Energy supply for muscle activity in 13- to 14-year-old boys depending on the rate of puberty

The energy supply for muscle activity in healthy boys aged 13–14 years (n = 162) at various puberty stages (PSs) has been studied using functional and ergometric working capacity indices. It has been established that boys at PSs II–IV significantly differ in the indices of power, capacity, and efficiency of bioenergy systems. Three groups of bioenergy indices have been distinguished that differ in the direction of variations in adolescents depending on the rate of puberty. The first group includes the physiological variables the highest levels of which are observed in adolescents with high rates of development. All these indices belong to the anaerobic alactic and anaerobic glycolytic components of physical capability. The second group includes the physiological variables the highest levels of which are observed in adolescents with medium rates of development; the lowest levels, in adolescents with accelerated rates of development. These indices mainly reflect the set of aerobic capacities. The third group includes the physiological variables the highest levels of which are observed in adolescents with low rates of development and the lowest levels, in boys with accelerated rates of maturation. These indices reflect the maximal aerobic power and endurance. It was found that adolescents aged 13–14 years with moderate rates of development are characterized by higher indices of power and capacity of the aerobic energy supply system as compared to adolescents with accelerated maturation. This group of adolescents has also been observed to exhibit a lower maximal aerobic power against a background of higher capacity and efficiency of the aerobic system functioning as compared to adolescents with slow maturation. Adolescents with moderate rates of maturation have been shown to surpass schoolboys with accelerated or slow development with respect to the power of mixed aerobic-anaerobic work. Boys aged 13–14 years with accelerated development have been found to differ from schoolboys with moderate or slow maturation by high anaerobic capacity, relatively low aerobic capacities and an increase in the tone of the parasympathetic nervous system. This should be taken into consideration in terms of a differentiated approach to the formation of load during physical education and athletic training of adolescents aged 13–14 years.     

Aerobic power as related to body growth and training in Japanese boys: a longitudinal study

Maximal aerobic power was measured for 5-6 successive years in 50 Japanese schoolboys starting from the age of 9 or 13 yr. and for 2-3 yr in 6 superior junior runners from the age of 14 yr. A large increase in aerobic power was observed during the adolescent growth spurt for 7 schoolboys who trained between the ages of 9 and 14 yr. Aerobic power for 43 average schoolboys increased from 45.0 to 52.2 ml/kg.min between the ages of 13 and 17 yr. The aerobic power of 6 superior junior runners increased from 63.4 to 73.4 ml/kg.min between the ages of 14 and 17 yr. A remarkable increase in aerobic power was not observed in trained boys before the age of peak height growth velocity (PHV). Beginning approximately 1 yr prior to the age of PHV and thereafter, training effectively increased aerobic power above the normal increase attributable to age and growth. The highly developed aerobic power found in superior junior runners may have been derived from strenuous training and partially by genetically superior endowment.     

Individual characteristics of somatotype and skeletal muscle power in girls in the age period from 7 to 11

Sixteen girls were observed for five years during the age period from 7 to 11. The longitudinal study included the annual assessment of constitutional characteristics according to Shtefko-Ostrovskii and the calculation of endomorphy, mesomorphy, and ectomorphy indices from anthropometric data according to Heath-Carter. The indices of skeletal muscle power (aerobic capacity and power; anaerobic power, and power indexa) were determined in a two-load ergometric test using Muller’s equation. The girls demonstrated a 2.5-time more stable somatotype than boys. The most pronounced changes in their constitutional characteristics were observed between the ages of 8 and 9, i.e., a year earlier than in boys. These changes occurred only within the dolichomorphic and brachymorphic groups without transitions between somatotypes. In girls of all ages, the constitutional characteristics were in good correlation with skeletal muscle power. In general, dolichomorphs were characterized by high aerobic indices: their mean aerobic capacity was as high as 83.1 kJ/kg vs. 4.1 kJ/kg in brachymorphs, who showed preferential development of anaerobic mechanisms.     

Energy supply of muscular activity of five- to six-year-old children and complex assessment of physical working capacity

A complex study of the physical working capacity of five- to six-year-old children (n = 106) was performed. It was found that the physical working capacity of preschool children at this age is determined by the following five major factors: (I) aerobic capacity, (II) anaerobic glycolytic working capacity, (III) absolute aerobic power, (IV) relative aerobic power, and (V) anaerobic alactic working capacity. Sex-related differences in some parameters reflecting the physical working capacity and fitness, characterizing the anaerobic alactic and anaerobic glycolytic productivity of the body were revealed. These differences are apparently related to an advanced development of anaerobic energy-supply mechanisms of girls compared to age-matched boys. The procedure of a complex assessment of the physical working capacity of five- to six-year-old children has been developed, which includes informative parameters characterizing the power and capacity of energy systems selected on the basis of results of factor analysis and expert assessment. A rapid procedure for a complex assessment of working capacity based on calculating the time during which a physical load (2 W/kg) can be sustained is proposed. The study showed that shifts in the intensity of physical activity within the optimal range resulted in multifold changes in its duration. Importantly, the duration of physical activity’s performance at an intensity of 175–180 bpm in children with a high working capacity is comparable to the maximum work duration at a heart rate of 140–145 bmp in preschool children with a low physical condition. Differences between children with high and low physical working capacity were found to increase with an increase in the physical load aerobicity. The physical working capacity of five- to six-year-old children can be differentiated best of all on the basis of aerobic capacity parameters. The enormous range of changes in the aerobic capacity parameters makes them especially valuable for characterizing the level of somatic health of preschool children. The results of this study were used to construct a nomogram for the determination of the allowable training load depending on its intensity and physical working capacity.     

Physical state of adolescents with high stress reactivity

The characteristics of the physical state were studied in 13- to 14-year-old adolescents with high (n = 97) and low (n = 85) stress reactivities. The data showed that, during the period of sexual maturation, the development of the mechanisms of energy for muscular activity was heterochronic and nonlinear. Hyperreactive boys exhibited relatively high anaerobic nonlactic and low aerobic capacities of the body and enhanced physiological costs of the high-power function. In hyperreactive adolescents, the motor function was specifically characterized by a combination of a high level of movement speed and power and a relatively low level of general endurance. In 13- to 14-year-old adolescents, the differences in muscular working capacities and motor abilities, associated with various stress reactivity, appear during different sexual maturation stages (SMSs). At SMSs II and III, hyper- and hyporeactive adolescents exhibit higher indices of aerobic body capacities and relatively low anaerobic capacities as compared to the children at SMS IV. It is supposed that, in the hyperreactive adolescents, the efficiency of the mechanisms of body protection from hypoxia is lower.     

Time course of meiotic progression after transferring primary spermatocyte into ooplasm at different stages

This study attempted to investigate the time course of meiotic progression after transferring primary spermatocyte (PS) into ooplasm at different maturing stages. In present experiments, PSs were introduced into maturing ooplasts or oocytes by electrofusion. Higher fusion rate was obtained by phytohemagglutinin (PHA) agglutination than by perivitelline space (PVS) insertion. When the ooplasms prepared at 0, 2, 5, and 8.5 hr of in vitro maturation (IVM) were used as recipients and PSs were used as donors, the reconstructed cells extruded the first polar body (PB1) approximately 8.5, 7, 5.5, and 3 hr after electrofusion, respectively. Especially, when ooplasm cultured for 8.5 hr in vitro after GV removal was fused with PS, the PB1 was emitted 7-11 hr after electrofusion. Additionally, the PB1 extrusions of GV and pro-MI oocytes fertilized with PSs were 2.5 hr earlier than control oocytes. The results suggest that (1) PSs undergo the first meiosis in different time courses when introduced into ooplasm at different maturing stages; (2) GV material plays an important role in determining the timing of PB1 extrusion; and (3) first meiotic division of GV and pro-MI oocytes can be accelerated by introducing PS.     

Leisure time sport activities and maximal aerobic power during late adolescence

The pattern of leisure time sport activity was estimated by retrospective recalls and expressed in terms of an annual sport activity score. The activity score was related to the development of maximal aerobic power during the period of late adolescence in German children. Both girls and boys reduced their activity pattern from 14 to 18 years of age, boys more than girls. At each age boys were more active than girls. A slight tendency towards better fitness with increased habitual physical activity was noticed, but many sedentary children exhibited a good performance capacity and some children with a high level of leisure time sport activity were characterized by a low level of maximal aerobic power. A statistical analysis revealed that the observed tendency to better fitness with increased habitual physical activity could be explained by an age factor with no additional effect of variation in sport activity score.     

Assessment of aerobic and anaerobic capacity of athletes in treadmill running tests.

The criteria of max VO2 and max O2D which are traditionally used in studying aerobic and anaerobic work capacity, have the different dimensions. While max VO2 is an index of the power of aerobic energy output, max O2D assesses the capacity of anaerobic sources. For a comprehensive assessment of physical working capacity of athletes, both aerobic and anaerobic capabilities should be represented in three dimensions, i.e. in indexes of power, capacity and efficiency. Experimental procedures have been developed for assessing these three parameters in treadmill running tests. It is proposed to assess anaerobic power by measuring excess CO2, concurrently with determination of max VO2. Maximal aerobic capacity is established as the product of max VO2 by the time of max VO2 maintenance determined in a special test with running at critical speed. The erogmetric criteria derived on the basis of the tests proposed, may be used for systematization of various physical work loads.     

High-speed running performance: a new approach to assessment and prediction.

We hypothesized that all-out running speeds for efforts lasting from a few seconds to several minutes could be accurately predicted from two measurements: the maximum respective speeds supported by the anaerobic and aerobic powers of the runner. To evaluate our hypothesis, we recruited seven competitive runners of different event specialties and tested them during treadmill and overground running on level surfaces. The maximum speed supported by anaerobic power was determined from the fastest speed that subjects could attain for a burst of eight steps (approximately 3 s or less). The maximum speed supported by aerobic power, or the velocity at maximal oxygen uptake, was determined from a progressive, discontinuous treadmill test to failure. All-out running speeds for trials of 3-240 s were measured during 10-13 constant-speed treadmill runs to failure and 4 track runs at specified distances. Measured values of the maximum speeds supported by anaerobic and aerobic power, in conjunction with an exponential constant, allowed us to predict the speeds of all-out treadmill trials to within an average of 2.5% (R2 = 0.94; n = 84) and track trials to within 3.4% (R2 = 0.86; n = 28). An algorithm using this exponent and only two of the all-out treadmill runs to predict the remaining treadmill trials was nearly as accurate (average = 3.7%; R2 = 0.93; n = 77). We conclude that our technique 1) provides accurate predictions of high-speed running performance in trained runners and 2) offers a performance assessment alternative to existing tests of anaerobic power and capacity.     

Physical working capacity and energy supply of muscle function during postnatal human ontogeny

On the basis of the results of our studies and literature data, an analysis of the physiological mechanisms responsible for the multifold increase in the physical working capacity during human development has been performed. Physiological and biochemical studies have shown that the aerobic energy system already has a high capacity during the second period of childhood, and the further increase in working capacity is mainly provided by the development of anaerobic mechanisms of energy supply. The maturation of mechanisms of energy production is related to considerable changes in the activity of tissue enzymes and radical rearrangement of the composition of muscular fibers. Puberty considerably influences the development of anaerobic muscle energetics in boys due to stimulation of the growth of type II fibers by testosterone. It has been shown that widespread tests for assessment of physical working capacity mainly reflect changes in the power of energy systems and only in rare cases may be used to characterize changes in their capacity. However, the capacity parameters, which depend to a greater extent on the quality of regulation at the cellular, tissue, and body levels, show multifold growth during ontogeny, which corresponds to the actual increase in the working capacity in the period from childhood to youth. A classification of tests of physical working capacity is proposed. The use and development of this classification may facilitate the development of new tests and an increased efficiency of testing involved in solving various applied and fundamental problems.     

Limitations on locomotor performance in squid

An empirical equation relating O2 consumption (power input) to pressure production during jet-propelled swimming in the squid (Illex illecebrosus) is compared with hydrodynamic estimates of the pressure-flow power output also calculated from pressure data. Resulting estimates of efficiency and stress indicate that the circularly arranged obliquely striated muscles in squid mantle produce maximum tensions about half those of vertebrate cross-striated muscle, that "anaerobic" fibers contribute to aerobic swimming, and that peak pressure production requires an instantaneous power output higher than is thought possible for muscle. Radial muscles probably contribute additional energy via elastic storage in circular collagen fibers. Although higher rates of aerobic power consumption are only found in terrestrial animals at much higher temperatures, the constraint on squid performance is circulation, not ventilation. Anaerobic power consumption is also among the highest ever measured, but the division of labor between "aerobic" and "anaerobic" fibers suggests a system designed to optimize the limited capacity of the circulation.     

Aerobic and anaerobic energy during a 2-km race simulation in female rowers

The maximal aerobic power (VO2max) and maximal anaerobic capacity (AODmax) of 16 female rowers were compared to their peak aerobic power (VO2peak) and peak anaerobic capacity (AODpeak, respectively) during a simulated 2-km race on a rowing ergometer. Each subject completed three tests, which included a 2-min maximal effort bout to determine the AODmax, a series of four, 4-min submaximal stages with subsequent progression to VO2max and a simulated 2-km race. Aerobic power was determined using an open-circuit system, and the accumulated oxygen deficit method was used to calculate anaerobic capacities from recorded mechanical power on a rowing ergometer. The average VO2peak (3.58 l min(-1)), which usually occurred during the last minute of the race simulation, was not significantly different (P > 0.05) from the VO2max (3.55 l min(-1)). In addition, the rowers' AODmax (3.40 l) was not significantly different (P > 0.05) from their AODpeak (3.50 1). The average time taken for the rowers to complete the 2-km race simulation was 7.5 min, and the anaerobic system (AODpeak) accounted for 12% of the rowers' total energy production during the race.     

Development of the Energetics of Muscular Exercise with Age: Summary of a 30-Year Study: I. Structural and Functional Rearrangements

The series of articles summarizes a 30-year study on the development of skeletal muscles, bioenergetics of muscular exercise, and physical working capacity with age in elementary and secondary school students. Communication I deals with the growth of human skeletal muscles and age-related changes in their fiber composition and the main parameters of aerobic working capacity. The key periods of growth were determined and a substantial rearrangement of skeletal muscle composition and associated age-related changes in aerobic and anaerobic working capacity were found in 7- to 17-year-old boys.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 4, 2005, pp. 37–42.Original Russian Text Copyright © 2005 by Kornienko, Son’kin, Tambovtseva.     

Circulatory and respiratory responses to muscular exercise in Czech and Norwegian children

This paper presents a comparison between Czech and Norwegian rural healthy children with regard to the functional characteristics of the circulatory and respiratory system based upon work physiological variables and measurements of some pulmonary volumes. The study included randomised samples of boys and girls at the age of 8, 12 and 16 years, 66 Czech boys and 63 girls, 54 Norwegian boys and 57 girls. At the age of 8 years the maximal aerobic power was closely similar in both countries, but in the older age groups the Norwegian children exhibited lower physical fitness. The maximal heart rate was close to 200 min-1 on the average without any sex, age or ethnic differences. In agreement with the higher maximal aerobic power the 12 and 16 year old Czech children had lower submaximal heart rates for the same oxygen uptake than the Norwegian children. The forced vital capacity and forced expiratory volume in one second was significantly higher on the average in Czech than in Norwegian children but the latter, expressed in percent age of the former, averaged 87 to 91% without any sex, age or ethnic differences. The maximal ventilation volumes during muscular exercise reached higher values in Czech than in Norwegian children of the same age, but the mean maximal respiratory rate was close to 60 min-1, being independent of age, sex and cultural differences. During heavy exercise only 40 to 50% of the vital capacity and 45 to 55% of the forced expiratory volume were taken into account and this index of pulmonary function did not differ with sex, age or ethnic differences.     

Enhancement of Anaerobic Respiration in Root Tips of Zea mays following Low-Oxygen (Hypoxic) Acclimation

Root tips (10-millimeter length) were excised from hypoxically pretreated (HPT, 4% [v/v] oxygen at 25°C for 16 hours) or nonhypoxically pretreated (NHPT, 40% [v/v] oxygen) maize (Zea mays) plants, and their rates of respiration were compared by respirometry under aerobic and anaerobic conditions with exogenous glucose. The respiratory quotient under aerobic conditions with 50 millimolar glucose was approximately 1.0, which is consistent with glucose or other hexose sugars being utilized as the predominant carbon source in glycolysis. Under strictly anaerobic conditions (anoxia), glycolysis was accelerated appreciably in both HPT and NHPT root tips, but the rate of anaerobic respiration quickly declined in NHPT roots. [U-¹⁴C]Glucose supplied under anaerobic conditions was taken up and respired by HPT root tips up to five times more rapidly than by NHPT roots. When anaerobic ethanol production was measured with excised root tips in 50 millimolar glucose, HPT tissues consistently produced ethanol more rapidly than NHPT tissues. These data suggest that a period of low oxygen partial pressure is necessary to permit adequate acclimation of the root tip of maize to subsequent anoxia, resulting in more rapid rates of fermentation and generation of ATP.     

鲫幼鱼游泳运动能力的个体变异与表型关联

为考察鲤科鱼类运动能力的个体变异和表型关联及不同加速度对匀加速游泳能力的影响, 研究在(25±0.5)℃条件下测定鲫(Carassius auratus)幼鱼的静止代谢率(Resting metabolic rate, RMR), 通过临界游泳速度(Critical swimming speed, U_crit)法和过量耗氧(EPOC)法获取实验鱼的最大代谢率(Maximum metabolic rate, MMR)、代谢空间(Aerobic scope, AS=MMR-RMR)、相对代谢空间(Factorial aerobic scope, FAS=MMR/RMR)、U_crit及步法转换速度(Gait transition speed, U_gt), 并在不同加速度(0.083、0.167、0.250、0.333 cm/s2)下测定鲫幼鱼的匀加速游泳能力(Constant accelerated test, U_cat)和U_gt。研究发现: 鲫幼鱼的MMR和AS与U_crit均呈正相关, 但RMR与U_crit不相关; 能量代谢参数(MMR、AS、RMR)与U_gt不相关。U_crit法获取的MMR、AS、FAS与EPOC法均无平均值的显著性差异, 但2种方法获得的上述参数具有较高的个体重复性; 鲫幼鱼的能量代谢参数之间存在表型关联并且关联方向不尽相同。鲫幼鱼的U_crit和U_gt均小于各加速度下的U_cat和U_gt, 加速度对U_cat测定无影响但对U_gt有影响。鲫幼鱼的U_gt与U_crit或U_cat呈正相关, 并且其匀加速游泳能力参数在不同加速度下保持较高的重复性。除0.333 cm/s2外, 其他加速度下鲫幼鱼U_cat的无氧代谢组分(U_cat-U_gt)与U_cat呈正相关; 然而, 鲫幼鱼的有氧代谢组分(U_gt)与无氧代谢组分(U_cat-U_gt)呈负相关。研究表明: U_crit法和EPOC法诱导鲫幼鱼的有氧代谢能力无方法学差异; 鲫幼鱼的能量代谢存在表型关联, 其匀加速游泳能力具有稳定个体差异, 并且该种鱼的有氧代谢与无氧代谢存在权衡。     

Kinetics of oxygen uptake and heart rate at onset of exercise in children

Requirements for cellular homeostasis appear to be unchanged between childhood and maturity. We hypothesized, therefore, that the kinetics of O2 uptake (VO2) in the transition from rest to exercise would be the same in young children as in teenagers. To test this, VO2 and heart rate kinetics from rest to constant work rate (75% of the subject's anaerobic threshold) in 10 children (5 boys and 5 girls) aged 7-10 yr were compared with values found in 10 teenagers (5 boys and 5 girls) aged 15-18 yr. Gas exchange was measured breath to breath, and phases I and II of the transition and phase III (steady-state exercise) were evaluated from multiple transitions in each child. Phase I (the VO2 at 20 s of exercise expressed as percent rest-to-steady-state exercise VO2) was not significantly correlated with age or weight [mean value 42.5 +/- 8.9% (SD)] nor was the phase II time constant for VO2 [mean 27.3 +/- 4.7 (SD) s]. The older girls had significantly slower kinetics than the other children but were also found to be less fit. When the teenagers exercised at work rates well below 75% of their anaerobic threshold, phase I VO2 represented a higher proportion of the overall response, but the phase II kinetics were unchanged. The temporal coupling between the cellular production of mechanical work at the onset of exercise and the uptake of environmental O2 appears to be controlled throughout growth in children.     

Adaptation of Phytoplankton-Degrading Microbial Communities to Thermal Reactor Effluent in a New Cooling Reservoir

In water column and sediment inocula from a nuclear reactor cooling reservoir, natural phytoplankton substrate labeled with ¹⁴C was used to determine aerobic and anaerobic mineralization rates for a range of temperatures (25, 40, 55, and 70°C) expected during reactor operation. For experiments that were begun during reactor shutdown, aerobic decomposition occurred at temperatures of <55°C. After 2 months of reactor operation, aerobic rates increased substantially at 55 and 70°C, although maximum rates were observed at temperatures of ≤40°C. The temperature range for which maximum anaerobic mineralization (i.e., the sum of CH₄ and CO₂) was observed was 25 to 40°C when the reactor was off, expanding to 25 to 55°C during reactor operation. Increased rates at 55°C, but not 70°C, correlated with an increase in the ratio of cumulative methane to carbon dioxide produced over 21 days. When reduced reactor power lowered the maximum temperature of the reservoir to 42°C, aerobic decomposition at 70°C was negligible, but remained substantial at 55°C. Selection for thermophilic decomposers occurred rapidly in this system in both aerobic and anaerobic communities and did not require prolonged exposure to elevated temperatures.     

A theoretical analysis of the effect of altitude on running performance

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

Comparison between a 30-s all-out test and a time-work test on a cycle ergometer

The relationship between the amount of work (Wlim) performed at the end of constant-power exhausting exercise and exhaustion time (tlim) has been studied for supramaximal exercise [105%, 120%, 135% and 150% of the individual maximal aerobic power, (MAP)] performed on a Monark cycle ergometer in nine men. The Wlim--tlim relationship was described by a linear relationship (Wlim = a + b . tlim). Intercept a was roughly equivalent to the work produced during a 1-min exercise performed at MAP. Slope b was equal to 79% of MAP. Intercept a has been correlated with the total amount of work (AW) performed during a 30-s all-out test supposed to assess anaerobic capacity. Intercept a was significantly (p less than 0.05) correlated with AW. The anaerobic capacity was not depleted at the end of the all-out test, as the mechanical power at the 30th s of this test was approximately equal to twice MAP. However, AW was significantly higher than intercept a. It was likely that the value of intercept a was an underestimation of the maximal anaerobic capacity because of the inertia of the aerobic metabolism. Indeed, an exponential model of the Wlim--tlim relationship, which takes the interia of the aerobic metabolism into account, shows that a linear approximation of the Wlim--tlim relationship yields a systematic underestimation of the anaerobic capacity. Consequently, intercept a of the Wlim--tlim relationship is not a more accurate estimation of the anaerobic capacity than the AW performed during a 30-s all-out test.(ABSTRACT TRUNCATED AT 250 WORDS)