Metabolic and ventilatory responses during very low level exercise

1. Nine male and six female healthy subjects were studied during supine bicycle exercise at workloads of 12 and 37 W; pedalling rates varied between 30 and 50 cycles/min at each workload. Measurements were made of oxygen consumption (VO2), carbon dioxide production (VCO2), minute ventilation (VE), tidal volume (VT), respiratory frequency (fR), inspiratory and expiratory time (TI, TE) and mean inspiratory flow (VT/TI) using a non-invasive canopy-computer-spirometer system. 2. At rest, males had greater values of VE, VT, TI, inspiratory duty cycle (TI/TTOT), VCO2 and VO2, and a lower fR, than females. 3. At the lower workload, VO2, VCO2, VE, VT and VT/TI increased linearly with increasing pedalling rate, whereas at the higher workload there was a decrease in VO2 and little or no change in ventilatory parameters from 30 to 50 cycles/min except for an increase in fR in females. 4. While performing supine exercise, there was an effect of pedalling rate on ventilatory and metabolic parameters at the low workload (12 W) which diminished at the higher workload (37 W). An increase in pedalling rate appears to enhance efficiency at these low workloads. 5. Differences between the sexes during exercise generally include: (a) a higher breathing frequency, (b) a greater mechanical efficiency, and (c) lower ventilatory equivalents of O2 and CO2 (VE/VO2 and VE/VCO2) during the higher workload in females than males.     

Target-flow inspiratory muscle training: breathing patterns and metabolic costs.

In target-flow inspiratory muscle training (TF-IMT), the generated inspiratory mouth pressure and the duration of the inspiration and expiration are standardized to given an adequate training stimulus to the inspiratory muscles. The acute effects of TF-IMT on the efficiency of breathing were studied in a group of 12 COPD patients with a ventilatory limitation of their exercise capacity (mean age 58, mean FEV1 46.2% of predicted) and in 15 normal subjects (mean age 30). Also, the effect of a 10 week period of TF-IMT on the maximal inspiratory mouth pressure (PImax) in the COPD patients was measured. After an unloaded baseline period, the subjects started to inspire through a target-flow device during 15 min, followed by a recovery phase of 5 min. During TF-IMT minute ventilation (VE) decreased only in the COPD group. The ventilatory equivalent for O2 (VE/VO2) and the dead space to tidal volume ratio (VD/VT) decreased in both groups. During recovery, VE, VE/VO2 and VD/VT remained below baseline values in the COPD group, but not in the control group. PCO2 and lactate concentrations did not change during TF-IMT. After the 10 week training period, PImax [means) (SD] increased from 5.7(2.2) to 8.2(2.7) kPa (p less than 0.05). The results indicate that with standardized TF-IMT, the inspiratory muscles can be trained effectively in COPD patients with a ventilatory limitation. The persistence of the decrease in VE, VE/VO2 and VD/VT after a training session may be an additional beneficial effect of TF-IMT.     

Comparison between arm and leg exercise in women and men.

Arm and leg work was performed on bicycle ergometers in sitting position by fourteen women and sixteen men. Heart rate, minute volume of ventilation (VE), and oxygen consumption (VO2) were measured. Arm exercise was performed until (muscular) exhaustion, leg exercise up to a heart rate of circa 170 beats/min. At comparable work loads arm exercise evoked higher VO2, VE, and heart rate than leg exercise irrespective of sex. At comparable VO2, the heart rate and VE were higher during arm work in both sexes, VE more so among the men. With the same limbs working, the mechanical efficiency was equal in both sexes. The regression coefficients of heart rate on load or VO2 was higher for the women irrespective of work type. A close correlation was obtained between working capacity at a heart rate of 170 beats/min (W170) during leg and arm exercise and between W170 of leg exercise and W150, similarly calculated during arm work. Thus W170 of leg exercise could be calculated from either a maximal or submaximal arm work.     

Effect of exercise intensity on oxygen consumption kinetics in non-exercising muscle during exercise

This study examined the effect of exercise intensity on the kinetics of muscle oxygen consumption in non-exercising forearm flexor muscles (VO(2mf)) during exercise. Seven healthy male subjects performed cycling exercise for 60 min at 30% of maximal oxygen consumption (%VO(2max)) and 30 min at 50% VO(2max) on separate days. The VO(2mf) values at rest and during exercise were measured by near-infrared spectroscopy. The VO(2mf) at 30% VO(2max) significantly increased to 1·2 ± 0·1-fold over resting value at 20 min after the beginning of exercise (P<0·05) and remained constant within 1·2- to 1·3-fold over resting value until 60 min during exercise. The VO(2mf) at 50% VO(2max) significantly increased to 1·2 ± 0·1-fold over resting value at 15 min after the beginning of exercise (P<0·05). Subsequently, the VO(2mf) at 50% VO(2max) increased with time to 1·3 ± 0·1-fold over resting value at 20 min after the beginning of exercise and to 1·5 ± 0·2-fold over resting value at 30 min. The VO(2mf) 15-30 min of exercise at 50% VO(2max) was significantly higher than that at 30% VO(2max) (P<0·05). These data suggest that the increase in VO(2mf) has a time lag from the beginning of exercise, and the kinetics of VO(2mf) during exercise differs with exercise intensity. Therefore, we conclude that the kinetics of VO(2mf) during exercise is dependent on exercise intensity.     

老年隐性高血压患者中心动脉压及增强指数与脉搏波传导速度的相关性

目的探讨老年隐性高血压(MH)患者中心动脉压(CAP)及增强指数(AI)与脉搏波传导速度(PWV)的相关性,为完善老年MH患者的诊疗方案提供参考。方法选择健康体检人群170例,根据《中国高血压防治指南》将其分为高血压组55例、MH组50例、对照组(血压正常)65例。观察比较三组受检者一般资料、动态血压及偶测血压情况、颈-桡动脉PWV与CAP参数。结果 MH组饮酒、吸烟、低密度脂蛋白胆固醇(LDL-C)及空腹血糖显著高于对照组(P<0.05)。MH组偶测舒张压与收缩压高于高血压组(P<0.05)。MH组颈-桡动脉PWV、AI、血压第一峰值与最小血压差(P1 Height)、增强压、收缩末压(CESP)、平均舒张压(CMDP)、平均收缩压(CMSP)、脉压(CPP)、舒张压(DBP)、收缩压(SBP)显著高于对照组(P<0.05)。颈-桡动脉PWV与LDL-C、CPP与SBP、体质量指数、TC、年龄、空腹血糖、DBP、P1 Height、CESP、AI及增强压呈正相关(P<0.05)。LDL-C、CPP及SBP为颈-桡动脉PWV的主要影响因素。结论老年MH患者CAP明显高于血压正常者,PWV明显升高。LDL-C、CPP及SBP增高为颈-桡动脉PWV的危险因素。     

个体化适度运动改善肺动脉高压患者心肺功能的效果

目的 分析病情稳定的肺动脉高压(PAH)患者心肺功能状况,探讨运用心肺运动试验(CEPT)精准制定个体化适度运动处方对PAH患者心肺功能储备及运动耐量的影响。方法 2018年4月至2019年7月,纳入病情稳定的PAH患者(PAH组,n= 31)和体检正常的健康人(正常组n = 32),入组前均进行CPET。PAH组行6分钟步行试验(6MWT)后,随机分为运动康复组(n = 16)和对照组(n = 15),运动康复组在规范靶向药物治疗的基础上进行个体化适度运动训练,每周5 d,共8周。对照组仅进行常规靶向药物治疗。治疗后两组再次行CPET和6MWT。结果 治疗前,与正常组相比,PAH组体质量、体质量指数(BMI)、用力肺活量(FVC)、第一秒用力呼气容积(FEV₁)、最大通气量(MVV)、无氧阈(AT)、峰值心率(HRpeak)、峰值收缩压(SBPpeak)、峰值负荷功率(WRpeak)、峰值摄氧量(VO₂peak)、峰值氧脉搏(VO₂/HRpeak)、峰值心排量(COpeak)、峰值分钟通气量(VEpeak)、峰值潮气末二氧化碳分压(P_ETCO₂peak)、峰值脉氧饱和度(SpO₂peak)、摄氧通气效率峰值平台(OUEP)均降低(t > 2.419, P < 0.05);静息心率(HRrest)、峰值生理无效腔与潮气量比值(V _D/V_Tpeak)、二氧化碳排出通气效率最低值(Lowest VE/VCO₂)、二氧化碳排出通气斜率(VE/VCO₂slope)均升高(|t| > 2.615, P< 0.05)。治疗后,对照组FEV₁、MVV、峰值千克摄氧量[VO₂peak (ml/min/kg)]、VO₂/HRpeak降低(t > 2.272, P < 0.05);运动康复组FVC、FEV ₁、MVV、AT、SBPpeak、WRpeak、VO₂peak、VO₂/HRpeak、COpeak、VEpeak、P_ETCO₂peak、SpO₂peak和6分钟步行距离(6MWD)升高(|t| >2.167,P < 0.05),Lowest VE/VCO ₂、VE/VCO₂slope降低(t > 2.264, P < 0.05)。与对照组相比,运动康复组FEV ₁/FVC、AT、WRpeak、VO₂peak、VO₂/HRpeak、COpeak、6MWD升高(|t| >2.168, P < 0.05)。 结论 病情稳定的PAH患者整体心肺功能较正常人仍有降低。CPET精准指导的个体化适度运动处方可以有效改善PAH患者的心肺功能储备,提高PAH患者的运动耐量。     

Exercise during gravity inversion: acute and chronic effects

The purpose of this study was to determine whether gravity inversion could correctly be called an exercise, and whether inversion and inverted exercise produced safe blood pressure responses. Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and oxygen consumption (VO2) were measured in 19 healthy young men (means = 20.31 years) in seven positions: (1) standing passive (STD), (2) inverted passive (INV), (3) standing recovery postpassive inversion (SRPI), (4) standing exercise (SDE), (5) standing recovery poststanding exercise (SRPSE), (6) inverted exercise (INVE), and (7) inverted recovery postinverted exercise (IRPIE). Ten of the subjects participated in a five-week inversion training program, after which all 19 subjects were retested. Compared to STD, INV elicited significant increases in SBP/DBP and a significant decrease in HR. The average INV blood pressure was 146/97 mmHg, which was further increased during INVE to 158/101 mmHg. These responses increase the workload of the heart and may be dangerous to some populations. No physiologic adaptations occurred in any of the inverted positions as a result of inversion training. Gravity inversion should not be compared to or classified as an exercise. Some previously suggested inverted exercises are not recommended. Because of the nature of the responses, medical screening before the use of inversion devices is critical.     

The effect of varied fractional inspired oxygen on arm exercise performance in spinal cord injury and able-bodied persons

OBJECTIVE: To examine the effect of different levels of fractional inspired oxygen (FiO(2)) (15%, 21%, 50%) on peak oxygen consumption (VO(2)peak) during arm exercise in persons with spinal cord injury and in able-bodied controls. DESIGN: Case-control study. SETTING: University medical center in the Netherlands. PARTICIPANTS: Ten able-bodied controls, 6 persons with paraplegia, and 6 persons with tetraplegia. INTERVENTIONS: Inspiration of 15%, 21%, and 50% oxygen during a 15-minute period before and during arm exercise. MAIN OUTCOME MEASURES: Oxygen uptake (VO(2)peak, VO(2)peak/kg), power output, ventilation, and base excess. RESULTS: In the able-bodied controls, significant FiO(2) dependency was seen in power output, VO(2)peak, and VO(2)peak/kg. Persons with paraplegia showed significant FiO(2) dependency in VO(2) and VO(2)/kg. In persons with tetraplegia, no FiO(2) dependency was observed; however, VO(2) and VO(2)/kg were significantly higher at 50% than at 15% FiO(2). Ventilation and base excess did not change in able-bodied controls or in persons with paraplegia with different levels of FiO(2). In persons with tetraplegia, ventilation was significantly higher at 15% than at 50% FiO(2), and base excess did not change. No significant interactions between groups and FiO(2) were observed. CONCLUSIONS: Oxygen consumption during peak arm-cranking exercise is enhanced with an increased inspiratory oxygen fraction in able-bodied controls as well as in persons with paraplegia and to a lesser extent in persons with tetraplegia, indicating that peak oxygen consumption during arm exercise is limited by oxygen supply rather than by the small muscle mass and related biochemical limitations.     

Acute and long-term effect of antihypertensive treatment on exercise-induced albuminuria in incipient diabetic nephropathy

The aim of the study was to clarify whether antihypertensive treatment could affect the systolic blood pressure (SBP) and urinary albumin excretion (UAE) in diabetics during exercise (450 kpm/min, followed by 600 kpm/min, 20 min each). Young male insulin-dependent diabetics with normal UAE (n = 9) and diabetics with incipient nephropathy (n = 7) were examined in an acute study. Five patients with incipient diabetic nephropathy participated in a long-term study. Incipient diabetic nephropathy is defined as persistently elevated UAE (greater than 15 micrograms/min), but no clinical proteinuria. In the acute study, using placebo/metoprolol 10 mg i.v. in patients with normal UAE, the maximal SBP at 600 kpm/min was reduced by 17 mmHg +/- 10 (SD) (2p less than 1.0%) and the maximal SBP at 600 kpm/min in the patients with incipient nephropathy was reduced by 15 mmHg +/- 11 (SD) (2p less than 1.0%). However, no difference was observed in UAE, in patients with normal UAE or those with incipient nephropathy. Five of the patients with incipient nephropathy were followed with repeated exercise tests before and during 2.6 years of antihypertensive treatment, using metoprolol 200 mg/24 h and subsequently also hydroflumethiazid 25 mg/24 h. The maximal SBP at 600 kpm/min at the end of the study compared to the pretreatment level was reduced by 38 mmHg +/- 12 (SD) (2p less than 1.0%), and furthermore the exercise-induced elevated UAE was reduced by 61% +/- 29 (SD) (2p = 2.0%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of ventilator resetting on indirect calorimetry measurement in the critically ill surgical patient

OBJECTIVE: To evaluate the effect of acute changes in minute ventilation (VE) on oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory quotient, and energy expenditure during volume-controlled mechanical ventilation in the critically ill surgical patient. The effects on some oxygen transport variables were assessed as well. DESIGN: Prospective, randomized clinical study SETTING: Adult surgical intensive care unit of a university teaching hospital. PATIENTS: Twenty adult critically ill surgical patients were studied during volume-controlled mechanical ventilation. INTERVENTIONS: After a basal period of stability (no changes over time in body temperature, energy expenditure, blood gases, acid-base status, cardiac output, and ventilatory parameters), VE was then randomly either increased or reduced (+/-35%) by a change in tidal volume (VT), while respiratory rate and inspiratory/expiratory ratio were kept constant. Settings were then maintained for 120 mins. During the study, patients were sedated and paralyzed. MEASUREMENTS AND MAIN RESULTS: VO2, VCO2, and respiratory quotient were measured continuously by a Nellcor Puritan Bennett 7250 metabolic monitor (Nellcor Puritan Bennett, Carlsbad, CA). Hemodynamic and oxygen transport parameters were obtained every 15 mins during the study. Despite large changes in VE, VO2 and energy expenditure did not change significantly either in the increased or in the reduced VE groups. After 15 mins, VCO2 and respiratory quotient changed significantly after ventilator resetting. VCO2 increased by 10.5 +/- 1.1% (from 2.5 +/- 0.10 to 2.8 +/- 0.12 mL/min/kg, p< .01) in the increased VE group and decreased by 12.4 +/- 2.1% (from 2.7 +/- 0.17 to 2.4 +/- 0.16 mL/min/kg, p< .01) in the reduced VE group. Similarly, respiratory quotient increased by 16.2% +/- 2.2% (from 0.87 +/- 0.02 to 1.02 +/- 0.02, p< .01) and decreased by 17.2% +/- 1.8% (from 0.88 +/- 0.02 to 0.73 +/- 0.02, p< .01). VCO2 normalized in the reduced VE group, but remained higher than baseline in the increased VE group. Respiratory quotient did not normalize in both groups and remained significantly different from baseline at the end of the study. Cardiac index, oxygen delivery, and mixed venous oxygen saturation increased, while oxygen extraction index decreased significantly in the reduced VE group. Neither of the mentioned parameters changed significantly in the increased VE group. CONCLUSIONS: We conclude that, during controlled mechanical ventilation, the time course and the magnitude of the effect on gas exchange and energy expenditure measurements caused by acute changes in VE suggest that VO2 and energy expenditure measurements can be used reliably to evaluate and quantify metabolic events and that VCO2 and respiratory quotient measurements are useless for metabolic purposes at least for 120 mins after ventilator resetting.     

Effects of graduated compression stockings on blood lactate following an exhaustive bout of exercise

To determine the effects of wearing graduated compression stockings (GCS) on the exercise response, twelve high fit males served as subjects in a series of two experiments. The first experiment consisted of six subjects performing two tests of maximal oxygen consumption (VO2 max) on a treadmill with and without GCS. The second experiment consisted of six subjects performing three separate three minute tests on a bicycle ergometer at 110% of their VO2 max. The experimental conditions for the three tests were: GCS worn during the test and recovery (GCS), GCS worn only during the test (GCS-O/O) and no stockings worn during either the test or recovery (NO-GCS). Oxygen consumption (VO2) was measured at rest, throughout the duration of all tests and during recovery in both experiments. Blood samples were obtained at rest and at 5, 15, 30, 45 and 60 minutes post exercise in the first experiment and at rest and at 5, 15 and 30 minutes post exercise in the second experiment for the determination of lactate and hematocrit. The use of GCS in the first experiment resulted in no significant difference in VO2 max, recovery VO2 or plasma volume shifts. Lactate values were lower throughout the duration of the recovery period with the 15 minute values being significantly different with the use of GCS. Significant differences in post exercise blood lactate values were found in the second experiment. The GCS trial resulted in significantly less lactate when compared to the GCS-O/O and the NO-GCS trials. There was no significant difference in post exercise lactate values between the NO-GCS and the GCS-O/O trials. Plasma volume changes were not significantly different among trials. Results of both experiments showed recovery lactate values to be lower with the use of GCS. These lower values are not ascribable to plasma volume shifts but rather appear to be due to an inverse gradient created by the GCS resulting in the lactate being retained in the muscular bed.     

Functional electrical stimulation leg cycle ergometer exercise: training effects on cardiorespiratory responses of spinal cord injured subjects at rest and during submaximal exercise.

This study investigated the cardiorespiratory (CR) responses at rest and during submaximal (0-W) functional electrical stimulation (FES)-induced leg cycle ergometer (LCE) exercise prior to and following a progressive intensity FES-LCEa exercise training program in spinal cord injured (SCI) subjects. Seven quadriplegics and six paraplegics participated in FES-LCE training three sessions per week for approximately 12 weeks (36 sessions). Monitored CR responses, including oxygen uptake (VO2), pulmonary ventilation (VE), respiratory exchange ratio (RER), arteriovenous O2 difference (a-vO2), blood pressure (BP), heart rate (HR), stroke volume (SV), total peripheral resistance (TPR), and cardiac output (Q), were determined before and after training. Power output (PO) increased significantly (p < .05) over the duration of the training program, indicating increased in strength and endurance of the paralyzed muscles used. Respiratory responses were not significantly altered by training in both groups. FES-LCE training significantly increased resting HR and SBP in quadriplegics and lowered SBP, DBP, and MAP in paraplegics. In both groups, HR and BP during submaximal exercise significantly decreased and SV and Q significantly increased after completion of the training program. These results suggest that FES-LCE training improves peripheral muscular and central cardiovascular fitness in SCI subjects. Posttraining HR and BP may also be more stable in quadriplegics and alleviate hypotension. This therapeutic exercise may ultimately lead to improved rehabilitation outcome and reduced stress during activities of daily living, and possibly reduce the risks for secondary CR disabilities.     

Significance of post-exercise increment of urinary bicarbonate and pH in subjects loaded with submaximal cycling exercise

We studied the changes in urinary bicarbonate, urinary pH and some physical parameters such as minute ventilation (VE), oxygen consumption (VO2), respiratory carbon dioxide (VCO2), heart rate, blood pressure, and blood lactate, before and after the submaximal exercise. Six male subjects aged 28-33 years were involved in the study. They performed the incremental exercise test using a bicycle ergometer until exhaustion. Levels of VE, VO2, VCO2, heart rate, and blood pressure increased continuously with an increase in cycling intensity. These parameters markedly decreased and reached the baseline levels within 5-10 minutes after the termination of exercise. According to an increase in cycling intensity, blood lactate increased continuously during exercise, but after termination of exercise the return of lactate to the baseline level was markedly retarded. Urinary bicarbonate and pH were within the range of those at 0 time (baseline levels) from the beginning until 30 minutes after the exercise. However, they began to increase abruptly about 30 minutes after the exercise, and continued to increase extensively for 2 hours thereafter. Such marked increase in urinary bicarbonate and pH seemed to be correlated with the aerobic metabolism of lactate in the muscles, liver, and kidney, finally producing CO2. It was also suggested that the measurement of urinary bicarbonate and pH may be useful for the estimation of physiological changes in the body after submaximal incremental cycling exercise loading.     

Similar hypotensive effects of combined aerobic and resistance exercise with 1 set versus 3 sets in women with metabolic syndrome

The aim of the present study was to compare the response of systolic blood pressure (SBP), mean blood pressure (MBP) and diastolic blood pressure (DBP) following combined training with 1 set or with 3 sets of resistance exercise (RE). Sixteen women with metabolic syndrome (MetS) were randomly assigned to perform two combined exercise protocols and a control session (CON): 1‐set, 30 min of aerobic exercise (AE) at 65–70% of reserve heart rate and 1 set of 8–12 repetitions at 80% of 10‐RM in six resistance exercises; 3‐sets, same protocol but with 3 sets; and CON, 30 min of seated rest. The SBP, MBP and DBP were measured before and every 15 min during 90 min following the experimental sessions. The SBP displayed a decrease (P≤0·05) during the 90 min following the RE session with 1‐set and 3‐set, while MBP was decreased (P≤0·05) up to 75 min after 1‐set and up to 30 min after the 3‐set exercise session compared with pre‐intervention values. There was a decrease in DBP only for the greatest individual decrease following 1‐set (?6·1 mmHg) and 3‐set (?4·9 mmHg) combined exercise sessions, without differences between them. The rate‐pressure product and heart rate remained significantly higher (P≤0·05) 75 min and 90 min after the combined exercise session with 1‐ and 3‐sets compared with the CON, respectively. In conclusion, a low‐volume RE combined with AE resulted in similar decrease of SBP when compared with RE with 3‐sets in women with MetS, which could be beneficial in situations of limited time.     

Ventilatory efficiency and rate of perceived exertion in obese and non-obese children performing standardized exercise

Sixty children, in the age span 6-17 years originally divided into two groups, matched by age, sex and height--30 obese subjects [15 girls/15 boys; body mass index (BMI) = 27.4 +/- 4.5 m kg-2; ideal body weight (IBW) range = 122-185%] and 30 controls (BMI = 18.8 +/- 2.7 m kg-2) performed incremental treadmill exercise test. Perceived exertion was assessed by means of Category-Ratio Borg scale. The duration of the exercise for the children in the obesity group was significantly shorter than controls (P = 0.010) but obese children have greater absolute values for oxygen uptake (VO2peak ml min-1 = 1907 +/- 671 versus 1495 +/- 562; P = 0.013) and ventilatory variables (VE, VT), which adjusted for body mass decrease significantly (VO2/kg ml min-1 kg-1 = 29.2 +/- 3.8 versus 33.6 +/- 3.5; P < 0.001). Among the various methods for 'normalizing' absolute values of VO2peak for body size, dividing it by body surface area (BSA) yielded the best results (VO2/BSA ml min-1 m-2 = 43.5 +/- 4.6 versus 44.7 +/- 5.6; P = 0.335). The ventilatory efficiency determined either as a slope of VE versus VCO2 or as a simple ratio at anaerobic threshold did not differ between obese and non-obese children in the incremental and recovery periods of exercise. There was a negative correlation of VE/VCO2 slope with age and anthropometric parameters. Obese children rated perceived exertion significantly higher than controls despite the standard workload (Borg score = 6.2 +/- 1.2 versus 5.2 +/- 1.1; P = 0.001). In conclusion, the absolute metabolic cost of exercise is higher in the obesity group compared with the control subjects. Both groups have similar ventilatory efficiency but an increased awareness of fatigue that furthermore limits their physical capacity.     

Left ventricular performance during prolonged exercise: absence of systolic dysfunction

We assessed left ventricular systolic and diastolic performance during and after prolonged exercise under controlled conditions in a group of healthy, trained men. Previous studies have examined the effects of prolonged effort on left ventricular function, yet it remains unclear whether or not left ventricular dysfunction (e.g. cardiac fatigue) can be produced under such conditions. We studied 15 healthy men, aged 27+/-1 years (mean+/-S.E.M.). Subjects exercised on bicycles at a constant work rate (60% of maximum oxygen uptake per min) for 150 min. Measurements of gas exchange, blood pressure and haematocrit were obtained, concurrent with the assessment of left ventricular function using equilibrium radionuclide angiography, at rest, during exercise (every 30 min) and after 30 min of recovery. Fluid replacement was provided and monitored during the exercise period. The baseline resting and exercise ejection fractions were 66+/-2% and 78+/-2% respectively. During exercise, subjects consumed 1816+/-136 ml of fluid, and the haematocrit had increased at 120 min of exercise (from 47.2%+/-0.6 to 49.9+/-0.8%; P<0.05). There was no change in either systolic or diastolic blood pressure throughout the exercise period, but heart rate drifted upwards from 141+/-2 beats/min after 30 min to 154+/-3 beats/min after 150 min (P<0.05). There was a small decline (8%; P<0.05) in end-diastolic volume at 150 min. No changes were observed in left ventricular ejection fraction, the pressure/volume ratio or end-systolic volume. After 30 min of sitting in recovery, heart rate was still higher than the pre-exercise value (84+/-3 compared with 69+/-2 beats/min; P<0.05), as were measures of peak filling rate and time to peak filling (P<0.05). The ejection fraction in the post-exercise recovery period was similar to the pre-exercise value. The results indicate that prolonged exercise of moderate duration may not induce abnormal left ventricular systolic function or cardiac fatigue during exercise.     

Study of blood flow parameters measured in femoral artery after exercise: correlation with maximum oxygen uptake

To study the recovery periods of blood flow parameters in muscles after anaerobic exercise, instantaneous and mean blood flow velocity curves were recorded in the femoral artery in 22 sportsmen at rest and during the first 4 min of recovery after exercise (Ruffier-Dickson test). A flat ultrasonic probe connected to a Doppler system (Flow-Tester) was fixed on the skin at the level of the common femoral artery. From Doppler recordings, we calculated periods of recovery (return to baseline) of femoral blood flow velocity (FBFV RP), heart rate (HR RP) and femoral stroke distance (FSD RP). Also, Ruffier-Dickson index (RDI), VO(2)max in mL/kg(-1)/min(-1) and number of training hours were determined. We observed a high correlation between FBFV RP and VO(2)max (p = 0. 0002), and significant correlation between FSD RP and VO(2)max (p = 0.0238) and RDI (p = 0.0451). In conclusion, there is a excellent correlation between blood flow velocity recovery period in femoral artery after moderate exercise and VO(2)max in high-level sportsmen. The method of testing is simple and based on conventional Doppler technique. It can be used for the follow-up of training levels in sportsmen.     

Oxygen consumption and cardiac response of short-leg and long-leg prosthetic ambulation in a patient with bilateral above-knee amputation: comparisons with able-bodied men

This study measured oxygen uptake (VO2), minute ventilation (VE), and heart rate (HR) in a bilateral above-knee (AK) amputee and in three able-bodied controls during progressive treadmill exercise. Walking conditions for the amputee included using bilateral short-leg (SL) and long-leg (LL) prostheses. A progressive treadmill protocol to maximal capacity was used for the amputee and duplicated by the control subjects. An automated system was used to measure VO2, VE, and HR throughout exercise. Data analysis was restricted to the use of parameter averages and percentages to describe differences between experimental conditions. Maximal VO2 for the amputee averaged 23.3mL/kg-1/min-1 with the LL and 22.8mL/kg-1/min-1 with the SL prostheses, a negligible difference between conditions; however, exercise duration was 27% longer when using the SL prostheses. In addition, when averaged over the first four stages of exercise, VO2, VE, and HR were 24%, 32%, and 14% higher, respectively, when the LL prostheses were used. Treadmill walking by unimpaired controls averaged 47% and 79% more economical than walking with the SL or LL prostheses, respectively. These results demonstrate that the use of currently available AK prostheses requires significant energy expenditure, which limits their use to only the most physically fit individuals.     

Combined exercise circuit session acutely attenuates stress-induced blood pressure reactivity in healthy adults

Objective

To investigate the blood pressure (BP) responses to cardiovascular stress test after a combined exercise circuit session at moderate intensity.

Method

Twenty individuals (10 male/10 fem; 33.4± 6.9 years; 70.2± 15.8 kg; 170.4± 11.5 cm; 22.3± 6.8% body fat) were randomized in a different days to control session with no exercise or exercise session consisting of 3 laps of the following circuit: knee extension, bench press, knee flexion, rowing in the prone position, squats, shoulder press, and 5 min of aerobic exercise at 75-85% of age-predicted maximum heart rate and/or 13 on the Borg Rating of Perceived Exertion [scale of 6 to 20]. The sets of resistance exercise consisted of 15 repetitions at ~50% of the estimated 1 repetition maximum test. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured at rest and during 1h of recovery in both experimental sessions. After that, blood pressure reactivity (BP_R) was evaluated using the Cold Pressor Test.

Results

During 1h of exercise recovery, there was a reduction in SBP (3-6 mmHg) and DBP (2-5 mmHg) in relation to pre-session rest (p<0.01), while this reduction was not observed in the control session. A decline in BP_R (4-7 mmHg; p<0.01) was observed 1h post-exercise session, but not in the control session. Post-exercise reductions in SBP and DBP were significantly correlated with BP_R reductions (r=0.50-0.45; p<0.05).

Conclusion

A combined exercise circuit session at moderate intensity promoted subsequent post-exercise hypotension and acutely attenuated BP_R in response to a cardiovascular stress test. In addition, the post-exercise BP reduction was correlated with BP_R attenuation in healthy adults of both genders.