高原（2260m）女子公路自行车运动员的通气无氧阈、乳酸阈和最大氧耗量的研究

采用实验室递增负荷运动试验和运动现场血乳酸的测定,研究了高原（２２６０ｍ）女子公路自行车运动员的通气无氧阈、乳酸阈及最大氧耗量。结果发现,通气无氧阈时的氧耗量为２．０３ｌ／ｍｉｎ,功率为１３１．４Ｗ;乳酸阈（以运动速度表示）为３３．０ｋｍ／ｈ。通气无氧阈时对应的心率（１３７次／ｍｉｎ）低于乳酸阈的心率（１５３次／ｍｉｎ）。最大氧耗量的绝对值（２．８ｌ／ｍｉｎ）和相对值（４７．４ｍｌ／ｋｇ．ｍｉｎ）分别比平原运动员低２２．２％和２２．９％,但与平原运动员高原训练期间的测试值（２．８ｌ／ｍｉｎ）比较,高原与平原运动员最大氧耗量的差异消失。在相同氧耗量（２．８ｌ／ｍｉｎ）条件下运动时,高原运动员完成的功率（２５１Ｗ）低于平原运动员（２７４Ｗ）。     

Threshold elemental ratios for carbon versus phosphorus limitation in Daphnia

1. The transition from carbon (C) to phosphorus (P) limited growth in Daphnia depends not only on the C : P ratio in seston, i.e. food quality, but also on food quantity. Carbon is commonly believed to be limiting at low food because of the energetic demands of basal metabolism. The critical C : P ratio in seston (otherwise known as the threshold elemental ratio, TER) above which P is limiting would then be high when food is scarce. 2. A new model that differentiates between the C : P requirements for growth and maintenance is presented that includes terms for both C and P in basal metabolism. At low food the calculated TERs for Daphnia of around 230 are only slightly higher than values of 200 or so at high intake. Seston C : P often exceeds 230, particularly in oligotrophic lakes where phytoplankton concentration is low and detritus dominates the diet, indicating the potential for limitation by P. 3. The analysis highlights the importance of P, as well as C, in maintenance metabolism and the overall metabolic budget, such that food quality is of importance even when intake is low. Further measurements of C and P metabolism at low food, in particular basal respiration and excretion rates, are needed in order to improve our understanding of the interacting roles of food quantity and quality in zooplankton nutrition.     

Biokinetic models for representing the complete inhibition of microbial activity at high substrate concentrations.

This paper reintroduces the Wayman and Tseng model for representing substrate inhibition effects on specific growth rate by further documenting its potential predictive capabilities. It also introduces a modification to this model in which an Andrews inhibition function is used in place of the Monod noninhibitory substrate function. This modification better represents the relationship between specific growth rate and substrate concentration for those substrates that show Andrews type inhibition at lower substrate concentrations, rather than the Monod type noninhibitory behavior described in the model of Wayman and Tseng. Results from nonlinear, least squares regression analysis are used to evaluate the ability of these models to empirically represent experimental data (both new and from the literature). The statistical goodness of fit is evaluated by comparing the regression results against those obtained using other empirical models. Finally, possible mechanisms of toxicity responsible for the observed inhibition trends are used to further justify use of these empirical models. The dominant mechanism considered to be relevant for conceptually explaining complete inhibition at high concentrations of solvents is the deterioration of cell membrane integrity. Literature citations are used to support this argument. This work should lead to improvements in the mathematical modeling of contaminant fate and transport in the environment and in the simulation of microbial growth and organic compound biodegradation in engineered systems.     

Failure to obtain a unique threshold on the blood lactate concentration curve during exercise

The purpose of this study was to compare various methods and criteria used to identify the anaerobic threshold (AT), and to correlate the AT obtained with each other and with running performance. Furthermore, a number of additional points throughout the entire range of lactate concentrations [La⁻] were obtained and correlated with performance. A group of 19 runners [mean age 33.7 (SD 9.6) years, height 173 (SD 6.3) cm, body mass 68.3 (SD 5.4) kg, maximal O₂ uptake (V˙O_{2 max} ) 55.2 (SD 5.9) ml · kg⁻¹ · min⁻¹] performed a maximal multistage treadmill test (1 km · h⁻¹ every 3.5 min) with blood sampling at the end of each stage while running. All AT points selected (visual [La⁻], 4 mmol · l⁻¹ [La⁻], 1 mmol · l⁻¹ above baseline, log-log breakpoint, and 45° tangent to the exponential regression) were highly correlated one with another and with performance (r > 0.90) even when there were many differences among the AT (P < 0.05). The additional points (ranging from 3 to 8 mmol · l⁻¹ [La⁻], 1 to 6 mmol · l⁻¹ [La⁻] above the baseline, and 30 to 70° tangent to the exponential curve of [La⁻]) were also highly correlated with performance (r > 0.90). These results failed to demonstrate a distinct AT because many points of the curve provided similar information. Intercorrelations and correlations between AT and performance were, however, reduced when AT were expressed as the percentage of maximal treadmill speed obtained at AT or percentage of V˙O_{2 max} . This would indicate that different attributes of aerobic performance (i.e. maximal aerobic power, running economy and endurance) are measured when manipulating units. Thus, coaches should be aware of these results when they prescribe an intensity for training and concentrate more on the physiological consequences of a chosen [La⁻] rather than on a “threshold”. Accepted: 22 October 1997     

Heart rate deflection compared to 4 mmol?·?l?1 lactate threshold during incremental exercise and to lactate during steady-state exercise on an arm-cranking ergometer in paraplegic athletes

The deflection point (DP) of the heart rate in relation to the work rate (WR) of 8 male endurance-trained paraplegics and 11 male physically active sports students was investigated during nonsteady-state incremental arm cranking ergometry (IT) and compared to the 4 mmol · l⁻¹ blood lactate concentration threshold and to blood lactate concentration in steady-state exercise (SST). Heart rate, and lactate concentration from capillary blood, were determined at rest, during IT and SST. The DP was calculated by linear regression analysis of the heart rate during IT. The SST consisted of three consecutive exercise intensities over a period of 8 min at exercise intensities of 10 W below, and at 10 W above the work rate at deflection point (WR_DP). No difference was found between the paraplegics and non-handicapped subjects regarding heart rate and blood lactate concentration at rest and during exercise. A DP was established in all the paraplegics and in 72.7% of the non-handicapped subjects, but lactate accumulation was observed in 75% of the paraplegics and in 62.5% of the non-handicapped subjects at the lowest intensity of SST. In summary, endurance-trained paraplegics with an injury level below T₅ showed heart rate and blood lactate concentration values comparable to non-handicapped subjects during IT. A linear increase at moderate exercise intensities and a levelling-off at higher to maximal intensities could be identified in all the paraplegics and in 72.7% of non-handicapped subjects. The determination of the anaerobic threshold by DP should be applied with caution, since no causal relationship of DP and the anaerobic threshold was found and the WR_DP tended to overestimate threshold values. Accepted: 9 February 1998     

Assessment of middle-distance running performance in sub-elite young runners using energy cost of running

The purpose of this study was to assess the validity of v _amax as an indicator of middle-distance running performance in sub-elite young runners, _amax being defined as the quotient maximal oxygen uptake (V˙O _2max) divided by the net energy cost of running (C _r) on a treadmill at a submaximal running velocity (280 m · min⁻¹). The V˙O _2max, ventilatory threshold, _amax, and C _r were assessed in 39 young male sub-elite runners having only small variations in performance level. The relationship between each variable and running performance (at 1500 m, 3000 m, and 5000 m) was evaluated. A trend toward a negative correlation existed between C _r and performance although this was not significant. The V˙O _2max and _amax were significantly related to performance. The _amax accounted for around 50% of the variability in performance whereas other physiological variables selected in this study were responsible, at best, for approximately 39%. The results presented in this study suggested that _amax was a useful indicator of middle-distance running performance in sub-elite young runners with similar performance levels as well as in top elite athletes. Accepted: 19 August 1997     

中长跑运动的心血管效应

本研究通过利用彩色多普勒超声心动图对２４例专业中长跑运动员的心脏形态、血液动力学改变及收缩舒张功能参数进行了观察,并与２０例从未参加过正规训练的同龄案牍工作者对照组进行了对比研究,结果显示：中长跑运动员的舒张末期左室内径（ＬＶＤｄ）、左室舒张末容量（ＬＶＥＤＶ）、收缩末容量（ＬＶＥＳＶ）、每搏量（ＳＶ）、左室心肌重量（ＬＶＭ）及左室心肌重量指数（ＬＶＭＩ）均高于对照组（Ｐ＜０．０１）;舒张早期峰值血流速度（ＰＦＶＥｃｍ／ｓ）高于对照组（Ｐ＜０．０１）;舒张晚期峰值血流速度（ＰＦＶＡｃｍ／ｓ）,Ｅ峰面积（Ｅａｒｅａｍ）,舒张早期峰值血流速度与舒张晚期峰值血流速度比（ＰＦＶＥ／ＰＦＶＡ）也高于对照组（Ｐ＜０．０５）。而出现三尖辩肺动脉返流的比例也明显高于对照组（Ｐ＜０．０１）。认为：中长跑运动员不仅心脏形态大小及收缩功能有显著改变,而且在舒张功能也有明显变化     

肺静脉多普勒血流图评价肥厚型心肌病左室舒张功能

为评价肺静脉多普勒血流频谱检测左室舒张功能的价值,我们对２３例正常人和２２例肥厚型心肌病患者进行了研究,结果发现,肥厚型心肌病二尖瓣血流频谱异常者肺静血流谱也能表现异常;在肥厚范围局限的心肌病患者,即使二尖瓣血流频谱正常,肺静脉血流频民可表现异常,特别是ＡＲ峰持续时间和Ｓ波减速时间更有诊断意义,因此用肺静脉血流频率谱评价左室舒张功能不仅交二尖瓣血流图敏感,而且可识别二尖瓣血流图假性正常化,深入研究     

左心室条束的体视学研究

本文用成年人,牛,猪,羊和狗的心脏对左心室条束（亦称假腱索）进行了体视学研究,人与动物左心室暗红色条束的心肌细胞体积密度之间有着非常显著性差别,狗左心室条束的心肌细胞体积密度和表面积密度比左心室壁低,束细胞体积密度低于室间隔,结果表明：左心室条束内含有丰富的传导组织,心肌细胞和毛细血管的表面积密度之间具有密切的正相关关系。