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Do racehorses and Greyhound dogs exhibit a gender difference in running speed?
Abstract
At any level of competition, men run faster than women. Consequently, a male speed advantage is often presumed for other species. This assumption was tested in two animals bred for speed: horses and dogs. Results from Thoroughbred (TB), Standardbred (STB) and Greyhound (GH) races were analysed by ANOVA to compare the speeds of victorious males, neutered males (TB and STB only) and females. Separate analyses were run for shorter (TB: ≤ 1609 m, GH: 503 m) and longer (TB: >1609 m, GH: 603.5 m) TB and GH races. All STB races (trotters and pacers) were 1609 m. In TB races, intact males were 0.7% faster than females at ≤ 1609 m (n = 305; P < 0.01) and 1.4% faster at >1609 m (n = 194; P < 0.01). The speed of neutered males was equivalent to that of females at both distances. Gender accounted for 3.8 and 10.7% of the variance in speed at short and long distances, respectively. In STB pacers, intact males were 1.5% faster than females and gender accounted for 10.1% of the variance in speed (n = 96; P < 0.01). Gender was not a significant predictor of STB trotter (n = 95) or GH speed at 503 m (n = 146) or 603.5 m (n = 23). In conclusion, gender has a significant effect on speed of TBs and STB pacers. Although the effect size is small, it may be significant for racing; in a 7 furlong (1408 m) TB race, the 0.7% difference translates to an advantage of several lengths.
... Seules les fonctions de survie et de reproduction ont été décrites pour une grande diversité d'espèces (8,10,25 (156)(157)(158). Les contraintes sélectives sur les capacités spécifiques de course, par la chasse pour le chien ou par le transport des humains et du fret pour les chevaux, ont progressivement accentué une capacité déjà exacerbée par le statut de proie (pour les chevaux) ou de prédateur (pour les chiens) qu'ils possédaient depuis des millions d'années (156,158,159). On trouve ainsi dès l'Antiquité des courses de lévriers, alors que chiens et chevaux seront utilisés dès le début du Moyen-âge pour la vènerie (156). ...
... Toutefois, après quelques années de pratique, l'aspect social semble aussi chez l'homme dominer l'envie de compétition (215,213). Cet écart est aussi lié au potentiel biologique, des différences entre femmes et hommes existent dans la dégradation graduelle de l'organisme (213)(214)(215) (159,195,204,205,207,216,217). La majorité des études comparatives s'est consacrée à la différence de durée de vie entre femelles et mâles (205,206). ...
... Pour d'autres comparaisons intégratives, les principales données concernent les chevaux et chiens de course (159,207). Ces données montrent peu d'écarts de vitesse maximale entre les meilleures femelles et les meilleurs mâles (de l'ordre de 1%) (151,159,207). Des données chez le lézard suggèrent de la même façon une vitesse maximale de sprint plus élevée chez les mâles par rapport aux femelles (207,217). ...
L’organisation biologique, du niveau moléculaire jusqu’au niveau des performances de l’organisme. La locomotion est une fonction neurophysiologique hautement intégrée illustrant un tel processus multi-échelle. Le déclin des performances de locomotion avec l’âge, comme la vitesse maximale, a été observé pour de nombreuses espèces, aussi bien en captivité qu’en milieu naturel. Cependant, ces descriptions restent souvent succinctes, sans précision sur la progression de ces performances au cours du vieillissement. Dans ces travaux, nous utilisons une équation bi-phasique pour décrire la relation entre performance de locomotion et âge sur l’ensemble de la durée de la vie pour Caenorhabditis elegans, Mus domesticus, Canis familiaris, Equus caballus et Homo sapiens. Les performances maximales de locomotion se révèlent être des bio-marqueurs robustes pour suivre la progression des performances sur l’ensemble de la durée de vie des animaux, permettant ainsi d’estimer le pic physiologique et le début du déclin des performances. De plus, dans tous les cas, nous remarquons que la forme de progression des performances maximales selon l’âge est similaire et conservée d’une espèce à l’autre ; seule varie la pente dans le temps, dépendant de l’espèce et la performance mesurée. L’observation des performances selon le genre ne montre pas de différence dans la forme de l’enveloppe. Néanmoins, elle révèle des écarts variables dans les performances maximales entre femelles et mâles selon les espèces. Enfin, les conditions thermiques affectent les performances maximales de locomotion, mais la forme de l’enveloppe reste aussi préservée. Nous avons ensuite étudié le développement et l’expansion de cette dynamique au cours du siècle dernier pour les performances athlétiques maximales d’Homo sapiens. Cette étude révèle que la forme s’est progressivement précisée au cours du temps en s’étendant à tous les âges et suivant homothétiquement la progression des records du monde. Néanmoins, la progression semble ralentir au cours des dernières décennies, laissant présager l’atteinte possible des limites biologiques d’Homo sapiens. Ces travaux offrent de nouvelles perspectives sur l’utilité des approches comparatives et l’utilisation d’un bio-marqueur comme les performances de locomotion pour suivre les dynamiques sur l’ensemble de la durée de vie à différentes échelles. Elles apportent aussi un regard novateur sur la progression des performances avec l’âge, en intégrant à la fois les processus de développement et de vieillissement, permettant ainsi de préciser les pics physiologiques et la forme des progressions des performances sur toute la durée de la vie.
... The performance superiority of males in racing was also proven in studies by other authors (Mota et al., 1998;Ekiz et al., 2005;Entin, 2007;Sobczyńska, 2011;Velie et al., 2015;Özen et al., 2021). According to Kopečná et al. (2017), the reason for this could be the fact that there is significant pressure on the colts to become breeding stallions and they need to have the highest performance to be selected for a stud. ...
... As is supported by the results of other studies, Moritsu et al. (1994) demonstrated better racing times for males at the distance of 1800 m but not at the distance of 1200 m in Japan. In addition, Entin (2007) found that intact males were statistically significantly 0.7 % faster than females at distances shorter than 1609 m and 1.4 % faster at distances longer than 1609 m. Research into horse populations has been used to examine the heritability of racing performance, and it is now recognized that many measures of racing performance (particularly race speed and ratings) are heritable (More, 1999). ...
The aim of the research was to assess how age, sex, sire, country of foaling, country of training and race distance influenced the international racing and performance of Thoroughbreds. The research was based on performance ratings of 6216 horses assigned by the International Federation of Racing Authorities between 2004 and 2022. The most common sex was stallion (58.54 %) and more than half of the population consisted of 3-and 4-year-old horses (54.68 %). The majority of the horses had the USA as their country of foaling (25.92 %) and also as their country of training (24.87 %
... Sex performance differences for competitive equine runners are minimal, ranging from one-half to 3%. The margins for canine runners are substantially smaller and perhaps nonexistent (9,10). Consequently, neither competitive dog nor select horse racing such as the Kentucky Derby has separate sex categories. ...
... Due to the differing across race time and velocity patterns for males and females, repeated measures ANOVA revealed a significant interaction between sex and segment distance for time per total distance [F (1,9) Step Numbers across the 100-m Event Females took more steps than males across each of the three within-race intervals appearing in Table 3. Differences in step number varied throughout the race with the largest difference being present in the 30-60-m segment at 11.4%. ...
Human, but not canine or equine running performance, is significantly stratified by sex. The degree of stratification has obvious implications for classification and regulation in athletics. However, whether the widely cited sex difference of 10-12% applies equally to sprint and endurance running events is unknown. Here, different determining factors for sprint (ground force/body mass) vs. endurance performance (energy supply & demand) and existing trends, led us to hypothesize that sex performance differences for sprint running would increase with distance and be relatively small. We quantified sex performance differences using: 1) the race times of the world's fastest males and females (n=40 each) over a 15-year period (2003-2018) at nine standard racing distances (60-10,000m), and 2) the 10-meter segment times of male (n=14) and female (n=12) athletes in World Championship 100-meter finals. Between-sex performance time differences increased with sprint event distance [60m-8.6%, 100m-9.6%, 200m-11.0%, 400m-11.7%] and were smaller than the relatively-constant mean (12.4±0.3%) observed across the five longer events from 800-10,000 meters. Between-sex time differences for the 10-meter segments within the 100-meter dash event, increased throughout spanning 5.6% to 14.2% from the first to last segment. We conclude that sex differences in sprint running performance increase with race and running distance.
... These findings are supported by previous analyses of sex differences in running speed by Entin who showed male Thoroughbred and Standardbred horses were only 3.8% and 1.4% faster than females respectively at races longer than one mile. 32 Greyhound racing dogs had only a 0.4% difference between sexes in average winning velocities at distances of ~500 m. Whereas in humans, there is generally a ~10% sex difference in performance in weight bearing activities. ...
... After the removal of the animal's reproductive organ through neutering, evidence suggests there are no short or long term decrements in exercise performances for horses or dogs. 32 The limited sex-related anatomical differences and blunted impact of androgen hormones on performance among animals likely explain, in part, the lack of sex-related differences observed in exercise performance of elite horses and dogs. Small observational studies and case studies of elite athletes undergoing hormone therapy, including transgender, cisgender and individuals with disorders of sex development (previously called "intersex"), provide evidence supporting the role of testosterone in potential athletic achievement. ...
Elite performing men continue to record faster record times in running events compared to women. These sex‐based differences in running speed and endurance in humans are expected based on sexual dimorphisms that contribute to differences in the determinants of aerobic performance. Comparatively, the sexual dimorphisms contributing to sex‐based differences in elite aerobic performance are not ubiquitous across other species that compete in running events. The purpose of this review is to offer a framework and model for ongoing discussions of the physiological determinants and ultimately limits of physical performance. The records for average running speed of champion athletes were delineated by sex for thoroughbred horses, greyhound dogs, and humans. Male and female performances within each of these species are being optimized by training, nutrition, and financial incentives, and are approaching a performance maximum. For horses and greyhounds breeding also plays a role. Analysis of athletic records shows that there is a sex‐related difference of ~10% or more in elite athletic performance for humans; however, the upper limit of performance does not appear to be different between sexes for thoroughbred horses and greyhound dogs. In the context of the nil sex differences in running performance in thoroughbreds and greyhounds, we discuss the physiological role of sexual dimorphisms on sex‐specific limits to running performance. We highlight that studies on both human and animal performance in athletic events stimulate critical physiological questions and drive novel research.
... Greyhounds, for example, also come in two sexes, male and female. However, there are no notable differences in athletic performance between the sexes, especially regarding their performance in track racing (Entin 2007;Senefeld et al. 2021). Consequently, the question of which female greyhound is fastest is not especially interesting. ...
Two distinct forms of fairness in sport are regularly conflated, which produces confusion in important debates concerning the participation of trans-gender women in female sporting contests. The distinct forms of fairness arise in two distinct forms of sporting contest: the handicap contest and the championship contest. Handicap contests seek to ‘level the playing field’ by ensuring that all participants have an equal or ‘sporting’, chance of winning.Championship contests seek to find the person or team that is best at a particular event – to find a champion. Each form of contest makes use of female categories, although for different reason. Arguments for and against the use of handicapping to ensure fairness in championship contests such as the Olympics conflate these forms of contest and their distinct accounts of fairness
... However, non-genetic factors like sex, age, and horse management had an impact on body conformation measurements [29]. Males often perform better than females due to differences in anatomy, physiology, and the hormone system [30], [31]. The average body lengths of the stallion and mare were found to be 120.86±0 ...
Background: The socio-economic importance of horses plays a decisive role in the dynamism of rural economies in remote regions of developing countries such as Bangladesh. Horses are particularly suitable for transportation and recreation in these areas. Methods: The study was conducted from January to March 2023 in 200 randomly selected horse families concentrated in Sherpur, Jamalpur, Tangail, Sirajganj, Natore, and Noagoan districts of Bangladesh. After the necessary corrections and modifications, the final questionnaire was created based on the objectives of the study. The data were collected by respondents individually through personal interviews. Results: The average number of horses per family was 1.18, with 70% of them being transported and only 11.5% participating in horse races. The average peak and the poor seasonal income of the farmers were recorded as BDT (12,920-6,717). On average, 2 kg of concentrate feed per day is supplied to each horse with forages in the morning and afternoon depending on the situation. All farmers practiced natural mating, but they did not perform vaccination (100%). The indigenous horse's face color was observed as a star of 30%, and 45% non-specific, while the coat color was chestnut 38.5%, bay 41.5%, grey 8%, pseudo-Albino 3.5%, black 3.5%, brown 1% and bay roan 4%. The chest stocking color was observed as black 48%, white 33%, black and white 19%. The average body length, chest girth, neck length, ear length, and body weight in the research region were 119.86±0.17 cm, 126.28±0.19 cm, 37.87±0.14 cm, 15.78±0.12 cm, and 160.43±0.65 kg. The body length and body weight (p=0.000) differ significantly from region to region. Age at first service, service per conception (no.), gestation length, and foaling interval were 2.34±0.07 years, 1.21±0.06 years, 10.91±0.33 months and 1.00±0.03 years, respectively. Conclusions: Horses have enormous potential for livelihoods in rural areas, so it is important to preserve and improve horse genetic resources and ensure sustainable horse rearing in Bangladesh.
... Size is a genetic trait with high heritability (34). Males generally perform better than females, resulting from a different morphology, physiology, and hormonal system (40,41). ...
This study aims to determine the morphometric characteristics of Purebred-Arab horses born and bred in Algeria specialized in horse racing depending on age and sex. Measurement of the study was taken at the Kaid-Ahmed racecourse in Tiaret (Algeria). The average size at the withers of the subjects (n=95) was 152.15±05.07 cm, and the thoracic girth was 166.44±06.43 cm. Compared to the height at the withers, the rump size was slightly lower 151.61±04.79 cm, and the body length was almost identical 152.82±06.30 cm with an average weight of 395.83±40.51 kg that is considered minor. Our sample horses appear pretty thick relative to their size with an average circumference of the anterior and posterior guns of 18.30±01.70 cm and 19.68±0 1.79 cm respectively, and in extent arm lengths 30.90±02.66 cm and forearm 31.77±02.81 cm. The various calculated indices qualify our horses as compact horses, light, square and long. The reading of the dress color of our model presents the dominance of the Alazan at 51.57%, and the shape of the chamfer is mostly Camus at 56.84%, giving it a short head with a broad forehead and concave chamfer. Statistical analysis determined that males were more significant than females and adults compared to young.
... The data are described in the Appendix. Factors which should be taken into account have been studied, for instance Entin (2007) concludes that gender does make a difference. The genetic trend is examined in Gaffney and Cunningham (1988). ...
Ranked events are pivotal in many important AI-applications such as Question Answering and recommendations systems. This paper studies ranked events in the setting of harness racing.
For each horse there exists a probability distribution over its possible rankings. In the paper, it is shown that a set of expected positions (and more generally, higher moments) for the horses induces this probability distribution.
The main contribution of the paper is a method, which extracts this induced probability distribution from a set of expected positions. An algorithm is proposed where the extraction of the induced distribution is given by the estimated expectations. MATLAB code is provided for the methodology.
This approach gives freedom to model the horses in many different ways without the restrictions imposed by for instance logistic regression. To illustrate this point, we employ a neural network and ordinary ridge regression.
The method is applied to predicting the distribution of the finishing positions for horses in harness racing. It outperforms both multinomial logistic regression and the market odds.
The ease of use combined with fine results from the suggested approach constitutes a relevant addition to the increasingly important field of ranked events.
... Sexual dimorphism is present in horses 1 and gender differences in sport exist in other species 2 and in other equestrian sports. 3 Therefore, there is a chance that gender differences can be observed in eventing, particularly between stallions and mares but also between stallions and geldings. ...
To test the hypothesis that gender affects horse scores in eventing competition, data on the scores and points awarded to 681 horses was collected from the British Eventing website. Equal numbers of mares, geldings and stallions were used, all foaled during or after 1994 and aged 4–10 years. The study included five levels of competition (BE90, BE100, Novice, Intermediate and Advanced) and investigated differences in mean phased scores, total scores and rank in competition. Additionally, the mean and median ‘BE points per competition’ of each gender were compared. Significant differences in performance between genders were found at all levels except Advanced. Differences were highlighted in average phased and total scores, rank and median points per competition. There was an overall pattern of stallions and geldings outperforming mares, though this was not found to be true at all levels. The only area in which mares were found to perform significantly better than geldings or stallions was showjumping time penalties at BE90.
... In some contexts, despite sexual dimorphism in long bone length and bodyweight, the sex of dogs appears to have no effect on their performance. For instance, the sex of greyhounds is reported to have no effect on speed [9], most probably because females are lighter and so can run as quickly as their male counterparts, despite having shorter long bones. In certain breeds of dog, Serpell and Hsu [10] observed sex differences only in trainability. ...
Working sheepdog trials test the attributes of dogs as well as the dogmanship and stockmanship skills of handlers. They generally include standard elements such as outrun, lift, fetch, drive, shed, pen and single to test all facets of the work that dogs perform on a farm. While both male and female handlers participate, these trials are traditionally dominated by male handlers. Both male and female dogs compete on equal terms within the same events. Drawing data from files (n = 60) downloaded from YouTube, the current study explores whether behaviours of dogs and their handlers during sheepdog trials differ between handler gender and dog sex at different levels of competition. It compared the stalking, crouching, chasing and stationary behaviours of dogs in open (n = 28 dogs: 10 females, 18 males) and not-open trials (n = 32 dogs: 20 females, 12 males). The dogs in this study had male (n = 38) and female (n = 22) handlers, whose movement and use of vocal cues and arm elevations were also compared. However, the small sample size and limitations of these videos as a data source should be noted before the results are generalised to the broader field of working-dog behaviour. The results of an REstricted Maximum Likelihood test showed that male handlers spent, on average, significantly more time in the fetch and drive elements than female handlers, but this difference between sexes was present only in not-open events (mean time to Fetch, female handler = 44.07s, male handler = 124.00s, P
... However, gender effects were often not significant. It was surprising that no gender effect was detected for cross-country, as there is clear evidence of an advantage for males as evidenced for racing (Entin, 2008). ...
Eventing competitions in Great Britain (GB) comprise three disciplines, each split into four grades, yielding 12 discipline-grade traits. As there is a demand for tools to estimate (co)variance matrices with a large number of traits, the aim of this work was to investigate different methods to produce large (co)variance matrices using GB eventing data. Data from 1999 to 2008 were used and penalty points were converted to normal scores. A sire model was utilised to estimate fixed effects of gender, age and class, and random effects of sire, horse and rider. Three methods were used to estimate (co)variance matrices. Method 1 used a method based on Gibbs sampling and data augmentation and imputation. Methods 2a and 2b combined sub-matrices from bivariate analyses; one took samples from a multivariate Normal distribution defined by the covariance matrix from each bivariate analysis, then analysed these data in a 12-trait multivariate analysis; the other replaced negative eigenvalues in the matrix with positive values to obtain a positive definite (co)variance matrix. A formal comparison of models could not be conducted; however, estimates from all methods, particularly Methods 2a/2b, were in reasonable agreement. The computational requirements of Method 1 were much less compared with Methods 2a or 2b. Method 2a heritability estimates were as follows: for dressage 7.2% to 9.0%, for show jumping 8.9% to 16.2% and for cross-country 1.3% to 1.4%. Method 1 heritability estimates were higher for the advanced grades, particularly for dressage (17.1%) and show jumping (22.6%). Irrespective of the model, genetic correlations between grades, for dressage and show jumping, were positive, high and significant, ranging from 0.59 to 0.99 for Method 2a and 0.78 to 0.95 for Method 1. For cross-country, using Method 2a, genetic correlations were only significant between novice and pre-novice (0.75); however, using Method 1 estimates were all significant and low to moderate (0.36 to 0.70). Between-discipline correlations were all low and of mixed sign. All methods produced positive definite 12 × 12 (co)variance matrices, suitable for the prediction of breeding values. Method 1 benefits from much reduced computational requirements, and by performing a true multivariate analysis.
The purpose of this study was to elucidate the skeletal muscle transcriptomic response unique to rest duration during high-intensity interval exercise. Thoroughbred horses performed three 1-min bouts of exercise at their maximal oxygen uptake (10.7-12.5 m/s), separated by 15 min (long) or 2 min (short) walking at 1.7 m/s. Gluteus medius muscle was collected before and at 4 h after the exercise and used for RNA sequencing. We identified 1,756 and 1,421 differentially expressed genes in response to the long and short protocols, respectively using DEseq2 analysis [false discovery rate (FDR) cutoff = 0.05, minimal fold change = 1.5]. The overall transcriptional response was partially aligned, with 43% (n=949) of genes altered in both protocols, whereas no discordant directional changes were observed. K-means clustering and gene set enrichment analyses based on gene ontology biological process terms showed that genes associated with muscle adaptation and development were upregulated regardless of exercise conditions; genes related to immune and cytokine responses were more upregulated following the long protocol, and protein folding and temperature response were highly expressed after the short protocol. We found that 11 genes were upregulated to a greater extent by the short protocol and one was by the long protocol, with GNA13, SPART, PHAF1, and PTX3 identified as potential candidates for skeletal muscle remodeling. Our results suggest that altered metabolic fluctuations dependent on the intermittent pattern of interval exercise modulate skeletal muscle gene expression, and therefore rest interval length could be an important consideration in optimizing skeletal muscle adaptation.
Elite individual sports in which success depends on power, speed or endurance are conventionally divided into male and female events using traditional binary definitions of sex. Male puberty creates durable physical advantages due to the 20-30-fold increase in circulating testosterone producing a sustained uplift in men’s muscle, bone, hemoglobin, and cardiorespiratory function resulting from male puberty and sustained during men’s lives. These male physical advantages provide strong justification for separate protected category of female events allowing women to achieve the fame and fortune from success they would be denied if competing against men. Recent wider social acceptance of transgender individuals, together with the less recognized involvement of intersex (46 XY DSD) individuals, challenge and threaten to defeat the sex classifications for elite individual female events. This can create unfair advantages if seeking inclusion into elite female events of unmodified male-bodied athletes with female gender identity who have gained the physical advantages of male puberty. Based on reproductive physiology, this paper proposes a working definition of sport sex based primarily on an individual’s experience of male puberty and can be applied to transgender and various XY intersex conditions. Consistent with the multidimensionality of biological sex (chromosomal, genetic, hormonal, anatomical sex), this definition may be viewed as a multistrand cable whose overall strength survives when any single strand weakens or fails, rather than as a unidimensional chain whose strength is only as good as its weakest link.
To date, the biomechanical dynamics in camelids have not been addressed, although it might be a factor that can affect selection and breeding in this species. Therefore, the aim of this article is to conduct curve fitting and discriminant canonical analysis to identify the mathematical function that best captures the dynamics of camel locomotion and to study the impact of kinematic, morphometric, physiological, and phaneroptic variables on gait performance in leisure riding and racing activities in dromedaries, respectively. The cubic function emerged as the most suitable mathematical model to represent the locomotive behavior of camels. Various factors were found to play a pivotal role in the athletic performance of leisure riding and racing dromedary camels. Concretely, angular measurements at the distal fore and rear extremity areas, pelvis inclination, relative volume of the hump, impact forces of the front limbs, post-neutering effects, and the kinematic behavior of the scapula, shoulder, carpus, hip, and foot are the factors that greatly impact gait performance in leisure riding and racing camels. The biomechanical performance at these specific body regions has a profound impact on weight absorption and minimization of mechanic impact during camel locomotion, static/dynamic balance, force distribution, energy of propulsion, movement direction and amplitude, and storage of elastic strain in leisure riding and racing dromedaries. In contrast, other animal- and environment-dependent factors do not exert significant influence on camel gait performance, which can be attributed to species-specific, inherited adaptations developed in response to desert conditions, including the pacing gait, broad foot pads, and energy-efficient movements. The outcomes of our functional data analysis can provide valuable insights for making informed breeding decisions aimed at enhancing animal functional performance in camel riding and racing activities. Furthermore, these findings can open avenues for exploring alternative applications, such as camel-assisted therapy.
To determine whether left-to-right asymmetry of the central tarsal bone (CTB) of racing greyhounds was detectable using computed tomography (CT) in live dogs; to quantify the asymmetry in terms of average bone volume, volumetric bone mineral density (vBMD), and dorsal cortical shape, and to determine if age, gender, bodyweight, number of starts or history of tarsal injury were significant covariates.
One trainer supplied 11 male and seven female, unrelated, skeletally mature, actively racing greyhounds, including dogs with a history of tarsal injury diagnosed by the trainer and/or track veterinarian (n=8), and dogs without a history of tarsal injury (n=10). Using CT, standardised parameters of the CTB were measured including volume and average vBMD of the left and right CTB, vBMD of regions within the CTB, and bone shape.
There was no difference in the volumes of the left and right CTB and no association with number of racing starts. Volume of CTB in dogs with a history of tarsal injury was greater than in dogs with no history of injury (p<0.001). Mean vBMD of the right was greater than the left CTB (p=0.004), and was independent of history of injury, gender, bodyweight, and number of starts. Males with a history of injury weighed more than those with no history of injury (p=0.004). The region of greatest difference in vBMD between right and left limbs was the centrodorsomedial aspect of the CTB. Middle plantar ligament enthesiopathies and fractures of tarsal bones other than the central tarsal bone were identified in dogs with and without a history of tarsal injury.
Significant left-to-right asymmetry of the CTB in racing greyhounds was detected using CT. Contrary to previous suggestions, the asymmetry was not associated with the number of racing starts. We propose that the majority of the adaptive modelling of the CTB occurred rapidly following the onset of counter-clockwise training, with little further modelling throughout the racing career of the dog, however further investigation is warranted.
This study described a technique using CT for imaging the CTB in live dogs, which opens the way for a longitudinal study of bone modelling of the CTB in response to training and racing in a counter-clockwise direction.
Variation in the risk of predation may profoundly affect the evolution of anti-predator behaviours. Theory predicts that selection would favour enhanced locomotor capacity in high-risk environments, such as open habitats. An earlier study demonstrated significant intra-population and intersexual variation in wariness and sprint speed among the lava lizards (Microlophus albemarlensis) that was concordant with presumed risk of predation on Isla Plaza Sur in the Galápagos Archipelago. In particular, males and females from sparsely vegetated areas had greater approach and flight distances than those of more highly vegetated areas; males were also faster than females. We now compare endurance capacities of males and females from the same population on Isla Plaza Sur. We predicted the higher presumed risk of predation in the sparsely vegetated region would favour enhanced performance capacities. In addition, we predicted that sexual selection for territory defence would favour males that had the ability to flee long distances. Lizards from the sparsely vegetated area did have higher endurance than those from the vegetated area. Males had higher endurance times than females, but this difference was an outcome of body size, which was inconsistent with the sexual selection hypothesis. The significant differences in endurance between locations combined with the absence of dimorphism in performance suggest that the intrapopulation differences are an outcome of natural selection for predator escape.
Locomotor performance is a fundamental link between an animal and its environment. Considerable evidence has accumulated about the biomechanical, physiological and morphological causes of variation in sprint speed and endurance in animals. Yet little information is available about the ecological role of locomotion and its relationship to fitness. This is largely due to the difficulty of acquiring survivorship data in known demographic populations. To address the selective significance of locomotor performance, I estimated the covariation between sprint speed and survivorship of juveniles in a population of the lizard, Urosaurus ornatus. Selection analyses based on mark-recapture data revealed significant directional selection for burst velocity and stride length. Faster lizards with longer stride lengths realized a survival advantage over slower lizards regardless of size. Significant non-linear selection was detected on initial velocity and mean velocity. The selection surface for initial velocity was concave up, hence juveniles with intermediate values for initial velocity had lower fitness. Conversely, the selection surface for mean velocity was concave down, thus juveniles with intermediate values for mean velocity had higher survivorship. I hypothesize that the differences in sprint performance influence prey capture and predator escape. Faster lizards may also select warmer microhabitats during favourable conditions, which may enhance growth rates but entail higher risks of predation.
It has been suggested in previous studies that the difference in endurance performance between males and females is related to gender-specific differences in cardiac function. Other studies have not equated males and females for physical condition, and this may have contributed to the findings. The purpose of this study was to determine the extent to which the difference in VO2max in groups of similarly trained males and females was explained by gender differences in cardiac size, fat-free weight (FFW) and hemoglobin concentration [( Hb]). Measurements of VO2max, FFW, [Hb] and cardiac size (LVM) were made on 19 males and 20 females comparable in age and cardiorespiratory capacity. The difference between men and women in LVM accounted for 68.3% of the gender difference in VO2max, and the combination of LVM and FFW accounted for 98.7% of the gender-related difference in VO2max. It was concluded that the gender difference in LVM accounts for a majority of the difference in VO2max in males and females, with other aspects of body size accounting for nearly all the remaining difference. The gender difference in heart size primarily reflects the smaller overall dimensions of women.
The aim of this study was to investigate the influence of gender on the possible contribution of tlim at Va max (minimal speed that elicits VO2max) in performance speeds. The male and female elite middle-distance runners had similar performance (IAAF scores). Fourteen female and fifteen male (25.2 +/- 3.6 and 25.1 +/- 4.2 yr old; VO2max = 63.2 +/- 4.2 and 77.7 +/- 6.4 ml.kg-1 min-1; Va max = 17.3 +/- 0.7 and 20.8 +/- 1.1 km.h-1, respectively) performed three exercise tests on a treadmill (3 degrees slope) within a 2-wk period: an incremental test to determine VO2max, Va max and the velocity at the onset of blood lactate accumulation (VOBLA); an exhaustive constant velocity test to determine tlim at Va max; and an exhaustive constant velocity test at 110% Va max to determine the accumulated oxygen deficit (AOD). There were no effects of gender, i.e., no significant differences were observed between female and male for tlim at Va max (421 +/- 129 vs 367 +/- 118 s respectively; P = 0.24), VOBLA as % Va max (88.4 +/- 2.7 vs 90.4 3% of Va max; P = 0.07), AOD (40.1 +/- 14.9 vs 48.9 +/- 21.3 ml.O2.kg-1; P = 0.22), running economy at the same absolute speed, i.e., 14 km.h-1 (53.4 +/- 2.6 vs 52.7 +/- 4.1 ml.O2.min-1.kg-1; P = 0.64) nor for gross oxygen cost of running (CR) at the same relative velocity (75% Va max) (0.214 +/- 0.001 vs 0.214 +/- 0.002 ml.O2.kg-1.m-1; P = 0.94). However, an effect of gender was found on the relationship between the bioenergetic parameters and performance. For male, v1500 was predicted by Va max, VOBLA, tlim at 110% of Va max, and CR (R2 = 0.96). For female, no bioenergetic parameters were strongly correlated with v1500 m. The inverse relationship found between Va max and tlim at Va max in previous literature was confirmed by the 29 runners in this study and for the subset of male only.
Numerous studies have examined sexual dimorphism in the morphology and behavior of vertebrates; very few, however, have explicitly investigated the possibility of gender differences in physiological performance, despite the observations of such differences in humans. In this study, I investigated physiological sexual dimorphism in the lizard genus Cnemidophorus by measuring five whole-animal traits, all of which are likely to influence fitness in these species: burst speed, endurance, maximal exertion capacity, standard metabolic rate, and evaporative water loss rate. Because at least some of these traits are known to be strongly influenced by body size, I tested for dimorphism using both absolute and size-corrected trait values. An examination of six Cnemidophorus species and subspecies revealed a strong trend toward higher absolute trait values in males for all variables except endurance. Most of the dimorphism in standard metabolic rate and evaporative water loss rate could be explained by differences in body mass between males and females; for the locomotor traits, however, body size explained only a small fraction of the overall sexual dimorphism. The portion of trait differences not explained by body size was likely due to gender differences in physiology, such as differences in relative muscularity and fat content.
Differences between sexes in physiological performance have received little attention in animals. We tested for sex differences in maximum sprint speed and maximal exertion over a range of temperatures in a population of Platysaurus intermedius wilhelmi lizards. We also examined sex-based differences in selected temperature range, mean field body temperatures (T(b)), and thermal activity limits. Finally, we conducted field studies to quantify male and female responses to a potential predator, which may be affected by their respective performance capabilities. Males were faster than females at all temperatures, and body size had no significant effect on sprint speeds. Males and females also selected similar T(b)'s when placed in a thermal gradient, but in the field, male lizards' T(b)'s were different from those of the females. However, predicted sprint speeds for males and females at their field T(b)'s are similar. No significant differences were found between males and females with regard to maximal exertion. When approached in the field, adult male lizards took refuge significantly earlier than did adult females and also fled over shorter distances, suggesting that females rely on crypsis as an escape strategy.
Individual racing records were used to estimate the effects of sex, age and handicap weight on racing performance in American Quarter Horses. Adjustment factors for pre- adjusting racing times were calculated for each of five distances. At 320 m, 2-yr-old stallions were .060 s faster than mares and .032 s faster than geldings of the same age. Multiplicative sex adjustment factors calculated from 2-yr-olds ranged from .9956 to .9988 for mares and .9946 to .9995 for geldings, depending on distance. Sex adjustments generally increased as distance increased. Additive age adjustments were calculated separately for males and females because young mares seemed to require larger adjustments than young stallions and geldings. Two-year-old males and females were .097 and .161 s slower than 4-yr-olds of the same sex in 320-m races. At the same distance, 3-yr-olds were .035 and .062 s slower than 4-yr-old males and females, respectively. Regression coefficients for racing time (s) on handi- cap weight (kg) ranged from -.0051 to .0158. A hierarchical ANOVA was used to evaluate the relative importance of tracks, years, days and individual races as sources of variation in racing time. Although tracks alone accounted for 10.6% to 31.8% of the variation, depend- ing on the distance of the race, individual races within tracks, years and days should be used as contemporary groups. Contemporary groups defined in this way accounted for 49.4% to 70.9% of the variation in racing time.
After analyzing published reports on thoroughbred running horses, the author concludes that "Many lines of evidence, some of which are weak when considered alone but acquire strength when aligned with others, support the belief that male thoroughbred horses, as a class, surpass female thoroughbreds in running ability. Also, the best of the females are inferior to the best of the males in running ability." (PsycINFO Database Record (c) 2012 APA, all rights reserved)
This brief review examines the athletic potential of mammals in general and the horse in particular as it relates to oxygen (O2) transport and utilization. The horse has been bred selectively for over six millennia based upon its ability to run fast. Whereas this has optimized cardiovascular and muscle function and the capacity to deliver and utilize O2, it has resulted in lung failure during intense exercise. Horses in their athletic prime are considered and attention is focused on their maximal capacities as related to O2 transport, irrespective of age per se. Following a few comments on the history of O2, this review moves from established principles of O2 transport at the integrative organ level to the microcirculation and the processes and principles that govern O2 offloading, where much remains to be discovered. Four principal questions are addressed: (1) as an athlete, what are the most outstanding physiological characteristics of the horse? (2) what anatomical and physiological capacities facilitate this superlative performance and such prodigious O2 fluxes (i.e. maximal VO2)? (3) do cardiovascular dynamics or intramuscular energetic processes limit VO2 kinetics (i.e. the speed at which VO2 increases at the onset of exercise)? VO2 kinetics determine the size of the O2 deficit and as such represent an important determinant of muscle metabolism and fatigue; and (4) what determines the efficacy of muscle microcirculatory O2 exchange?
Twenty-three recreational triathletes, 16 male and 7 female (mean = 21.7 yrs), performed max tethered swim (TS), cycle ergometer (CE), and treadmill run (TR) tests prior to participation in a competitive triathlon (0.91 km swim, 40 km cycle, 10 km run). The VO2max values on the TS, CE and TR were similar to those reported for trained athletes in each sport. As a group, cycling times were significantly correlated to both absolute (p less than 0.01) and relative (p less than 0.001) cycling VO2max (r = -0.57 and r = -0.78, respectively); running times significantly correlated with relative (p less than 0.001, r = -0.84) but not absolute (p greater than 0.05) running VO2max; and swimming times significantly correlated with absolute (p less than 0.01, r = -0.49) but not relative (p greater than 0.05) swimming VO2max. With the exception of absolute swim VO2max, the total performance times were significantly correlated to all VO2max values when expressed in both absolute and relative values. This study indicates the important role a moderately trained individual's aerobic power has in determining performances in endurance events such as the triathlon.
The extent to which differences between men and women in cardiorespiratory capacity (VO2max in ml X min-1 X kg FFW-1), percent fat, and running economy (VO2 in ml X min-1 X kg BW-1 at 188 m X min-1) account for the sex difference in 12-min run performance was investigated in 34 male and 34 female recreational runners, 19-35 yr of age. Men differed significantly (P less than 0.05) from women in VO2max (68.6 vs 65.1 ml X min-1 X kg FFW-1), percent fat, (10.8 vs 19.8%), and 12-min run performance (3294 vs 2747 m), but not in running economy (39.0 vs 39.1 ml X min-1 X kg BW-1). Simple and multiple regression and correlation analyses indicated that relations of the biological variables to 12-min run performance were similar within groups of men and women. Multiple regression analysis revealed that percent fat, VO2max (ml X min-1 X kg FFW-1), and running economy accounted for 74, 20, and 2% of the average sex difference in 12-min run performance, respectively. It was concluded that for men and women similarly trained, the average sex difference in 12-min run performance is primarily due to differences in percent fat and cardiorespiratory capacity. If the observed differences between men and women on these variables are truly a function of sex, results of this study provide a biological basis for different distance running performance expectations for men and women.
A standardized treadmill test was used to compare metabolic and ventilatory measurements between 10 standardbred racehorses. The horses were divided into two groups: group A (n = 5) had mean racing speeds of 4.4 s faster than group B (n = 5) over a 1-mi. distance. Each horse was fitted with a venous catheter and connected to a valved gas-collection system. The exercise test consisted of 1-min incremental workloads ranging from 4.0 to 12.0 m/s at a treadmill incline of 3 degrees. Group A had significantly higher (P < 0.05) measurements of maximal O2 consumption (VO2max), O2 pulse, and tidal volume. Venous lactate concentration and respiratory exchange ratio measured at VO2max were also significantly higher (P < 0.05) in group A. Similar treadmill velocities were required to achieve a respiratory exchange ratio of > 1 and venous blood lactate concentration of > 4 mmol/l; however, group A was able to complete a significantly higher (P < 0.01) number of workloads before fatigue. The high aerobic and anaerobic capacity of group A horses may be a major contributor to a faster racing performance.
Heart and body weights were obtained from 230 Greyhounds during necropsy. Sex and age were recorded for each Greyhound. Twenty-nine racing and 21 nonracing Greyhounds among the 230 dogs were compared. Heart-to-body weight ratio was calculated. Statistical analysis was done to determine the effects of age, sex, and racing on heart and body weights and heart-to-body weight ratio.
In adult Greyhounds, mean ± SD body weight was 28.4 ± 3.1 and 31.5 ± 2.8 kg, heart weight was 355.6 ± 52.8 and 381.4 ± 50.8 g, and heart-to-body weight ratio was 1.3 ± 0.2 and 1.2 ± 0.2% for females and males, respectively. Heart and body weights were significantly different between sex and age groups and among nonracing and racing males. However, heart-to-body weight ratio was not significantly different among age, sex, or racing groups.
To examine and compare the exercise cardiac function of endurance-trained (ET) women and men.
Six ET women aged 20 to 29 years (mean VO2max = 64 ml.kg-1.min-1) and 9 ET men aged 20 to 29 years (mean VO2max = 69 ml.kg-1.min-1) were included in the study.
Cardiac output (Q), stroke volume (SV), diastolic filling rate (DFR), and left ventricular ejection rate (LVER) were compared at rest and during exercise at heart rates (HRs) of 110, 130, 150, 170 bpm, and max. Resting blood volume (BV) and hemoglobin concentration ([Hb]) were also compared.
Compared to women, men had a higher BV and [Hb]. At HRmax, men had a higher Q (31.0 +/- 0.6 versus 24.1 +/- 0.9 l.min-1), SV, DFR, and LVER than women. When expressed relative to body mass (kg), there were no gender differences in SVmax, and women had a significantly higher a-v DO2max (approximately 19%) than men. The SV of the men and women did not plateau at a submaximal level but continued to increase progressively to HRmax. During maximal exercise, the DFR was significantly faster than the LVER in the men and the women.
When ET men and women are matched for body mass, the gender difference in SVmax is reduced so that it is no longer statistically significant. However, there are still significant gender differences in Q, DFR, LVER, BV, and [Hb] that contribute to a higher VO2max (ml.kg-1.min-1) in ET men compared to women. To augment SVmax, women and men rely to a greater extent on diastolic filling than on left ventricular emptying.
The purpose of this study was to investigate neuromuscular characteristics and muscle power as determinants of distance running performance.
Seventeen male endurance athletes performed a 5-km time trial (5K) that included three separate constant-velocity 200-m laps during the course and a maximal 20-m speed (V20m) test on an indoor track, and running economy (RE) tests on a treadmill and on the track. Maximal anaerobic (MART) and aerobic running tests on the treadmill were used to determine maximal velocity in the MART (VMART), maximal oxygen uptake (VO2max), peak treadmill performance (VO2max demand), and respiratory compensation threshold (RCT).
Velocity in the 5K (V5K) correlated positively (P < 0.05) with VO2max, VO2max demand, RCT, and RE, as well as with V20m and VMART. Regression analysis showed that RCT, track RE, and VMART were the most important determinants of V5K. V5K also correlated (P < 0.05) with contact times (CT) and stride rates in the maximal 20-m run (r = -0.49 and 0.58, respectively), as well as with the mean CT of the constant velocity laps during the 5K (r = -0.50). VMART correlated significantly with peak blood lactate concentration in MART (r = 0.59, P < 0.05), V20m (r = 0.87, P < 0.001), and CT in the maximal 20-m run (r = -0.61, P < 0.01).
We conclude that neuromuscular characteristics and VMART were related to 5-km running performance in well trained endurance athletes. Relationships between VMART and neuromuscular and anaerobic characteristics suggest that VMART can be used as a measure of muscle power in endurance athletes.
To examine the role of gender differences in cardiac functional capacity in explaining higher mean values for maximal oxygen uptake (VO(2)max) in boys than in girls.
Comparative group exercise testing.
Pediatric exercise testing laboratory.
Twenty-five prepubertal boys (mean [+/- SD] age, 12 +/- 0.4 years) and 24 premenarcheal girls (mean age, 11.7 +/- 0.5 years).
Maximal incremental upright cycle exercise.
Mean values for VO(2)max were the following: boys, 47.2 +/- 6.1 mL/kg/min; and girls, 40.4 +/- 5.8 mL/kg/min (16.8% difference; p < 0.05). The average maximal stroke index with Doppler echocardiography was 62 +/- 9 mL/m(2) for boys and 55 +/- 9 mL/m(2) for girls (12.7% difference; p < 0.05). No significant gender differences were seen in maximal heart rate or arterial venous oxygen difference. When VO(2)max and maximal stroke volume (SV) were expressed relative to lean body mass, gender differences declined but persisted, falling to 6.2% and 5.2%, respectively.
These findings indicate that differences in SV as well as in body composition contribute to gender-related variations in VO(2)max during childhood. Whether this reflects small gender differences in relative heart size or dynamic factors influencing ventricular preload and contractility during exercise is unknown.
This study sought to determine how lactate threshold (LT) is related to running performance in older male and female runners, if LT changes significantly with age, and if gender alters the relationship between LT and performance in older runners.
Subjects were 168 master runners (111 men, 57 women) selected from a longitudinal study, who ran at least 10 miles x wk(-1) for 5 yr or more. VO2max was measured on a treadmill and body composition by hydrostatic weighing. Blood samples taken each minute of exercise were analyzed for lactate concentration and LT determined as the breakpoint in lactate accumulation. Performance times and training histories were self-reported by questionnaire.
Men had significantly greater body mass, fat-free mass (FFM), and VO2max (L x min(-1); mL x kg(-1) x min(-1)) than women. FFM and VO2max (L x min(-1); mL x kg(-1) x min(-1)) declined with age in both men and women. Running performance was significantly different between men and women and declined with age in both. LT (L x min(-1); mL x kg(-1) x min(-1)) was significantly different between men and women, and declined significantly with age in men, whereas LT (%VO2max) did not differ between men and women and increased significantly with age in both. VO2max (mL x kg(-1) x min(-1)) was the most significant predictor of performance in both men and women, whereas LT (L x min(-1)) added to the prediction of 5-km and 10-km performance in women.
The results of this study demonstrate that VO2max (mL x kg(-1) x min(-1)) is a better predictor of performance than LT in older male and female runners. Additionally, LT as a percentage of VO2max increases significantly with age.
Basal metabolic rate is scaled to body mass to the power of 0.73, and we evaluated whether a similar scaling applies when the O2 transport capacity of the body is challenged during maximal exercise (i.e. at maximal O2 uptake, V˙O
2max). The allometric relationship between V˙O
2max and body mass (y=a · x
b, where y is V˙O
2max and x is body mass) was developed for 967 athletes representing 25 different sports, with up to 157 participants in each sport. With an increasing number of observations, the exponent approached 0.73, while for ventilation the exponent was only 0.55. By using the 0.73 exponent for V˙O
2max, the highest value [mean (SD)] for the males was obtained for the runners and cyclists [234 (16) ml · kg−0.73 · min−1], and for the females the highest value was found for the runners [189 (14) ml · kg−0.73 · min−1]. For the females, aerobic power was about 80% of the value achieved by the males. Scaling may help both in understanding variation in aerobic power and in defining the physiological limitations of work capacity.
To determine quantitative values for components of body composition in clinically normal dogs of various breeds by use of dual energy x-ray absorptiometry (DEXA) and validate the precision and accuracy of DEXA technology in dogs.
103 clinically normal sexually intact adult dogs.
In a cross-sectional study, Beagles, Pembroke Welsh Corgis, Golden Retrievers, Great Danes, Pointers, Rottweilers, and nonpurebred dogs received total body DEXA scans. For the validation portion of the study, the results of DEXA scans of 6 dogs were compared with values obtained by chemical analyses of tissues from euthanatized dogs to determine the accuracy of this modality in dogs.
Results (coefficient of variation) of the precision tests ranged from 0.10% for lean tissue to 5.19% for fat tissue, whereas accuracy tests revealed a difference between percentage bone mineral content and ash values. Body composition differed by sex, such as higher lean tissue and bone mineral content in males within some breeds, and among breeds. Regardless of body size or weight, the percentage of body weight that was bone mineral ranged from 3 to 4.0% [corrected].
Results of this cross-sectional study provide valuable body composition data for clinically normal adult dogs, which may have research and clinical applications.
The primary purpose of this study was to determine the maximal cardiorespiratory responses of 48, 5- to 6-year-old children (24 girls and 24 boys), who were tested on a treadmill (TM) and an electronically braked cycle ergometer (CE). We also examined the percentage of boys and girls who were able to achieve the criteria for reaching maximal oxygen consumption (
) on each testing mode. After an orientation period, each child was tested twice (once on the TM and once on the CE), with an interval of 1 week between tests.
was measured during progressive, all out, continuous TM and CE tests using standardized procedures. A 2×2 analysis of variance test (gender×exercise mode) with Bonferroni adjustment revealed the following: (1) there were no gender differences in any of the measured dependent variables, (2) the children produced a significantly higher relative
(ml·kg–1·min–1) and a higher absolute
(l·min–1) on the TM than on the CE (P<0.001), (3) the children produced a higher heart rate on the TM than on the CE (P<0.001), (4) the CE generated significantly higher values for respiratory exchange ratio (P<0.001), (5) the criteria necessary to establish a maximal exercise effort were achieved on both the TM and the CE, and (6) all of the children reached two of the criteria associated with a maximal effort, while only 46% of the children reached three criterion measures. There were no significant differences in the attainment of criterion measures between the TM and the CE. The results of this study indicate a lack of gender differences in maximal exercise testing in 5- to 6-year-old children, and that both the CE and the TM are effective modes of maximal cardiorespiratory testing in this age group.
This study examined whether body composition was predictive of competitive success in elite standardbreds (STB). Rump fat and muscle thickness (MTH) (vastus lateralis/intermedius [VL], extensor carpi radialis [ECR]) were measured in vivo in male n=6; female n=8 by B-mode ultrasound. Percentage body fat (%fat) was calculated from rump fat. There were no gender differences for age, body mass (males 432+/-11 kg; females 443+/-13 kg), fat-free mass (FFM) (males 400+/-12 kg; females 400+/-11 kg), ECR MTH (males 61+/-2 cm; females 60+/-2 cm) or race time (RT) (males 113+/-3 s; females 114+/-2 s). Males had less (P<0.05) fat mass (males 32+4 kg; females 44+/-3 kg) and %fat (males 7.4+/-0.9%; females 9.9+/-0.5%) and larger (P<0.05) VL MTH (males 88+/-7 cm; females 81+/-3 cm). RT was correlated to %fat and fat mass in males (r=0.89; r=0.82, P<0.05) not females (r=0.51; r=0.14). FFM tended to relate to RT in males (r=-0.76, P=0.07) and females (r=-0.59, P=0.12). Combined %fat and FFM data were correlated to RT (%fat r=0.70, P<0.01; FFM r=-0.65, P<0.01). RT was not correlated to MTH (VL r=-0.28; ECR r=-0.31). In conclusion, FFM was related to RT in elite STB with %fat negatively related to RT in males.
Body size is one of the most important characteristics of any animal because it affects a range of behavioral, ecological, and physiological traits including energy requirements, choice of food, reproductive strategies, predation risk, range size, and locomotor style. This article focuses on the implications of being large bodied for Homo erectus females, estimated to have been over 50% heavier than average australopithecine females. The energy requirements of these hominins are modeled using data on activity patterns, body mass, and life history from living primates. Particular attention is given to the inferred energetic costs of reproduction for Homo erectus females based on chimpanzee and human reproductive scheduling. Daily energy requirements during gestation and lactation would have been significantly higher for Homo erectus females, as would total energetic cost per offspring if the australopithecines and Homo erectus had similar reproductive schedules (gestation and lactation lengths and interbirth intervals). Shortening the interbirth interval could considerably reduce the costs per offspring to Homo erectus and have the added advantage of increasing reproductive output. The mother would, however, incur additional daily costs of caring for the dependent offspring. If Homo erectus females adopted this reproductive strategy, it would necessarily imply a revolution in the way in which females obtained and utilized energy to support their increased energetic requirements. This transformation is likely to have occurred on several levels involving cooperative economic division of labor, locomotor energetics, menopause, organ size, and other physiological mechanisms for reducing the energetic load on females.
Locomotion requires skeletal muscle to sustain and generate force. A muscle's force potential is proportional to its weight. Since the larger the muscle the larger its potential power output, a better understanding of the proportion of skeletal muscle a horse possesses may lead to a better understanding of horse performance. Several techniques exist to assess body composition, which include dual energy X-ray absorption, underwater (hydrostatic) weighing, derivation from total body water, bio-electric impedance, air displacement, body condition scoring, cadaver dissection and ultrasound. The relevance of each method to the equine industry will be discussed as will the practical information that the existing horse body composition studies have provided. Attention will be given to the data regarding the implications of body composition on the performance horse. The limited number of studies discussing different varieties of muscle architectures and the functional importance of these muscles will also be addressed. These body composition data may provide a better understanding of important issues in horse care that can lead to more optimal horse care techniques and a healthier and safer environment for horses.
Maximum oxygen uptake also appears to correlate to athletic performance in horses. In the Thoroughbred industry, there has long been an empirical theory that heart size is related to athletic performance, despite a lack of scientific evidence supporting this assertion. To investigate the relationship between peak oxygen consumption (VO2max) and cardiac size measured by echocardiography, guided M-mode and 2-dimensional echocardiography were performed in 17 conditioned Thoroughbreds with a range of VO2max from 126 to 217 ml/min/kg STPD (mean +/- s.d. 158 +/- 28 m/min/kg). Horses were age 2-10 years and weighed 430-510 kg. Echocardiography was performed using a Vingmed System V echocardiograph with a 2.25 MHz phased array ultrasound transducer. All images were obtained from the right hemithorax using a short axis view of the left ventricle (LV) at the level of the chordae tendinae. All horses were free from significant regurgitation at the aortic or mitral valves. Maximal oxygen uptake was measured during a standardised incremental treadmill exercise test to fatigue. Maximal oxygen uptake was correlated significantly with LVIDd (r = 0.71; P = 0.001), MWT (r = 0.72; P = 0.001), LV mass (r = 0.78; P = 0.0002) and LV short-axis area (r = 0.69; P = 0.003). When indices of heart size were indexed to bodyweight, the correlation between VO2max and indices of heart size were LVIDd (r = 0.57; P = 0.01), MWT (r = 0.44; P = 0.07), LV mass (r = 0.78; P = 0.0002) and LV short-axis area (r = 0.69; P = 0.003). The current study suggests there is a strong relationship between VO2max and measurements of left ventricular size in Thoroughbred horses when individuals with a range of VO2max are compared.
Cardiac morphology in human athletes is known to differ, depending on the sports-specific endurance component of their events, whereas anecdotes abound about superlative athletes with large hearts. As the heart determines stroke volume and maximum O(2) uptake in mammals, we undertook a study to test the hypothesis that the morphology of the equine heart would differ between trained horses, depending on race type, and that left ventricular size would be greatest in elite performers. Echocardiography was performed in 482 race-fit Thoroughbreds engaged in either flat (1,000-2,500 m) or jump racing (3,200-6,400 m). Body weight and sex-adjusted measures of left ventricular size were largest in horses engaged in jump racing over fixed fences, compared with horses running shorter distances on the flat (range 8-16%). The observed differences in cardiac morphologies suggest that subtle differences in training and competition result in cardiac adaptations that are appropriate to the endurance component of the horses' event. Derived left ventricular mass was strongly associated with published rating (quality) in horses racing over longer distances in jump races (P < or = 0.001), but less so for horses in flat races. Rather, left ventricular ejection fraction and left ventricular mass combined were positively associated with race rating in older flat racehorses running over sprint (<1,408 m) and longer distances (>1,408 m), explaining 25-35% of overall variation in performance, as well as being closely associated with performance in longer races over jumps (23%). These data provide the first direct evidence that cardiac size influences athletic performance in a group of mammalian running athletes.
To determine the chemical body composition of Thoroughbred foals born in two consecutive years, and to investigate several techniques used to predict body composition in foals born in the second year, with particular reference to fat.
The chemical composition of 20 foals at around 160 days of age, born in two years, was determined. In vivo techniques to predict body composition were assessed in 23 foals born in Year 2, before and after euthanasia; 10 of these foals were used for chemical body composition analysis. Techniques to assess body composition in vivo included liveweight (LW), overall and regional condition scores, ultrasonic fat thickness measurements over the ribs and rump, linear measurements and bioelectrical impedance analysis. Correlations were determined between ultrasonic fat thickness, and bioelectrical impedance analysis, before and after euthanasia. Stepwise regression analysis was used to determine the relationships between in vivo techniques used to assess body composition and the chemical body composition of 10 animals.
Foals used for analysis of chemical composition weighed between 220.5 and 260.0 kg before euthanasia. Fat content ranged from 5.5-13.0% of the partial empty bodyweight (LW less head, gastrointestinal contents, distal limbs and skin). Fillies had significantly more fat mass and percentage fat than colts (p=0.031 for both measurements). The mean chemical composition of the fat-free partial empty body was 73.2% (SD 0.6) water, 22.7% (SD 0.9) protein, and 4.1% (SD 0.4) ash. Most of the variation in the concentration of empty body water was associated with variation in the concentration of fat (p<0.001). The live animal overall condition scores were correlated with fat mass and concentration (p=0.006 and p=0.013, respectively; n=10). Condition score over the rib region was highly correlated with fat mass and fat concentration (p=0.004 and p<0.001; n=10). Ultrasound measurements taken 10 cm cranial to the tailhead and 4 cm from midline, used to assess the thickness of rump fat, were correlated with condition score (p=0.001), and explained 71% of the variation in body fat mass (p=0.002; n=10).Nearly 50% of the variation in fat-free mass and partial empty body water mass were associated with variation in the impedance indices calculated from length and bioelectrical impedance analysis measurements (p=0.023 and p=0.026, respectively; n=10).
At around 42% of expected mature weight, fillies were significantly more fat than colts. Condition scores were correlated with partial empty body fat mass, and there was a trend for higher scores in fillies compared to colts. Much of the variation in water or protein mass of the partial empty body could be explained by variations in LW.
Measurements of LW, rump fat and condition score are useful predictors of the chemical composition of foals at 5 months of age.
This paper investigates the changes in upper and lower limb robusticity and activity patterns that accompanied the transition to a Neolithic subsistence in western Liguria (Italy). Diaphyseal robusticity measures were obtained from cross-sectional geometric properties of the humerus and femur in a sample of 16 individuals (eight males and eight females) dated to about 6,000-5,500 BP. Comparisons with European Late Upper Paleolithics (LUP) indicate increased humeral robusticity in Neolithic Ligurian (NEOL) males, but not in females, with a significant reduction in right-left differences in both sexes. Sexual dimorphism in robusticity increases in upper and lower limb bones. Regarding the femur, while all female indicators of bending strength decrease steadily through time, values for NEOL males approach those of LUP. This suggests high, and unexpected, levels of mechanical stress for NEOL males, probably reflecting the effects of the mountainous terrain on lower limb remodeling. Comparisons between NEOL males and a small sample of LUP hunter-gatherers from the same area support this interpretation. In conclusion, cross-sectional geometry data indicate that the transition to Neolithic economies in western Liguria did not reduce functional requirements in males, and suggest a marked sexual division of labor involving a more symmetrical use of the upper limb, and different male-female levels of locomotory stress. When articulated with archaeological, faunal, paleopathological, and ethnographic evidence, these results support the hypothesis of repetitive, bimanual use of axes tied to pastoral activities in males, and of more sedentary tasks linked to agriculture in females.