Fast reduction of peripheral blood endothelial progenitor cells in healthy humans exposed to acute systemic hypoxia.

There are hints that hypoxia exposure may affect the number of circulating endothelial progenitor cells (EPCs) in humans. To test this hypothesis, the concentration of EPCs was determined by flow cytometry in the peripheral blood of 10 young healthy adults before (0 h), at different times (0.5 h, 1 h, 2 h and 4 h) during a 4 h normobaric hypoxic breathing simulating 4100 m altitude, and in the following recovery breathing room air. Results were interpreted mainly on the basis of the changes in surface expression of CXC chemokine receptor-4 (CXCR-4, a chemokine receptor essential for EPC migration and homing) and the percentage of apoptotic cells, the plasmatic levels of markers of oxidative stress induced by hypoxic breathing. Compared to 0 h, the concentration of EPCs, identified as either CD45(dim)/CD34(+)/KDR(+) or CD45(dim)/CD34(+)/KDR(+)/CD133(+) cells, decreased from 337 ± 83 ml(-1) (mean ± SEM) to 223 ± 52 ml(-1) (0.5 h; P < 0.005) and 100 ± 37 ml(-1) (4 h; P < 0.005), and from 216 ± 91 to 161 ± 50 ml(-1) (0.5 h; P < 0.05) and 45 ± 23 ml(-1) (4 h; P < 0.005), respectively. Upon return to normoxia, their concentration increased slowly, and after 4 h was still lower than at 0 h (P < 0.05). During hypoxia, CXCR-4 expression and plasmatic stromal derived cell factor-1 (SDF-1) increased abruptly (0.5 h: +126% and +13%, respectively; P < 0.05), suggesting cell marginalization as a possible cause of the rapid hypoxia-induced EPC reduction. Moreover, hypoxia exposure induced an increase in EPC apoptosis and markers of oxidative stress, which was significantly evident only starting from 2 h and 4 h after hypoxia offset, respectively, suggesting that EPC apoptosis may contribute to the later phase of hypoxia-induced EPC reduction. Overall, these observations may provide new insights into the understanding of the mechanisms operated by EPCs to maintain endothelial homeostasis.

Metabolic myopathies: functional evaluation by analysis of oxygen uptake kinetics.

PURPOSE: The aim was to identify additional noninvasive tools allowing to detect and to quantify the metabolic impairment in patients with mitochondrial myopathies (MM) or McArdle's disease (McA). METHODS: Kinetics of adjustment of pulmonary oxygen uptake (VO2 kinetics) during transitions to constant-load moderate-intensity cycle ergometer exercise were determined on 15 MM, 8 McA, 21 patients with signs and/or symptoms of metabolic myopathy but a negative biopsy ("patient controls"; P-CTRL), and 22 healthy untrained controls (CTRL). RESULTS: VO2 kinetics were slower in MM and in McA versus P-CTRL and CTRL, slower in McA versus MM, and not significantly different between P-CTRL and CTRL. The time constants (tau) of the monoexponential function describing the VO2 kinetics were (X +/- SE) 59.2 +/- 8.5 s in MM, 87.6 +/- 16.4 s in McA, 36.9 +/- 3.1 s in P-CTRL, and 35.4 +/- 1.9 s in CTRL. In a subgroup of the patients (eight MM and seven McA), tau of VO2 kinetics were negatively correlated with two variables determined in a previous study (Grassi B, Marzorati M, Lanfranconi F, et al. Impaired oxygen extraction in metabolic myopathies: detection and quantification by near-infrared spectroscopy. Muscle Nerve. 2007;35:510-20): a) a muscle oxygenation index, obtained by near-infrared spectroscopy, estimating the peak capacity of skeletal muscle fractional O2 extraction; and b) VO2 peak. CONCLUSIONS: In MM and McA patients, analysis of pulmonary VO2 kinetics during moderate-intensity exercise allows to identify and to quantify, noninvasively, the impairment of skeletal muscle oxidative metabolism. In these patients, the slower VO2 kinetics can be considered a marker of the impaired exercise tolerance. The present data could be useful for clinicians who need an objective, quantitative, and longitudinal evaluation of the impairment to be used in the follow-up of these patients as well as in the assessment of therapeutic interventions.

Muscle bioenergetics and metabolic control at altitude.

High altitude functional data, particularly those obtained on humans in the field by conventional techniques, appear to be often affected by a large variability that does not seem to be justified by the characteristics of the research protocols and by the adopted experimental procedures which, in most cases, are "state of the art". This is also evident by the frequent occurrence of debates (e.g. "point--counterpoint" contributions by specialists in the Journal of Applied Physiology) on issues whose interpretation was taken for granted. The appearance of an exclusive new player, the multi-gene transcription protein Hypoxia Inducible Factor (HIF-1) recognized as the master regulator of cell hypoxic signaling, opens a new scenario. Indeed, among the genes regulated by HIF-1, besides those expressing EPO and VEGF controlling erythropoiesis and angiogenesis, respectively, there are hundreds of other genes whose products play a large number of metabolic and transport functions. The aim of the present work is to revisit some earlier results that have been generally overlooked, in order to provide them with a more comprehensive interpretation. This has been done on the basis of work on cell hypoxic signaling including some metabolic players recently identified by muscle proteome analysis. Particular emphasis has been laid on the molecular interpretation of findings such as improved metabolic efficiency of locomotion in chronic hypoxia, origin and significance of an apparent misnomer such as the so-called "lactate paradox", and the physiological meaning of the muscle mitochondrial mass reduction in both altitude natives and acclimatized lowlanders.

Fatty acid profiles of blood lipids in a population group in Tibet: correlations with diet and environmental conditions.

The aim of this study was to compare blood fatty acid profiles of two population groups: Italian and Tibetan, differing with regard to ethnic, life style and environmental aspects. Additionally the collection of two staple foods provided the opportunity to analyze typical Tibetan dishes. A new, simple, rapid, and substantially non invasive method for fatty acid (FA) analysis of blood lipids was applied to healthy Italian (n=14) and Tibetan (n=13) subjects. Blood drops obtained from the ear lobe of Tibetans or the fingertip of Italians were adsorbed by a special strip of paper and processed for fatty acid analysis. The fatty acid profiles of the two groups are different, and environmental factors, such as dietary fats and altitudes of Milan, Italy (a low altitude site), and Lhasa, Tibet (a high altitude site) appear to contribute to these differences. More specifically, in Ti-betans higher levels of monounsaturated fatty acids, including the 22 and 24 carbon molecules, were found. This appears to be derived mainly from locally consumed fats (mustard seed oil), and are associated with lower levels of total polyunsaturated fatty acids and higher levels of selected omega 3 fatty acids, when compared to the Italians. These relatively higher levels of monounsaturated fatty acids may also indicate means of adaptation to local prooxidant conditions. The observed differences in blood fatty acid profiles in Tibetans vs. Italians appear to result both from dietary factors and adaptation to local environmental conditions such as the high altitude of the Tibetan location.

Impaired oxygen extraction in metabolic myopathies: detection and quantification by near-infrared spectroscopy.

Patients with mitochondrial myopathies (MM) or myophosphorylase deficiency (McArdle's disease, McA) show impaired capacity for O(2) extraction, low maximal aerobic power, and reduced exercise tolerance. Non-invasive tools are needed to quantify the metabolic impairment. Six patients with MM, 6 with McA, 25 with symptoms of metabolic myopathy but negative biopsy (patient-controls, P-CTRL) and 20 controls (CTRL) underwent an incremental cycloergometric test. Pulmonary O(2) uptake (VO(2)) and vastus lateralis oxygenation indices (by near-infrared spectroscopy, NIRS) were determined. Concentration changes of deoxygenated hemoglobin and myoglobin (Delta[deoxy(Hb + Mb)]) were considered an index of O(2) extraction. Delta[deoxy(Hb + Mb)] peak (percent limb ischemia) was lower in MM (25.3 +/- 12.0%) and McA (18.7 +/- 7.3) than in P-CTRL (62.4 +/- 3.9) and CTRL (71.3 +/- 3.9) subjects. VO(2) peak and Delta[deoxy(Hb + Mb)] peak were linearly related (r(2) = 0.83). In these patients, NIRS is a tool to detect and quantify non-invasively the metabolic impairment, which may be useful in the follow-up of patients and in the assessment of therapies and interventions.

Work capacity of permanent residents of high altitude.

Tibetan and Andean natives at altitude have allegedly a greater work capacity and stand fatigue better than acclimatized lowlanders. The principal aim of the present review is to establish whether convincing experimental evidence supports this belief and, should this be the case, to analyze the possible underlying mechanisms. The superior work capacity of high altitude natives is not based on differences in maximum aerobic power (V(O2 peak)), mL kg(-1)min(-1)). In fact, average V (O2 peak) of both Tibetan and Andean natives at altitude is only slightly, although not significantly, higher than that of Asian or Caucasian lowlanders resident for more than 1 yr between 3400 and 4700 m (Tibetans, n = 152, vs. Chinese Hans, n = 116: 42.4 +/- 3.4 vs. 39.2 +/- 2.6 mL kg(-1)min(-1), mean +/- SE; Andeans, n = 116, vs. Caucasians, n = 70: 47.1 +/- 1.7 vs. 41.6 +/- 1.2 mL kg(-1)min(-1)). However, compared to acclimatized lowlanders, Tibetans appear to be characterized by a better economy of cycling, walking, and running on a treadmill. This is possibly due to metabolic adaptations, such as increased muscle myoglobin content and antioxidant defense. All together, the latter changes may enhance the efficiency of the muscle oxidative metabolic machinery, thereby supporting a better prolonged submaximal performance capacity compared to lowlanders, despite equal V(O2 peak). With regard to Andeans, data on exercise efficiency is scanty and controversial and, at present, no conclusion can be drawn as to the origin of their superior performance.

Economy of locomotion in high-altitude Tibetan migrants exposed to normoxia.

High-altitude Tibetans undergo a pattern of adaptations to chronic hypoxia characterized, among others, by a more efficient aerobic performance compared with acclimatized lowlanders. To test whether such changes may persist upon descent to moderate altitude, oxygen uptake of 17 male Tibetan natives lifelong residents at 3500-4500 m was assessed within 1 month upon migration to 1300 m. Exercise protocols were: 5 min treadmill walking at 6 km h(-1) on increasing inclines from +5 to +15% and 5 min running at 10 km h(-1) on a +5% grade. The data (mean +/- S.E.M.) were compared with those obtained on Nepali lowlanders. When walking on +10, +12.5 and +15% inclines, net V(O2) of Tibetans was 25.2 +/- 0.7, 29.1 +/- 1.1 and 31.3 +/- 0.9 ml kg(-1) min(-1), respectively, i.e. 8, 10 and 13% less (P < 0.05) than that of Nepali. At the end of the heaviest load, blood lactate concentration was lower in Tibetans than in Nepali (6.0 +/- 0.9 versus 8.9 +/- 0.6 mM; P < 0.05). During running, V(O2) of Tibetans was 35.1 +/- 0.8 versus 39.3 +/- 0.7 ml kg(-1) min(-1) (i.e. 11% less; P < 0.01). In conclusion, during submaximal walking and running at 1300 m, Tibetans are still characterized by lower aerobic energy expenditure than control subjects that is not accounted for by differences in mechanical power output and/or compensated for by anaerobic glycolysis. These findings indicate that chronic hypoxia induces metabolic adaptations whose underlying mechanisms still need to be elucidated, that persist for at least 1 month upon descent to moderate altitude.

Second generation Tibetan lowlanders acclimatize to high altitude more quickly than Caucasians.

Tibetan highlanders develop at altitude peak aerobic power levels close to those of Caucasians at sea level. In order to establish whether this feature is genetic and, as a consequence, retained by Tibetan lowlanders, altitude-induced changes of peak aerobic performance were assessed in four groups of volunteers with different ethnic, altitude exposure and fitness characteristics, i.e. eight untrained second-generation Tibetans (Tib 2) born and living at 1300 m; seven altitude Sherpas living at approximately 2800-3500 m; and 10 untrained and five trained Caucasians. Measurements were carried out at sea level or at Kathmandu (1300 m, Nepal) (PRE), and after 2-4 (ALT1), 14-16 (ALT2), and 26-28 (ALT3) days at 5050 m. At ALT3, of untrained and trained Caucasians was -31% and -46%, respectively. By contrast, of Tib 2 and Sherpas was -8% and -15%, respectively. At ALT3, peak heart rate (HR(peak)) of untrained and trained Caucasians was 148 +/- 11 and 149 +/- 7 beats min(-1), respectively; blood oxygen saturation at peak exercise was 76 +/- 6% and 73 +/- 6%, and haemoglobin concentration ([Hb]) was 19.4 +/- 1.0 and 18.6 +/- 1.2 g dl(-1), respectively. Compared to Caucasians, Tib 2 and Sherpas exhibited at ALT3 higher HR(peak) (179 +/- 9 and 171 +/- 4 beats min(-1), P < 0.001), lower [Hb] (16.6 +/- 0.6 and 17.4 +/- 0.9 g dl(-1), respectively, P < 0.001), and slightly but non-significantly greater average values (82 +/- 6 and 80 +/- 7%). The above findings and the time course of adjustment of the investigated variables suggest that Tibetan lowlanders acclimatize to chronic hypoxia more quickly than Caucasians, independent of the degree of fitness of the latter.

New aspects of altitude adaptation in Tibetans: a proteomic approach.

A prolonged sojourn above 5500 m induces muscle deterioration and accumulation of lipofuscin in Caucasians, probably because of overproduction of reactive oxygen species (ROS). Because Sherpas, who live at high altitude, have very limited muscle damage, it was hypothesized that Himalayan natives possess intrinsic mechanisms protecting them from oxidative damage. This possibility was investigated by comparing the muscle proteomes of native Tibetans permanently residing at high altitude, second-generation Tibetans born and living at low altitude, and Nepali control subjects permanently residing at low altitude, using 2D gel electrophoresis and mass spectrometry. Seven differentially regulated proteins were identified: glutathione-S-transferase P1-1, which was 380% and 50% overexpressed in Tibetans born and living at high and low altitude, respectively; Delta2-enoyl-CoA-hydratase, which was up-regulated in both Tibetan groups; glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase, which were both slightly down-regulated in Tibetans born and living at high altitude; phosphoglycerate mutase, which was 50% up-regulated in the native Tibetans; NADH-ubiquinone oxidoreductase, slightly overexpressed in Tibetans born and living at high altitude; and myoglobin, which was overexpressed in both Tibetan groups. We concluded that Tibetans at high altitude, and to some extent, those born and living at low altitude, are protected from ROS-induced tissue damage and possess specific metabolic adaptations.

Exercise after heart transplantation.

Exercise intolerance in heart transplant recipients (HTR) has a multifactorial origin, involving complex interactions among cardiac, neurohormonal, vascular, skeletal muscle and pulmonary abnormalities. However, the role of these abnormalities may differ as a function of time after transplantation and of many other variables. The present review is aimed at evaluating the role of cardiac, pulmonary and muscular factors in limiting maximal aerobic performance of HTR, and the benefits of chronic exercise. Whereas pulmonary function does not seem to affect gas exchange until a critical value of diffusing lung capacity is attained, cardiac and skeletal muscle function deterioration may represent relevant factors limiting maximal and submaximal aerobic performance. Cardiac function is mainly limited by chronotropic incompetence and diastolic dysfunction, whereas muscle activity seems to be limited by impaired oxygen supply as a consequence of the reduced capillary network. The latter may be due to either immunosuppressive regimen or deconditioning. Endurance and strength training may greatly improve muscle function and maximal aerobic performance of HTR, and may also reduce side effects of immunosuppressive therapy and control risk factors for cardiac allograft vasculopathy. For the above reasons exercise should be considered an important therapeutic tool in the long-term treatment of heart transplant recipients.

Muscle oxygenation and pulmonary gas exchange kinetics during cycling exercise on-transitions in humans.

Near-infrared spectroscopy (NIRS) was utilized to gain insights into the kinetics of oxidative metabolism during exercise transitions. Ten untrained young men were tested on a cycle ergometer during transitions from unloaded pedaling to 5 min of constant-load exercise below (VT) the ventilatory threshold. Vastus lateralis oxygenation was determined by NIRS, and pulmonary O2 uptake (Vo --> Vo2) was determined breath-by-breath. Changes in deoxygenated hemoglobin + myoglobin concentration Delta[deoxy(Hb + Mb)] were taken as a muscle oxygenation index. At the transition, [Delta[deoxy(Hb + Mb)]] was unmodified [time delay (TD)] for 8.9 +/- 0.5 s at VT (both significantly different from 0) and then increased, following a monoexponential function [time constant (tau) = 8.5 +/- 0.9 s for VT]. For >VT a slow component of Delta[deoxy(Hb + Mb)] on-kinetics was observed in 9 of 10 subjects after 75.0 +/- 14.0 s of exercise. A significant correlation was described between the mean response time (MRT = TD + tau) of the primary component of Delta[deoxy(Hb + Mb)] on-kinetics and the tau of the primary component of the pulmonary Vo2 on-kinetics. The constant muscle oxygenation during the initial phase of the on-transition indicates a tight coupling between increases in O2 delivery and O2 utilization. The lack of a drop in muscle oxygenation at the transition suggests adequacy of O2 availability in relation to needs.

Energetics of walking in patients with peripheral arterial disease: a proposed functional evaluation protocol.

The energy cost of walking (at 3.2 km x h(-1)) per unit distance (J x kg(-1) x m(-1)) at gradients of 0%, +7%, and +12% and during a progressive test (2% increase in gradient every 2 min), as well as the overall (aerobic plus anaerobic) net cumulative energy consumption and the corresponding maximal exercise duration were assessed in 19 patients with peripheral arterial disease (PAD) and in 13 moderately active control subjects. With a 0% gradient, the energy cost of walking was approximately 40% greater in patients with PAD than in controls (2.93+/-0.52 and 2.13+/-0.33 J x kg(-1) x m(-1) respectively; P <0.01). In contrast, at gradients of +7% and +12%, the energy cost of walking was similar in the two groups (+7%: PAD, 4.15+/-0.74 J x kg(-1) x m(-1); controls, 4.18+/-0.54 J x kg(-1) x m(-1); +12%: PAD, 5.59+/-1.03 J x kg(-1) x m(-1); controls, 5.64+/-0.75 J x kg(-1) x m(-1)). In patients with PAD, maximal exercise duration with gradients of 0%, +7% and +12% was 449+/-254, 322+/-200 and 229+/-150 s respectively, whereas the net cumulative energy consumption at fatigue was almost constant at approximately 1100 J x kg(-1) for all gradients. The greater energy cost of walking in PAD patients compared with controls in level, but not uphill, walking is interpreted as being mainly the consequence of an altered mechanical locomotory pattern, and not of lower metabolic efficiency. For a wide range of loads, net cumulative energy consumption appears to be independent of maximal exercise duration, a finding that provides a practical criterion for assessing the degree of functional impairment of patients with PAD on metabolic grounds.

Early effects of exercise training on on- and off-kinetics in 50-year-old subjects.

We tested the hypothesis that, in healthy middle-aged subjects ( n=11, age 51.0 +/- 3.0 years, x +/- SD), the effects of exercise training on pulmonary O(2) uptake (VO(2)) on- and off-kinetics would appear earlier than those on peak. The subjects underwent a standard training program (combined endurance and resistance training) in a health club, and were evaluated before training ("time 0", T0), and after 7 (T7), 15 (T15), 30 (T30), 60 (T60) and 90 (T90) days of training. Breath-by-breath pulmonary O(2) uptake (VO(2)), heart rate (HR), systolic (SBP) and diastolic blood pressure, and capillary blood lactate concentration ([La](b)) were determined at rest and at each workload (w during a cycle ergometer incremental exercise test. The "heart rate x blood pressure product" was calculated as (HR x SBP). The day following the incremental test, the subjects performed three repetitions of a square-wave exercise at 50% of VO(2), for the determination of pulmonary VO(2) on- and off-kinetics. VO(2) and [La](bpeak) tended to increase with training; the increases became significant at T60 or T90. HR(peak)and (HR x SBP)(peak) were unaffected by training. The time constant of the "primary" component of the VO(2) on-kinetics (tau(2)) was 46.9 +/- 17.3 s (T0), 38.1 +/- 14.2 s (T7), 34.4 +/- 12.6 s (T15), 28.8 +/- 6.8 s (T30), 30.2 +/- 8.0 s (T60), and 30.4 +/- 12.4 s (T90); a significant difference compared to T0 was observed from T15 onward. From T15 onward, tau(2) were not significantly different from values obtained (29.2 +/- 5.3 s) from a group of healthy untrained young controls ( n=7, 21.6 +/- 0.5 years). The same pattern of change as a function of training was described for the VO(2) off-kinetics. It is concluded that in 50-year-old subjects VO(2) on- and off-kinetics are more sensitive to exercise training than other physiological variables determined at peak exercise.

Age-related heart rate response to exercise in heart transplant recipients. Functional significance.

The heart rate (HR) and O(2) uptake (VO(2)) responses to cycle ergometer exercise and the role of O(2) transport in limiting submaximal and maximal aerobic performance were assessed in 33 heart transplant recipients (HTR) [14 children (P-HTR), 11 young adults (YA-HTR) and 8 middle-age adults (A-HTR)] and in 28 age-matched control subjects (CTL). In 7 P-HTR ("responders") the HR response to the onset of exercise (on-response) was as fast as that of CTL, whereas in all other patients ("non-responders") the HR on-response was typical of the denervated heart. Compared with non-responder P-HTR, responder P-HTR were also characterized by a normal peak HR (177+/- 16 vs. 151+/- 25 beats/min), an equally slow time constant for the VO(2) on-response (tau: 54 +/- 11 vs. 62+/- 13 s) and a similar low (approximately 60% of that of CTL) peak VO(2) (28 +/- 7 vs. 26 +/- 10 ml/kg per min). On the other hand non-responder YA-HTR and A-HTR were characterized by a relatively low peak HR (151 +/- 21 and 144 +/- 29 beats/min, respectively), a slow tau for the on-response (63 +/- 12 and 70 +/- 11 s) and a low peak (28 +/- 7 and 19 +/- 6 ml/kg per min). In conclusion, a sizeable number of paediatric patients (responder P-HTR) may reacquire the normal HR response to exercise, both in terms of kinetics and maximal level. Despite the almost complete recovery of cardiovascular function, and, probably, oxygen delivery, both the kinetics of the VO(2) on-response and the maximal aerobic power of the responder P-HTR were similar to those of non-responder P-HTR. The latter finding is probably attributable to peripheral limitations, due to inborn and/or pharmacological muscle deterioration.

The heart rate response to exercise and circulating catecholamines in heart transplant recipients.

The plasma concentration of noradrenaline ([NA]) is higher than that of adrenaline ([A]) both in normal subjects and in heart transplant recipients (HTR). Since in both groups the myocardial density of beta1-adrenergenic receptors is much greater than that of beta2-adrenergenic receptors, the chronotropic response of a denervated heart to changes in plasma [NA] and [A] in the absence of reinnervation should be similar to that of agonist stimulation of beta1-receptors. To test this hypothesis, 17 HTR and 9 healthy subjects (CTL) performed incremental exercise on a cycle ergometer to voluntary exhaustion. Heart rate (HR) was recorded by electrocardiography. [NA] and [A] were measured by high-pressure liquid chromatography at rest and at increasing workloads (w). In both groups, HR and [NA+A] increased with w, and HR with [NA+A]. Normalized HR values, plotted against the logarithm of [NA+A], fitted significantly logistic curves. The affinity constants were different, i.e. 2599+/-350 and 487+/-37 ng.l(-1), for HTR and CTL, respectively. The chronotropic effect of changes in [NA+A] in HTR was similar to that of combined beta1- and beta2-adrenergic activation evoked by applying isoprenaline to isolated heart myocytes (Brodde OE, Pharmacol Ther 60:405-430, 1993). These findings suggest that over time sympathetic reinnervation and the modulation of beta-receptors may take place in HTR, ruling out the hypothesis of persistent heart denervation.

VE response to VCO2 during exercise is unaffected by exercise training and different exercise limbs.

We designed two experiments to investigate the relationship between ventilation (VE) and CO2 output (VCO2) during exercise under the conditions of exercising different limbs, the arms as opposed to the legs (experiment 1), and of different physical training states after undergoing standard exercise training for 90 d (experiment 2). Six healthy young subjects underwent submaximal ramp exercise at an incremental work rate of 15 W/min for the arm and leg, and 11 healthy middle-aged subjects underwent an incremental exercise test at the rate of 30 W/3 min before and after exercise training. We measured pulmonary breath-by-breath VE, VCO2, oxygen uptake (VO2), tidal volume (VT), breathing frequency (bf), and end-tidal O2 and CO2 pressures (PETO2, PETCO2) via a computerized metabolic cart. In experiment 1, arm exercise produced significantly greater VE than did leg exercise at the same work rates, as well as significantly higher VO2, VCO2, and bf. The slopes of the regression lines in the VE-VCO2 relationship were not significantly different: the values were 27.8 +/- 2.1 (SD) during the arm exercise, and 25.3 +/- 3.9 during the leg exercise, with no differences in their intercepts. In experiment 2, the VO2, VCO2, and VE responses at the same work rates were similar in both before and after the 90-d exercise training, whereas the heart rate (HR) and mean blood pressure (MBP) were significantly reduced after training. Exercise training did not alter the VE-VCO2 relationship, the slope of which was 31.9 +/- 4.9 before exercise training and 34.2 +/- 4.4 after exercise training. We concluded that the VE-VCO2 relationship during exercise is unaltered, independent of not only working muscle regions but also exercise training states.