Effect of 120 days of bed-rest with and without countermeasures on the mechanical properties of the triceps surae muscle in young women

The effect of a 120-day 6° head-down tilt (HDT) bed rest with and without countermeasures on the mechanical properties of the human triceps surae muscle was studied in eight healthy young women subjects. One group [n = 4, mean age 31.5 (SEM 1.7) years] underwent a 120-day HDT only and a second group [n = 4; mean age 28.0 (SEM 1.1) years] underwent HDT with countermeasures (physical training). The results showed that the contractile properties of the skeletal muscle studied changed considerably. After HDT without countermeasures the maximal voluntary contraction (MVC) had decreased by 36% (P < 0.05), and the electrically evoked tetanic tension at 150 Hz (P _o) and isometric twitch contraction (P _t) had decreased by 24% (P < 0.02) and 12% (P < 0.05), respectively. Time- to-peak tension (TPT) of the twitch had significantly increased by 14% (P<0.05), but half-relaxation time (1/2RT), and total contraction time (TCT) had decreased by 19% (P<0.05) and 18% (P<0.05), respectively. The difference between P _o and MVC expressed as a percentage of P _o and referred to as force deficiency (FD), was also calculated. The FD had increased by 40% (P<0.001). The rate of increase of voluntary contractions calculated according to a relative scale had significantly reduced, but for the electrically evoked contraction no substantial changes were observed. After HDT with countermeasures TPT, 1/2RT and TCT of the twitch had decreased by 4%, 7%, 19%, respectively in relation to the control condition. Training had caused a decrease of 3% (P>0.05) in MVC, and P _t, and in P _o of 14%, and of 9% (P>0.05), respectively. The FD had decreased significantly by 10% (P<0.02). The rate of increase of electrically evoked tetanic tension did not change significantly during HDT with countermeasures but the rate of increase in isometric voluntary tension development was increased. Physical training provided a reserve of neuromuscular function, which attenuated the effect of bed rest. The experimental findings indicated that neural as well as muscle adaptation occurred in response to HDT with countermeasures. Accepted: 7 November 1997     

Differential activation of the plantar flexor muscles in balance control across different feet orientations on the ground

The ankle plantar flexor muscles act synergistically to control quiet and dynamic body balance. Previous research has shown that the medial (MG) and lateral (LG) gastrocnemii, and soleus (SOL) are differentially activated as a function of motor task requirements. In the present investigation, we evaluated modulation of the plantar flexors' activation from feet orientation on the ground in an upright stance and the ensuing reactive response to a perturbation. A single group of young participants (n = 24) was evaluated in a task requiring initial stabilization of body balance against a backward pulling load (5% or 10% of body weight) attached to their trunk, and then the balance was suddenly perturbed, releasing the load. Four feet orientations were compared: parallel (0°), outward orientation at 15° and 30°, and the preferred orientation (M = 10.5°). Results revealed a higher activation magnitude of SOL compared to MG-LG when sustaining quiet balance against the 10% load. In the generation of reactive responses, MG was characterized by earlier, steeper, and proportionally higher activation than LG-SOL. Feet orientation at 30° led to higher muscular activation than the other orientations, while the activation relationship across muscles was unaffected by feet orientation. Our results support the conclusion of task-specific differential modulation of the plantar flexor muscles for balance control.     

Salivary testosterone does not predict mental rotation performance in men or women

Multiple studies report relationships between circulating androgens and performance on sexually differentiated spatial cognitive tasks in human adults, yet other studies find no such relationships. Relatively small sample sizes are a likely source of some of these discrepancies. The present study thus tests for activational effects of testosterone (T) using a within-participants design by examining relationships between diurnal fluctuations in salivary T and performance on a male-biased spatial cognitive task (Mental Rotation Task) in the largest sample yet collected: 160 women and 177 men. T concentrations were unrelated to within-sex variation in mental rotation performance in both sexes. Further, between-session learning-related changes in performance were unrelated to T levels, and circadian changes in T were unrelated to changes in spatial performance in either sex. These results suggest that circulating T does not contribute substantially to sex differences in spatial ability in young men and women. By elimination, the contribution of androgens to sex differences in human performance on these tasks may be limited to earlier, organizational periods.     

模拟失重对白假丝酵母菌增殖和毒性的影响

【背景】近年来研究发现,失重条件可对一些致病微生物的增殖和毒性产生影响,白假丝酵母菌(Candida albicans)是典型的条件性致病真菌,在太空环境和人体中普遍存在,研究失重条件下白假丝酵母菌的增殖和毒性意义重大。【目的】利用旋转细胞培养系统(Rotary cell culture system,RCCS)模拟失重环境对白假丝酵母菌进行连续传代培养,检测模拟失重环境对白假丝酵母菌增殖情况、毒性以及基因表达的变化。【方法】将白假丝酵母菌接种在旋转生物反应器(High aspect rotating vessel,HARV)中,利用旋转细胞培养系统连续传代培养14 d,然后对菌株进行增殖速率测定、不同pH条件下增殖能力测定、生物膜相对形成能力测定和细胞毒性和动物毒力测定;利用转录组测序技术找出差异表达基因,结合性状分析模拟失重可能对白假丝酵母菌增殖和毒力的影响。【结果】与对照组相比,模拟失重组白假丝酵母菌对数期提前,增殖速率加快,在适宜pH条件下的增殖能力普遍提高,但其生物膜形成能力相对减弱,对LoVo细胞和小鼠的毒性减弱;转录组测序发现,模拟失重组共有280个基因表达差异达1.5倍以上(P0.05),其中248个上调、32个下调。差异基因经基因功能注释(Gene ontology,GO)和京都基因及基因组百科全书(Kyoto encyclopedia of genes and genomes,KEGG)富集分析发现,相关胞膜形成及细胞分裂基因表达上调,生物膜形成、细胞黏附及共生粘连宿主基因表达下调。【结论】模拟失重环境可引起白假丝酵母菌增殖和毒性水平发生变化,相关改变可为研究失重环境对微生物的影响提供参考。     

Neuromuscular Efficiency of the Triceps Surae in Induced and Voluntary Contractions: Morning and Evening Evaluations

Variations in force and electromyographic (EMG) activities of skeletal muscles with the time-of-day have been previously described, but not for a postural muscle, submitted to daily postural and locomotor tasks. In this article, mechanical performances, EMGs, and the ratio between these parameters, i.e., the neuromuscular efficiency (NME), were measured on the triceps surae (TS) of eight subjects, two times each day, at 6:00 and 18:00 h. NME was evaluated under different experimental conditions (electrically induced contractions, reflex contractions, maximal and submaximal voluntary isometric contractions, and during a natural movement, a drop jump) to determine whether mechanisms, peripheral or central in origin, were responsible for the eventual changes in NME with time-of-day. To calculate NME in induced conditions (NME_ind), a supramaximal electrical stimulus was applied to the tibial nerve, and the maximal M wave of TS (TS Mmax) and the amplitude of the twitch tension (Pt_Mmax) in response to this electrical stimulation were quantified. TS Mmax was significantly lower in the evening (mean gain value ?10.7 ± 5.5%, p < 0.05), whereas Pt_Mmax was not significantly modified. NME_ind (Pt_Mmax/TS Mmax) was significantly higher in the evening (mean gain of 17.6 ± 5.8%, p < 0.05), and this increase was necessarily peripheral in origin. Secondly, maximal tendon taps were applied to the Achilles tendon in order to quantify at the two times-of-day the reflexes in response to a mechanical stimulus. The maximal reflex, TS Tmax/Mmax (%), the peak amplitude of the twitch tension associated to this tendon jerk (Pt_Tmax), and the corresponding NME (NME_reflex = Pt_Tmax/TS Tmax/Mmax) were not affected by time-of-day, indicating that reflex excitability did not present daytime variations when tested under these conditions. Voluntary isometric contractions were required under maximal (MVC) and submaximal (25% MVC) conditions, and the corresponding torques and TS EMG were measured. MVC was higher in the evening (mean gain: 8.6 ± 2.7%, p < 0.05) and TS EMGmax (normalized with regard to TS Mmax) also increased in the evening but not significantly; thus, NME_MVC was not modified. At 25% of MVC, TS EMG was significantly higher in the evening (mean gain of 23 ± 13.9%, p < 0.05) and a trend for a lower NME_25%MVC in the evening was observed, a result probably representative of a higher muscle fatigue state in the evening. Finally, to test the muscle capacities during a natural task, a NME index was calculated during a drop jump (DJ). The NME_DJ was defined as the ratio between jump height and mean amplitude of TS EMG (% of TS Mmax) between the drop and the jump. Both jump height and NME_DJ were significantly higher in the evening (mean gains of 10.9 ± 4.5% and 15.7 ± 7.4%, respectively, p < 0.05). In conclusion, daytime changes in the efficiency of postural muscles seem to depend on both peripheral and central mechanisms. According to the experimental conditions, NME of the postural muscle could increase, remain constant, or even decrease in the evening, and this result may reflect reverse effects of better contractile capacities and higher fatigue state.     

低聚木糖对模拟失重大鼠肠道微生态的影响

目的 研究低聚木糖对模拟失重大鼠肠道微生态的影响。方法 采用大鼠尾部悬吊法模拟失重。32只雄性SD大鼠随机分为4组,每组8只：FC组（地面对照组,饲喂基础饲料）,FS组（地面处理组,饲喂添加低聚木糖的饲料）,SC组（尾吊对照组,饲喂基础饲料）。SS组（尾吊处理组,饲喂添加低聚木糖的饲料）,实验21d,SC和SS组解除尾吊继续观察。实验21d。采用选择性培养基对大鼠粪便肠杆菌、肠球菌、类杆菌、双歧杆菌以及乳杆菌进行定量测定。结果 SC组与FC组相比,双歧杆菌数量减少,肠杆菌和肠球菌数量增加;FS组比FC组双歧杆菌数量增加显著,肠杆菌和肠球菌有不同程度的减少,SS组比SC组双歧杆菌数量增加显著,肠杆菌和肠球菌也有不同程度的减少。类杆菌和乳杆菌变化不明显。尾吊解除期,SS组双歧杆菌数量比SC组更快恢复到正常水平。结论 低聚木糖可促进尾吊大鼠肠道益生菌主要是双歧杆菌的增殖,一定程度上促进由于模拟失重造成肠道微生态失调的平衡,并对条件致病菌具有一定的抑制作用。     

模拟微重力对肺动脉和胸主动脉的影响

目的 :通过对模拟微重力 (SM)、肺动脉 (PA)和胸主动脉 (TA)局部调节机理研究 ,为大小循环动脉对SM适应机理和SM后立位耐力降低机理研究积累资料。方法 :XXH 2 0 0 0型小循环心功能检测仪检测人体头低位 6°卧床(HDT) 7d心肺循环功能变化。 - 30°尾部悬吊 (TS)大鼠模拟微重力 (microgravity ,M)的生理效应 ,测量 7d、1 4dPA和TA的反应性。结果 :人体HDT初期每搏PA(hz)、静脉 (hc)容量和左心前负荷 (hc/hz)均显著增加 ,96～ 1 4 4h大小循环均出现超调现象 ,前者出现时间早、幅度大。 7d尾部悬吊大鼠 (TS7)与对照组 (CON)比PA舒张反应显著增强 ,TS1 4有降低趋势。TS7TA与CON比舒张反应显著增强 ,TS1 4轻度升高。TS7PA收缩反应与CON比轻度降低 ,TS1 4显著降低。TS1 4TA收缩反应显著降低。去VECPA对KCl、苯肾上腺素和硝普钠的反应在所有组间无差异。结论 :SM对大小循环动脉影响不同 ,可能是SM时局部调节功能降低的重要表现 ,主要由于动脉血管内皮细胞功能变化 ,对立位耐力降低可能有贡献     

Sequence of pituitary-adrenal cortical hormone responses to low-dose physostigmine administration in young adult women and men

We previously demonstrated greater HPA axis activation in adult men compared to adult women following low-dose administration of the anticholinesterase inhibitor, physostigmine (PHYSO). Because blood sampling was done infrequently following PHYSO, the rise times of AVP, ACTH1-39, and cortisol could not be determined. In the present study, we determined the sequence of hormone increases by frequent blood sampling following PHYSO. Twelve adult women and 12 adult men underwent three test sessions 5-7 days apart: PHYSO, saline control, and repeat PHYSO. As in the earlier study, PHYSO produced no side effects in half the subjects and mild side effects in the other half, with no significant female-male differences. None of the hormone responses was significantly correlated with the presence or absence of side effects. In both women and men, the AVP increase preceded the ACTH1-39 increase, which in turn preceded the cortisol increase. The AVP and ACTH AUCs were significantly positively correlated in both women and men, supporting AVP as an acute stimulus to ACTH secretion. Also as in the earlier study, the AVP response to PHYSO was more than twice as great in men as in women, but the difference was not statistically significant. We therefore analyzed the results of both studies combined (N=26 women and 26 men). The men had a significantly greater AVP response and a trend toward a greater ACTH1-39 response compared to the women. These findings further support the concept of sexual diergism (functional sex difference) in the influence of CNS cholinergic systems on HPA hormone secretion.     

槲皮素对模拟微重力条件下体外培养大鼠心肌细胞骨架的影响

采用细胞免疫双荧光染色观察离体培养的大鼠心肌细胞微丝和微管分布 ,探讨模拟微重力条件下槲皮素对心肌细胞骨架分布的影响。结果表明 :模拟微重力条件下心肌细胞微丝、微管在近胞核区的分布增多 ;模拟微重力处理的同时加入槲皮素 ,则使近胞核处微丝、微管分布明显减少 ,微丝束的粗细与对照组无异。提示模拟微重力可显著影响心肌细胞微丝、微管的分布 ,槲皮素可对抗该效应而发挥其心肌细胞保护作用 [动物学报49(1) :98～ 10 3 ,2 0 0 3]。     

Effects of simulated microgravity on male gametophyte of Prunus, Pyrus, and Brassica species

Summary. In this study we evaluated the effect of simulated microgravity on pollen germination of both herbaceous and woody species in order to investigate the possibility of applying gametophytic selection for plant growth in the space environment. The behaviour of gametophytes exposed to the stress of clinostat rotation could be used to screen the degree of tolerance of the sporophyte to simulated microgravity. The use of male gametophyte selection overcomes the problems generally encountered by sporophytic selection in space especially for woody plants: the large size of plants and their long juvenile phase. In this experiment, pollen collected from just bloomed flowers of Prunus persica, P. avium, P. domestica, Pyrus communis, and Brassica rapa was subjected to tests assessing its viability by techniques such as fluorochromatic reaction. Once pollen viability was ascertained by fluorescence microscopy, pollen was placed on the growth medium in petri dishes both at 1 g and on the clinostat. After incubating for 1 day at room temperature, pollen was observed under a light microscope in order to detect parameters such as the percentage of germination and the growth direction. Then histochemical analyses were performed in order to verify the presence and distribution of nuclei, cytoplasm, and storage substances. Moreover, the presence, size, and morphology of callose plugs were observed. Results showed that the response of gametophytes to simulated microgravity is dependent on the species, some showing altered metabolism, others being unaffected. Correspondence and reprints: Laboratorio di Botanica ed Ecologia Riproduttiva, Dipartimento di Arboricoltura, Botanica e Patologia Vegetale, Università degli Studi di Napoli Federico II, Via Università 100, I 80055 Portici (Naples), Italy.     

The effects of a customized over-the-counter mouth guard on neuromuscular force and power production in trained men and women

Although mouth guards were originally designed for injury prevention, even elite athletes are now using performance mouth guards to improve athletic success. Both expensive custom models and over-the-counter models are available, but the efficacy is not well known. Some athletes remain wary of the perceived potential for detriments using a mouth guard to their performance. Thus, the purpose of this study was to examine various physical performance tests when using a mouth guard including a customized over-the-counter mouth guard. Twenty-six trained men (25 ± 4 years; 1.78 ± 0.07 m; 83.3 ± 11.4 kg) and 24 trained women (23 ± 3 years; 1.65 ± 0.08 m; 62.6 ± 7.8 kg) volunteered for the investigation. The subjects completed a familiarization period and then balanced and randomized treatment conditions that included: (a) a customized Power Balance performance mouth guard (PB MG); (b) a regular over the counter boil-and-bite mouth guard (Reg MG); and (c) a no mouth guard (No MG) treatment condition. At each visit, the subjects completed a testing protocol that was sequenced in the following order: sit-and-reach flexibility, medial-lateral balance, visual reaction time, vertical jump, 10-m sprint, bench throw, and plyo press power quotient (3PQ). Heart rate and rating of perceived exertion (RPE) were recorded around the 3PQ. Significance was set at p ≤ 0.05. Expected significant sex differences existed for all power, strength, and speed variables. Bench throw power (watts) and force (newtons) were significantly higher under PB MG than either Reg MG or No MG or in both men and women. The 3PQ power and force production were higher than that for the other 2 treatments for the PB MG for men only. There were no significant differences for treatment conditions in the heart rate or RPE after the 3PQ test. Men were better able to maintain significantly higher 3PQ power production under PB MG treatment condition compared with the other 2 treatment conditions. Rate of power development was significantly higher in men for the vertical jump when using the PB MG compared with that for other treatment conditions in men only. No differences were observed in flexibility, balance, visual reaction time, or sprint time. The PB MG performance mouth guard improves performance of upper-body loaded power exercises in both men and women and lower body power exercise in men without compromising performance on any other performance parameters.     

Reproducibility of isokinetic leg strength and endurance characteristics of adult men and women

Day-to-day variability and single-measurement reliability of selected isokinetic knee extension-flexion strength and endurance indices were assessed in 10 adult men and 8 adult women. On three occasions separated by at least 5 days, the subjects completed 4 reciprocal maximal voluntary contractions (MVC) at different angular velocities (1.05 rad.s-1 and 3.14 rad.s-1). The men also completed a muscular endurance test consisting of 30 reciprocal, MVC at 3.14 rad.s-1. Coefficient of variation, intra-class correlation coefficient and standard error of single-measurement scores support the continued use of gravity corrected peak torque (PT) and average peak torque (APT) as indices of isokinetic leg strength. Similarly, gravity corrected APT and total work should be the recommended indices of isokinetic leg muscular endurance in men. The results suggest that these isokinetic indices must be assessed using multiple day-to-day trial protocols adequately to describe performance capacity. Composite indices such as the ratio of Knee flexion to extension PT and fatigue measurements offer considerably reduced reliability and a greater potential for misinterpretation. The reliability of knee extension indices generally exceeds that of flexion indices. Similar variability and reproducibility of responses were observed between men and women and between reciprocal contractions performed at angular velocities of 1.05 rad.s-1 and 3.14 rad.s-1.     

Maximal heart rates and plasma lactate concentrations observed in middle-aged men and women during a maximal cycle ergometer test

The purpose of this study was to investigate criteria for maximal effort in middle-aged men and women undertaking a maximal exercise test until they were exhausted if no measurements of oxygen uptake are made. A large group of 2164 men and 975 women, all active in sports and aged between 40 and 65 years, volunteered for a medical examination including a progressive exercise test to exhaustion on a cycle ergometer. In the 3rd min of recovery a venous blood sample was taken to determine the plasma lactate concentration ([la^–]_{p, 3min}). Lactate concentration and maximal heart rate (f _{c, max}) were lower in the women than in the men (P<0.001). Multiple regression analyses were performed to assess the contribution of sex to [la^–]_{p, 3 min}, independent of age and f _c max, It was found that [la^–]_{p,3 min} was about 2.5 mmol·l^–1 lower in women than in men of the same age and f _{c, max}. In our population 88% of the men and 85% of the women met a combination of the following f _{c, max} and [la^–]_{p, 3min} criteria: f _{c, max} equal to or greater than 220 minus age beats·min^–1 and/or [la^–]_{p, 3min} equal to or greater than 8 mmol·l^–1 in the men and f _{c, max} equal to or greater than 220 minus age beats·min^–1 and/or [la^–]_{p, 3min} equal to or greater than 5.5 mmol·1^–1 in the women.     

Induction of three-dimensional assembly and increase in apoptosis of human endothelial cells by simulated microgravity: Impact of vascular endothelial growth factor

Endothelial cells play a crucial role in the pathogenesis of many diseases and are highly sensitive to low gravity conditions. Using a three-dimensional random positioning machine (clinostat) we investigated effects of simulated weightlessness on the human EA.hy926 cell line (4, 12, 24, 48 and 72 h) and addressed the impact of exposure to VEGF (10 ng/ml). Simulated microgravity resulted in an increase in extracellular matrix proteins (ECMP) and altered cytoskeletal components such as microtubules (alpha-tubulin) and intermediate filaments (cytokeratin). Within the initial 4 h, both simulated microgravity and VEGF, alone, enhanced the expression of ECMP (collagen type I, fibronectin, osteopontin, laminin) and flk-1 protein. Synergistic effects between microgravity and VEGF were not seen. After 12 h, microgravity further enhanced all proteins mentioned above. Moreover, clinorotated endothelial cells showed morphological and biochemical signs of apoptosis after 4 h, which were further increased after 72 h. VEGF significantly attenuated apoptosis as demonstrated by DAPI staining, TUNEL flow cytometry and electron microscopy. Caspase-3, Bax, Fas, and 85-kDa apoptosis-related cleavage fragments were clearly reduced by VEGF. After 72 h, most surviving endothelial cells had assembled to three-dimensional tubular structures. Simulated weightlessness induced apoptosis and increased the amount of ECMP. VEGF develops a cell-protective influence on endothelial cells exposed to simulated microgravity.     

Effect of maximal-intensity exercise on systemic nitro-oxidative stress in men and women

Objectives: The aim of this study was to test the hypotheses: (1) there is a negative correlation between protein and lipid oxidative damage following maximal-intensity exercise, and oxygen uptake and work intensity (%VO_2max) at the respiratory compensation point (RCP) in women and men; (2) nitro-oxidative stress following maximal-intensity exercise results from the intensification of anaerobic processes and muscle fibre micro-damage.

Methods: Study participants comprised 20 women (21.34±1.57 years) and 20 men (21.97±1.41 years) who performed a treadmill incremental test (IT); VO_2max: 45.08?±?0.91 and 57.38?±?1.22?mL?kg^?1?min^?1 for women and men, respectively. The oxidized low-density lipoprotein (ox-LDL), 3-nitrotyrosine (3-NT) concentration and creatine kinase (CK) as well as lactate dehydrogenase (LDH) activity were measured in the blood serum, and total antioxidative capacity (TAC) and lactate concentration (Lac) were determined in blood plasma before and after IT.

Results: After the IT, increases in ox-LDL, 3-NT, CK, and LDH were seen in both groups (P?P?P?Conclusions: The gain of ox-LDL and 3-NT following maximal-intensity exercise is independent of VO_2max, oxygen consumption and exercise intensity at RCP. This increase of ox-LDL and 3-NT is indicative of similar lipid and protein damage in women and men. A significant increase in TAC in women following maximal-intensity exercise is the result of muscle fibre micro-injuries.     

肌卫星细胞在失重肌萎缩中的可塑性变化及机制

肌卫星细胞在骨骼肌生长发育和出生后骨骼肌损伤修复中起着重要的作用,但是有关肌萎缩中肌卫星细胞的可塑性变化、作用及其机制尚不清楚.本研究采用小鼠尾悬吊模拟失重效应诱导失重肌萎缩,动态分析了失重肌萎缩发生过程中不同类型肌纤维的肌卫星细胞数量和增殖、分化潜能可塑性的改变,发现在失重肌萎缩过程中,处于安静状态的肌卫星细胞显著增多、激活增殖的肌卫星细胞显著减少,而具有成肌分化潜能的肌卫星细胞有持续减少趋势.此外,在失重肌萎缩比目鱼肌单根肌纤维移出的体外培养中,证明了失重肌萎缩肌纤维肌卫星细胞可塑性降低的特征性变化.进一步,通过对比分析Smad3基因敲除及其同窝野生型小鼠,在失重肌萎缩中肌卫星细胞可塑性的差异性变化,揭示了Smad3在调控失重肌萎缩肌卫星细胞可塑性变化中的关键作用.     

Energy cost of running in similarly trained men and women

The energy demand of running on a treadmill was studied in different groups of trained athletes of both sexes. We have not found any significant differences in the net energy cost (C) during running (expressed in J.kg-1.m-1) between similarly trained groups of men and women. For men and women respectively in adult middle distance runners C = 3.57 +/- 0.15 and 3.65 +/- 0.20, in adult long-distance runners C = 3.63 +/- 0.18 and 3.70 +/- 0.21, in adult canoeists C = 3.82 +/- 0.34 and 3.80 +/- 0.24, in young middle-distance runners C = 3.84 +/- 0.18 and 3.78 +/- 0.26 and in young long-distance runners C = 3.85 +/- 0.12 and 3.80 +/- 0.24. This similarity may be explained by the similar training states of both sexes, resulting from the intense training which did not differ in its relative intensity and frequency between the groups of men and women. A negative relationship was found between the energy cost of running and maximal oxygen uptake (VO2max) expressed relative to body weight (for men r = -0.471, p less than 0.001; for women r = -0.589, p less than 0.001). In contrast, no significant relationship was found in either sex between the energy cost of running and VO2max. We conclude therefore that differences in sports performance between similarly trained men and women are related to differences in VO2max.kg-1. The evaluation of C as an additional characteristic during laboratory tests may help us to ascertain, along with other parameters, not only the effectiveness of the training procedure, but also to evaluate the technique performed.