Maximal oxygen uptake,anaerobic threshold and running economy in women and men with similar performances level in marathons

Sex differences in running economy (gross oxygen cost of running, C_R), maximal oxygen uptake (VO_2max), anaerobic threshold (Th_an), percentage utilization of aerobic power (% VO_2max), and Th_an during running were investigated. There were six men and six women aged 20–30 years with a performance time of 2 h 40 min over the marathon distance. The VO_2max, Th_an, and CR were measured during controlled running on a treadmill at 1° and 3° gradient. From each subject's recorded time of running in the marathon, the average speed (v _M) was calculated and maintained during the treadmill running for 11 min. The VO_{2 max} was inversely related to body mass (m _b), there were no sex differences, and the mean values of the reduced exponent were 0.65 for women and 0.81 for men. These results indicate that for running the unit ml·kg^–0.75·min^–1 is convenient when comparing individuals with different m _b. The VO_2max was about 10% (23 ml·kg^–0.75·min^–1) higher in the men than in the women. The women had on the average 10–12 ml·kg^–0.75·min^–1 lower VO₂ than the men when running at comparable velocities. Disregarding sex, the mean value of C_R was 0.211 (SEM 0.005) ml·kg^–1·m^–1 (resting included), and was independent of treadmill speed. No sex differences in Th_an expressed as % VO_2max or percentage maximal heart rate were found, but Than expressed as VO₂ in ml·kg^–0.75·min^–1 was significantly higher in the men compared to the women. The percentage utilization of f _emax and concentration of blood lactate at v _M was higher for the female runners. The women ran 2 days more each week than the men over the first 4 months during the half year preceding the marathon race. It was concluded that the higher VO_2max and Th_an in the men was compensated for by more running, superior C_R, and a higher exercise intensity during the race in the performance-matched female marathon runners.     

Physiological differences between black and white runners during a treadmill marathon

Summary To determine why black distance runners currently out-perform white distance runners in South Africa, we measured maximum oxygen consumption (V _{O 2max}), maximum workload during a V _{O 2max} test (L _max), ventilation threshold (V _Thr), running economy, inspiratory ventilation (V _I), tidal volume (V _T), breathing frequency (f) and respiratory exchange ratio (RER) in sub-elite black and white runners matched for best standard 42.2 km marathon times. During maximal treadmill testing, the black runners achieved a significantly lower (P<0.05) L _max (17 km h^–1, 2% grade, vs 17 km h^–1, 4% grade) and V _I max (6.21 vs 6.821 kg^–2/3 min^–1), which was the result of a lower V _T (101 vs 119 ml kg^–2/3 breath^–1) as f _max was the same in both groups. The lower V _T in the black runners was probably due to their smaller body size. The V _Thr occurred at a higher percentage V _{O 2max} in black than in white runners (82.7%, SD 7.7% vs 75.6%, SD 6.2% respectively) but there were no differences in the V _{O 2max}. However, during a 42.2-km marathon run on a treadmill, the black athletes ran at the higher percentage V _{O 2max} (76%, SD 7.9% vs 68%, SD 5.3%), RER (0.96, SD 0.07 vs 0.91, SD 0.04) and f (56 breaths min^–1, SD 11 vs 47 breaths min^–1, SD 10), and at lower V _T (78 ml kg^–2/3 breath^–1, SD 15 vs 85 ml kg^–2/3 breath^–1, SD 19). The combination of higher f and lower V _T resulted in an identical V _I. Blood lactate levels were lower in black than in white runners (1.3 mmol l^–1, SD 0.6 vs 1.59 mmol l^–1, SD 0.2 respectively). It appeared that the only physiological difference that may account for the superior performance of the black runners was their ability to run at a higher percentage V _{O 2max} max during competition than white runners.     

The role of anaerobic ability in middle distance running performance

Summary 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 (VO_2max), 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 theVO_2max test (r ²=0.63) and measures from the Margaria power test (W·kg^–1,r ²=0.18 ; W,r ²=0.05) accounted for 86% of the total variance in race times (P<0.05). Regression analysis demonstrated that TTE was influenced by both anaerobic ability [vertical jump, power (W·kg^–1) and aerobic capacity (VO_2max, ml·kg^–1·min^–1)]. These results indicate that the anaerobic systems influence middle distance performance in runners of similar abilities.     

Heart rate overshoot at the beginning of muscle exercise

Summary A characteristic notch in the heart rate (f _c) on-response at the beginning of square-wave exercise is described in 7 very fit marathon runners and 12 sedentary young men, during cycle tests at 30% and 60% of maximal oxygen consumption (VO_2max). The (f _c) notch revealed af _c overshoot with respect to the (f _c) values predicted from exponential beat-by-beat fitted models. While at 30% of (VO_2max). all subjects showed af _c over-shoot, at 60% of (VO_2max). it occurred in the marathon runners but not in the sedentary subjects. The mean time of occurrence of thef _c overshoot from the onset of the exercise was 16.7 (SD 4.7) s and 12.2 (SD 3.2) s at 30% of (VO_2max). in the runners and the sedentary subjects respectively, and 23.8 (SD 8.8) s at 60% of (VO_2max). in the runners. The amplitude of the overshoot, with respect to rest, was 41 (SD 12) beats·min^–1and 31 (SD 4) beats·min^–1 at 30% of (VO_2max). in the runners and the sedentary subjects respectively, and 46 (SD 19) beats·min^–1 at 60% of (VO_2max). in the runners. The existence and the amplitude of thef _c overshoot may have been related to central command and muscle heart reflex mechanisms and thus may have been indicators of changes in the balance between sympathetic and parasympathetic activity occurring in fit and unfit subjects.     

Intermittent short-term graded running performance in middle-distance runners in hypobaric hypoxia

This study investigated whether in trained middle-distance runners, intermittent short-term graded running performance is affected by a hypobaric hypoxic environment (simulated 2,500 m) (H). Seven male middle-distance runners performed an aerobic performance test and an intermittent short-term graded anaerobic running-performance test (MART) both in H and in a normobaric normoxic environment (N). VO_2max and OBLA were markedly lower (by 18.1% and 8.7%, respectively) in H than in N. In MART, neither maximal running velocity (V_max) nor exhaustion-time was different between N and H (454 (7) m min^–1 vs. 451 (6) m min^–1, respectively, and 208.7 (5.2) s vs. 205.7 (4.2) s, respectively). The blood lactate concentration at sub-maximal running speed (425 m min^–1) was significantly greater in H than in N (paired t-test: P<0.05). These results suggest that, in trained middle-distance runners, intermittent short-term graded running performance is not affected by H, despite a considerable decrease in aerobic power in H during the aerobic performance test.     

Carbohydrate supercompensation and muscle glycogen utilization during exhaustive running in highly trained athletes

Summary Three female and three male highly trained endurance runners with mean maximal oxygen uptake (VO_2max) values of 60.5 and 71.5 ml·kg^–1·min^–1, respectively, ran to exhaustion at 75%–80% of VO_2max on two occasions after an overnight fast. One experiment was performed after a normal diet and training regimen (Norm), the other after a diet and training programme intended to increase muscle glycogen levels (Carb). Muscle glycogen concentration in the gastrocnemius muscle increased by 25% (P<0.05) from 581 mmol·kg^–1 dry weight, SEM 50 to 722 mmol·kg^–1 dry weight, SEM 34 after Carb. Running time to exhaustion, however, was not significantly different in Carb and Norm, 77 min, SEM 13 vs 70 min, SEM 8, respectively. The average glycogen concentration following exhaustive running was 553 mmol· kg^–1 dry weight, SEM 70 in Carb and 434 mmol·kg^–1 dry weight, SEM 57 in Norm, indicating that in both tests muscle glycogen stores were decreased by about 25%. Periodic acid-Schiff staining for semi-quantitative glycogen determination in individual fibres confirmed that none of the fibres appeared to be glycogen-empty after exhaustive running. The steady-state respiratory exchange ratio was higher in Carb than in Norm (0.92, SEM 0.01 vs 0.89, SEM 0.01; P<0.05). Since muscle glycogen utilization was identical in the two tests, the indication of higher utilization of total carbohydrate appears to be related to a higher utilization of liver glycogen. We have concluded that glycogen depletion of the gastrocnemius muscle is unlikely to be the cause of fatigue during exhaustive running at 75%–80% of VO_2max in highly trained endurance runners. Furthermore, diet- and training-induced carbohydrate supercompensation does not appear to improve endurance capacity in such individuals.     

Use of recoveryVO2 to predict running economy

Summary The purpose of this study was to determine whether running economy. (RE) could be predicted accurately using recoveryVO₂ values. Twelve runners (VO_2max=61.9, SD 4.9 ml·kg^–1·min^–1) completed three treadmill RE sessions over a 2-week period. During each session, subjects performed three 6-min runs at 69%, 78%, and 87%VO_2max. RE was calculated from a single 2-min gas collection during the last 2 min of running. Immediately following each run, recoveryVO₂ data obtained during randomly assigned 15-s, 20-s, or 25-s gas collections were used to predict exerciseVO₂. Correlations and mean absolute percentage variation (%VAR) between actual and predictedVO₂ at each relative intensity and recovery period are reported. Although the relationship between actual and predictedVO₂ was significant and more pronounced at higher exercise intensities, the overall magnitude of the association was low to moderate (r range= 0.50–0.81). The range of % VAR between actual and predicted aerobic demands also obscured marked underprediction (–6.5% to –12.5%) and overprediction (+ 10.1% to + 17.4%) of actualVO₂ in some subjects. These data suggest that 15-, 20-, and 25-s recoveryVO₂ values do not correlate strongly with steady-stateVO₂, nor do they adequately account for variation in individual economy profiles.     

Training effects of cross-country skiing and running on maximal aerobic cycle performance and on blood lipids

Summary Two experiments were carried out to compare the cardiorespiratory and metabolic effects of cross-country skiing and running training during two successive winters. Forty-year-old men were randomly assigned into skiing (n = 15 in study 1,n = 16 in study 2), running (n = 16 in study 1 andn = 16 in study 2) and control (n = 17 in study 1 andn = 16 in study 2) groups. Three subjects dropped out of the programme. The training lasted 9–10 weeks with 40-min exercise sessions three times each week. The training intensity was controlled at 75%–85% of the maximal oxygen consumption (VO_2max) using portable heart rate metres and the mean heart rate was 156–157 beats·min^–1 in the training groups. In the pooled data of the two studies the mean increase in theVO_2max (in ml·min^–1·kg^–1) on a cycle ergometer was 17% for the skiing group, 13% for the running group and 2% for the control group. The increase inVO_2max was highly significant in the combined exercise group compared to the control group but did not differ significantly between the skiing and running groups. The fasting serum concentrations of lipoproteins and insulin did not change significantly in any of the groups. These results suggested that training by cross-country skiing and running of the same duration and intensity at each session for 9–10 weeks improved equally the cardiorespiratory fitness of untrained middle-aged men.     

Optimising high-intensity treadmill training using the running speed at maximal O(2) uptake and the time for which this can be maintained

The aim of this study was to compare the effects of two high-intensity, treadmill interval-training programs on 3000-m and 5000-m running performance. Maximal oxygen uptake (V˙O_2max), the running speed associated with V˙O_2max (vV˙O_2max), the time for which vV˙O_2max can be maintained (T _max), running economy (RE), ventilatory threshold (VT) and 3000-m and 5000-m running times were determined in 27 well-trained runners. Subjects were then randomly assigned to three groups; (1) 60% T _max, (2) 70% T _max and (3) control. Subjects in the control group continued their normal training and subjects in the two T _max groups undertook a 4-week treadmill interval-training program with the intensity set at vV˙O_2max and the interval duration at the assigned T _max. These subjects completed two interval-training sessions per week (60% T _max=six intervals/session, 70% T _max group=five intervals/session). Subjects were re-tested on all parameters at the completion of the training program. There was a significant improvement between pre- and post-training values in 3000-m time trial (TT) performance in the 60% T _max group compared to the 70% T _max and control groups [mean (SE); 60% T _max=17.6 (3.5) s, 70% T _max =6.3 (4.2) s, control=0.5 (7.7) s]. There was no significant effect of the training program on 5000-m TT performance [60% T _max=25.8 (13.8) s, 70% T _max=3.7 (11.6) s, control=9.9 (13.1) s]. Although there were no significant improvements in V˙O_2max, vV˙O_2max and RE between groups, changes in V˙O_2max and RE were significantly correlated with the improvement in the 3000-m TT. Furthermore, VT and T _max were significantly higher in the 60% T _max group post- compared to pre-training. In conclusion, 3000-m running performance can be significantly improved in a group of well-trained runners, using a 4-week treadmill interval training program at vV˙O_2max with interval durations of 60% T _max. Electronic Publication     

Are there differences in running economy at different velocities for well-trained distance runners?

The present study investigated whether there are differences in running economy at different velocities for well-trained distance runners, and to what extent a commonly used incremental protocol for measuring oxygen uptake (VO₂) at different velocities affects the reliability of these measurements. Fifteen well-trained distance runners (9 male and 6 female) participated in this study. Gross oxygen cost of running (C _R), heart rate (HR) and [La⁻]_b during 5-min runs at velocities ranging from 8.0 to 17 km h⁻¹, representing intensities ranging from 60 to 90% of maximal oxygen consumption (VO_2max) was measured on two different days in random order. The athletes were also tested for lactate threshold, VO_2max and time to exhaustion at MAS (_tMAS). No significant differences in C _R between the different relative velocities or the different set velocities were found up to 90% of VO_2max. The incremental protocol for measuring VO₂ at different velocities was found not to affect the reliability of these measurements. All athletes reached their VO_2max whilst running to exhaustion at MAS. The females showed significantly lower VO_2max, but significantly better C _R than the males. At velocities representing intensities between 60 and 90% of VO_2max, no differences in C _R were found. The commonly used incremental protocol for measuring oxygen uptake (VO₂) at different velocities was found not to affect the reliability of these measurements. This means that C _R measured at sub-maximal velocities are representative for C _R at race velocity for distances above 10,000 m for most runners.     

Physical work capacity and effect of endurance training in visually handicapped boys and young male adults

Summary The purpose of the present study was to evaluate the relationship between several physical fitness parameters and eyesight divided into 3 grades in visually handicapped boys and young male adults, and to investigate the effect of mild exercise training on physical and psychic symptoms as well as cardiorespiratory fitness. Four subjects were totally blind (TB), 6 were semi-blind (SB) and 27 had amblyopia (AM). Physical fitness tests consisted of maximal oxygen uptake (V _{O 2max}), maximal pedalling speed and power, maximal stepping rate, and isometric knee extention strength. Compared with AM and SB groups, the TB group was inferior in all physical fitness parameters. Especially,V _{O 2max} in TB (26 ml · kg^–1 · min^–1) was about 56% of that in agematched Japanese sighted subjects and was significantly low compared with the AM and SB groups. Both muscle strength and maximal pedalling power corresponded to about 50% that of the age-matched sighted group. Six SB and 4 TB students (¯x=17.7 years) were trained for 6 weeks on a bicycle ergometer at an intensity of 50%V _{O 2max}. Training was undertaken for 3 days per week and maintained for 60 min per session. After training, physical and psychic symptoms determined by the Cornell Medical Index improved significantly. These results indicate that low physical work capacity in visually handicapped boys and young male adults is due to the lack of physical activity, and that mild endurance training is effective in improving physical and psychic symptoms as well as cardiorespiratory fitness.     

Gender differences in the physiological responses and kinematic behaviour of elite sprint cross-country skiers

Gender differences in performance by elite endurance athletes, including runners, track cyclists and speed skaters, have been shown to be approximately 12%. The present study was designed to examine gender differences in physiological responses and kinematics associated with sprint cross-country skiing. Eight male and eight female elite sprint cross-country skiers, matched for performance, carried out a submaximal test, a test of maximal aerobic capacity (VO_2max) and a shorter test of maximal treadmill speed (V _max) during treadmill roller skiing utilizing the G3 skating technique. The men attained 17% higher speeds during both the VO_2max and the V _max tests (P < 0.05 in both cases), differences that were reduced to 9% upon normalization for fat-free body mass. Furthermore, the men exhibited 14 and 7% higher VO_2max relative to total and fat-free body mass, respectively (P < 0.05 in both cases). The gross efficiency was similar for both gender groups. At the same absolute speed, men employed 11% longer cycles at lower rates, and at peak speed, 21% longer cycle lengths (P < 0.05 in all cases). The current study documents approximately 5% larger gender differences in performance and VO_2max than those reported for comparable endurance sports. These differences reflect primarily the higher VO_2max and lower percentage of body fat in men, since no gender differences in the ability to convert metabolic rate into work rate and speed were observed. With regards to kinematics, the gender difference in performance was explained by cycle length, not by cycle rate.     

Aerobic capacity and fractional utilisation of aerobic capacity in elite and non-elite male and female marathon runners

Summary The physiology of marathon running has been extensively studied both in the laboratory and in the field, but these investigations have been confined to elite competitors. In the present study 28 competitors who took part in a marathon race (42.2 km) have been studied; 18 male subjects recorded times from 2 h 19 min 58 s to 4 h 53 min 23 s; 10 female subjects recorded times between 2 h 53 min 4 s and 5 h 16 min 1 s. Subjects visited the laboratory 2–3 weeks after the race and ran on a motor driven treadmill at a series of speeds and inclines; oxygen uptake O₂ was measured during running at average marathon racing pace. Maximum oxygen uptake ( O₂ max) was measured during uphill running. For both males (r=0.88) and females (r=0.63), linear relationships were found to exist between marathon performance and aerobic capacity. Similarly, the fraction of O₂ max which was sustained throughout the race was significantly correlated with performance for both male (r=0.74) and female (r=0.73) runners. The fastest runners were running at a speed requiring approximately 75% of O₂ max; for the slowest runners, the work load corresponded to approximately 60% of O₂ max. Correction of these estimates for the additional effort involved in overcoming air resistance, and in running on uneven terrain will substantially increase the oxygen requirement for the faster runners, while having a much smaller effect on the work rate of the slowest competitors. Five minutes of treadmill running at average racing pace at zero gradient did not result in marked elevation of the blood lactate concentration in any of the subjects.     

Energetics of locomotion in African pygmies

Summary The energy cost of walking (C _w). and running (C _r), and the maximal O₂ consumption (VO_2max) were determined in a field study on 17 Pygmies (age 24 years, SD 6; height 160 cm, SD 5; body mass 57.2 kg, SD 4.8) living in the region of Bipindi, Cameroon. TheC _w varied from 112 ml·kg^–1·km^–1, SD 25 [velocity (), 4 km·h^–1] to 143 ml·kg^–1·km^–1, SD 16 (, 7 km·h^–1). Optimal walking was 5 km·h^–1. TheC _r was 156 ml·kg^–1·km^–1, SD 14 (, 10 km·h^–1) and was constant in the 8–11 km·h^–1 speed range. TheVO_2max was 33.7 ml·kg^–1· min^–1, i.e. lower than in other African populations of the same age. TheC _r andC _w were lower than in taller Caucasian endurance runners. These findings, which challenge the theory of physical similarity as applied to animal locomotion, may depend either on the mechanics of locomotion which in Pygmies may be different from that observed in Caucasians, or on a greater mechanical efficiency in Pygmies than in Caucasians. The lowC _r values observed enable Pygmies to reach higher running speeds than would be expected on the basis of theirVO_2max.     

Metabolic cost of exercise and physical performance in children with some observations on external loading

Summary The metabolic cost (VO₂) of running was studied on a motor-driven treadmill in nine athletic boys, five athletic girls, and nine active boys aged 11–13 years and the results compared with their performance times during racing out of doors. On 15 of the children, additional observations of the effects of external loading on aerobic power output were made. The results showed that VO₂ was proportional to body weight in children but when expressed in ml·kg^–1·min^–1, VO₂ for a given speed of running was significantly higher in children than expected from previously collected data on adults. There were no significant differences between aerobic cost of running of the athletic boys, girls, or the active boys. The increased VO₂ ml·kg^–1·min^–1 in children appeared to be independent of stride length and frequency but external loading equivalent to 5% of body weight reduced VO₂ (ml·kg^–1·min^–1), particularly at the higher speeds. It was suggested in young active and athletic children due to their relatively light body weights and highly developed aerobic power outputs, that the required frequency of leg movement was not optimally matched to the force necessary to produce the most economic conversion of aerobic energy into mechanical work. Thus, in competitive events their performance times were related to their maximal aerobic power output (r=–0.75) but their times were always inferior to those which one might have expected from previous aerobic power weight data collected on adult male and female athletes.     

Neuromuscular factors determining 5 km running performance and running economy in well-trained athletes

This study investigated the effects of the neuromuscular and force–velocity characteristics in distance running performance and running economy. Eighteen well-trained male distance runners performed five different tests: 20 m maximal sprint, running economy at the velocity of 4.28 m s⁻¹, 5 km time trial, maximal anaerobic running test (MART), and a treadmill test to determine VO_2max. The AEMG ratio was calculated by the sum average EMG (AEMG) of the five lower extremity muscles during the 5 km divided by the sum AEMG of the same muscles during the maximal 20 m sprinting. The runners’ capacity to produce power above VO_2max (MART VO_2gain) was calculated by subtracting VO_2max from the oxygen demand of the maximal velocity in the MART (V _MART). Velocity of 5 km (V _5K) correlated with V _MART (r=0.77, p<0.001) and VO_2max (r=0.49, p<0.05). Multiple linear regression analysis showed that MART VO_2gain and VO_2max explained 73% of the variation in V _5K. A significant relationship also existed between running economy and MART VO_2gain (r=0.73, p<0.01). A significant correlation existed between V _5K and AEMG ratio during the ground contact phase at the 3 km (r=0.60, p<0.05) suggesting that neural input may affect distance running performance. The results of the present study support the idea that distance running performance and running economy are related to neuromuscular capacity to produce force and that the V _MART can be used as a determinant of distance-running performance.     

Interference of strength development by simultaneously training for strength and endurance

Summary The purpose of this study was to determine how individuals adapt to a combination of strength and endurance training as compared to the adaptations produced by either strength or endurance training separately. There were three exercise groups: a strength group (S) that exercised 30–40 min·day^–1, 5 days·week^–1, an endurance group (E) that exercised 40 min·day^–1, 6 days·week^–1; and an S and E group that performed the same daily exercise regimens as the S and E groups. After 10 weeks of training, VO_{2 max} increased approx. 25% when measured during bicycle exercise and 20% when measured during treadmill exercise in both E, and S and E groups. No increase in VO_{2 max} was observed in the S group. There was a consistent rate of development of leg-strength by the S group throughout the training, whereas the E group did not show any appreciable gains in strength. The rate of strength improvement by the S and E group was similar to the S group for the first 7 weeks of training, but subsequently leveled off and declined during the 9th and 10th weeks. These findings demonstrate that simultaneously training for S and E will result in a reduced capacity to develop strength, but will not affect the magnitude of increase in VO_{2 max}.This research was supported by a University of Illinois at Chicago Circle Research Board Grant and by a NIH Biomedical Research Support Grant (HEW RR07158-2) to the University of Illinois at Chicago Circle     

The effect of exercise intensity and duration on salivary immunoglobulin A

Summary Two experiments were performed to examine salivary immunoglobulin A (s-IgA) responses to varying levels of exercise intensity and duration. For experiment 1, 9 college men (mean age, SD=23.56, 1.64 years) completed treadmill runs of 15, 30, and 45 min at approximately 60% of maximum oxygen consumption (VO_2max). For experiment 2, 9 other college men (mean age, SD=23.67, 2.0 years) ran for 20 min at approximately 50, 65 and 80% of VO_2max. Unstimulated salivary samples were collected before, and immediately, 1 and 2 h after the exercise. Samples were assayed for s-IgA using an enzyme-linked immunosorbent assay. Mean s-IgA levels did not change significantly (P>0.05) at any of the post-exercise collection times when compared to pre-exercise levels. The results of this investigation indicated that running at intensities of 50–80% of VO_2max and for durations of 15–45 min did not affect s-IgA levels.     

Changes in acid-base status of marathon runners during an incremental field test

Summary Four top-class runners who regularly performed marathon and long-distance races participated in this study. They performed a graded field test on an artificial running track within a few weeks of a competitive marathon. The test consisted of five separate bouts of running. Each period lasted 6 min with an intervening 2-min rest bout during which arterialized capillary blood samples were taken. Blood was analysed for pH, partial pressure of oxygen and carbon dioxide (P0₂ and PCO₂) and lactate concentration ([la^–]_b). The values of base excess (BE) and bicarbonate concentration ([HCO₃ ^–]) were calculated. The exercise intensity during the test was regulated by the runners themselves. The subjects were asked to perform the first bout of running at a constant heart rate f _c which was 50 beats · min^–1 below their own maximal f _c. Every subsequent bout, each of which lasted 6 min, was performed with an increment of 10 beats · min^–1 as the target f _c. Thus the last, the fifth run, was planned to be performed with fc amounting to 10 beats · min^–1 less than their maximal f _c. The results from these runners showed that the blood pH changed very little in the bouts performed at a running speed below 100% of mean marathon velocity ( _m). However, once _mwas exceeded, there were marked changes in acid-base status. In the bouts performed at a velocity above the _mthere was a marked increase in [la^–]_b and a significant decrease in pH, [HCO₃ ^–], BE and PCO₂. The average marathon velocity ( _m) was 18.46 (SD 0.32) km·h^–1. The [la^–]_b at a mean running velocity of 97.1 (SD 0.8) % of _mwas 2.33 (SD 1.33) mmol ·l^–1 which, compared with a value at rest of 1.50 (SD 0.60) mmol·l^–1, was not significantly higher. However, when running velocity exceeded the vm by only 3.6 (SD 1.9) %, the [la^–]b increased to 6.94 (SD 2.48) mmol·l-1 (P<0.05 vs rest). We concluded from our study that the highest running velocity at which the blood pH still remained constant in relation to the value at rest and the speed of the run at which [la^–]_b began to increase significantly above the value at rest is a sensitive indicator of capacity for marathon running.     

The influence of body position on maximal performance in cycling

Summary Six healthy male subjects performed a 3-min supramaximal test in four different cycling positions: two with different trunk angles and two with different saddle-tube angles. Maximal power output and maximal oxygen uptake (VO_2max) were measured. Maximal power output was significantly higher in a standard sitting (SS, 381 W, SD 49) upright position compared to all other positions: standard racing (SR, 364 W, SD 49), recumbent backwards (RB, 355 W, SD 44) and recumbent forwards (RF, 341 W, SD 54). Although VO_2max was also highest in SS (4.31 l · min^–1, SD 0.5) upright position, the differences in VO_2max were not significant (SR, 4.21 · min^–1, SD 0.53; RB, 4.17 l · min^–1, SD 0.58; RF, 4.11 l · min^–1, SD 0.66). It is concluded that (supra)maximal tests on a cycle ergometer should be performed in a sitting upright position and not in a racing position. In some cases when cycling on the road, higher speeds can be attained when sitting upright. This is especially true when cycling uphill when high power must be generated to overcome gravity but the road speed, and hence the power required to overcome air resistance, is relatively low.