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Impaired O(2) delivery relative to O(2) demands at the onset of exercise might influence the response profile of muscle fractional O(2) extraction (≅Δ[deoxy-Hb/Mb] by near-infrared spectroscopy) either by accelerating its rate of increase or creating an "overshoot" (OS) in patients with pulmonary arterial hypertension (PAH). We therefore assessed the kinetics of O(2) uptake [Formula: see text] Δ[deoxy-Hb/Mb] in the vastus lateralis, and heart rate (HR) at the onset of heavy-intensity exercise in 14 females with PAH (connective tissue disease, IPAH, portal hypertension, and acquired immunodeficiency syndrome) and 11 age- and gender-matched controls. Patients had slower [Formula: see text] and HR dynamics than controls (τ[Formula: see text] = 62.7 ± 15.2 s vs. 41.0 ± 13.8 s and t (1/2)-HR = 61.3 ± 16.6 s vs. 43.4 ± 8.8 s, respectively; p < 0.01). No study participant had a significant reduction in oxyhemoglobin saturation. In OS(-) subjects (6 patients and 7 controls), the kinetics of Δ[deoxy-Hb/Mb] relative to [Formula: see text] were faster in patients (p = 0.05). Larger area under the OS and slower kinetics (MRT) of the "downward" component indicated greater O(2) delivery-to-utilization mismatch in OS(+) patients versus OS(+) controls (477.4 ± 330.0 vs. 78.1 ± 65.6 a.u. and 74.6 ± 18.8 vs. 46.0 ± 17.0 s, respectively; p < 0.05). Resting pulmonary vascular resistance was higher in OS(+) than OS(-) patients (23.1 ± 12.0 vs. 10.7 ± 4.0 Woods, respectively; p < 0.05). We conclude that microvascular O(2) delivery-to-utilization inequalities slowed the rate of adaptation of aerobic metabolism at the start of heavy-intensity exercise in women with PAH. [ABSTRACT FROM AUTHOR]

Inspiratory pressure support (IPS) plus positive end-expiratory pressure (PEEP) ventilation might potentially interfere with the "central" hemodynamic adjustments to exercise in patients with chronic obstructive pulmonary disease (COPD). Twenty-one non- or mildly-hypoxemic males (FEV(1) = 40.1 +/- 10.7% predicted) were randomly assigned to IPS (16 cmH(2)O) + PEEP (5 cmH(2)O) or spontaneous ventilation during constant-work rate (70-80% peak) exercise tests to the limit of tolerance (T (lim)). Heart rate (HR), stroke volume (SV), and cardiac output (CO) were monitored by transthoracic cardioimpedance (Physioflow, Manatec, France). Oxyhemoglobin saturation was assessed by pulse oximetry (SpO(2)). At similar SpO(2), IPS(16) + PEEP(5) was associated with heterogeneous cardiovascular effects compared with the control trial. Therefore, 11 patients (Group A) showed stable or increased Delta "isotime" - rest SV [5 (0-29) mL], lower DeltaHR but similar DeltaCO. On the other hand, DeltaSV [-10 (-15 to -3) mL] and DeltaHR were both lower with IPS(16) + PEEP(5) in Group B (N = 10), thereby reducing DeltaCO (p < 0.05). Group B showed higher resting lung volumes, and T (lim) improved with IPS(16) + PEEP(5) only in Group A [51 (-60 to 486) vs. 115 (-210 to 909) s, respectively; p < 0.05]. We conclude that IPS(16) + PEEP(5) may improve SV and exercise tolerance in selected patients with advanced COPD. Impaired SV and CO responses, associated with a lack of enhancement in exercise capacity, were found in a sub-group of patients who were particularly hyperinflated at rest. [ABSTRACT FROM AUTHOR]

Exercise critical power (CP) has been shown to represent the highest sustainable work rate (WR) in patients with chronic obstructive pulmonary disease (COPD). Parameter estimation, however, depends on 4 high-intensity tests performed, on different days, to the limit of tolerance (T(lim)). In order to establish a milder protocol that would be more suitable for disabled patients, we contrasted CP derived from 4, 3 and 2 tests (CP4, CP3 and CP2) in 8 males with moderate COPD. In addition, CP was calculated from 2 single-day tests performed on an inverse sequence (CP(2AB) and CP(2BA)): CP values within 5 W from CP4 were assumed as "clinically-acceptable" estimates. We found that [CP4-CP3] and [CP4-CP2] differences were within 5 W in 8 and 6 patients, respectively (95% confidence interval of the differences = -1.3 to 3.5 W and -11.5 to 6.5 W). There was a systematic decline on T(lim) when an exercise bout was performed after a previous test on the same day (P<0.05). Consequently, substantial differences were found between CP4 and any of the CP estimates obtained from single-day tests. In conclusion, clinically-acceptable estimates of CP can be obtained by using 3 or, in most circumstances, 2 constant WR tests in patients with moderate COPD--provided that they are not performed on the same day. [ABSTRACT FROM AUTHOR]

The time to fatigue (t) in response to high-intensity constant-load exercise decreases hyperbolically with increasing power (W), at least in active and younger individuals [i.e. (W-θF)t=W′, where θF is the critical power asymptote and W′ is the curvature constant]. Little is known, however, about the combined effects of age and sedetarity on these parameters. We therefore evaluated 17 non-trained males (9 aged 60–75 years and 8 aged below 30 years) who underwent ramp-incremental cycle ergometry and, on different days, 4 high-intensity constant-load tests to t. Compared to their younger counterparts, the older subjects presented significantly lower maximum oxygen uptake (i.e. the maximum value of oxygen uptake attained at the end of a progressive exercise with the subject exerting a presumably maximal effort, μVO2), estimated lactate threshold (VO2θL), VO2θF, and W′ (P < 0.05). Interestingly, however, both VO2θL and VO2θF, when expressed as a percentage of μVO2, were higher in older than in younger men [61.8 (6.2)% versus 45.4 (4.6)% and 87.8 (7.3)% versus 79.0 (8.2)%, P < 0.05, respectively]. Therefore, age was associated with an increase in the relative magnitude of the “moderate”, sub-θL exercise-intensity domain (+30.4%), mainly at the expense of the “very-heavy”, supra-θF domain (-56%). Our results demonstrate that age and sedentarity are associated with: (1) marked reductions in both the aerobic (θF) and anaerobic (W′) determinants of the W/t relationship, and (2) changes in either the absolute or relative magnitudes of the exercise-intensity domains. These findings are consistent with the notion that endurance-related parameters are less diminished with ageing than the maximal capacity, thereby mitigating the deleterious effects of senescence in the functional capacity. [ABSTRACT FROM AUTHOR]

To investigate the relationships between the age-associated decline in peak oxygen uptake (peak V˙O2), leg muscle mass (LMM) and leg strength (LS) under the modulating effect of gender and level of physical activity (LPA, as assessed by questionnaire), we evaluated 71 sedentary subjects [males(M):females(F), 34:37], aged 20–80 years. Peak V˙O2 at maximum cycle ergometry was related to LMM (dual energy X-ray absorptiometry) and LS (isokinetic dynamometry) using both standard ( y · x−1) and power function ratios (allometry). Absolute values of all variables were higher in males and declined with age ( P < 0.01). Differences between the genders disappeared after peak V˙O2·LS−1.46 (M) or −1.62 (F) adjustment but remained significant between peak V˙O2·LMM-−0.51 (M) or −0.45 (F) and LS·LMM-−0.91 (M) or −1.10 (F) corrected values. Allometric correction of peak V˙O2 and LS by LMM slowed their age-related declines; the flattening effect however, was more evident in the females. Interestingly, while no age-related decrement in peak V˙O2·LS−1 was found, power function ratio values also declined with age, and at a slower rate in females. These findings are consistent with those obtained following a multiple regression analysis using LPA as an independent covariate ( P < 0.01). We conclude that using adequate scaling methods and controlling by LPA: (1) no gender differences are observed in peak V˙O2 adjusted for LS, (2) loss of LS and LMM are important determinants of the age-associated reduction in physical fitness in both genders but (3) age per se has an LS- and LMM-independent influence on the functional decline, although this intrinsic effect of senescence is less pronounced in females. [ABSTRACT FROM AUTHOR]