The bioenergetics of optimal performances in middle-distance and long-distance track running.

Aspects of anaerobic and aerobic energy conversion are investigated using a mathematical model of running in conjunction with world-record statistics. Analysis of the data shows that over distances from 1500 to 10,000 m the anaerobic energy utilised is constant and independent of running distance. This result is consistent with the view that the full potential of the anaerobic capacity is available for conversion during extended periods of running; the opinions of Gollnick and Hermansen (1973) and Peronnet and Thibault (1989) that the anaerobic energy contribution declines with race duration are not corroborated. The analysis supports the finding of Peronnet and Thibault (1989) that, for running times below about T = 420 s, the maximum sustainable aerobic power is constant, and that for larger T it then declines progressively. The present analysis shows it falls by some 4.5% over 10,000 m, T approximately 1600 s, indicating that in establishing current world records at 5000 and 10,000 m athletes did not rely solely on glycogen as the source of aerobic metabolism; limited use was made of free fatty acids. For elite male runners, the anaerobic capacity and maximal aerobic power are evaluated as 1570 J/kg and 27.1 W/kg, respectively.     

Significance of the contribution of aerobic and anaerobic components to several distance running performances in female athletes

To assess the most important determinant for successful distance running (800 m, 1500 m and 3000 m events) in female athletes, measurements of several anaerobic indices were made (peak power, mean power) using the Wingate anaerobic test (WAnT), and aerobic indices such as oxygen uptake (VO2) or running velocity (v) at lactate threshold (LT), VO2 or v at onset of blood lactate accumulation (OBLA), running economy (RE), and maximal oxygen uptake were determined using the incremental treadmill test. The RE was represented by a VO2 value measured at 240 m.min-1 of a standard treadmill velocity. A stepwise multiple regression analysis (SAS stepwise procedure) combined the best features of forward inclusion and backward elimination to determine the most important factors in predicting the performance of running these distances as dependent variables. The stepwise procedure showed that the blood lactate variables such as LT and/or OBLA are highly correlated with, and contributed to predicting performance running 800 m-3000 m, whereas the anaerobic component was related only to running 800 m. In conclusion, blood lactate variables account for a large part of the variation in distance running performance in female as in male runners. The component of the anaerobic system which can be measured by the WAnT was shown to contribute to performance in running 800 m, but not in longer distances.     

Personal best marathon time and longest training run, not anthropometry, predict performance in recreational 24-hour ultrarunners

In recent studies, a relationship between both low body fat and low thicknesses of selected skinfolds has been demonstrated for running performance of distances from 100 m to the marathon but not in ultramarathon. We investigated the association of anthropometric and training characteristics with race performance in 63 male recreational ultrarunners in a 24-hour run using bi and multivariate analysis. The athletes achieved an average distance of 146.1 (43.1) km. In the bivariate analysis, body mass (r = -0.25), the sum of 9 skinfolds (r = -0.32), the sum of upper body skinfolds (r = -0.34), body fat percentage (r = -0.32), weekly kilometers ran (r = 0.31), longest training session before the 24-hour run (r = 0.56), and personal best marathon time (r = -0.58) were related to race performance. Stepwise multiple regression showed that both the longest training session before the 24-hour run (p = 0.0013) and the personal best marathon time (p = 0.0015) had the best correlation with race performance. Performance in these 24-hour runners may be predicted (r2 = 0.46) by the following equation: Performance in a 24-hour run, km) = 234.7 + 0.481 (longest training session before the 24-hour run, km) - 0.594 (personal best marathon time, minutes). For practical applications, training variables such as volume and intensity were associated with performance but not anthropometric variables. To achieve maximum kilometers in a 24-hour run, recreational ultrarunners should have a personal best marathon time of ～3 hours 20 minutes and complete a long training run of ～60 km before the race, whereas anthropometric characteristics such as low body fat or low skinfold thicknesses showed no association with performance.     

A mathematical analysis of the influence of adverse and favourable winds on sprinting

A mathematical analysis of running performance, based on the first law of thermodynamics and originally derived for still air conditions, is extended to account for the effects of favourable and adverse winds. Solutions to the full theory have been obtained by numerical integration of the governing equations. Simplifications to the full calculation procedure have also been investigated. Calculations for races over a distance of 100 m show that the advantage to an athlete of a following wind increases progressively with increasing wind speed. A favourable wind of 2 ms-1 provides a benefit of about 0.18 s on running time.     

A metabolic limit on the ability to make up for lost time in endurance events.

It has been repeatedly demonstrated that the tolerable duration (t) of high-intensity cycling is well characterized as a hyperbolic function of power (P) with an asymptote that has been termed the "fatigue threshold" and with a curvature constant. This hyperbolic P-t relationship has also been confirmed in running and swimming, when speed (V) is used instead of P; that is, (V - V(F)). t = D', where V(F) is the V at the fatigue threshold, and D' is the curvature constant. Therefore, we theoretically analyzed herein the consequences of an athlete performing the initial part of an endurance event at a V different from the constant rate that would allow the performance time to be determined by the hyperbolic V-t relationship. We considered not only the V-t constraints that limit the athlete's ability to make up the time lost by too slow an early pace but also the consequences of a more rapid early pace. Our analysis demonstrates that both the V(F) and D' parameters of the athlete's V-t curve play an important role in the pace allocation strategy of the athlete. That is, 1) when the running V during any part of the whole running distance is below V(F), the athlete can never attain the goal of achieving the time equivalent to that of running the entire race at constant maximal V (i.e., that determined by one's own best V-t curve); and 2) the "endurance parameter ratio" D'/V(F) is especially important in determining the flexibility of the race pace that the athlete was able to choose intentionally.     

Prerequisites in distance running performance of female runners

We investigated which attribute or what combination of attributes would best account for distance running performance of female runners. The subjects were 30 well-trained female distance runners, aged 19 to 23 years. Anthropometric and body composition characteristics, pulmonary function characteristics, blood properties, and cardiorespiratory function characteristics were measured at rest or during submaximal and maximal exercise. Analyses of the data showed that the relationship of oxygen uptake corresponding to lactate threshold (VO2T, ml.kg-1.min-1) with each distance running performance was substantially higher as compared with the relationship of other independent variables including maximal oxygen uptake (VO2max). Furthermore, multiple regression analysis indicated that running performances in 3,000m, 5,000m, and 10,000m are best accounted for by a combination of VO2/LT (X1), fat-free weight (X2), and/or mean corpuscular volume (X3). A multiple regression equation for predicting the 5,000m (Y, s) running performance was formulated as Y = -14.75X1-3. 03X2-5.79X3 + 2282.1. We suggest that VO2max would not stand alone as a decisive factor of distance running success in female runners, and that the distance running performance could be better accounted for by a combination of several attributes relating to lactate threshold, body composition, and/or hematological status. The linear regression of the predicted running performance on the actually measured running performance can be accepted in the range of 986-1197s.     

The role of anaerobic ability in middle distance running performance

The purpose of this study was to assess the relationship between anaerobic ability and middle distance running performance. Ten runners of similar performance capacities (5 km times: 16.72, SE 0.2 min) were examined during 4 weeks of controlled training. The runners performed a battery of tests each week [maximum oxygen consumption (VO2max), vertical jump, and Margaria power run] and raced 5 km three times (weeks 1, 2, 4) on an indoor 200-m track (all subjects competing). Regression analysis revealed that the combination of time to exhaustion (TTE) during the VO2max test (r2 = 0.63) and measures from the Margaria power test (W.kg-1, r2 = 0.18; W, r2 = 0.05) accounted for 86% of the total variance in race times (P less than 0.05). Regression analysis demonstrated that TTE was influenced by both anaerobic ability [vertical jump, power (W.kg-1) and aerobic capacity (VO2max, ml.kg-1.min-1)]. These results indicate that the anaerobic systems influence middle distance performance in runners of similar abilities.     

Power frequency magnetic fields and risk of childhood leukaemia: Misclassification of exposure from the use of the ‘distance from power line’ exposure surrogate

A recent study examining the relationship between distance to nearby power lines and childhood cancer risk re‐opened the debate about which exposure metrics are appropriate for power frequency magnetic field investigations. Using data from two large population‐based UK and German studies we demonstrate that distance to power lines is a comparatively poor predictor of measured residential magnetic fields. Even at proximities of 50 m or less, the positive predictive value of having a household measurement over 0.2 µT was only 19.4%. Clearly using distance from power lines, without taking account of other variables such as load, results in a poor proxy of residential magnetic field exposure. We conclude that such high levels of exposure misclassification render the findings from studies that rely on distance alone uninterpretable. Bioelectromagnetics 30:183–188, 2009. © 2008 Wiley‐Liss, Inc.     

Relationship between the 4 mmol running velocity, the time-distance relationship and the Léger-Boucher's test

The relationship between distance and best time is roughly linear for distances between 1500 and 5000 m. The slope of this relationship has the dimension of a velocity (Vlim) which can be sustained during a long time. The individual time-distance relationships and the resulting Vlim have been studied in 32 subjects practicing different athletic activities by measuring exhaustion time for 2 to 4 constant-velocity running exercises performed to exhaustion. The velocity corresponding to 4 mmol.l-1 of blood lactate (V4 mmol) has been compared with Vlim. As maximal oxygen uptake is a major factor determining V4 mmol, Vlim and V4 mmol have also been correlated with the result of a field test which is assumed to measure maximal aerobic power (Léger-Boucher's test). This test consists in running until exhaustion at a velocity which increases every two minutes. The higher the velocity at exhaustion (Vléger) is, the higher the maximal oxygen uptake is assumed. Both Vlim and Vléger were very well correlated with V4 mmol (r greater than 0.90) and the average value of Vlim was almost equal to the average value of V4 mmol (13.89 vs 13.71 km.h-1). However, it was not possible to estimate V4 mmol accurately from the values of Vlim or Vléger because the standard errors of estimates were too large.     

Kinematic analysis of the 100-m wheelchair race

The purpose of this study was to compare the speed and selected stroke cycle characteristics during different phases of the 100-m wheelchair race for paraplegic athletes. Four male and two female wheelchair racers in T4 classification and one male and three female athletes in T3 classification served as the participants. Two S-VHS camcorders (60 fields/s) were panned horizontally to cover the first and second 50 m of the 100-m race, respectively. Average speed, stroke length and frequency, contact and recovery times during the first 10 m (initial acceleration phase, IAP), the maximum speed phase (MSP), and the last 10 m (final phase, FP) of the race were determined. For each parameter, an ANOVA with repeated measures was performed and Tukey post hoc tests were completed when appropriate (alpha=0.01). The 100-m times ranged from 16.10 to 22.18 s. Significant differences were found between IAP and MSP and between IAP and FP in stroke speed, stroke length, and push and recovery times, but not in stroke frequency. The relatively constant stroke frequency across different phases may suggest that wheelchair racers like to maintain the same stroking rhythm throughout a 100-m race. The distance and time needed to reach the maximum speed ranged from 43.9 m and 11.2 s to 82.2 m and 18.9 s, respectively. The significant correlation between 100-m time and maximum speed (p<0.001) signifies the importance of maximum speed in determining 100-m performance.     

Air resistance and its influence on the biomechanics and energetics of sprinting at sea level and at altitude

Following an examination of the processes by which chemical energy is converted into useful work during running, a mathematical model of the energetics of sprinting is constructed. This is used in conjunction with a careful analysis of Olympic records, in particular those obtained in the 1968 Games at Mexico City, to determine the magnitude of the rate of working against air resistance during running. It is established that times in the 100 m, 200 m and 400 m events at the Mexico Olympics were approximately 1.7% lower than they would otherwise have been if the races had been run at sea level. This information is used to deduce that the external work done per unit time against air resistance is about 7.5-9% of the total power output of a sprinter, running at maximum speed at sea level. These figures compare well with the value of 7.8% obtained independently by Davies (J. appl. Physiol 48, 702-709, 1980). The analysis provides evidence that a linear relation exists between running speed and the rate of degradation of mechanical energy into thermal energy up to the highest sprinting speeds attainable. The maximum power generated by a sprinter is approximately 3 kW.     

Relationship between distance running mechanics, running economy, and performance

The relationships between biocmechanical aspects of distance running, running economy (VO2 submax), and performance were investigated. A variety of biomechanical measures for 31 subjects running at 3.6 m/s was obtained, including three-dimensional angular and translational kinematics, ground reaction forces and center of pressure patterns, mechanical power, and anthropometric measures. Physiological measures obtained included maximal and submaximal O2 consumption, muscle fiber composition, and measures of the ability to store and return elastic energy during knee bends. A subset of 16 runners was also evaluated in relation to performance in a 10-km run. Biomechanical variables were identified which showed significant differences or consistent trends between groups separated on the basis of VO2 submax, establishing the importance of biomechanical influences on running economy. It appears that no single variable or small subset of variables can explain differences in economy between individuals but rather that economy is related to a weighted sum of the influences of many variables.     

Post-competition blood lactate concentrations as indicators of anaerobic energy expenditure during 400-m and 800-m races

The relationships between anaerobic glycolysis and the average velocity (v) sustained during running were studied in 17 top level athletes (11 males and 6 females). A blood sample was obtained within 10 min of the completion of major competitions over 400 m, 800 m and 1500 m and the blood lactate concentration [la]b was measured. In both male and female athletes [la]b was related to the relative performance, as expressed as a percentage of the athlete's best v of the season. Over 400 m, r = 0.85 (P less than 0.01) and r = 0.80 (P less than 0.05) in males and females, respectively. Over 800 m, the corresponding values were r = 0.76 (P less than 0.01) and r = 0.91 (P less than 0.01). In male runners [la]b was correlated to v: r = 0.89 (P less than 0.01) and r = 0.71 (P less than 0.02) over 400 m and 800 m, respectively. No relationship to relative performance or v was obtained over 1500 m. Energy expenditure during competition running was estimated in male runners from the [la]b values. This estimate was based mainly on the assumption that a 1 mmol.1-1 increase in [la]b corresponded to the energy produced by the utilization of 3.30 ml.O kg-1. The energy cost of running was estimated, by dividing the estimated total energy expenditure by the race distance, at 0.211 ml.kg-1.min-1 over 800 m and 0.274 ml.kg-1.m-1 over 400 m.(ABSTRACT TRUNCATED AT 250 WORDS)     

A theoretical analysis of the effect of altitude on running performance

A theoretical analysis of the effect of altitude on running performance is presented using a mathematical model we have recently described and validated (J. Appl. Physiol. 67: 453-465, 1989). This model relates the average power output available over a given running time for a given combination of anaerobic capacity, maximal aerobic power, and endurance capability. For short sprinting distances, the contribution of aerobic metabolism to the energy requirement is small and the speed sustained is high. The reduction of maximal aerobic power with altitude is, thus, negligible, whereas the reduction of aerodynamic resistance is beneficial. Accordingly the performance steadily increases with altitude (e.g., average speed for 100 m at Mexico City is 101.9% of the average speed at sea level). On the other hand, the reduction in maximal aerobic power with altitude is associated with a reduction in performance over middle and long distances (800 m to marathon). For 400 m an improvement in performance is observed up to an altitude of approximately 2,400-2,500 m (average speed approximately 101.4% of sea level speed). Beyond this altitude the reduction in air density cannot compensate for the reduction in maximal aerobic power, and the performance deteriorates. Tables of performances equivalent to the current world records for selected altitudes ranging from 0 to 4,000 m are proposed.     

Digit ratio (2D:4D) and rowing ergometer performance in males and females

Fetal and adult testosterone may be vital in the establishment and maintenance of sex-dependent abilities associated with male physical competitiveness. It has been shown that digit ratio (2D:4D) is negatively associated with prenatal testosterone, and it is also negatively associated with ability in sports such as football, skiing, middle distance running, and endurance running, which are dependent upon an efficient cardiovascular system. The relationship between digit ratio and sports requiring high power (physical strength) output in addition to well-developed cardiovascular systems has not been defined. This study investigated this association in male and female young adult rowers. Participants (77 male and 70 female) were student rowers encompassing a range of abilities from the University of Cambridge. Bilateral digit measurements were taken blind from each subject using Mitutoyo vernier calipers. Rowing performance over 2,000 m was assessed using the Concept 2 rowing ergometer. Significant negative correlations were observed between 2,000 m ergometer performance and male digit ratios, which persisted following adjustment for rowing experience and height. However, no such significant association was found in females despite a comparable sample size. Our data indicate that digit ratio is a predictor of ability in rowing, a sport which requires both cardiovascular efficiency and high power output, in males but not females. This in turn suggests that fetal testosterone exposure has long-term effects on traits associated with physical power in males but not females, suggesting a sex-difference in the capacity to respond to such exposures.     

Exercise-induced inspiratory muscle fatigue during swimming: the effect of race distance

Exercise-induced inspiratory muscle fatigue (IMF) has been quantified for several sports. However, it is not yet known if, or to what extent, IMF is determined by the competition distance. The aim of the present study was to assess the influence of 3 different competitive front-crawl swimming race distances on the magnitude of IMF. Ten well-trained swimmers from a local swim team participated in the study and on separate days completed maximal 100-, 200-, and 400-m time trials (TTs). Before and after each trial, maximal inspiratory pressure (MIP) was measured and %IMF determined from pre- and post-time-trial differences in MIP. The heart rate (HR) and rate of perceived dyspnea (RPD) was also assessed. For all distances, posttrial MIP was lower than pretrial MIP, though this was only significant for 100 m (p < 0.05). There were no differences between distances for absolute posttrial MIP. The %IMF after the 100-m TT (8.2 ± 4.1%) was, however, significantly greater than the 400 m (4.9 ± 3.8%) TT (p < 0.05) but not 200-m TT. There were no differences between trials for HR or RPD (p > 0.05). There were no relationships between %IMF and mean pretrial MIP (r = -0.28, p > 0.05) or between %IMF and time for any TT (100 m, r = 0.25; 200 m, r = 0.34; 400 m r = 0.18; p > 0.05). The lack of difference between trials for posttrial absolute MIP suggests that race distance during swimming does not substantially influence the degree of IMF.     

Aerial distribution, flight behaviour and eggload: their inter-relationship during dispersal by the sweetpotato whitefly

1. The aerial distribution of Bemisia tabaci Gennadius (the sweetpotato whitefly) was studied during the early ascent phase of flight, to test the degree to which dispersal patterns reflect the flight behaviour of individuals.
2. Marked whiteflies were trapped at four heights between 0 and 7·2 m above fallow ground, and at six distances between 0 and 100 m from the insect source. Insects were trapped during a 2–3 h period after the initiation of flight activity during the summers of 1995 and 1996.
3. Analysis of trap catch data revealed a clear negative exponential relationship between height and aerial distribution, and a slightly weaker negative power relationship between distance and aerial distribution. Marked insects were caught in the uppermost traps adjacent to the source, indicating that a portion of the population had a strong capacity for ascent out of the flight boundary layer.
4. Eggload decreased with the height, but not the distance, at which whiteflies were trapped. Mean eggload close to the ground was significantly greater than that for those trapped at 4·8 and 7·2 m, supporting the hypothesis that there is a trade-off between flight and oogenesis in weak-flying insects.
5. Air temperatures during the trapping periods were positively correlated with the proportion of male and female B. tabaci caught in the highest traps, but not in the most distant traps.
6. The significance of these results for accurate prediction of whitefly dispersal is discussed, and the importance of individual's behaviour in determining dispersal patterns of small insects is emphasized.     

Calculation of record-time in the 800-meter run: predictive value of Margaria's equation

Margaria's equation (1976)--describing the relationship between the minimum time necessary to cover a distance equal or longer than 1,000 m (record-time TR) and the maximal oxygen consumption (VO2 max)--has been modified in order to be applied to the calculation of TR in the 800 m foot race. Fifteen subjects participated in this study (VO2 max = 63 +/- 3.5 ml O2 X kg-1 X min-1, measured TR = 131 +/- 10 seconds). It has been found the TR calculated from Margaria's equation (TRc) are underestimated (TRc = 104 +/- 10 seconds). By taking into account the actual energy cost of running (0.19 ml O2 X kg-1 X m-1) and the kinetics of VO2 at the onset of exercise, TRc averaged 133 +/- 8.5 seconds. Moreover, the relationship between TRc and measured TR (TRm) is highly significant (TRc = 50.4 + 0.65 TRm; r = 0.75; P less than 0.01). These results validate Margaria's equation modifications.     

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

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

LONG-DISTANCE GENE FLOW IN THE SEDENTARY BUTTERFLY,EUPHILOTES ENOPTES (LEPIDOPTERA: LYCAENIDAE)

The relationship between gene flow and geographic proximity has been assessed for many insect species, but dispersal distances are poorly known for most of these. Thus, we are able to assess the concordance between vagility and gene flow for only a few species. In this study, I documented variation at six allozyme loci among Washington and Oregon populations of the sedentary, patchily distributed, lycaenid butterfly, Euphilotes enoptes (Boisduval) to assess whether the relationship between gene flow and geographic distance is consistent with the dispersal biology of this species. Both a phenogram based on genetic distances between populations and a regression analysis of gene flow estimates on geographic distances showed a pattern consistent with genetic isolation by distance. Many estimates of gene flow among pairs of populations separated by more than 100 km exceeded the equivalent of 10 individuals exchanged per generation, a value much greater than would be predicted from the limited dispersal ability of this species. However, based on the allozyme data, genetic neighborhood size was estimated to be approximately 39 individuals, a value that is consistent with poor vagility. The results of this study speak to the power of stepping-stone gene flow among populations and are compared to the results of other studies that have examined the relationship between dispersal and gene flow in sedentary insects.