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.     

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.     

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.     

Sex differences in performance-matched marathon runners

Summary Six male and six female runners were chosen on the basis of age (20–30 years) and their performance over the marathon distance (mean time = 199.4, SEM 2.3 min for men and 201.8, SEM 1.8 min for women). The purpose was to find possible sex differences in maximal aerobic power (VO_2max), anaerobic threshold, running economy, degree and utilization of VO_2max (when running a marathon) and amount of training. The results showed that performance-matched male and female marathon runners had approximately the same VO_2max (about 60 ml·kg^–1·min^–1). For both sexes the anaerobic threshold was reached at an exercise intensity of about 83% of VO_2max, or 88%–90% of maximal heart rate. The females' running economy was poorer, i.e. their oxygen uptake during running at a standard submaximal speed was higher (P<0.05). The heart rate, respiratory exchange ratio and blood lactate concentration also confirmed that a given running speed resulted in higher physiological. strain for the females. The percentage utilization of VO_2max at the average marathon running speed was somewhat higher for the females, but the difference was not significant. For both sexes the oxygen uptake at average speed was 93%–94% of the oxygen uptake corresponding to the anaerobic threshold. Answers to a questionnaire showed that the females' training programme over the last 2 months prior to running the actual marathon comprised almost twice as many kilometres of running per week compared to the males (60 and 33 km, respectively). The better state of training of the females was also confirmed by a 10% higher VO_2max, in relation to lean body mass than that of the male runners. Apart from the well-known variation in height and differences in the percentage of fat, the difference between performance-matched male and female marathon runners seemed primarily to be found in running economy and amount of training.     

Treadmill validation of an over-ground walking test to predict peak oxygen consumption

Summary The purpose of this study was to determine whether a test developed to predict maximal oxygen consumption (VO_2max) during over-ground walking, was similarly valid as a predictor of peak oxygen consumption (VO₂) when administered during a 1-mile (1.61 km) treadmill walk. Treadmill walk time, mean heart rate over the last 2 full min of the walk test, age, and body mass were entered into both generalized (GEN Eq.) and gender-specific (GSP Eq.) prediction equations. Overall results indicated a highly significant linear relationship between observed peakVO₂ and GEN Eq. predicted values (r=0.91), a total error (TE) of 5.26 ml · kg^–1 · min^–1 and no significant difference between observed and predicted peakVO₂ mean values. The peakVO₂ for women (n = 75) was predicted accurately by GSP Eq. (r = 0.85; TE = 4.5 ml · kg^–1 · min^–1), but was slightly overpredicted by GEN Eq. (overall mean difference = 1.4 ml · kg^–1 · min^–1;r=0.86; TE = 4.56 ml · kg^–1 · min^–1). No significant differences between observed peakVO₂ and either GEN Eq. (r=0.85; TE=4.3 ml · kg^–1 · min^–1) or GSP Eq. (r=0.85; TE = 4.8 ml · kg^–1 · min^–1)predicted values were noted for men (n=48) with peakVO₂ values less than or equal to 55 ml · kg^–1 · min^–1. However, both equations significantly underpredicted peakVO₂ for the remaining high peakVO₂ men (n = 22). In conclusion, the over-ground walking test, when administered on a treadmill, is a valid method of predicting peakVO₂ but underpredicts peakVO₂ of subjects with observed high peakVO₂ values. Present address: Human Performance Laboratory State University, Muncie, IN 47306, USA     

Physiology of difficult rock climbing

The purpose of this review is to explore existing research on the physiological aspects of difficult rock climbing. Findings will be categorized into the areas of an athlete profile and an activity model. An objective here is to describe high-level climbing performance; thus the focus will primarily be on studies that involve performances at the 5.11/6c (YDS/French) level of difficulty or higher. Studies have found climbers to be small in stature with low body mass and low body fat. Although absolute strength values are not unusual, strength to body mass ratio is high in accomplished climbers. There is evidence that muscular endurance and high upper body power are important. Climbers do not typically possess extremely high aerobic power, typically averaging between 52–55 ml·kg^–1·min^–1 for maximum oxygen uptake. Performance time for a typical ascent ranges from 2 to 7 min and oxygen uptake (O₂) averages around 20–25 ml·kg^–1·min^–1 over this period. Peaks of over 30 ml·kg^–1·min^–1 for O₂ have been reported. O₂ tends to plateau during sustained climbing yet remains elevated into the post-climb recovery period. Blood lactate accumulates during ascent and remains elevated for over 20 min post-climbing. Handgrip endurance decreases to a greater degree than handgrip strength with severe climbing. On the basis of this review, it appears that a specific training program for high-level climbing would include components for developing high, though not elite-level, aerobic power; specific muscular strength and endurance; ATP–PC and anaerobic glycolysis system power and capacity; and some minimum range of motion for leg and arm movements.     

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.     

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.     

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.     

Intravenous instrumentation alters the autonomic state in humans

Intravascular instrumentation may induce syncope or presyncope. It is not known whether asymptomatic subjects also have autonomic reactions, albeit concealed. We addressed this issue by studying 44 healthy young male subjects of various levels of fitness, ranging from inactivity to athletic [mean maximal oxygen uptake was 49.1 (SD 10.7) ml·kg^–1·min^–1, range 28.7–71.9 ml·kg^–1·min^–1]. The autonomic response to venous cannulation was quantified by measuring heart rate before cannulation (HR1), after cannulation (HR₂), and after complete pharmacological autonomic blockade (HR₀ = the intrinsic heart rate). The sympathovagal balance before and after cannulation was computed as HR₁/HR₀ and HR₂/HR₀, respectively. The group means of heart rate and sympathovagal balance decreased significantly (paired Student's t-test P <0.01) from 62.5 to 59.9 beats·min^–, and from 0.71 to 0.68, respectively. The maximal decrease in heart rate was 8.8 beats·min^–1, and in the sympathovagal balance was 0.11. Our study demonstrated that the asymptomatic subjects responded to intravenous instrumentation with a concealed autonomic reaction. Thus, from our findings it would seem that intravenous instrumentation interferes with measurements relating to autonomic nervous system activity.     

Physiological and subjective responses to maximal repetitive lifting employing stoop and squat technique

Summary To establish safe levels for physical strain in occupational repetitive lifting, it is of interest to know the specific maximal working capacity. Power output, O₂ consumption, heart rate and ventilation were measured in ten experienced forestry workers during maximal squat and stoop repetitive lifting. The two modes of repetitive lifting were also compared with maximal treadmill running. In addition, electromyogram (EMG) activity in four muscles was recorded and perceived central, local low-back and thigh exertion were assessed during the lifting modes. No significant difference was found in power output between the two lifting techniques. Despite this the mean O₂ consumption was significantly greater during maximal squat lifting [38.7 (SD 5.8) ml·kg^–1-·min^–1] than maximal stoop lifting [32.9 (SD 5.7) ml·kg^–1·min^–1] (P<0.001). No significant correlation was found between O₂ consumption (in millilitres per kilogram per minute) during maximal treadmill running and maximal stoop lifting, while O₂ consumption during maximal squat lifting correlated highly with that of maximal treadmill running (r=0.928, P<0.001) and maximal stoop lifting (r=0.808, P<0.01). While maximal heart rates were significantly different among the three types of exercise, no such differences were found in the central rated perceived exertions. Perceived low-back exertion was rated significantly lower during squat lifting than during stoop lifting. The EMG recordings showed a higher activity for the vastus lateralis muscle and lower activity for the biceps femoris muscle during squat lifting than during stoop lifting. Related to the maximal voluntary contraction, the erector spinae muscle showed the highest activity irrespective of lifting technique.     

Neuromuscular characteristics and fatigue in endurance and sprint athletes during a new anaerobic power test

The purpose of this study was to investigate neuromuscular and energy performance characteristics of anaerobic power and capacity and the development of fatigue. Ten endurance and ten sprint athletes performed a new maximal anaerobic running power test (MARP), which consisted ofn x 20-s runs on a treadmill with 100-s recovery between the runs. Blood lactate concentration [la^–]_b was measured after each run to determine submaximal and maximal indices of anaerobic power (P _3mmol·1 ^–1,P_5mmol·1 ^–1,P_10mmol·1 ^–1andP _max) which was expressed as the oxygen demand of the runs according to the American College of Sports Medicine equation: the oxygen uptake (ml·kg^–1·min^–1)=0.2·velocity (m·min^–1) +0.9·slope of treadmill (frac)·velocity (m·min^–1)+3.5. The height of rise of the centre of gravity of the counter movement jumps before (CMJ_rest) and during (CMJ) the MARP test, as well as the time of force production (t _F) and electromyographic (EMG) activity of the leg muscles of CMJ performed after each run were used to describe the neuromuscular performance characteristics. The maximal oxygen uptake ( _max), anaerobic and aerobic thresholds were determined in the _max test, which consisted ofn x 3-min runs on the treadmill. In the MARP-testP _max did not differ significantly between the endurance [116 (SD 6) ml·kg^–1·min^–1] and sprint [120 (SD 4) ml·kg^–1·min^–1] groups, even though CMJ_rest and peak [la^–]_b were significantly higher and _max was significantly lower in the sprint group than in the endurance group and CMJ_rest height correlated withP _max (r=0.50,P<0.05). The endurance athletes had significantly higher mean values ofP _3mmol·1 ^–1andP _5mmol·1 ^–1[89 (SD 7) vs 76 (SD 8) ml·kg^–1·min^–,P<0.001 and 101 (SD 5) vs 90 (SD 8) ml·kg^–1·min^–1,P<0.01. Significant positive correlations were observed between theP _3mmol·l ^–1and _max, anaerobic and aerobic thresholds. In the sprint group CMJ and the averaged integrated iEMG decreased andt _F increased significantly during the MARP test, while no significant changes occurred in the endurance group. The present findings would suggest thatP _max reflected in the main the lactacid power and capacity and to a smaller extent alactacid power and capacity. The duration of the MARP test and the large number of CMJ may have induced considerable energy and neuromuscular fatigue in the sprint athletes preventing them from producing their highest alactacidP _max at the end of the MARP test. Due to lower submaximal [la^–]_b (anaerobic sprinting economy) the endurance athletes were able to reach almost the sameP _max as the sprint athletes.     

Influence of acute maximal exercise on lecithin: cholesterol acyltransferase activity in healthy adults of differing aerobic performance

Summary To document the possible influence of a single episode of maximal aerobic stress on the serum lecithin: cholesterol acyltransferase (LCAT) activity in subjects with differing histories of training, two groups of healthy male adults [controls (C),n = 18, 28.6 years, SD 5.2, 50.1 ml · kg^–1 · min^–1 maximal O₂ uptake (VO_2max), SD 5.3; endurance trained athletes (T),n = 18, 31.4 years, SD 8.8, 65.0 ml · kg^–1 · min^–1 VO_2max, SD 2.8] were examined in a maximal aerobic stress test. In addition to the routine assessment of lipid status, LCAT activity was measured immediately before and after exercise. At rest nearly identical LCAT activity values were found in both groups: C 64.4 nmol · ml^–1 · h^–1, SD 16.7 vs T 65.0 nmol · ml^–1 · h^–1, SD 20.9. The post-exercise LCAT values induced by the maximal stress test increased significantly to (C) 95.7 nmol · ml^–1 · h^–1, SD 23.5, +48.6%,P<0.001; (T) 83.5 nmol · ml^–1 · h^–1, SD 24.3, +29.1%,P<0.01. Neither the pre nor the post-exercise individual LCAT activity values showed any significant correlation to the corresponding data on physical performance.     

The peak oxygen uptake of British children with reference to age,sex and sexual maturity

Summary The purposes of this study were to provide baseline data on the peak oxygen consumption (VO₂) of British children, aged 11–16 years and to examine the peakVO₂ of children in relation to their pubertal stage of development. The peakVO₂ of 226 boys and 194 girls was determined during either treadmill running or cycle ergometry. The sexual maturity of 320 of the children was estimated using Tanner's indices. PeakVO₂ increased with chronological age in both sexes and from about the age of 12 years boys exhibited significantly higher (P<0.05) values than girls. Boys' peakVO₂ in relation to body mass was consistent over the age range studied and was superior (P<0.05) to girls' values at all ages. It appears that mass-related peakVO₂ is independent of sexual maturity in both sexes. The more mature boys demonstrated a significantly higher (P<0.05) peakVO₂ (l·min^–1) than the less mature boys on both ergometers. The more mature girls demonstrated significantly higher (P<0.05) peakVO₂ (l·min^–1) than the less mature girls only on the cycle ergometer. On both ergometers the differences between the peakVO₂ of the girls and boys were more pronounced in the mature children whether expressed in relation to body mass or not. Comparison of the results with earlier data drawn from smaller samples failed to provide evidence to suggest that British children's peakVO₂ has declined in recent years. No study with which to compare our maturity peakVO₂ data appears to be available.     

Sweat lactate response between males with high and low aerobic fitness

Sweat lactate indirectly reflects eccrine gland metabolism. However the potential influence of aerobic fitness on sweat lactate is not well-understood. Six males with high aerobic fitness [peak oxygen consumption (O₂peak): 61.6 (2.5) ml·kg^–1·min^–1] and seven males with low aerobic fitness [O₂peak: 41.8 (6.4) ml·kg^–1·min^–1] completed a maximal exertion cycling trial followed on a different day by 60 min of cycling (60 rev·min^–1) in a 30°C wet bulb globe temperature environment. Intensity was individualized at 90% of the ventilatory threshold ( _E/O₂ increase with no concurrent _E/CO₂ increase). Sweat samples were collected from the lumbar region every 10 min and analyzed for lactate concentration. Sweat rate (SR) was significantly greater (p<0.05) for subjects with a high [1445 (254) ml·h^–1] versus a low [1056 (261) ml·h^–1] fitness level. Also, estimated total lactate excretion (SR×mean sweat lactate concentration) was marginally greater (p=0.2) in highly fit males. However, repeated measures ANOVA showed no significant differences (p>0.05) between groups for sweat lactate concentration at any time point. Current results show highly fit (vs. low fitness level) males have a greater sweat rate which is consistent with previous literature. However aerobic fitness and subsequent variations in SR do not appear to influence sweat lactate concentrations in males.     

Comparison of haemodynamic effects during venous air infusion and after decompression in pigs

We have compared haemodynamic effects of venous gas emboli during continuous air infusion into the right atrium and after rapid decompression in pigs. Eight anaesthetized and spontaneously breathing pigs received continuous air infusion at a rate of either 0.05 ml·kg^–1 · min^–1 (six pigs, air infusion group) or 0.10 ml·kg^–1 · min^–1 (two pigs). Another eight pigs (decompression group) underwent a 30-min compression to 5 bar (500 kPa, absolute pressure), followed by a rapid decompression (2 bar·min^–1). Haemodynamic variables were measured or calculated, and bubbles in the pulmonary artery were monitored using transoesophageal echocardiography. The results showed less variation in the maximal increase in mean pulmonary arterial pressure ( _{a, pulm}) during air infusion (0.05 ml·kg^–1 · min^–1) than after decompression, although the mean maximal increase did not differ between the two groups [28.0 mmHg (3.73 kPa), 95% confidence interval (CI) 23.5–32.5, vs 32.0 mmHg (4.27 kPa), 95% CI 25.3-38.7, P=0.3]. The _a,pulm stabilized or decreased very slowly after peak values were reached in the air infusion group, whereas the _a,pulm decreased rapidly during the same period in the decompression group. No significant changes in mean arterial pressure were observed during air infusion (0.05 ml· kg^–1 · min^–1), in contrast to the rapid increase and the subsequent decrease, that appeared after decompression. Finally, the maximal bubble count was much lower in the air infusion group than in most of the pigs in the decompression group. The two pigs that received 0.10 ml·kg^–1 · min^–1 stopped breathing after 5-min infusion, developed arterial hypotension and died.     

Bio-energetic profile in 144 boys aged from 6 to 15 years with special reference to sexual maturation

Summary The effects of growth and pubertal development on bio-energetic characteristics were studied in boys aged 6–15 years (n = 144; transverse study). Maximal oxygen consumption (VO_2max, direct method), mechanical power at (VO_2max ( ), maximal anaerobic power (P_max; force-velocity test), mean power in 30-s sprint (P _30s; Wingate test) were evaluated and the ratios between P_max,P _30s and were calculated. Sexual maturation was determined using salivary testosterone as an objective indicator. Normalized for body massVO_2max remained constant from 6 to 15 years (49 ml· min^–1 · kg^–1, SD 6), whilst P_max andP _30s increased from 6–8 to 14–15 years, from 6.2 W · kg^–1, SD 1.1 to 10.8 W · kg^–1, SD 1.4 and from 4.7 W · kg^–1, SD 1.0 to 7.6 W · kg^–1, SD 1.0, respectively, (P < 0.001). The ratio P_max: was 1.7 SD 3.0 at 6–8 years and reached 2.8 SD 0.5 at 14–15 years and the ratioP _30s: changed similarly from 1.3 SD 0.3 to 1.9 SD 0.3. In contrast, the ratio P_max:P _30s remained unchanged (1.4 SD 0.2). Significant relationships (P < 0.001) were observed between P_max (W · kg^–1),P _30s (W · kg^–1), blood lactate concentrations after the Wingate test, and age, height, mass and salivary testosterone concentration. This indicates that growth and maturation have together an important role in the development of anaerobic metabolism.     

Lung diffusion capacity,oxygen uptake,cardiac output and oxygen transport during exercise before and after an Himalayan expedition

Studies were made of pulmonary diffusion capacity and oxygen transport before and after an expedition to altitudes at and above 4900 m. Maximum power (P _max) and maximal oxygen uptake (VO _2max) were measured in 11 mountaineers in an incremental cycle ergometer test (25W · min^–1) before and after return from basecamp (30 days at 4900 m or higher). In a second test, cardiac output (Q _c) and lung diffusion capacity of carbon monoxide (D _L,CO) were measured by acetylene and CO rebreathing at rest and during exercise at low, medium and submaximal intensities. After acclimatization, VO_2max and P _max decreased by 5.1% [from 61.0 (SD 6.2) to 57.9 (SD 10.2) ml·kg^–1, n.s.] and 9.9% [from 5.13 (SD 0.66) to 4.62 (SD 0.42) W·kg^–1, n.s.], respectively. The maximal cardiac index and DL,co decreased significantly by 15.6% [14.1 (SD 1.41) 1·min^–1 · m^–2 to 11.9 (SD 1.44)1·min^–1 m^–2, P<0.05] and 14.3% [85.9 (SD 4.36)ml·mmHg^–1 min^–t to 73.6 (SD 15.2) ml · mmHg^–1 -min^–1, P<0.05], respectively. The expedition to high altitude led to a decrease in maximal Q _c, oxygen uptake and D_L,CO. A decrease in muscle mass and capillarity may have been responsible for the decrease in maximal Q_c which may have resulted in a decrease of D _L,CO and an increase in alveolar-arterial oxygen difference. The decrease in D _L,CO especially at lower exercise intensities after the expedition may have been due to a ventilation-perfusion mismatch and changes in blood capacitance. At higher exercise intensities diffusion limitation due to reduced pulmonary capillary contact time may also have occurred.     

Energy cost and energy sources in karate

Energy costs and energy sources in karate (wado style) were studied in eight male practitioners (age 23.8 years, mass. 72.3 kg, maximal oxygen consumption (VO_2max) 36.8 ml · min^–1 · kg^–1) performing six katas (formal, organized movement sequences) of increasing duration (from approximately. 10 s to approximately 80 s). Oxygen consumption (VO₂) was determined during pre-exercise rest, the exercise period and the first 270 s of recovery in five consecutive expired gas collections. A blood sample for lactate (la^–) analysis was taken 5 min after the end of exercise. The overall amount of O₂ consumed during the exercise and in the following recovery increased linearly with the duration of exercise (t) from approximately 1.51 (for t equal to 10.5 s (SD 1.6)) to approximately 5.81, for t equal to 81.5 s (SD 1.0). The energy release from la^– production (VO_21a ^–) calculated assuming that an increase of 1 mmol · l^–1 la^– corresponded to a VO₂ of 3 mlO₂ · kg^–1 was negligible for t equal to or less than 20 s and increased to 17.3 ml · kg^–1 (la^– = 5.8 mmol · l^–1 above resting values) for t equal approximately to 80 s. The overall energy requirement (VO_2eq) as given by the sum of VO₂ and VO_2la ^– was described by VO_2eq = 0.87 + 0.071 · t (n = 64; r ² = 0.91), where VO_2eq is in litres and t in seconds. This equation shows that the metabolic power (VO_2eq · t ^–1) for this karate style is very high: from approximately 9.51 · min^–1 for t equal to 10 s to approximately 4.91 · min^–1 for t equal to 80 s, i.e. from 3.5 to 1.8 times the subjects' VO_2max. The fraction of VO_2eq derived from the amount of O₂ consumed during the exercise increased from 11% for t equal to 10 s to 41 % for t equal to 80 s whereas VO_21a ^– was negligible far t equal to or less than 20 s and increased to 13 % o for t equal to 80 s. The remaining fraction (from 90% for t equal to 10 s to 46% for t equal to 80 s), corresponding to the amount of O₂ consumed in the recovery after exercise, is derived from anaerobic alactic sources, i.e. from net splitting of high energy phosphates during the exercise.     

Validity and reliability of pedometers in habitual activity research

Summary In 12–18 year old boys actual steprate on a treadmill was compared to the scores of two types of mechanical pedometers (Russian and German), attached to the waist. Both types show deviations from actual steprate in running at speeds of 8 and 10 km·h^–1 of ca. 5% (±9%). In walking or running at 6 km·h^–1 and in running at 14 km·h^–1 both types give an overestimation of ca. 8.5% (±8%). In walking at a speed of 2 and 4 km·h^–1 the scores are not reliable because of the big standard deviation of ca. 34%. Oxygen uptake (ml·kg^–1) and heart rate (beats·min^–1) increase more in running than in walking, actual steprate (steps·min^–1) however increases less in running compared to walking. If pedometers register only during running they reflect actual steprate fairly good and give a good estimation of the change in oxygen uptake as speed gathers.