The Effect of 400 µg Inhaled Salbutamol on 3 km Time Trial Performance in a Low Humidity Environment.

The Objectives of the study were to investigate whether 400 µg inhaled salbutamol influences 3 km running time-trial performance and lung function in eucapnic voluntary hyperpnoea positive (EVH+ve) and negative (EVH-ve) individuals. Fourteen male participants (22.4 ± 1.6yrs; 76.4 ± 8.7kg; 1.80 ± 0.07 m); (7 EVH+ve; 7 EVH-ve) were recruited following written informed consent. All participants undertook an EVH challenge to identify either EVH+ve (↓FEV1>10%) or EVH-ve (↓FEV1<10%). Participants performed three separate 3 km running time-trials in a low-humidity (20-25%) environment on a non-motorized treadmill, 15 minutes following inhalation of salbutamol (400 µg), placebo (non-active inhalant) or control (no inhalant), in a randomized, single-blind, repeated measures design. Forced vital capacity maneuvers were performed at baseline, 10 minutes post inhalation and post time-trial. Time to complete 3 km and lung function data were analyzed using mixed model repeated measures ANOVA. Significance was assumed at p < 0.05. All EVH+ve participants had FEV1 falls from baseline between 10-25% post-challenge. There was no difference in performance time between trial conditions in EVH+ve (1012.7 ± 129.6s; 1002.4 ± 123.1s; 1015.9 ± 113.0s) (p = 0.774) and EVH-ve (962.1 ± 99.2s; 962.0 ± 76.2s; 950.8 ± 84.9s) (p = 0.401) groups for salbutamol, placebo and control trials, respectively. Exercising heart rate was significantly higher (p = 0.05) in the salbutamol trial (183 ± 8 beatsˑmin-1) compared to control (180 ± 9 beatsˑmin-1) with a trend towards significance (p=0.06) in the placebo trial (179 ± 9 beatsˑmin-1) for the pooled groups, no differences were seen between trials in groups individually. There was an increase in FEV1 in both EVH+ve (4.01 ± 0.8L; 4.26 ± 0.7L; 4.25 ± 0.5L) and EVH-ve (4.81 ± 0.4L; 5.1 ± 0.4L; 5.1 ± 0.5L) groups which was significant post-inhalation (p = 0.01; p = 0.02), but not post-time-trial (p = 0.27; p = 0.06), respectively, following salbutamol. EVH+ve participants did not demonstrate significant falls (>10% from baseline) in FEV1 following any time-trial. Administration of 400µg inhaled salbutamol does not improve 3 km time-trial performance in either mild EVH+ve or EVH-ve individuals despite significantly increased HR and FEV1.

Is iron treatment beneficial in, iron-deficient but non-anaemic (IDNA) endurance athletes? A systematic review and meta-analysis.

PURPOSE: The aim of this study was to determine whether iron treatments improve the iron status and aerobic capacity of iron deficient non-anaemic endurance athletes. METHOD: A meta-analysis of studies that investigated the effects of iron treatment on serum ferritin (sFer), serum iron (sFe), transferrin saturation (Tsat), haemoglobin concentration ([Hb]) and (VO(2max)). Seventeen eligible studies were identified from online databases. RESULTS: Analysis of pooled data indicated that iron treatments had a large effect on improving sFer (Hedges' g=1.088, 95% CI 0.914 to 1.263, p<0.001), sFe (Hedges' g=1.004, 95% CI 0.828 to 1.181, p<0.001) and Tsat (Hedges g=0.741, 95% CI 0.564 to 0.919, p<0.001) and a moderate effect on improving [Hb] (Hedges' g=0.695, 95% CI 0.533 to 0.836, p<0.001) and (VO(2max)) (Hedges' g=0.610, 95% CI 0.399 to 0.821, p<0.001). Regression analysis revealed a significant interaction between the effect of iron treatment on sFer and treatment duration, suggesting treatments that lasted beyond 80 days appear to have the least effect on sFer. CONCLUSIONS: These results indicate iron treatments improve the iron status and aerobic capacity of iron deficient non-anaemic endurance athletes.

ECG and morphologic adaptations in Arabic athletes: are the European Society of Cardiology's recommendations for the interpretation of the 12-lead ECG appropriate for this ethnicity?

AIMS: To examine the cardiac structure and function of Arabic athletes and to establish if the European Society of Cardiology (ESC) guidelines for the interpretation of an athlete's ECG are applicable to this ethnicity. METHODS: 600 high-level Arabic, 415 Black African, 160 Caucasian male athletes (exercising ≥6 h/week) and 201 Arabic controls presented for ECG and echocardiographic screening. RESULTS: 9 athletes (0.7%) were identified with a cardiac pathology associated with sudden cardiac death. Two Arabics (0.3%) and five Black Africans (1.2%) were diagnosed with hypertrophic cardiomyopathy; a prevalence four times greater in Black African compared to Arabic athletes. Arabic athletes had significantly greater (p<0.05) left ventricular (LV) end-diastolic diameters, maximal LV wall thicknesses and LV mass compared with controls; yet were significantly smaller than Black African and Caucasian athletes. The percentage of athletes demonstrating LV hypertrophy (≥12 mm) was comparable between Arabic, Black African and Caucasian populations (0.5%, 0.5% and 0.6%, respectively). There was no difference in the frequency of an uncommon and training-unrelated ECG between Arabic and Caucasian. However, Black Africans demonstrated a significantly greater prevalence than Arabic and Caucasian athletes (20% vs 8.4% and 6.9%, p<0.001); specifically more right/left atrial enlargement and T wave inversion. CONCLUSIONS: Arabic athletes present significantly smaller cardiac dimensions than Black African and Caucasian athletes. There was no significant difference between the frequency of an uncommon and training-unrelated ECG between Arabic and Caucasian athletes. Therefore, the use of ESC guidelines for the interpretation of an athlete's ECG is clinically relevant and acceptable for use within Arabic athletes.

Challenges in Maintaining Emotion Regulation in a Sleep and Energy Deprived State Induced by the 4800Km Ultra-Endurance Bicycle Race; The Race Across AMerica (RAAM).

Multiday ultra-endurance races present athletes with a significant number of physiological and psychological challenges. We examined emotions, the perceived functionality (optimal-dysfunctional) of emotions, strategies to regulate emotions, sleep quality, and energy intake-expenditure in a four-man team participating in the Race Across AMerica (RAAM); a 4856km continuous cycle race. Cyclists reported experiencing an optimal emotional state for less than 50% of total competition, with emotional states differing significantly between each cyclist over time. Coupled with this emotional disturbance, each cyclist experienced progressively worsening sleep deprivation and daily negative energy balances throughout the RAAM. Cyclists managed less than one hour of continuous sleep per sleep episode, high sleep latency and high percentage moving time. Of note, actual sleep and sleep efficiency were better maintained during longer rest periods, highlighting the importance of a race strategy that seeks to optimise the balance between average cycling velocity and sleep time. Our data suggests that future RAAM cyclists and crew should: 1) identify beliefs on the perceived functionality of emotions in relation to best (functional-optimal) and worst (dysfunctional) performance as the starting point to intervention work; 2) create a plan for support sufficient sleep and recovery; 3) create nutritional strategies that maintain energy intake and thus reduce energy deficits; and 4) prepare for the deleterious effects of sleep deprivation so that they are able to appropriately respond to unexpected stressors and foster functional working interpersonal relationships. Key PointsCompleting the Race Across AMerica (RAAM); a 4856km continuous cycle race associated with sleep disturbance, an energy-deficient state, and experiencing intense unwanted emotions.Cyclists reported experiencing an optimal emotional state for less than 50% of total competition and actual sleep and sleep efficiency was better maintained during longer rest periods.We suggest that future RAAM cyclists and crew should:Identify individual beliefs on the perceived functionality of emotional states in relation to best (optimal) and worst (dysfunctional) performance as the starting point to identifying if emotion regulation strategies should be initiated.Plan for enhanced sleep and recovery not just plan and train for maintaining a high average velocity;Create nutritional strategies that maintain energy intake and thus reduce energy deficits;Psychologically prepare cyclists and crew for the deleterious effects of sleep deprivation so that they both are able to appropriately respond to unexpected stressors and foster functional interpersonal working relationships.

Do big athletes have big hearts? Impact of extreme anthropometry upon cardiac hypertrophy in professional male athletes.

AIM: Differentiating physiological cardiac hypertrophy from pathology is challenging when the athlete presents with extreme anthropometry. While upper normal limits exist for maximal left ventricular (LV) wall thickness (14 mm) and LV internal diameter in diastole (LVIDd, 65 mm), it is unknown if these limits are applicable to athletes with a body surface area (BSA) >2.3 m(2). PURPOSE: To investigate cardiac structure in professional male athletes with a BSA>2.3 m(2), and to assess the validity of established upper normal limits for physiological cardiac hypertrophy. METHODS: 836 asymptomatic athletes without a family history of sudden death underwent ECG and echocardiographic screening. Athletes were grouped according to BSA (Group 1, BSA>2.3 m(2), n=100; Group 2, 2-2.29 m(2), n=244; Group 3, <1.99 m(2), n=492). RESULTS: There was strong linear relationship between BSA and LV dimensions; yet no athlete with a normal ECG presented a maximal wall thickness and LVIDd greater than 13 and 65 mm, respectively. In Group 3 athletes, Black African ethnicity was associated with larger cardiac dimensions than either Caucasian or West Asian ethnicity. Three athletes were diagnosed with a cardiomyopathy (0.4% prevalence); with two athletes presenting a maximal wall thickness >13 mm, but in combination with an abnormal ECG suspicious of an inherited cardiac disease. CONCLUSION: Regardless of extreme anthropometry, established upper limits for physiological cardiac hypertrophy of 14 mm for maximal wall thickness and 65 mm for LVIDd are clinically appropriate for all athletes. However, the abnormal ECG is key to diagnosis and guides follow-up, particularly when cardiac dimensions are within accepted limits.

Physiological correlates of emotion-regulation during prolonged cycling performance.

We proposed that experiencing unpleasant emotions during performance represents unsuccessful emotion-regulatory efforts, and that such effort concurrently tax physiological resources. We used data from 2-h cycling trials (N = 28) at a power output equivalent to lactate threshold. Emotions were calculated before and during cycling with ongoing assessments of ventilation, respiratory quotient, heart rate, and oxygen uptake. Emotion data indicated significant changes over time with all participants reporting decreases in vigour and increases in fatigue, with 14 cases of concurrent increases in anger, depression, and tension. After grouping participants into positive and negative emotion groups, a time x unpleasant emotion group ANOVA indicated a significant interaction effect for changes in ventilation (F (6,21) = 3.09, P = .03, Partial Eta(2) = .47) over time, with no significant difference in other physiological variables or perceived exertion. Among athletes reporting negative emotions, ventilation increased during the middle section, whereas among athletes reporting positive emotions, ventilation increased shortly before completion. Findings suggest that regulating negative emotion is an effortful process taxing physiological substrates.

The effectiveness of compression garments and lower limb exercise on post-exercise blood pressure regulation in orthostatically intolerant athletes.

OBJECTIVE: Orthostatic intolerance (OI) may occur postexercise in normotensive individuals due to gravitational stress and removal of muscle pump. DESIGN: Six subjects performed 3 maximal bouts of exercise associated with (1) no intervention (CONTROL) (initial trial), (2) with use of lower limb compression garment (TROU), and (3) lower limb exercise (HEEL). SETTING: In each trial, 10 minutes of supine rest was followed by 10 minutes of standing before and immediately after maximal exercise. PARTICIPANTS: All subjects were OI during the CONTROL trial. INTERVENTIONS: In the TROU trial, the compression garment was worn during the supine and standing phases. In the HEEL trial, heel raises were performed every 60 seconds during standing periods. MAIN OUTCOME MEASURES: Systolic blood pressure and heart rate were continuously recorded, and stroke, cardiac output, and total peripheral resistance were estimated (PortAPres, TNO Biomedical Instrumentation, Amsterdam, the Netherlands). Positional changes were compared preexercise and postexercise in CONTROL, TROU, and HEEL via 2-way analysis of variance. RESULTS: All 6 subjects experienced OI in the CONTROL trial, but this was reduced to 2 after the HEEL and 1 after the TROU. Minor increases in systolic blood pressure (CONTROL, 3 +/- 11; TROU, 12 +/- 18; HEEL, 7 +/- 15 mm Hg) and heart rate (CONTROL, 10 +/- 12; TROU, 16 +/- 8; HEEL, 15 +/- 13 beats.min) were observed, but total peripheral resistance did not alter significantly during orthostasis postexercise (CONTROL, 0.462 +/- 0.351; TROU, 0.325 +/- 0.212; HEEL, 0.746 +/- 0.412 medical units). CONCLUSIONS: It seems that simple methods/practices adopted by athletes can have a positive impact on OI.

The Effects of Inhaled Terbutaline on 3-km Running Time-Trial Performance.

Terbutaline is a prohibited drug except for athletes with a therapeutic use exemption certificate; terbutaline's effects on endurance performance are relatively unknown. Purpose: To investigate the effects of 2 therapeutic (2 and 4 mg) inhaled doses of terbutaline on 3-km running time-trial performance. Methods: A total of 8 men (age 24.3 [2.4] y; weight 77.6 [8] kg; and height 179.5 [4.3] cm) and 8 women (age 22.4 [3] y; weight 58.6 [6] kg; and height 163 [9.2] cm) free from respiratory disease and illness provided written informed consent. Participants completed 3-km running time trials on a nonmotorized treadmill on 3 separate occasions following placebo and 2- and 4-mg inhaled terbutaline in a single-blind, repeated-measures design. Urine samples (15 min postexercise) were analyzed for terbutaline concentration. Data were analyzed using 1-way repeated-measures analysis of variance, and significance was set at P < .05 for all analyses. Results: No differences were observed for completion times (1103 [201] s, 1106 [195] s, 1098 [165] s; P = .913) for the placebo or 2- and 4-mg inhaled trials, respectively. Lactate values were higher (P = .02) after 4 mg terbutaline (10.7 [2.3] mmol·L-1) vs placebo (8.9 [1.8] mmol·L-1). Values of forced expiratory volume in the first second of expiration (FEV1) were greater after inhalation of 2 mg (5.08 [0.2]; P = .01) and 4 mg terbutaline (5.07 [0.2]; P = .02) compared with placebo (4.83 [0.5] L) postinhalation. Urinary terbutaline concentrations were mean 306 (288) ng·mL-1 and 435 (410) ng·mL-1 (P = .2) and peak 956 ng·mL-1 and 1244 ng·mL-1 after 2 and 4 mg inhaled terbutaline, respectively. No differences were observed between the male and female participants. Conclusions: Therapeutic dosing of terbutaline does not lead to an improvement in 3-km running performance despite significantly increased FEV1. The findings suggest that athletes using inhaled terbutaline at high therapeutic doses to treat asthma will not gain an ergogenic advantage during 3-km running performance.

Physiological and performance effects of low- versus mixed-intensity rowing training.

PURPOSE: To examine the impact of low-intensity and a mixture of low- and high-intensity training on physiological and performance responses in rowing. METHODS: Eighteen experienced rowers undertook a 12-wk program of 100% < or = lactate threshold (LT) training (LOW) or 70% training at < or = LT and 30% at halfway (50%Delta) between the V O2 at LT and V O2peak (MIX). Responses were assessed before and after training by a progressive exercise test to exhaustion; multiple "square-wave" rest-to-exercise transitions of 6-min duration at 50%Delta; and a maximal 2000-m ergometer time trial. RESULTS: Improvements (P < 0.001) in 2000-m ergometer performance and V O2peak occurred independently of groups (P = 0.8 and 0.42, respectively). LOW improved the power at LT (23.5 +/- 12.2 vs 5.1 +/- 5.0 W, P = 0.013) and power at a [blood lactate] of 4 mM (32.3 +/- 6.9 vs 13.1 +/- 3.7 W, P = 0.03) compared with MIX. The time constant and gain of the primary component were unchanged with training, whereas the gain of the V O2 slow component was reduced with training, but independently of group. CONCLUSIONS: Both LOW and MIX training programs improved performance and V O2peak by the same magnitude, whereas LOW attenuated the blood lactate response to a given exercise intensity more so than MIX.

Determinants of 800-m and 1500-m running performance using allometric models.

PURPOSE: To identify the optimal aerobic determinants of elite, middle-distance running (MDR) performance, using proportional allometric models. METHODS: Sixty-two national and international male and female 800-m and 1500-m runners undertook an incremental exercise test to volitional exhaustion. Mean submaximal running economy (ECON), speed at lactate threshold (speedLT), maximum oxygen uptake (.VO(2max)), and speed associated with .VO(2max) (speed.VO(2max)) were paired with best performance times recorded within 30 d. The data were analyzed using a proportional power-function ANCOVA model. RESULTS: The analysis identified significant differences in running speeds with main effects for sex and distance, with .VO(2max) and ECON as the covariate predictors (P < 0.0001). The results suggest a proportional curvilinear association between running speed and the ratio (.VO(2max).ECON(-0.71))(0.35) explaining 95.9% of the variance in performance. The model was cross-validated with a further group of highly trained MDR, demonstrating strong agreement (95% limits, 0.05 +/- 0.29 m.s(-1)) between predicted and actual performance speeds (R(2) = 93.6%). The model indicates that for a male 1500-m runner with a .VO(2max) of 3.81 L.min(-1) and ECON of 15 L.km(-1) to improve from 250 to 240 s, it would require a change in .VO(2max) from 3.81 to 4.28 L.min(-1), an increase of Delta0.47 L.min(-1). However, improving by the same margin of 10 s from 225 to 215 s would require a much greater increase in .VO(2max), from 5.14 to 5.85 L.min(-1), an increase of Delta0.71 L.min(-1) (where ECON remains constant). CONCLUSION: A proportional curvilinear ratio of .VO(2max) divided by ECON explains 95.9% of the variance in MDR performance.

Comparison of the oxygen uptake kinetics of club and olympic champion rowers.

PURPOSE: To test the hypothesis that elite rowers would possess a faster, more economic oxygen uptake response than club standard rowers. METHODS: Eight Olympic champion (ELITE) rowers were compared with a cohort of eight club standard (CLUB) rowers. Participants completed a progressive exercise test to exhaustion, repeated 6-min moderate and heavy square-wave transitions, and a maximal 2000-m ergometer time trial. RESULTS: The time constant (tau) of the primary component (PC) was faster for the ELITE group compared with CLUB for moderate-intensity (13.9 vs 19.4 s, P = 0.02) and heavy-intensity (18.7 vs 22.4 s, P = 0.005) exercise. ELITE rowers consumed less oxygen for moderate (14.2 vs 15.6 mL x min(-1) x W(-1); P = 0.009) and heavy (12.1 vs 13.7 mL x min(-1) x W(-1); P = 0.01) exercise. A greater absolute slow component was observed in the ELITE group (P = 0.009), but no differences were noted when the slow component was expressed relative to work rate performed (P = 0.14). Intergroup correlation with time trial performance speed was significant for tauPC during heavy-intensity exercise (r = -0.59, P = 0.02). CONCLUSIONS: Compared with CLUB rowers, the shorter time constant response and greater economy observed in ELITE rowers may suggest advantageous adjustment of oxidative processes from rest to work. Training status or performance level do not seem to be associated with a smaller slow component when comparing CLUB and ELITE oarsmen.

Impact of repeated prolonged exercise bouts on cardiac function and biomarkers.

PURPOSE: The present study examined the impact of repeated bouts of prolonged (< 60 min) exercise on left ventricular function and cardiac biomarkers. METHODS: Ten athletes completed a 15.3-mile hill run on three consecutive days and were assessed before, immediately after, 1 h after, and 20 h after each bout. Six of the athletes completed a fourth bout. Left ventricular (LV) function was examined echocardiographically using two-dimensional M-mode, Doppler, and flow propagation velocity (Vp). Venous blood samples were analyzed for cardiac biomarkers including cardiac troponin T (cTnT). RESULTS: Ejection fraction (EF) significantly decreased (P = 0.027) after the third exercise bout compared with baseline (mean +/- SD: 56.3 +/- 4.4 vs 51.3 +/- 5.9%), accompanied by a nonsignificant decrease in systolic blood pressure/end systolic volume (SBP/ESV) ratio. A sustained depression in systolic function 20 h after bout 3 also persisted in the subset who completed a fourth bout, yet this did not reach clinical levels. Significant (P < 0.01) reductions in early to late diastolic filling (E:A) ratio pre-to post-bout 1 (mean +/- SD: 1.9 +/- 0.5 vs 1.4 +/- 0.3) and pre- to post-bout 3(2.0 +/- 0.5 vs 1.3 +/- 0.4) normalized after each 20-h recovery period. A similar pattern of change was observed in Vp. Cardiac troponin T was elevated in four individuals 1 h after bout 1 (range: 0.013-0.125 microg.L(-1)) but was undetectable thereafter except in one athlete. CONCLUSION: Repeated bouts of prolonged exercise induce short-term reductions in diastolic filling and a cumulative decrease in systolic function, yet these alterations seem to have minimal clinical or functional impact. Elevated cTnT after the initial bout, but not thereafter, may represent an adaptive response to prolonged exercise.

Physiological upper limits of left ventricular dimensions in highly trained junior tennis players.

BACKGROUND: The differentiation between physiological cardiac enlargement and cardiomyopathy is crucial, considering that most young non-traumatic deaths in sport are due to cardiomyopathy. Currently, there are few data relating to cardiac dimensions in junior elite tennis players. The aim of this study was to define the upper limits of left ventricular dimensions in a large cohort of national adolescent tennis players. METHODS: Between 1996 and 2003, 259 adolescent tennis players (152 males), mean (SD) age 14.8 (1.4) years (range 13-19) and 86 healthy age, gender and body surface matched sedentary controls underwent 12-lead ECG and 2D-transthoracic echocardiography. RESULTS: Inter-ventricular septal end diastolic dimension (IVSd), left ventricular end diastolic dimension (LVEDd) and left ventricular end diastolic posterior wall dimension (LVPWd) in tennis players were significantly higher than in controls (8.9 mm vs 8.3 mm p<0.001, 48.9 mm vs 47.9 mm p<0.05 and 9 mm vs 8.3 mm p<0.001 respectively), however in absolute terms, the difference did not exceed 7%. None of the tennis players had a wall thickness exceeding 12 mm or a left ventricular cavity size exceeding 60 mm. CONCLUSIONS: Tennis players exhibit modest increases in cardiac dimensions, which do not resemble those seen in individuals with cardiomyopathy affecting the left ventricle.

Left ventricular function immediately following prolonged exercise: A meta-analysis.

PURPOSE: Evidence supporting cardiac fatigue following prolonged endurance exercise remains equivocal. The purpose of this meta-analysis was to quantify all data fulfilling the specified inclusion criteria, examining the short-term effect of prolonged endurance exercise on left ventricular function. METHODS: A random effects meta-analysis of the weighted mean change in ejection fraction (EF), systolic blood pressure/end systolic volume (SBP/ESV) ratio, and early-to-late diastolic filling (E/A) was conducted on 23 studies using the SE of the between-subjects SD. HR, SBP, and left ventricular internal diameter during diastole (LVIDd) were also analyzed. Studies were coded according to exercise duration and training status: moderate duration trained (MDt) and untrained (MDu), 60-150 min; long duration (LD), 166-430 min; and ultra duration (UD), 640-1440 min. Relationships were assessed via Pearson's product-moment correlation. RESULTS: A significant (P < 0.05) overall decrease in EF (mean, confidence interval (CI): -1.95%, -1.03 to -2.88%), SBP/ESV (mean, CI: -0.8, -0.63 to -0.97), and E/A (mean, CI: -0.45, -0.39 to -0.51) was observed. Only UD and MDu subgroups demonstrated a reduction in EF. All subgroups demonstrated significant (P < 0.05) decreases in E/A. Alterations in LVIDd and SBP were related to respective decreases in EF and SBP/ESV, but not to E/A. CONCLUSION: The decrease in EF and SBP/ESV observed in UD and MDu indicates a reduction in systolic function, partially explained by altered cardiac loading. A decrease in E/A in all subgroups, unrelated to changes in loading, suggests an intrinsic impairment of left ventricular relaxation. Future investigators should employ load-independent indices of cardiac function and attempt to uncover the mechanisms of this phenomenon.

Are there limits to running world records?

PURPOSE: Previous researchers have adopted linear models to predict athletic running world records, based on records recorded throughout the 20th century. These linear models imply that there is no limit to human performance and that, based on projected estimates, women will eventually run faster than men. The purpose of this article is to assess whether a more biologically sound, flattened "S-shaped" curve could provide a better and more interpretable fit to the data, suggesting that running world records could reach their asymptotic limits some time in the future. METHODS: Middle- and long-distance running world record speeds recorded during the 20th century were modeled using a flattened S-shaped logistic curve. RESULTS: The logistic curves produce significantly better fits to these world records than linear models (assessed by separating/partitioning the explained variance from the logistic and linear models using ANOVA). The models identify a slow rise in world-record speeds during the early year of the century, followed by a period of "acceleration" in the middle of the century (due to the professionalization of sport and advances in technology and science), and a subsequent reduction in the prevalence of record-breaking performances towards the end of the century. The model predicts that men's world records are nearing their asymptotic limits (within 1-3%). Indeed, the current women's 1500-m world record speed of 6.51 m x s(-1) may well have reached its limit (time 3:50.46). CONCLUSIONS: Many of the established men's and women's endurance running world records are nearing their limits and, consequently, women's world records are unlikely to ever reach those achieved by men.