Sex Differences In Performance Research Articles

The Autoregulation Rest-Redistribution Training Method Mitigates Sex Differences in Neuromuscular and Perceived Fatigue During Resistance Training.

To examine the sex differences in performance and perceived fatigue during resistance training prescribed using traditional (TRA) and autoregulation rest-redistribution training (ARRT) approaches. Twelve resistance-trained men and 12 women completed 2 sessions including the bench-press exercise matched for load (75% of 1-repetition maximum), volume (24 repetitions), and total rest (240s). Sessions were performed in a counterbalanced randomized design with TRA consisting of 3 sets of 8 repetitions with 120-second interset rest and ARRT employing a personalized combination of clusters, repetitions per cluster, and between-clusters rest regulated with a 20% velocity-loss threshold. The effects of TRA and ARRT on velocity loss, unilateral isometric peak force, and rating of fatigue (ROF) were compared between sexes. The velocity loss was generally lower during ARRT compared with TRA (-0.47% [0.11%]), with velocity loss being mitigated by ARRT to a greater extent among males compared with females (-0.37% [0.15%]). A smaller unilateral isometric peak force decline was observed after ARRT than TRA among males compared with females (-38.4 [8.4]N). Lower ROF after ARRT than TRA was found among males compared to females (-1.97 [0.55]AU). Additionally, males reported greater ROF than females across both conditions (1.92 [0.53]AU), and ARRT resulted in lower ROF than TRA overall (-0.83 [0.39]AU). The ARRT approach resulted in decreased velocity loss, peak force impairment, and ROF compared with TRA in both sexes. However, male subjects exhibited more pronounced acute within-session benefits from the ARRT method.

Sex differences in spontaneous behavior and cognition in mice using an automated behavior monitoring system

Isolation of sex differences as a key characteristic underlying neurobehavioral differentiation is an essential component of studies in neuroscience. The current study sought to address this concern by observing behavioral differences using an automated home cage system for neurobehavioral assessment, a method rapidly increasing in use due to advances in technology and advantages such as reduced handling stress and cross-lab variability. Sex differences in C57BL/6 mice arose for motor activity and circadian-linked behavior, with females being more active compared to males, and males having a stronger anticipatory increase in activity leading up to the onset of the light phase compared to females. These activity differences were observed not only across the lifespan, but also in different genetic background mouse strains across different testing sites showing the generalizability and robustness of these observed effects. Activity differences were also observed in performance on a spatial learning and reversal task with females making more responses and receiving a corresponding elevation in reward pellets. Notably, there were no sex differences in learning nor achieved accuracy, suggesting these observed effects were predominantly in activity. The outcomes of this study align with previous reports showcasing differences in activity between males and females. The comparison across strains and testing sites showed robust and reproducible differences in behavior between female and male mice that are relevant to consider when designing behavioral studies. Furthermore, the observed sex differences in performance on the learning and reversal procedure raise concern for interpretation of behavior differences between sexes due to the attribution of these differences to motor activity rather than cognition.

Sex Differences in Youth Elite Swimming Performance

Purpose: While it is well-known that elite males are faster than elite females in all Olympic-length swimming events, less is known about the age of the divergence in swimming performance between the sexes. Thus, this observational study compared swimming performance of elite male and female youths. Methods: We collected the all-time best 100 U.S. freestyle swimming performance times of boys and girls aged 5 to 18 years for six freestyle swimming events from 50m to 1500m. We compared data using univariate ANOVAs and Chi-squared tests. Results: Swimming performance improved with increasing age for both boys and girls (p<0.001) until a plateau— which began at a younger age for girls (15 years) than boys (17 years; sex × age; p<0.001). Before age 8, there was no sex difference in swimming performance (p>0.05). Beginning at age 9 however, boys swimming performance was faster than girls (1.0% to 1.3% depending on distance), and this sex difference in performance increased in magnitude until 18 years (p<0.001; 6.6% to 11.0% depending on distance). While boys represent 50% of the top 100 age-group performances at ages 5 and 6, boys represent an increasingly larger proportion of top performances across years of age including nearly 100% of all top 100 age-group performances beginning at age 15—except for one notable female swimmer in the 1500m Conclusion: Among elite youth swimmers, boys have increasingly faster performances than girls beginning at age 9 years, with minimal sex differences in swimming performance before 9 years. Additionally, boys represent an increasingly larger proportion of the top 100 age-group performances of all-time. No funding. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Exploring sex differences in performance: expanding the concept of force unsteadiness.

Exploring sex differences in performance: expanding the concept of force unsteadiness.

Sex Differences in Track and Field Elite Youth.

To understand athletic performance before and after puberty, this study determined: 1) the age at which the sex difference increases among elite youth track and field athletes for running and jumping events; and 2) whether there is a sex difference in performance prior to ages associated with puberty among elite youth athletes. Track and field records of elite USA male and female youth (7-18 years) across three years (2019, 2021, and 2022) were collected from an online database ( athletic.net ). The top 50 performances were recorded for 100 m, 200 m, 400 m, and 800 m track running, long jump, and high jump. Males ran faster than females at every age in the 100, 200, 400 and 800 m ( P < 0.001). When combining all running events, the sex difference (%) was 4.0 ± 1.7% between 7-12 years and increased to 6.3 ± 1.1% at 13 years, and 12.6 ± 1.8% at 18 years ( P < 0.001). Similarly, males jumped higher and farther than females at every age ( P < 0.001). For long jump, the sex difference was 6.8 ± 2.8% between 7-12 years, increasing to 8.5 ± 1.7% at 13 years, and 22.7 ± 1.4% at 18 years ( P < 0.001). For high jump, the sex difference was 5.3 ± 5.2% between 7-12 years, increasing to 12.4 ± 2.9% at 15 years, and 18.4 ± 2.04% at 18 years ( P < 0.001). Prior to 12 years of age in elite youth track and field athletes, there was a consistent and significant sex difference of ~5%, such that males ran faster and jumped higher and farther than females. The magnitude of the sex difference in performance increased markedly at 12-13 years for running and long jump and 14 years for high jump and thus was more pronounced after ages associated with puberty.

Hormonal Basis of Biological Sex Differences in Human Athletic Performance.

Biological sex is a primary determinant of athletic human performance involving strength, power, speed, and aerobic endurance and is more predictive of athletic performance than gender. This perspective article highlights 3 key medical and physiological insights related to recent evolving research into the sex differences in human physical performance: (1) sex and gender are not the same; (2) males and females exhibit profound differences in physical performance with males outperforming females in events and sports involving strength, power, speed, and aerobic endurance; (3) endogenous testosterone underpins sex differences in human physical performance with questions remaining on the roles of minipuberty in the sex differences in performance in prepubescent youth and the presence of the Y chromosome (SRY gene expression) in males, on athletic performance across all ages. Last, females are underrepresented as participants in biomedical research, which has led to a historical dearth of information on the mechanisms for sex differences in human physical performance and the capabilities of the female body. Collectively, greater effort and resources are needed to address the hormonal mechanisms for biological sex differences in human athletic performance before and after puberty.

INTERACTIVE SPATIAL TRAINING ANIMATES SEX DIFFERENCES IN PERFORMANCE AMONG FIRST-YEAR ENGINEERING STUDENTS

In a 2 &amp;times; 2 (sex &amp;times; intervention) experiment we investigated sex differences in performance gains and transfer after training on a brief intervention that used interactive animation and virtual objects to improve performance on a spatial visualization task. Participants were male and female first-year engineering students at a large public university who scored in the lower 60th percentile of a distribution of their peers on the Purdue Spatial Visualization Test. Compared to the control group, trained participants of both sexes showed significant improvement on stimuli viewed during the intervention. Further, trained participants significantly outperformed untrained participants on a transfer task, with trained female participants significantly outperforming trained male participants. We suggest possible explanations for the lack of sex differences in performance on the trained task and for the significant advantage demonstrated by trained female participants on the transfer task. We propose that a female engineering role model may confer a motivational advantage to female entry-level engineering students.

The influence of the design of mental rotation trials on performance and possible differences between sexes: A theoretical review and experimental investigation.

Sex differences in mental rotation performance are one of the largest in cognitive psychology. Men outperform women by up to 1 SD in psychometric mental rotation tests, but it is often neglected that there are no or only small sex differences for chronometric tests. As both tests are supposed to measure the same ability, we suspect some features of the tests themselves to affect sex differences in performance. Following a theoretical review of the test features, we evaluate the effects of the number of possible answer alternatives, whether they are presented as pairwise mirrored, and their interaction on sex differences in mental rotation performance. In an online experiment, 838 German-speaking participants, 421 women, 417 men, Mage = 42.58 (SD = 12.54) years, solved four blocks of mental rotation trials with two or eight alternatives, which were either pairwise mirrored or not. The results show that that the overall performance was lower for more alternatives and for mixed alternatives but not for their interaction. We could not determine explanations for sex differences as we did not observe meaningful sex differences at all. Possible reasons include the differences between men and women in age and education. This study suggests that the differences between tests affect performance. Sex differences, however, need more investigation, including possible effects and interactions of the test design, education, and age.

Comparing the Performance Gap Between Males and Females in the Older Age Groups in IRONMAN® 70.3: An Internet-Based Cross-Sectional Study of More Than 800,000 Race Records

BackgroundThe sex difference in the three split disciplines (swimming, cycling, and running) and overall race times in triathlon races has mainly been investigated for the Olympic distance and IRONMAN® triathlon formats, but not for the half IRONMAN® distance, i.e., the IRONMAN® 70.3. The aim of the present study was to investigate the sex differences in IRONMAN® 70.3 by age group in 5-year intervals for the split disciplines of this race. Data from 823,459 records (625,393 males and 198,066 females) of all age group finishers (in 5-year intervals) competing in all official IRONMAN® 70.3 races held worldwide between 2004 and 2020 were analyzed, and sex differences by age group and split disciplines were evaluated.ResultsMales were faster than females in all split disciplines and all age groups. The sex difference was lower in swimming than in cycling and running and less pronounced for triathletes between 20 and 50 years of age. After the age of 60 years, females were able to reduce the sex difference to males in swimming and cycling, but not in running, where the reduction in the sex difference started after the age of 70 years. The lowest sex difference was in the age group 75 + years for swimming and cycling and in the age group 30–34 years for running. Across age groups, the sex difference was U-shaped in swimming and running, with an increase after 18–24 years in swimming and after 40–44 years in running. In contrast, the sex difference decreased continuously with the increasing age for cycling.ConclusionsIn conclusion, the study found that the sex difference in performance decreases with age in the IRONMAN® 70.3 race distance. However, females did not outperform males at older ages. Notably, sex differences were observed across different disciplines, with swimming displaying lower differences compared to cycling and running. These findings underscore the complex interplay between age, sex, and performance in endurance sports, emphasizing the need for additional research to understand the factors influencing these differences.

Sex Differences In Performance Of Elite Youth Track And Field Athletes

Sex Differences In Performance Of Elite Youth Track And Field Athletes

Elderly female ultra-marathoners reduced the gap to male ultra-marathoners in Swiss running races

Recent studies showed that female runners reduced the performance gap to male runners in endurance running with increasing age and race distance. However, the investigated samples were generally small. To investigate this further, the present study examined sex differences by age across various race distances (5, 10 km, half-marathon, marathon, and ultra-marathon) using a large dataset of over 1,100,000 race records from Switzerland over two decades (1999–2019). The study explored performance and participation disparities between male and female runners by employing diverse methods, such as descriptive statistics, histograms, scatter and line plots, correlations, and a predictive machine learning model. The results showed that female runners were more prevalent in shorter races (5, 10 km, half-marathon) and outnumbered male runners in 5 km races. However, as the race distance increased, the male-to-female ratio declined. Notably, the performance gap between sexes reduced with age until 70 years, after which it varied depending on the race distance. Among participants over 75 years old, ultra-marathon running exhibited the smallest sex difference in performance. Elderly female ultra-marathoners (75 years and older) displayed a performance difference of less than 4% compared to male ultra-marathoners, which may be attributed to the presence of highly selected outstanding female performers.

Sports Physiology in Adolescent Track-and-Field Athletes: A Narrative Review.

The present study aimed to review the physiological aspects of adolescent track-and-field (TAF) athletes. A search of Scopus on 27/12/2022 using the syntax ABS (track-and-field) AND ABS (children) OR ABS (adolescent) showed 121 documents, and 45 were considered for further analysis. In addition, handsearching was conducted to identify Russian literature missing in Scopus. Differences were shown in performance characteristics among disciplines, especially between throwers and the other athletes. The sex difference in performance (ie, a better performance in boys than in girls) started in early adolescence. A relative age effect was more pronounced in athletes under 13 years old. Despite the wide use of nutritional supplements, an insufficient intake of vitamins has been found. The age of training onset and body weight were identified as risk factors for problems with menarche. The inclusion of track-and-field training programs in physical education was beneficial for health and physical fitness. The need to collaborate closely with parents and coaches was identified, especially, regarding education in topics such as the age of training onset, relative age effect, and doping. In conclusion, the existence of many disciplines with different anthropometric and physiological characteristics highlighted the need for a discipline-specific approach.

Sex Differences in Maximal Oxygen Uptake Adjusted for Skeletal Muscle Mass in Amateur Endurance Athletes: A Cross Sectional Study.

Male athletes tend to outperform female athletes in several endurance sports. Maximum cardiac output can be estimated by maximal oxygen consumption (V˙O2max), and it has been established that men present V˙O2max values about 20% higher than women. Although sex differences in V˙O2max have already been well studied, few studies have assessed sex differences with regard to muscle oxidative capacity. The aim of this study was to compare aerobic muscle quality, accessed by V˙O2max and adjusted by lower limb lean mass, between male and female amateur triathletes. The study also aimed to compare sex differences according to V˙O2 submaximal values assessed at ventilatory thresholds. A total of 57 participants (23 women and 34 men), who had been training for Olympic-distance triathlon races, underwent body composition evaluation by dual-energy X-ray absorptiometry and performed a cardiorespiratory maximal test on a treadmill. Male athletes had significantly higher V˙O2max, both absolutely and when adjusted to body mass. Conversely, when V˙O2max was adjusted for lean mass, there was no significant difference between sexes. The same was observed at submaximal exercise intensities. In conclusion, differences in V˙O2max adjusted to body mass but not lean mass may explain, at least in part, sex differences in performance in triathlons, marathons, cycling, and other endurance sports.

Sex Differences in Marathon Running: Physiology and Participation

ABSTRACT Introduction Males are faster than females in the marathon, largely due to sex differences in physiology, but sociological factors influencing lower participation rates of females than males may also contribute. Purpose This study aimed to determine whether the sex difference in marathon performance is predicted by the proportion of male to female runners and how this prediction changes among lower-placed runners across age groups. Methods The number of male and female finishers within 5-yr age groups (20–79 yr) and times of the first 10 age-group runners in the Chicago (CHI; 1996–2018) and New York City (NYC; 1980–2019) marathons were analyzed. Results The male/female participation ratio declined across years for the CHI (1996–2018: 2.19–1.16, P &lt; 0.001) and NYC (1980–2019: 6.76–1.36, P &lt; 0.001) marathons, but increased with age (P &lt; 0.001) and place (1st–10th place, P &lt; 0.001). Male runners were faster than female runners across all age groups for the CHI (17.2% ± 6.8%, n = 2328) and NYC (18.8% ± 7.4%, n = 4226) marathons. The sex difference in performance was smallest for 1st-place and largest for 10th-place finishers for both marathons. The ratio of the number of male to female runners was associated with the sex difference in velocity for NYC (r 2 = 0.32, P &lt; 0.001) and CHI (r 2 = 0.28, P &lt; 0.001). The strength of the associations increased between 1st and 10th places. Conclusions Fewer female relative to male runners in an age group predicted a larger sex difference in performance in two world-class marathons. Low participation rates of female runners mask an accurate understanding of the sex differences in marathon performance due to physiology, with broader implications for women’s health in biomedical research.

Differences in structural MRI and diffusion tensor imaging underlie visuomotor performance declines in older adults with an increased risk for Alzheimer's disease.

Visuomotor impairments have been demonstrated in preclinical AD in individuals with a positive family history of dementia and APOE e4 carriers. Previous behavioral findings have also reported sex-differences in performance of visuomotor tasks involving a visual feedback reversal. The current study investigated the relationship between grey and white matter changes and non-standard visuomotor performance, as well as the effects of APOE status, family history of dementia, and sex on these brain-behavior relationships. Older adults (n = 49) with no cognitive impairments completed non-standard visuomotor tasks involving a visual feedback reversal, plane-change, or combination of the two. Participants with a family history of dementia or who were APOE e4 carriers were considered at an increased risk for AD. T1-weighted anatomical scans were used to quantify grey matter volume and thickness, and diffusion tensor imaging measures were used to quantify white matter integrity. In APOE e4 carriers, grey and white matter structural measures were associated with visuomotor performance. Regression analyses showed that visuomotor deficits were predicted by lower grey matter thickness and volume in areas of the medial temporal lobe previously implicated in visuomotor control (entorhinal and parahippocampal cortices). This finding was replicated in the diffusion data, where regression analyses revealed that lower white matter integrity (lower FA, higher MD, higher RD, higher AxD) was a significant predictor of worse visuomotor performance in the forceps minor, forceps major, cingulum, inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), superior longitudinal fasciculus (SLF), and uncinate fasciculus (UF). Some of these tracts overlap with those important for visuomotor integration, namely the forceps minor, forceps major, SLF, IFOF, and ILF. These findings suggest that measuring the dysfunction of brain networks underlying visuomotor control in early-stage AD may provide a novel behavioral target for dementia risk detection that is easily accessible, non-invasive, and cost-effective. The results also provide insight into the structural differences in inferior parietal lobule that may underlie previously reported sex-differences in performance of the visual feedback reversal task.

The Biological Basis of Sex Differences in Athletic Performance: Consensus Statement for the American College of Sports Medicine

ABSTRACT Biological sex is a primary determinant of athletic performance because of fundamental sex differences in anatomy and physiology dictated by sex chromosomes and sex hormones. Adult men are typically stronger, more powerful, and faster than women of similar age and training status. Thus, for athletic events and sports relying on endurance, muscle strength, speed, and power, males typically outperform females by 10%–30% depending on the requirements of the event. These sex differences in performance emerge with the onset of puberty and coincide with the increase in endogenous sex steroid hormones, in particular testosterone in males, which increases 30-fold by adulthood, but remains low in females. The primary goal of this consensus statement is to provide the latest scientific knowledge and mechanisms for the sex differences in athletic performance. This review highlights the differences in anatomy and physiology between males and females that are primary determinants of the sex differences in athletic performance and in response to exercise training, and the role of sex steroid hormones (particularly testosterone and estradiol). We also identify historical and nonphysiological factors that influence the sex differences in performance. Finally, we identify gaps in the knowledge of sex differences in athletic performance and the underlying mechanisms, providing substantial opportunities for high-impact studies. A major step toward closing the knowledge gap is to include more and equitable numbers of women to that of men in mechanistic studies that determine any of the sex differences in response to an acute bout of exercise, exercise training, and athletic performance.

Verbal Abilities: Sex Differences in Children at Different Ages.

The assertion of sex differences in verbal abilities is a highly controversial subject. Some studies have demonstrated a female advantage; other studies have found higher rates in males. The results depended on the type of verbal ability that was studied, the cultural context, and the ages of the subjects. There are two types of theories that have been developed to explain the existence of sex differences in cognitive abilities. Social theories explain the differences as caused by social determinants. Biological theories consider biological factors such as prenatal development conditions and hormone levels, among others, as the cause of sex differences. To investigate sex differences in verbal abilities in children of different ages. Two different editions of Wechsler tests were used. For children age 2.5 to 5 years, the Wechsler Preschool Primary Scale of Intelligence (WPPSI-IV) was used. For children age 6 and older, we administered the Wechsler Intelligence Scale for Children (WISC-V). The total sample included 313 children. The study found significant sex differences in performance on the Verbal Comprehension Scale in children of different ages. At the age of 2 to 4 years, the girls performed better than the boys. In the group of boys, there was a significant increase in verbal abilities at the age of 8-9 years. By the age of 10-11 years, boys began outperforming girls on the Verbal Comprehension Index. Scores on the Verbal Comprehension and Visual Spatial subtests for the boy sample showed stronger correlations than in the girl sample in all age groups. Sex differences in verbal abilities varied depending on the age of the children. The boys showed a stronger integration of their verbal abilities into the structure of their intelligence than the girls.

Cognitive mechanisms underlying decision making involving risk of explicit punishment in male and female rats.

Individuals engage in the process of risk-based decision making on a daily basis to navigate various aspects of life. There are, however, individual differences in this form of decision making, with some individuals exhibiting preference for riskier choices (risk taking) and others exhibiting preference for safer choices (risk aversion). Recent work has shown that extremes in risk taking (e.g., excessive risk taking or risk aversion) are not only cognitive features of neuropsychiatric diseases, but may in fact predispose individuals to the development of such diseases. To better understand individual differences in risk taking, and thus the mechanisms by which they confer disease vulnerability, the current study investigated the cognitive contributions to risk taking in both males and females. Rats were first behaviorally characterized in a decision-making task involving risk of footshock punishment and then tested on a battery of cognitive behavioral assays. Individual variability in risk taking was compared with performance on these tasks. Consistent with prior work, females were more risk averse than males. With the exception of the Set-shifting Task, there were no sex differences in performance on other cognitive assays. There were, however, sex-dependent associations between risk taking and specific cognitive measures. Greater risk taking was associated with better cognitive flexibility in males whereas greater risk aversion was associated with better working memory in females. Collectively, these findings reveal that distinct cognitive mechanisms are associated with risk taking in males and females, which may account for sex differences in this form of decision making.

Sex Differences In Marathon Performance Are Larger In The Past Decade Than Expected Physiologically

The sex difference in performance of marathon runners historically has been larger than explained by physiological differences, possibly reflecting lower participation of females (1). The number of female participants across all age groups has increased in recent decades, but it is unclear if the sex difference in performance has continued to diminish. PURPOSE: To determine the sex difference in performance in the New York City (NYC) marathon across age groups, and with the place of runner (1st-10th place), in the past decade and relative to earlier published data (1980-2010) (1). METHODS: Running times of the top 10 placed male and female finishers (5-year age groups) who competed in the NYC marathon (2009-2019) were retrieved from a public database (https://results.nyrr.org/races). Univariate ANOVA determined the sex difference in the mean running velocity; (% Δ males and females/males) across age groups and place. RESULTS: The sex difference in running velocity increased across age groups (p < 0.001). For 2015-2019, the 30-39-year olds had the smallest difference (12.9 ± 0.5%) and the 70-79 year olds the largest (22.9 ± 0.9%). Across all age groups, the sex difference in running velocity decreased across years from 22.0 ± 0.4% in 1980-84 to 16.1 ± 0.2% in 2005-2009 and plateaued for the subsequent decade. The largest drop was in the two older age groups (60-79 years, 36% to 21%) and the least for youngest (20-49 years, 18% to 12.5%). Across all age groups, the sex difference in running velocity for 1st placed runners was 15.9 ± 0.4 % and increased to 20.3 ± 0.3% for 10th (P < 0.001). The greatest increase in the sex difference (1st to 10th) was in the 70-79 age group (21.9 ± 1.5% to 31.6 ± 1.7%) and the least in the 40-49 age group (13.9 ± 0.6% to 17.8 ± 0.4%). CONCLUSION: The largest sex differences in marathon performance were within the older age groups and lower (slower)-placed runners. Across all age groups, the sex difference in performance plateaued in the past 15 years despite more female participants and the continued decrease in male:female participation ratios. These results also suggest that physiological and sociological factors that impact the sex difference in running velocity vary by age group. (1) Hunter SK, et al Med Sci Sports Exerc 45: 148-156, 2013.

Participation Rates Of Female And Male Runners Predict Marathon Performance

Males are ~11% faster than females in marathon running at the elite level, largely due to sex differences in physiology. This sex difference in performance, however, is often greater than 11% especially in older runners with lower proportion of female runners. PURPOSE: To determine whether the sex difference in marathon performance is predicted by the number of male to female runners and how this prediction changes among lower placed runners within an age group. METHODS: The number of male and female finishers within 10-year age groups (20 - 79 years) and the running times of the top 10 age group runners who competed in the Chicago marathon (1996-2018) and New York City (NYC) marathon (1980-2019) were retrieved from public databases. Univariate ANOVA and correlation analysis determined differences and associations between the ratios of male:female finishers and the sex difference in velocity. RESULTS: The ratio of male:female runners increased with older age groups (p < 0.001) and place of the runner from 1st to 10th place (p < 0.001) for both marathons. Males were faster than females across all age groups for the Chicago (17.4% ± 0.2%) and NYC marathon (18.8% ± 0.1%). The sex difference, however, was smallest for 1st placed runners and largest for the 10th placed for Chicago (14.8 ± 0.5% to 18.5 ± 0.4%) and NYC (15.9 ± 0.4% to 20.3 ± 0.3%). The ratio of the number of males:females was correlated with the sex difference in velocity (%) for Chicago (n = 2325, r2 = 0.28, p < 0.001) and NYC (n = 4223, r2 = 0.32, p < 0.001) in that fewer females relative to males indicated a larger sex difference in velocity. The strength of the associations progressively increased between 1st and 10th place. Combined for both marathons, the association for 1st place was r2 = 0.20 (p < 0.001, n = 709) and 10th place was r2 = 0.38 (p < 0.001, n = 614). Thus, the number of males:females explained 20% of the variance in the sex differences in velocity of 1st placed runners but 38% of the sex difference in 10th placed runners. CONCLUSION: Lower participation rates of females in the marathon potentially masks an accurate understanding of the contribution of physiological sex differences, especially in lower ranked and older runners. This data provides a window into the impact of the inequity of testing less females than males in studies of human performance.