. The primary purpose of this study was to compare the weight transfer characteristics between slow and fast post-stroke ambulators. Participants (N = 36) with chronic post-stroke hemiparesis walked at their comfortable and maximal walking speeds on a treadmill. Participants were stratified into 2 groups based on their comfortable walking speeds (≥0.8 m/s or <0.8 m/s). Minimum body center of mass (COM) to center of pressure (COP) distance, weight transfer timing, step width, lateral foot placement relative to the COM, hip moment, peak vertical and anterior ground reaction forces, and changes in walking speed were analyzed. Results showed that slow walkers walked with a delayed and deficient weight transfer to the paretic limb, lower hip abductor moment, and more lateral paretic limb foot placement relative to the COM compared to fast walkers. In addition, propulsive force and walking speed capacity was related to lateral weight transfer ability. These findings demonstrated that deficits in lateral weight transfer and stability could potentially be one of the limiting factors underlying comfortable walking speeds and a determinant of chronic stroke survivors’ ability to increase walking speed.     

Effects of size, sex, and voluntary running speeds on costs of locomotion in lines of laboratory mice selectively bred for high wheel-running activity

Selective breeding for over 35 generations has led to four replicate (S) lines of laboratory house mice (Mus domesticus) that run voluntarily on wheels about 170% more than four random-bred control (C) lines. We tested whether S lines have evolved higher running performance by increasing running economy (i.e., decreasing energy spent per unit of distance) as a correlated response to selection, using a recently developed method that allows for nearly continuous measurements of oxygen consumption (VO2) and running speed in freely behaving animals. We estimated slope (incremental cost of transport [COT]) and intercept for regressions of power (the dependent variable, VO2/min) on speed for 49 males and 47 females, as well as their maximum VO2 and speeds during wheel running, under conditions mimicking those that these lines face during the selection protocol. For comparison, we also measured COT and maximum aerobic capacity (VO2max) during forced exercise on a motorized treadmill. As in previous studies, the increased wheel running of S lines was mainly attributable to increased average speed, with males also showing a tendency for increased time spent running. On a whole-animal basis, combined analysis of males and females indicated that COT during voluntary wheel running was significantly lower in the S lines (one-tailed P=0.015). However, mice from S lines are significantly smaller and attain higher maximum speeds on the wheels; with either body mass or maximum speed (or both) entered as a covariate, the statistical significance of the difference in COT is lost (one-tailed P> or =0.2). Thus, both body size and behavior are key components of the reduction in COT. Several statistically significant sex differences were observed, including lower COT and higher resting metabolic rate in females. In addition, maximum voluntary running speeds were negatively correlated with COT in females but not in males. Moreover, males (but not females) from the S lines exhibited significantly higher treadmill VO2max as compared to those from C lines. The sex-specific responses to selection may in part be consequences of sex differences in body mass and running style. Our results highlight how differences in size and running speed can account for lower COT in S lines and suggest that lower COT may have coadapted in response to selection for higher running distances in these lines.     

Advantages of a smaller bodymass in humans when distance-running in warm, humid conditions

Using a 65-kg athlete running a 2 h 10 min marathon as an example, we estimated that imbalances between approximately 1400 W of heat production and dissipation would occur in ambient temperatures of 17 degrees C at 90% relative humidity (rh) to 37 degrees C at 50% rh. Because heat production during running depends on body mass and heat loss depends on surface area, intercepts between predicted heat production and maximal heat loss with increasing speeds depend on an athlete's body mass. At 35 degrees C and 60% rh, a 45-kg athlete could maintain thermal balance by running a 2 h 13 min marathon at 19.1 km x h(-1) but a 75-kg athlete would only be able run a 3 h 28 min marathon at 12.2 km x h(-1). In both cases, the production of 970-1020 W of heat would necessitate the evaporation of at least 1.5-1.6 l of sweat per hour. A lower metabolic heat production in lighter runners at any given speed may be one reason why smallness of stature is an asset in distance running.     

Energy expenditure during level locomotion in large desert ungulates: the one-humped camel and the domestic donkey

This study sought to quantify the rate of energy expenditure (     ), the total cost of transport (COT_tot) and the net cost of transport (COT_net) in camels Camelus dromedaries and donkeys Equus asinus during level locomotion.     of camels and domestic donkeys were measured at exercise speeds between 0 and 4.17 m s⁻¹. Resting     for camels was significantly ( P <0.05) lower than predicted, while donkeys exhibited resting values similar to mammals of the same body mass. In both camels and donkeys     increased in a nearly linear fashion over the range of exercise speeds. The minimum COT_tot of camels in the walking and pacing gaits were not significantly different ( P =0.27). Similarly, donkeys exhibited no significant difference ( P =0.09) in the minimum COT_tot while walking and trotting. In both camels and donkeys, the minimum COT_tot was significantly ( P <0.05) lower than the predicted COT_tot for mammals of the same body mass. The COT_net in both camels and donkeys was determined to be gait dependent and significantly ( P <0.05) lower than the predicted minimum COT_net values for walking and running. The low COT seen in camels and donkeys results in energy and water savings.     

The evolution of body armor in mammals: plantigrade constraints of large body size

Predictions associated with opposing selection generating minimum variance in basal metabolic rate (BMR) in mammals at a constrained body mass (CBM; 358 g) were tested. The CBM is presumed to be associated with energetic constraints linked to predation and variable resources at intermediate sizes on a logarithmic mass scale. Opposing selection is thought to occur in response to energetic constraints associated with predation and unpredictable resources. As body size approaches and exceeds the CBM, mammals face increasing risks of predation and daily energy requirements. Fast running speeds may require high BMRs, but unpredictable and low resources may select for low BMRs, which also reduce foraging time and distances and thus predation risks. If these two selection forces oppose each other persistently, minimum BMR variance may result. However, extreme BMR outliers at and close to the CBM should be indicative of unbalanced selection and predator avoidance alternatives (escapers vs. defenders), and may therefore provide indirect support for opposing selection. It was confirmed that body armor in defenders evolves at and above the CBM, and armored mammals had significantly lower BMRs than their nonarmored counterparts. However, analyses comparing the BMR of escapers--the fastest nonarmored runners (Lagomorpha)--with similar-sized counterparts were inconclusive and were confounded by limb morphology associated with speed optimization. These analyses suggest that the risks and costs of predation and the speed limitations of the plantigrade foot may constrain the evolution of large body sizes in plantigrade mammals.     

A biomechanical model for size, speed and anatomical variations of the energetic costs of running mammals

Here we propose a model of energetic costs and the muscle-tendon unit function on running mammals. The main goal is to set a simple theoretical framework which gives an understanding of the biomechanical principles behind the size, speed and anatomical variations of the energetic costs of running mammals. The model is a point-like mass withstood by a two-segment leg with an extensor muscle serially attached to a tendon. We considered withstanding body weight during the stance phase as the main role of the muscle-tendon unit during fast locomotion. The ground reaction force dependence on speed and the time of stance phase as well as other biomechanical characteristics were taken from previous empirical studies of running. At the same time, the morphological variations with body mass were taken from empirically well-established allometric equations for mammals. The metabolic cost was estimated from an empirical equation relating metabolic power with muscular force and speed in shortening and stretching. Our model predicts the pattern of mass specific metabolic rate variations with both speed and body mass. It also gives an explanation of the experimentally reported linear inverse relationship between the rate of energy used for running and the time of application of force by the foot to the ground during each stride. It also suggests an explanation of the unusual energy saving adaptations of large macropodids. It provides some predictions on the relationship, between energy costs and muscle-tendon unit characteristics, testable on further experiments.     

Metabolism during flight in two species of bats, Phyllostomus hastatus and Pteropus gouldii.

The energetic cost of flight in a wind-tunnel was measured at various combinations of speed and flight angle from two species of bats whose body masses differ by almost an order of magnitude. The highest mean metabolic rate per unit body mass measured from P. hastatus (mean body mass, 0.093 kg) was 130.4 Wkg-1, and that for P. gouldii (mean body mass, 0.78 kg) was 69.6 Wkg-1. These highest metabolic rates, recorded from flying bats, are essentially the same as those predicted for flying birds of the same body masses, but are from 2.5 to 3.0 times greater than the highest metabolic rates of which similar-size exercising terrestrial mammals appear capable. The lowest mean rate of energy utilization per unit body mass P. hastatus required to sustain level flight was 94.2 Wkg-1 and that for P. gouldii was 53.4 Wkg-1. These data from flying bats together with comparable data for flying birds all fall along a straight line when plotted on double logarithmic coordinates as a function of body mass. Such data show that even the lowest metabolic requirements of bats and birds during level flight are about twice the highest metabolic capabilities of similar-size terrestrial mammals. Flying bats share with flying birds the ability to move substantially greater distance per unit energy consumed than walking or running mammals. Calculations show that P. hastatus requires only one-sixth the energy to cover a given distance as does the same-size terrestrial mammal, while P. gouldii requires one-fourth the energy of the same-size terrestrial mammal. An empirically derived equation is presented which enables one to make estimates of the metabolic rates of bats and birds during level flight in nature from body mass data alone. Metabolic data obtained in this study are compared with predictions calculated from an avian flight theory.