Showing papers in "European Journal of Applied Physiology in 1982"

A maximal multistage 20-m shuttle run test to predict VO2 max

Abstract: In order to validate a maximal multistage 20-m shuttle run test for the prediction of $$\dot V$$ O2 max, 91 adults (32 females and 59 males, aged 27.3±9.2 and 24.8±5.5 year respectively and with mean $$\dot V$$ O2 max (± SD) of 39.3±8.3 and 51.6±7.8 ml·kg−1·min−1 respectively) performed the test and had $$\dot V$$ O2 max estimated by the retroextrapolation method (extrapolation to time zero of recovery of the exponential least squares regression of the first four 20-s recovery $$\dot V$$ O2 values). Starting at 8 km·h−1 and increasing by 0.5 km·h−1 every 2 min, the 20-m shuttle run test enabled prediction of the $$\dot V$$ O2 max (y, ml·kg−1·min−1) from the maximal speed (x, km·h−1) by means of the following regression equation: y=5.857x — 19.458; r=0.84 and SEE=5.4. Later, the multistage protocol was slightly modified to its final version, in which the test started at stage 7 Met and continued with a 1 Met (3.5 ml O2·kg−1·min−1) increment every 2 min. Twenty-five of the 91 subjects performed the 20-m shuttle test twice, once on a hard, low-friction surface (vinyl-asbestos tiles) and another time on a rubber floor, as well as a walking maximal multistage test on an inclined treadmill. There was no difference between the means of these tests or between the slopes of the $$\dot V$$ O2max — maximal speed regressions for the two types of surfaces. The 20-m shuttle run test and another maximal multistage field test involving continuous track running gave comparable results (r=0.92, SEE=2.6 ml O2·kg−1·min−1, n=70). Finally, test and retest of the 20-m shuttle run test also yielded comparable results (r=0.975, SEE=2.0 ml O2·kg−1·min−1, n=50). It is concluded that the 20-m shuttle run test is a valid and reliable test for the prediction of the $$\dot V$$ O2 max of male and female adults, individually or in groups, on most gymnasium surfaces.

Recommendations for the standardization of lead positions in surface electromyography

Abstract: Standardized lead positions for recording myoelectric signals are given for various muscles. The positions are given in terms of (1) the ‘lead line’ connecting two anatomical landmarks and (2) the ‘central lead point’ about which the electrodes are placed symmetrically on the lead line.

Catecholamines, growth hormone, cortisol, insulin, and sex hormones in anaerobic and aerobic exercise.

Abstract: Seventeen male physical education students performed three types of treadmill exercise: (1) progressive exercise to exhaustion, (2) prolonged exercise of 50 min duration at the anaerobic threshold of 4 mmol·1−1 blood lactate (AE), (3) a single bout of short-term high-intensity exercise at 156% of maximal exercise capacity in the progressive test, leading to exhaustion within 1.5 min (ANE).

Changes in onset of blood lactate accumulation (OBLA) and muscle enzymes after training at OBLA

Abstract: Eight well-trained middle and long distance male runners added to their regular training program a weekly 20-min treadmill run at a velocity calculated to elicit a blood lactate concentration of 4 mmol X 1-1. VO2 max, the running velocity eliciting 4 mmol X 1-1 blood lactate (VOBLA), and the activities of citrate synthase (CS), phosphofructokinase (PFK), lactate dehydrogenase (LDH) and LDH isozymes in the M. vastus lateralis were determined before and after 14 weeks of this training. Significant increases were observed in VOBLA and the relative fraction of heart-specific LDH, while the activity of PFK and the ratio of PFK/CS decreased after training. The change in VOBLA was negatively correlated to the mean rate of blood lactate accumulation during the last 15 min of the treadmill training runs, and positively correlated to the percentage of slow twitch fibers in the M. vastus lateralis. The data support the hypothesis that a steady state training intensity which approximates VOBLA will increase VOBLA, and will result in measureable local metabolic adaptations in the active skeletal muscles of well-trained runners without a significant change in maximal aerobic power. Muscle fiber type composition may be an indicator of the "trainability" of the musculature.

Muscle ultrastructural characteristics of elite powerlifters and bodybuilders.

Abstract: Muscle ultrastructure of a group of subjects possessing extreme hypertrophy was compared with that of a control group which had undergone 6 months of heavy resistance training. Two needle biopsies were taken from triceps brachii of two international calibre powerlifters and five elite bodybuilders. In addition, samples were taken from five healthy volunteers before and after 6 months of training of the elbow extensors. One biopsy was prepared for electron microscopy and analyzed stereologically, and the other was stained for myosin ATPase activity and photographed under the light microscope. Despite large differences in elbow extension strength and arm girth there was no significant difference in fibre areas or percentages of fibre types between the elite group and the trained controls. This suggests that the elite group possessed a greater total number of muscle fibres than the controls did. Mitochondrial volume density of the elite group was similar to that of the control group following training but significantly less (p<0.05) than the pretraining control measurements. Myofibrillar volume density was significantly lower and cytoplasmic volume density significantly higher in the elite group than in the trained controls. There was a considerably higher incidence of structural abnormalities including central nuclei and atrophied fibres in the elite group than in the control group, which might possibly have been associated with the use of anabolic steroids by the elite group.

Relationships of the anaerobic threshold with the 5 km, 10 km, and 10 mile races

Abstract: The purpose of present study was to assess the relationship between anaerobic threshold (AT) and performances in three different distance races (ie, 5 km, 10 km, and 10 mile) AT, VO2 max, and related parameters for 17 young endurance runners aged 16--18 years tested on a treadmill with a discontinuous method The determination of AT was based upon both gas exchange and blood lactate methods Performances in the distance races were measured within nearly the same month as the time of experiment Mean AT-VO2 was 510 ml kg-1 min-1 (2837 l min-1), while VO2 max averaged 641 ml kg-1 min-1 (3568 l min-1) AT-HR and %AT (AT-VO2/VO2 max) were 1747 beats min-1 and 796%, respectively The correlations between VO2 max (ml kg-1 min-1) and performances in the three distance races were not high (r = -0645, r = -0674, r = -0574), while those between AT-VO2 and performances was r = -0945, r = -0839, and r = -0835, respectively The latter results indicate that AT-VO2 alone would account for 839%, 704%, and 697% of the variance in the 5 km, 10 km, and 10 mile performances, respectively Since r = -0945 (5 km versus AT-VO2) is significantly different from r = -0645 (5 km versus VO2 max), the 5 km performance appears to be more related to AT-VO2 than VO2 max It is concluded that individual variance in the middle and long distance races (particularly the 5 km race) is better accounted for by the variance in AT-VO2 expressed as milliliters of oxygen per kilogram of body weight than by differences in VO2 max

Predicting sweat loss response to exercise, environment and clothing

Abstract: Metabolic heat production (M), clothing heat transfer characteristics, and the environment dictate a required evaporative cooling (Ereq) from the body to maintain thermal balance. However, the maximal evaporative capacity (Emax) is dictated by vapor transfer properties of the clothing and environment. Relationships between metabolic load, environmental conditions, clothing and sweat loss were studied in 34 heat-acclimatized males categorized into four groups (eight, eight, eight, and ten subjects) and exposed to various environmental conditions (ambient temperature, 20–54‡ C, and relative humidity, 10–90%), three levels of metabolic rate (resting; walking 1.34 m·s−1, level; or walking 1.34 m·s−1, 5% grade) while wearing various clothing ensembles (shorts and T-shirts, fatigues, fatigues plus overgarment, or sweat suit). Individual groups were not exposed to all combinations. Exposures lasted 120 min: either 10 min rest — 50 min exercise — 10 min rest — 50 min exercise, or 120 min at rest. Physiological measurements included heart rate, rectal temperature, mean skin temperature, energy expenditure and sweat loss (δmsw). Emax and Ereq were calculated from environmental conditions, metabolism, clothing insulation and permeability. The ratio Ereq/δmsw was found to correlate with Emax and not with M. The predictive equation for sweat loss was: δmsw=18.7×Ereq×(Emax)−0.455 within the limits 50

Muscle glycogen and diet in elite soccer players.

Abstract: The top players in an elite soccer team volunteered as subjects in a study to determine intramuscular glycogen concentrations after a regular season match, and whether optimal glycogen levels could be re-attained prior to the team's next match. Fifteen players were biopsied in the M. vastus lateralis following a regular season game (Day I). Of these, eight were biopsied 24 h later in the evening of a free day during which no training session was held (Day II), and again 24 h later after a very light training session (Day III). Muscle glycogen concentrations for the eight players averaged (+/- SD) 45.9 +/- 7.9, 68.9 +/- 2.7, and 72.8 +/- 8.3 mmol glucose units x kg-1 wet muscle weight on Day I, Day II, and Day III respectively. Dietary records were analysed during a week of peak, season competition and training. The average daily total energy consumption and total quantity of carbohydrates consumed were less than what is normally consumed by athletes in similar sports. The inability of the players to maintain even normal, resting levels of muscle glycogen is probably related to their dietary practices.

Muscle hypertrophy in bodybuilders

Abstract: Muscle biopsy samples were obtained from m. vastus lateralis and m. deltoideus of three high caliber bodybuilders. Tissue specimens were analysed with respect to relative distribution of fast twitch (FT) and slow twitch (ST) fiber types and different indices of fiber area. In comparison to a reference group of competitive power/weight-lifters the following tendencies were observed: the percentage of FT fibers was less, mean fiber area was smaller and selective FT fiber hypertrophy was not evident. Values for fiber type composition and fiber size were more similar to values reported for physical education students and non-strength trained individuals. The results suggest that weight training induced muscle hypertrophy may be regulated by different mechanisms depending upon the volume and intensity of exercise.

Force-velocity-power characteristics and fiber composition in human knee extensor muscles.

Abstract: To investigate the influence of skeletal muscle fiber composition on the mechanical characteristics of human skeletal muscle under isometric and dynamic conditions, ten well-trained track athletes with different muscle compositions (m. vastus lateralis) were used. The subjects were instructed to perform maximum isometric and dynamic knee extensions at maximal speed against increasing load. To determine the mechanical properties of the knee extensors a special dynamometer was used. The load was increased by adding weight discs to the electromagnetic part of the dynamometer. The load increased from 0.33-2.33 kg2 moment of inertia in six stages. The data were handled on the basis of Hill's characteristic equation. The subjects were divided into two equal groups, one with more and one with less than 50% of fast twitch fibers. The force-velocity curve was found to be different in the two groups, the subjects with a predominance of fast twitch fibers being able to develop higher power output at a given load. Significant correlations between percentage of fast twitch fiber and power, as well as velocity, were found at the four greater loads only. However, when the percentage of fast twitch fiber and fast twitch fiber cross-sectional areas were combined, significant correlations were also found between this combined parameter and power output at the two lowest loads.

Contractile properties of the human triceps surae with some observations on the effects of temperature and exercise.

Abstract: The contractile properties of the triceps of five healthy male subjects (mean age 22 years) during electrically stimulated and voluntary isometric muscle contractions were investigated and some observations made on the effects of muscle heating and cooling and dynamic exercise. The times to peak twitch tension (TPT) and half relaxation time (1/2RT) were 111 +/- 20 ms and 83 +/- 13 ms respectively. Heating and prior exercise decreased, and cooling severely prolonged, TPT and 1/2RT. Exercise and heating had no effect on supramaximal twitch tension (Pt0) but cooling the muscle to a temperature of 24.3 degrees C reduced it by 52%. The effects of repetitive stimuli on Pt0 were dependent on frequency; at 0.2 Hz potentiation was observed but at 2 Hz, Pt0 was depressed under control conditions. Heating had no effect on these responses but cooling reversed the 2 Hz and abolished 0.2 Hz response. Post-tetanic potentiation of the twitch was observed under all conditions of measurement. At submaximal stimulation voltages, heating and exercise enhanced twitch and tetanic tensions, but at supramaximal voltages heating reduced tetanic tension (P0) at 10 Hz (by 115 N), though not at 20 Hz. Exercise decreased P0 at both frequencies of stimulation. Cooling significantly reduced the maximal voluntary contraction and P0 at 20 Hz. At submaximal voltages, heating enhanced and cooling severely depressed tetanic tensions at high frequency (100 Hz) stimulation. A 2-min fatigue test was unaffected by heating but cooling reduced force generation at the onset of, and the decline of force during, the test. It was concluded that studies of the contractile properties of human muscle in vivo should be based on supramaximal stimulation, and that temperature and prior exercise should be carefully standardised in order to obtain reliable and meaningful results.

The spectral characteristics of postural sway behaviour.

Abstract: To determine whether recognisable profiles of sway behaviour are characteristically found among normal subjects the energy content of a contiguous series of bandwidths were computed from power density spectra of the sway behaviour of 29 young men and 29 young women. No significant differences were observed over time either in the energy content or in the profile shape of the power spectral density (PSD) records when these were subjected to a multivariate profile analysis of variance.

Relation between EMG power spectrum shifts and muscle fibre action potential conduction velocity changes during local muscular fatigue in man

Abstract: Muscular fatigue was studied in the human m. biceps brachii by contracting the muscle as long as possible at 50% of maximum voluntary strength. For 8 subjects changes in the muscle fibre action potential conduction velocity could successfully be measured using the cross-correlation technique between two surface EMG signals. Shifts in the EMG power spectrum were quantified using the mean power frequency (MPF) of the EMG power spectral density function. During fatigue the EMG power spectrum gradually shifted to lower frequencies. The mean value and standard deviation of the MPF value decreased from (115±20) Hz at the beginning of the experiment to (60±18) Hz at the end. For 4 of the 8 subjects the decrease in MPF value was accompanied by a substantial decrease in conduction velocity (mean decrease was 33% of the initial velocity value). For the other 4 subjects, despite the great MPF changes, there was hardly any change in conduction velocity (mean decrease was 3%). The present study shows that great EMG power spectral shifts during muscular fatigue may occur without a concomitant change in muscle fibre action potential conduction velocity.

Myoelectric power spectrum dependence on muscular contraction level of elbow flexors

Abstract: The influence of the strength of contraction on surface recorded myoelectric power spectra was studied for three elbow flexors. Four subjects performed brief (3–5 s) isometric contraction levels (5–80% MVC). The experiment was repeated 23–26 times on different days. The surface myoelectric signal was recorded from the biceps brachii, the brachialis and the brachioradialis. By fast Fourier transform the myoelectric power spectrum was computed. The mean power frequency (MPF) was calculated and used as a single estimate of the myoelectric power spectrum. The MPF was found to increase with contraction strength with low level contractions. At levels in excess of 25–30% of MVC, the MPF became independent of contraction level. This dependence of the MPF on low level contractions is explained by tissue filtering effects and the recruitment order and distribution of motor units.

Endurance training regimen based upon arterial blood lactate: effects on anaerobic threshold.

Abstract: The purpose of this investigation was to assess the effect of endurance training based upon the intensity as determined by the arterial blood lactate concentration (LA). Seven healthy male college students performed endurance training on a Monark bicycle ergometer for 15 min on 3 days/week for 8 weeks, at an intensity corresponding to 4 mmol X l-1 arterial blood LA determined during an incremental exercise test (25 watts increment every minute on a bicycle at 50 rpm). Another six male students served as the control group. To assess the training effect, both an incremental exercise test and a submaximal exercise test were performed before and after the endurance training. In the incremental exercise test, VO2max, VE at VO2max, anaerobic threshold (AT), and the onset of respiratory compensation for metabolic acidosis (RCMA) were measured. AT was determined as the point at which arterial LA rose above the resting value, and RCMA was determined as the point at which Paco2 decreased during the incremental exercise test. After training, AT increased significantly (37% increment expressed in VO2, p less than 0.05). There was a significant increase (p less than 0.05) in RCMA (17%) and VO2max (14%). This training decreased VO2 (4%), VE (15%), heart rate (10%), respiratory exchange ratio (5%), and LA (23%) significantly (p less than 0.05) during the submaximal exercise test after training. On the other hand, there were no significant changes in the control group through the period when the training group performed their training. These results showed that the endurance training intensity corresponding to 4 mmol X l-1 arterial blood LA was effective for the improvement in AT as well as VO2max. It is suggested that the present training regimen could delay the onset of anaerobic glycolysis, thus shifting AT to the higher workload and decreasing LA at a given submaximal exercise after training.

Square-wave endurance exercise test (SWEET) for training and assessment in trained and untrained subjects. I. Description and cardiorespiratory responses.

Abstract: A new 45 min Square-Wave Endurance Exercise Test (SWEET) performed on a cycle ergometer and designed for endurance training was studied in 43 normal subjects: Untrained (U), twelve women and seven men and Trained (T), eight women and 16 men. Among them seven were elite sportsmen (E). Preliminary measurements were made of VO2 max by constant power and Maximal Tolerated Power (MTP) in a progressive test (+ 30 W/3 min). To the SWEET's base, established as a % of individual MTP, a peak of 1 min at MTP was added every 5 minutes. Maximum Intensity of Endurance during the SWEET (MIE45) is defined by both maximal heart rate (HR) at the end of the test and the impossibility of maintaining 5% above the percent MTP of the MIE45 for 45 min. Exhaustion was reached at the end of the MIE45, which could be expressed as % MTP, as total energy expenditure (TEE) in liters of O2, or as total mechanical work (TMW) in kiloJoules per kg of weight (kJ . kg-1). VE, VCO2, VO2 and HR were continuously measured. VO2 max, TMW and % MTP were significantly higher in T than in U subjects. The E subjects show the highest values of those parameters. TMW and TEE were well correlated (r = 0.992, p less than 0.001, n = 43) indicating good efficiency. TMW in T (r = 0.453) and in E men (r = 0.442) were however less well correlated to the VO2 max. MIE45 therefore gives different information in the evaluation of "endurance capacity" at the time of measurement than that provided by VO2 max. Because of the high TEE per session it could be useful for endurance training of T and U subjects.

Respiratory control of heart rate

Abstract: Cross spectrum techniques have been used to characterise the relationships between breathing rate, sinus rhythm and peripheral blood flow. The breathing rate modulates both sinus rhythm and peripheral blood flow between certain limits, with a characteristic frequency amplitude pattern and entrains the Traube-Hering-Mayer waves within set limits. Beyond the upper limit of 0.4 Hz (24 breath min−1) no modulation occurs. The lower limit is estimated in our subjects able to breathe at rates of 0.033 Hz (2 breath min−1) the lower limit of modulation is approximately 0.05 Hz (3 breath min−1) in most individuals. These observations have serious implications for heart rate measurements in sinus rhythm below 90 beat min−1.

Electromechanical behaviour of human muscles in vertical jumps.

Abstract: The relationships of muscle structure to the potentiation of myoelectrical activity and to the use of prestretching in five lower limb muscles were studied in different vertical jumping conditions. The subjects for the study were six male students, divided according to the muscle fiber distribution in m. vastus lateralis into “fast” and “slow” groups. The subjects performed vertical jumps (1) from a static squatting position (SJ), (2) with a preliminary counter movement (CMJ) and (3) after dropping (DJ) from five different heights. Myoelectrical (EMG) activity was recorded from mm. gluteus maximus, vastus lateralis, vastus medialis, rectus femoris and gastrocnemius in each jumping condition and integrated (IEMG) for the eccentric and concentric phases of contact. EMG activity showed potentiation during the eccentric phase of movement when compared to the concentric phase. The “fast” and “slow” groups did not differ significantly in this respect, whereas in DJ conditions the relative (% from SJ) height of rise of the center of gravity was greater in the “slow” than in the “fast” group. The result indicated that the utilization of elastic energy during jumping was possible better in subjects having a high percentage of slow twitch muscle fibres in their vastus lateralis muscles.

Some sources of error in the calculation of relative change in plasma volume

Abstract: The effects of alterations in the F-cell ratio (i.e., the ratio of the whole body haematocrit to the peripheral haematocrit) on calculations of relative (percentage) change in plasma volume have been considered. Errors introduced by failing to correct the measured haematocrit for an assumed value for the F-cell ratio are small, and are negligible compared with the random measurement errors. Errors introduced by a change in the value of the F-cell ratio from some control value to a new value during an experimental procedure (such as exercise or exposure to heat stress) are large, and could lead to gross misrepresentations of the direction and magnitude of any induced change in intravascular volume, and of solute concentration changes assumed to reflect only loss or gain of fluid by the intravascular space.

A comparison of plasma cholesterol, triglycerides. and high density lipoprotein-cholesterol in speed skaters, weightlifters and non-athletes

Abstract: Venous plasma cholesterol, triglycerides and high-density lipoprotein cholesterol (HDL-C) were measured after a 12–16 h overnight fast in three groups of men with different physical training histories. The groups consisted of 11 untrained men (aged 19–25 years), 11 well-trained weightlifters (20–32 years), who had not trained aerobically for at least 6 months, and 11 candidates for an Olympic speed skating team (17–27 years), whose training was both endurance (aerobic) and anaerobic. Mean maximal oxygen uptakes for the groups were 47.7, 45.7, and 62.3 ml·kg−1·min−1 respectively. Groups were similar with respect to diet, smoking and alcohol consumption, but the nonathletes were fatter, the weightlifters older and the speed skaters lighter, than the others. There were no significant differences in total cholesterol or triglycerides between the groups. Mean HDL-C was similar in the non-athletes and weightlifters [about 47±7 (SD) mg·dl−1], but was significantly higher (53.7±10.2 mg·dl−1, p<0.05) in the speed skaters. It was not correlated significantly with maximal oxygen uptake or relative fat in any group or when all data were combined. The total cholesterol/HDL-C ratio was significantly higher in the weightlifters. The HDL-C values are compared with previously reported values for non-athletes and athletes, and it is concluded that extensive weight-training, in contrast to endurance training, does not increase venous plasma HDL-C. Further work is required to elucidate the biochemical basis of these observations.

Hematological changes following a marathon race in male and female runners.

Abstract: The subjects of this experiment were well-trained men (6) and women (4) participating in a marathon race in Phoenix, Arizona, on a cool, cloudy, windy day. Venous blood was collected one week prior to the run, immediately after, and 4,8, and 24 h after the race. There were no significant changes in hematocrit, hemoglobin, or red blood cell counts following the race. The sample collected immediately after the race showed a pronounced leucocytosis. Differential counts showed that this increase in white blood cell count was limited to polymorphonuclear cells, suggesting that an inflammatory response to stress of the race was involved. Percentage changes in blood volume, red blood cell volume, and plasma volume were calculated from hematocrit and hemoglobin changes. These changes showed that there was reduction of plasma volume of 8% for females and 13% for males immediately after the race, with return to initial values within 8 h. We suggest that the increase in protein following the race was contributed by the flow of lymph from muscle to the vascular compartment.

Evaluation of a maximal predictive cycle ergometer test of aerobic power

Abstract: A maximal predictive cycle ergometer (CE) test for estimating maximal oxygen uptake ( $$\dot V$$ O2 max) was evaluated in 15 male and 12 female subjects. The test consisted of pedalling a cycle ergometer (Monark) at 75 rev·min−1, beginning at an intensity of 37.5 watts and increasing by this amount each min until the subject could no longer maintain pedal rate. The highest work rate achieved was recorded as the endpoint of the test and used to construct regression equations to predict $$\dot V$$ O2 max. This was compared with two direct measures of $$\dot V$$ O2 max [an interrupted treadmill (TM) run and an interrupted CE procedure at 60 rev·min−1] and with the submaximal predictive test of astrand-Rhyming. When compared to TM $$\dot V$$ O2 max, $$\dot V$$ O2 measured during the final 30 s of the maximal predictive CE test was 16.0% and 16.2% lower for males and females respectively; compared to $$\dot V$$ O2 max determined by the direct CE test, it was lower by 2.9% for males and 5.2% for females. Correlation coefficients for $$\dot V$$ O2 max predicted from the maximal predictive CE test and $$\dot V$$ O2 max measured directly by CE and TM were 0.89 and 0.87 for males and 0.88 and 0.83 for females (p<0.01), respectively. The $$\dot V$$ O2 max predicted from the astrand-Rhyming test correlated significantly with $$\dot V$$ O2 max max measured by CE and TM only in the male group. Test-retest reliability coefficients for intensity (watts) on the maximal predictive CE test were 0.95 and 0.81 for males and females respectively (p<0.01). The data suggest that this CE test gives a reliable and valid estimate of $$\dot V$$ O2 max.

Peak blood lactate after short periods of maximal treadmill running.

Abstract: Blood lactate was determined in 19 untrained subjects after maximal treadmill exercise lasting for about 1 min. It was found that blood lactate increases after exercise, reaching a maximum level 6–9 min after the cessation of exercise, and the average time for the appearance of the peak blood lactate concentration was 7.65 min. Peak blood lactate concentration at 7.65 min (CLA7.65), which was calculated by substituting t (7.65) into the equation for the lactate recovery curve for each subject, agreed well with the observed peak blood lactate concentration (r=0.98, p<0.001). In addition, correlations of r=−0.65, r=−0.78, r=−0.79 were found between CLA7.65 and the running times of 100 m, 200 m, and 400 m sprints, respectively. These results suggest that CLA7.65 may be used as a valid indicator of anaerobic work capacity in man.

Effects of prolonged warm-up exercise above and below anaerobic threshold on maximal performance

Abstract: The purpose of the present study was to determine the effects of prolonged warm-up exercise above and below anaerobic threshold (AT) on maximal performance. Warm-up exercise consisted of pedalling the Monark cycle ergometer at either 40% (Below AT) or 68% (Above AT) of VO2max for 60 min. Each maximal performance consisted of two 40 s bouts of "all out" pedalling on the Monark cycle ergometer against 5.5 kg resistance separated by a 5 min rest period. These tests were administered on two occasions without warm-up exercise and were found to be reproducible for work output and peak blood lactate concentration. Below AT warm-up exercise significantly increased core temperature with no increase in steady state blood lactate concentration and was thus representative of a desired warmed-up status. This condition did not contribute to an improved maximal performance. Above AT warm-up exercise resulted in significant increases in core temperature and steady state blood lactate concentration. Work output and peak blood lactate concentration for maximal exercise were significantly decreased. It was concluded that task specific prolonged warm-up exercise below AT does not contribute to an improved maximal performance of the type employed in the present study. Following warm-up exercise above AT, maximal performance was impaired. This was attributed to probable glycogen depletion in fast twitch muscle fibers which in turn may have contributed to a decreased lactate production.

Muscle cell leakage due to long distance training

Abstract: Abnormal myoglobinemia (above 77 Μg/1) and free hemoglobin in plasma were found in 16 runners and in nine non runners immediately following distance running. The same abnormalities were found in six elite rowers following rowing. In parallel with the rise in myoglobin and free hemoglobin a rise was found in serum concentrations of cellular enzymes (LDH, CK, ASAT, alkaline phosphatase) and of various metabolites. We found no proteinuria nor casts in the urine. Non runners had a higher rise in serum myoglobin than runners. Competitive running caused a rise in the serum concentration of the heart specific fraction of creatine kinase in seven of the nine (healthy) elite runners. The abnormal findings are only explainable on the basis of leakage of proteins from muscle cells to the circulation in otherwise healthy, well trained persons. Myoglobinemia and a transient rhabdomyolysis is a common phenomenon in long distance running, but evidently also occurs in distance rowing. Three months of running training prevented most of the muscle damage from relaxed jogging in the nine previous non runners. Neither the observed myoglobinemia nor the hemoglobinemia resulted in any significant loss of iron in the urine.

The responses of plasma biochemical parameters to a 56-km race in novice and experienced ultra-marathon runners

Abstract: A number of blood biochemical parameters, including the activities of the plasma enzymes creatine kinase (CK), aspartate aminotransferase (ASAT), lactate dehydrogenase and alkaline phosphatase, were measured in 23 athletes before, and immediately after a 56-km running race. Of the 23 athletes, 18 had previously completed standard 42-km marathon or longer (up to 90-km) ultra-marathon races, whereas not one of the other five athletes had previously run in a long-distance race. After the race, plasma CK and ASAT activities had both risen at least 280% more in the novice runners despite their much slower mean running speed (9.8 +/- 0.4 vs. 13.8 +/- 0.3 hm/h). There were no other inter-group differences in the absolute levels of the other measured biochemical parameters, although the rise in plasma calcium during the race was significantly greater in the experienced marathon runners. This study shows that either higher levels of training, or previous ultra-marathon racing experience, or both, is associated with lower immediate post-exercise levels of plasma enzyme activity. This is compatible with the finding that physical training reduces post-exercise plasma enzyme levels.

Differences between swimming and running as stimuli for exercise-induced asthma.

Abstract: Thirteen children each exercised for 6 min by running on a treadmill and by tethered swimming, breathing air at room temperature and either 8% or 99% relative humidity continuously. Ventilation, gas exchange and heart rate were closely matched in all four tests in each child, with a mean oxygen consumption of 32.3 +/- 1.7 ml x min-1 x kg-1. The post-exercise fall in FEV1 expressed as a percentage of the baseline FEV1 (delta FEV1) was significantly greater after running compared with swimming breathing either humid or dry air. The delta FEV1 was also related to respiratory heat loss (RHL) calculated from measurements of inspired and expired gas temperature and humidity. At a standardised RHL, the difference between running and swimming was highly significant [delta FEV1 (%) +/- SE = 39 +/- 5 and 28 +/- 4 respectively, p less than 0.01]. These experiments suggest that the type of exercise influences the severity of exercise-induced asthma even under conditions of the same metabolic stress and respiratory heat loss.

Differentiated perceptions of exertion and energy cost of young women while carrying loads.

Abstract: Differentiated local ratings of perceived exertion from the legs and central ratings from the chest, and oxygen consumption, were determined during load carriage in seven young women. Subjects walked for 6 min at 3.22, 4.83, 6.44, or 8.05 km·h−1 carrying (1) no load, (2) a load equal to 7.5% of body weight (mean: 4.66 kg) or (3) a load equal to 15% of body weight (mean: 9.32 kg). Thus, each subject underwent 12 separate tests. The external loads were in the form of lead pellets carried in a plastic scuba belt worn around the waist. A differentiation threshold was found at 6.44 km·h−1 for the 0% and 7.5% loads and at 4.83 km·h−1 for the 15% load. At speeds below the threshold, the perception of exertion was similar in the legs, chest and overall. At higher speeds, exertion was perceived to be more intense in the legs than overall and less intense in the chest than overall, suggesting that the local legs signal was the dominant factor in shaping the overall sensation of exertion. The oxygen uptake was greater for the 15% load than for either the 0% or 7.5% loads, but was similar for the 0% and 7.5% loads. Findings suggested a critical weight limit for external loads that could be transported without increasing the metabolic cost beyond that required to move the body weight alone. This limit fell between 7.5% and 15% of the body weight. When oxygen uptake was expressed per kg of total weight transported, there was no loss of metabolic efficiency while carrying loads up to 15% of the body weight.

Decreased serum levels of oestradiol, testosterone and prolactin during prolonged physical strain and sleep deprivation, and the influence of a high calory diet

Abstract: The changes in oestradiol, testosterone and prolactin, and the effects of a high calory diet, were investigated in eleven young male cadets participating in a 5 days' ranger training course involving heavy and continuous physical activities with less than 1500 kcal·day−1 and almost without sleep.

Isokinetic strength, endurance, and fiber type composition in elite American paddlers.

Abstract: Muscle fiber type and isokinetic strength and fatigue were examined in nine highly trained canoe and kayak paddlers. Needle biopsies were taken from the right vastus lateralis and biceps brachii muscles and the samples stained for myofibrillar ATPase. Baseline elbow flexion and knee extension isometric (0 degrees . s-1) and isokinetic (60 degrees . s-1 or 1.05 rad . s-1 and 180 degrees . s-1 or 3.14 rad . s-1) peak torques were determined. Each subject then performed two series of 50 isokinetic contractions at an angular velocity of 180 degrees . s-1: elbow flexion and knee extension series, separated by 3 h. The percentage of slow twitch fibers was similar in the biceps brachii (43.9%) and the vastus lateralis (43.3%). The fast twitch/slow twitch fiber area ratio was significantly higher in the more highly trained biceps brachii due to larger FT fibers. No relationship was found between fiber type composition and baseline peak torques or decline in peak torque due to the fatigue regimens. Baseline peak torque correlated with initial strength level, body weight, and limb girth. The results suggested that for these paddlers muscle strength and the decline in strength induced by repetitive isokinetic contractions were more dependent on characteristics of body size than on fiber type composition.