Peak oxygen uptake and maximal power output of Olympic wheelchair-dependent athletes.

To extend the existing data base on the cardiovascular capacity of wheelchair-dependent athletes, a maximum wheelchair exercise test was conducted by 48 athletes (8 females and 40 males) on a motor driven treadmill. Athletes were selected on availability from the representatives of eight different disciplines. For 36 subjects maximal external power was calculated on the basis of a separate drag test. Maximal oxygen uptake (VO2max) for the male population was 2.23 l.min-1 (32.9 ml.kg-1.min-1). Subjects were divided into functional categories according to the International Stoke Mandeville Classification, with one nonambulatory, nonparaplegic group classified as "LA." The LA group displayed the highest values while the class IC tetraplegic showed the lowest performance level. Classified over sports disciplines, male track and field representatives showed the highest VO2max (2.86 l.min-1, 44.9 ml.kg-1.min-1) and target shooting athletes the lowest (1.32 l.min-1, 16.3 ml.kg-2.min-1). Maximal power output was on average 81.1 W for the male population and varied from 65.8 W for class II athletes to 92.2 W for class LA. Between sports values ranged from 96.8 W for basketball players to 48.2 W for the archery representative. These data are useful for setting standards for maximally attainable performance levels in relation to sport, functional classification, or sex and underline the capability of the wheelchair-dependent to improve cardiovascular fitness.     

Maximal oxygen uptake and power of lower limbs during a competitive season in triathletes

BACKGROUND: In order to study the effect of a competitive triathlon season on maximal oxygen uptake (VO2max), aerobic power (AeP) and anaerobic performance (AnP) of the lower limbs, eight triathletes performed exercise tests after: (1) a pre-competition period (Pre-COMP) (2) a competitive period (COMP), and (3) a low (volume and intensity) training period (Post-COMP). The tests were a vertical jump-and-reach test and an incremental exercise test on a cycle ergometer. Ventilatory data were collected every minute during the incremental test with an automated breath-by-breath system and the heart-rate was monitored using a telemetric system. RESULTS: No changes in VO2max were observed, whereas AeP decreased after Post-COMP compared to Pre-COMP and COMP and AnP decreased during COMP compared to Pre-COMP and Post-COMP. In addition, second ventilatory threshold (VT2) and power output at first ventilatory threshold (VT1) and VT2 decreased after Post-COMP. CONCLUSION: This study showed that six weeks of low volume and intensity of training is too long a period to preserve adaptations to training, although a stable maximal oxygen uptake throughout the triathlon season was observed. Moreover, the AnP decrease during COMP was probably in relation with the repetitive nature of the training mode and/or triathlon competitions.     

Faster pulmonary oxygen uptake kinetics in children vs adults due to enhancements in oxygen delivery and extraction

This study aimed to examine if the faster pulmonary oxygen uptake (VO_2p) phase 2 in children could be explained by increased O ₂ availability or extraction at the muscle level. For that purpose, O ₂ availability and extraction were assessed using deoxyhemoglobin (HHb) estimated by near‐infrared spectroscopy during moderate‐intensity constant load cycling exercise in children and young adults. Eleven prepubertal boys and 12 men volunteered to participate in the study. They performed one maximal graded exercise to determine the power associated with the gas exchange threshold (GET) and four constant load exercises at 90% of GET. VO_2p and HHb were continuously monitored. VO_2p, HHb, and estimated capillary blood flow () kinetics were modelled after a time delay and characterized by the time to achieve 63% of the amplitude (τ) and by mean response time (MRT: time delay + τ), respectively. Mean values of τ for VO_2p (P < 0.001), of MRT for HHb (P < 0.01) and of MRT for (P < 0.001) were significantly shorter in children. Faster VO_2p kinetics have been shown in children; these appear due to both faster O ₂ extraction and delivery kinetics as indicated by faster HHb and kinetics, respectively.     

Relationship between the slow component of oxygen uptake and the potential reduction in maximal power output during constant-load exercise.

BACKGROUND: The purpose of the present study was to examine the relationship between the slow component of oxygen uptake (VO2) and muscle fiber fatigue. Maximal power output (MPO) was used as an index of muscle fiber fatigue. METHODS: Two constant exercises were carried out at exercise intensities of 40% and 80% of maximal oxygen uptake (VO2max). Each exercise was repeated three times, once for the measurement for VO2, and the other two times for MPO testing, at 3 and 6 minutes after work output. RESULTS: Reproducibility of MPO at rest was assessed by correlation coefficient. Its value was 0.933. At 40% VO2max, MPO did not significantly decrease from the resting value. At 80% VO2max, MPO significantly decreased by 129+/-77 watts at 3 min and by 178+/-108 watts at 6 min. The VO2 kinetic at 40% VO2 was well described by a monoexponential function with a time constant of 0.432 min. However, at 80% VO2max, a slow component of the form of a linear drift superimposed on a monoexponential function with an essentially equal time constant (0.469 min) was unambiguously detected. This slow component was significantly related to the decrease in MPO (r=0.567). CONCLUSIONS: The present results suggested that the fatigue of muscle fibers may be one of the factors that produce the slow component of VO2 during high intensity exercise.     

A steep ramp test is valid for estimating maximal power and oxygen uptake during a standard ramp test in type 2 diabetes

A short maximal steep ramp test (SRT, 25 W/10 s) has been proposed to guide exercise interventions in type 2 diabetes, but requires validation. This study aims to (a) determine the relationship between W_max and reached during SRT and the standard ramp test (RT); (b) obtain test‐retest reliability; and (c) document electrocardiogram (ECG) abnormalities during SRT. Type 2 diabetes patients (35 men, 26 women) performed a cycle ergometer‐based RT (women 1.2; men 1.8 W/6 s) and SRT on separate days. A random subgroup (n = 42) repeated the SRT. ECG, heart rate, and were monitored. W_max during RT: 193 ± 63 (men) and 106 ± 33 W (women). W_max during SRT: 193 ± 63 (men) and 188 ± 55 W (women). The relationship between RT and SRT was described by men RT (mL/min) = 152 + 7.67 × W_max SRT1 (r: 0.859); women RT (mL/min) = 603 + 4.75 × W_max SRT1 (r: 0.771); intraclass correlation coefficients between first (SRT1) and second SRT W_max (SRT2) were men 0.951 [95% confidence interval (CI) 0.899–0.977] and women 0.908 (95% CI 0.727–0.971). No adverse events were noted during any of the exercise tests. This validation study indicates that the SRT is a low‐risk, accurate, and reliable test to estimate maximal aerobic capacity during the RT to design exercise interventions in type 2 diabetes patients.     

Effects of Hemopure on maximal oxygen uptake and endurance performance in healthy humans

Haemoglobin-based oxygen carriers (HBOCs) such as Hemopure are touted as a tenable substitute for red blood cells and therefore potential doping agents, although the mechanisms of oxygen transport of HBOCs are incompletely understood. We investigated whether infusion of Hemopure increased maximal oxygen uptake (V.O 2max) and endurance performance in healthy subjects. Twelve male subjects performed two 4-minute submaximal exercise bouts equivalent to 60 % and 75 % of V.O (2max) on a cycle ergometer, followed by a ramped incremental protocol to elicit V.O (2max). A crossover design tested the effect of infusing either 30 g (6 subjects) or 45 g (6 subjects) of Hemopure versus a placebo. Under our study conditions, Hemopure did not increase V.O (2max) nor endurance performance. However, the infusion of Hemopure caused a decrease in heart rate of approximately 10 bpm (p=0.009) and an average increase in mean ( approximately 7 mmHg) and diastolic blood pressure ( approximately 8 mmHg) (p=0.046) at submaximal and maximal exercise intensities. Infusion of Hemopure did not bestow the same physiological advantages generally associated with infusion of red blood cells. It is conceivable that under exercise conditions, the hypertensive effects of Hemopure counter the performance-enhancing effect of improved blood oxygen carrying capacity.     

Self‐rated physical fitness and estimated maximal oxygen uptake in relation to all‐cause and cause‐specific mortality

This study investigated the longitudinal associations of self‐rated physical fitness and estimated maximal oxygen uptake (VO2max) with all‐cause and cause‐specific mortality. A total of 59 741 participants in the Finnish National FINRISK Study Cohort had data on self‐rated physical fitness and covariates. A subsample of 4823 participants had estimated VO2max data. Follow‐up ranged from 3 to 38 years. Associations of self‐rated physical fitness and VO2max with mortality were analyzed using multivariate Cox proportional hazard models. The study showed that poor self‐rated physical fitness was related to all‐cause mortality (hazard ratio [HR] 1.9; 95% confidence interval [CI] 1.8‐2.0) and mortality due to cardiovascular (HR 2.0, 95% CI 1.9‐2.2), cerebrovascular (HR 1.9, 95% CI 1.6‐2.2) and respiratory diseases (HR 2.1, 95% CI 1.9‐2.4), trauma (HR 1.7, 95% CI 1.3‐2.0), infections (HR 1.8, 95% CI 1.3‐2.7), dementia (HR 1.9, 95% CI 1.6‐2.3), and cancer (HR 1.7, 95% CI 1.5‐1.9). Coexisting higher age, physical inactivity, male gender, and severe chronic conditions further increased the risk. In men, higher VO2max was associated with a lower risk of lung cancer mortality (HR 0.8, 95% CI 0.7‐0.96). Based on the results, s elf‐rated physical fitness reflects a combination of unfavorable biological and lifestyle‐related factors, which increase mortality risk. A simple question about perceived physical fitness may reveal at‐risk individuals who would benefit from more intensive treatment of chronic conditions and other interventions aiming to promote better fitness and well‐being.     

Effect of beta2‐adrenergic agonist and resistance training on maximal oxygen uptake and muscle oxidative enzymes in men

While beta₂‐adrenoceptor stimulation has been shown to increase lean mass and to alter metabolic properties of skeletal muscle, adaptations in muscle oxidative enzymes and maximal oxygen uptake (O_2max) in response to beta₂‐adrenergic agonist treatment are inadequately explored in humans, particularly in association with resistance training. Herein, we investigated beta₂‐adrenergic‐induced changes in O_2max, leg and arm composition, and muscle content of oxidative enzymes in response to treatment with the selective beta₂‐adrenergic agonist terbutaline with and without concurrent resistance training in young men. Forty‐six subjects were randomized to 4 weeks of lifestyle maintenance (n = 23) or resistance training (n = 23). Within the lifestyle maintenance and resistance training group, subjects received daily terbutaline (8 × 0.5 mg) (n = 13) or placebo (n = 10) treatment. No apparent treatment by training interactions was observed during the study period. Terbutaline increased leg and arm lean mass with the intervention, whereas no treatment differences were observed in absolute O_2max and incremental peak power output (iPPO). Treatment main effects were observed for O₂‐reserve (P < .05), O_2max relative to body mass (P < .05), O_2max relative to leg lean mass (P < .01), and iPPO relative to leg lean mass, in which terbutaline had a negative effect compared with placebo. Furthermore, content of electron transport chain complex I‐V decreased by 11% (P < .05) for terbutaline compared with placebo. Accordingly, chronic treatment with the selective beta₂‐adrenergic agonist terbutaline may negatively affect O_2max and iPPO in relative terms, but not in absolute.     

俯卧位对不同类型手术病人全身麻醉机械通气下肺顺应性的影响

目的观察俯卧位对全身麻醉机械通气下不同手术类型病人肺顺应性的影响。方法选择择期行脊柱手术患者53例(其中脊柱侧弯手术病人20例,脊柱普通手术病人33例)。麻醉诱导气管插管后,间歇正压通气模式机械呼吸,潮气量6～10 ml/kg,呼吸频率12次/min。术前仰卧位通气10 min后改为手术俯卧位通气10min,分别经麻醉机采集不同潮气量时压力-容积曲线,计算肺顺应性。结果全身麻醉机械通气下,脊柱侧弯手术病人术前仰卧位肺顺应性为(33.6±10.0)ml/cmH2O,术前俯卧位的肺顺应性降低为(28.2±8.6)ml/cmH2O,术前仰卧位与俯卧位的肺顺应性之间差异有统计学意义(P<0.05);普通手术组病人术前仰卧位肺顺应性为(40.2±9.1)ml/cmH2O,其术前俯卧位肺顺应性降低为(36.1±4.2)ml/cmH2O,差异有统计学意义(P<0.05)。结论俯卧位时全身麻醉机械通气下手术病人的肺顺应性下降。     

温泉游泳训练对飞行员心肺功能影响的研究

目的探讨温泉自然因子和游泳训练对飞行员心肺功能指标的影响。方法 24名现役飞行员连续20 d室内温泉游泳训练,并采集训练前后心肺功能指标。结果游泳训练20 d后飞行员每搏输出量(SV)和射血分数(EF)均显著增加(P<0.01),心率(HR)显著降低(P<0.01)。用力肺活量(FVC)、最大自然换气量(MVV)、呼出峰值流量(PEF)、慢吸气肺活量(IVC)、慢呼出肺活量(VC)均有显著增加(P<0.01)。结论温泉游泳锻炼可提高心功能及肺活量,但对小气道功能的改变不明显。     

siRNA沉默EPAS1基因对低氧条件下大鼠PASMCs增殖的影响

目的 探讨应用siRNA技术沉默EPAS1 (HIF-2α)基因表达对低氧条件下培养的大鼠肺动脉平滑肌细胞(PASMCs)增殖的影响.方法 原代培养大鼠PASMCs共采用免疫荧光法进行鉴定.构建特异性EPAS1 siRNA脂质体,转染PASMCs,从3个干扰靶点中选取效果最好的靶点进行干扰;在常氧(37℃、5％CO2、20％O2)和低氧(37℃、5％CO2、2％O2)条件下分别培养24、48、72h,采用Western blotting检测PASMCs中EPAS1、VEGF蛋白的表达水平,CCK-8法检测细胞增殖情况.结果 成功分离培养原代大鼠PASMCs并经免疫荧光鉴定证实.将特异性的EPAS1 siRNA脂质体转染到PASMCs,选择干扰效果最好的靶点2进行干扰.与常氧条件比较,低氧条件下PASMCs中VEGF蛋白的表达及细胞增殖水平均明显升高;沉默EPAS1后,无论低氧还是常氧条件下,PASMCs中VEGF蛋白的表达及细胞增殖水平均明显降低.结论 EPAS1基因参与了低氧条件下大鼠PASMCs增殖的调控,其调节可能是通过VEGF介导完成的.     

机械通气在高龄低肺功能食管癌患者术后的临床应用

目的探讨机械通气在高龄肺功能低下食管癌术后的应用价值。方法选取56例术前肺功能(MVV≤50%和FEV1/FVC>45%)低下的食管癌患者,年龄(72.3±4.1)岁。其中术后行呼吸机辅助呼吸的37例为A组;术后常规治疗,未行呼吸机辅助呼吸的19例为B组。观察两组患者血氧饱和度、心律失常、动脉血气以及住院时间等情况。结果两组患者均无死亡病例。A组中脉搏血氧饱和度(97.6±1.4)%,心律失常发生率29.7%(11/37),呼吸机辅助呼吸时间(33.2±5.4)h,术后住院时间(7.6±2.3)d;B组中脉搏血氧饱和度(92.4±1.2)%,心律失常发生率47.4%(9/19),术后住院时间(10.1±3.1)d,其中2例因血氧饱和度降至80%,立刻行呼吸机辅助呼吸;两组术后血气的变化差异有统计学意义。结论对于肺功能低下的食管癌手术患者,应用机械通气辅助呼吸可扩大手术适应证,减少术后并发症。     

Relationship between vertical jump and maximal power output of legs and arms: Effects of ethnicity and sport

The hypothesis that ethnicity and sport practice influence the relationship between maximal power in cycling (P_max) and countermovement jump (CMJ) has been studied by relating CMJ and P_max in two groups (volleyball players, VB, and physical education students, PES) including subjects with Caucasian (67 C) or West African (39 WA) origins. Maximal power of the arms (P_max Arms) was also measured. A two‐way analysis of variance (groups × ethnicity) showed significant effects of both factors upon CMJ, which was higher in WA and VB, P = 0.002 and P < 0.001, respectively. Within WA, CMJ was significantly higher in VB (0.732 ± 0.057 m) than in PES (0.661 ± 0.082 m), although there was no difference in P_max (14.7 ± 1.7 vs 14.7 ± 1.9 W/kg). CMJ was significantly higher in WA (0.69 ± 0.08 vs 0.65 ± 0.09 m in C, P = 0.002) without significant interethnic difference in P_max (14.7 ± 1.8 in WA, and 14.8 ± 1.9 W/kg in C). The CMJ–P_max relationships were different in C and WA (P = 0.003). Therefore, CMJ predicted from P_max would be underestimated in WA. The same difference was observed for the relationship between CMJ and P_max Arms. These results were confirmed by the comparison with previous P_max–CMJ relationship in the literature, collected in Caucasian and African subjects with the same protocols.     

氧烛对缺氧性肺动脉高压青年血氧饱和度与心率的影响

目的在高海拔地区(5 200 m)利用氧烛建立富氧室观察对缺氧性肺动脉高压移居青年血氧饱和度(SaO2)及心率(HR)的影响。为防治高原缺氧性肺动脉高压,减少高原移居者急慢性高原病的发生,寻觅新的方法和途径。方法选择驻守在海拔5 200 m以上地区1年、经超声心动图和心电图检测拟诊为肺动脉高压的8名受试者在该海拔夜间睡眠时,分别监测常氧和富氧(氧浓度为24%～25%)条件下的SaO2和HR。结果富氧较常氧条件下SaO2增高,有统计学差异(P<0.01);富氧较常氧下HR降低,有统计学差异(P<0.01)。结论用氧烛制作富氧室可显著改善低氧环境条件下肺的氧合效率、提高动脉血氧饱和度,降低心率,从而使人体缺氧状态得以充分改善。     

有氧运动对单纯性肥胖小学生肺通气功能和心电图的影响

目的:探讨有氧运动对单纯性肥胖小学生肺通气功能和心电活动的影响。方法:选择10～11岁单纯性肥胖男生30人,进行12周有氧运动,每周4次,每次40min,并于实验前后对受试者身体成分、肺通气功能和心电图进行观察分析。结果:12周有氧运动后体脂肪量(FM)和体脂肪百分率(BF)均显著下降(P<0.05),去脂肪量(FFM)显著增加(P<0.05),腰/臀围比(WHR)有所下降但无统计学意义;肺通气功能指标中,每分最大通气量(MVV)、用力呼吸第一秒钟呼气量(FEV1)、50%肺活量时的单位身高呼气流速(V50/Ht)和单位身高呼气高峰流速(PEFR)等指标实验后明显升高,与实验前比较差异均有统计学意义(P<0.05,P<0.01);心电图指标中,与实验前比较,QT离散度(QTd)和校正QT离散度(QTcd)均显著减小(P<0.05,P<0.01)。结论:有氧运动可以改善肥胖小学生肺通气功能,对心电活动状态具有良性调节作用。     

高频喷射通气对兔海水淹溺肺水肿时肺CYTO与血PaO_2和SO_2的影响

目的　探讨高频喷射通气（ＨＦＪＶ）对海水淹溺肺水肿（ＰＥ－ＳＷＤ）兔肺毛细血管内皮细胞的细胞色素氧化酶（ＣＹＴＯ）、动脉血氧分压（ＰａＯ２ ）和血氧饱和度（ＳＯ２ ）的影响及其机制。方法　复制兔ＰＥ－ＳＷＤ模型,用细胞化学和图像定量分析法测定兔肺ＣＹＴＯ 活性,血气分析仪测定ＰａＯ２ 和ＳＯ２。结果　通气组ＣＹＴＯ 活性、ＰａＯ２ 和ＳＯ２ 比未通气组有明显升高（Ｐ＜ ０．０１ 或Ｐ＜ ０．０５）,但未恢复到海水淹溺前水平。结论　ＨＦＪＶ 改善肺泡通气功能,提高ＰａＯ２ 和ＳＯ２ ,改善低氧血症,恢复ＣＹＴＯ活性,减轻细胞水肿,减轻或延缓肺不张,改善肺换气功能。同时,ＣＹＴＯ活性的恢复,又有利于肺换气功能和通气功能的改善。