Control of blood‐gas and acid‐base status during isometric exercise in humans.

Poole, David C.; Ward, Susan A.; Whipp, Brian J.

doi:10.1113/jphysiol.1988.sp016966

Cited by 22 publications

(13 citation statements)

References 34 publications

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“…2, the presence of the slow component resulted in significant increases in the end-exercise gain as exercise intensity increased. Contrary to what has been shown in previous work in cycling (Poole et al 1988b), the slow component did not cause to reach when working just above the CV. During the 60% D trial, in which all subjects except one were above their CV, increased to only @96% and appeared to plateau.…”

Section: Discussioncontrasting

confidence: 85%

Oxygen uptake kinetics during treadmill running across exercise intensity domains

et al. 2002

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The purpose of the present study was to examine comprehensively the kinetics of oxygen uptake (VO2) during treadmill running across the moderate, heavy and severe exercise intensity domains. Nine subjects [mean (SD age, 27 (7) years; mass, 69.8 (9.0) kg; maximum VO2, VO2max, 4,137 (697) ml x min(-1)] performed a series of "square-wave" rest-to-exercise transitions of 6 min duration at running speeds equivalent to 80% and 100% of the VO2 at lactate threshold (LT; moderate exercise); and at 20%, 40%, 60%, 80% and 100% of the difference between the VO2 at LT and VO2max (delta heavy and severe exercise). Critical velocity (CV) was also determined using four maximal treadmill runs designed to result in exhaustion in 2-15 min. The VO2 response was modelled using non-linear regression techniques. As expected, the amplitude of the VO2 primary component increased with exercise intensity [from 1,868 (136) ml x min-( 1) at 80% LT to 3,296 (218) ml x min-(1) at 100% delta, P < 0.05]. However, there was a non-significant trend for the "gain" of the primary component to decrease as exercise intensity increased [181 (7) ml x kg(-1) x km(-1) at 80% LT to 160 (6) ml x kg(-1) x km(-1) at 100% delta]. The time constant of the primary component was not different between supra-LT running speeds (mean value range = 17.9-19.1 s), but was significantly shorter during the 80% LT trial [12.7 (1.4) s, P < 0 .05]. The VO2 slow component increased with exercise intensity from 139 (39) ml x min(-1) at 20% delta to 487 (57) ml x min(-1) at 80% delta (P < 0.05), but decreased to 317 (84) ml x min(-1) during the 100% delta trial (P < 0.05). During both the 80% delta and 100% delta trials, the VO2 at the end of exercise reached VOmax [4,152 (242) ml x min(-1) and 4,154 (114) ml x min(-1), respectively]. Our results suggest that the "gain" of the primary component is not constant as exercise intensity increases across the moderate, heavy and severe domains of treadmill running. These intensity-dependent changes in the amplitudes and kinetics of the VO2 response profiles may be associated with the changing patterns of muscle fibre recruitment that occur as exercise intensity increases.

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Section: Discussioncontrasting

confidence: 85%

Oxygen uptake kinetics during treadmill running across exercise intensity domains

et al. 2002

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“…Table 1 presents the main results of our study. Physiology (1996) 491T.P stimulation has, however, been proposed to account for the recurrence of hyperventilation reported to occur early in the recovery; this was associated with decreasing arterial pH and could be attributed to release of metabolic products from previously underperfused muscle (Poole et al 1988). We have reported a comparable pattern on cessation of isometric exercise in simulated dinghy sailing (Vogiatzis et al 1995).…”

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confidence: 57%

Human Physiology

1996

The Journal of Physiology

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It is generally assumed that shivering and exercise are analogous processes. This assumption most often finds expression in mathematical models of human thermoregulation where substrate utilization during exercise is used as the model for shivering. This may be erroneous given the different patterns of muscle recruitment, temperatures, and levels of stress associated with each activity. The present experiment compared, for the first time in humans, substrate utilization during shivering and exercise.The protocol was approved by the Ethics Committee of Simon Fraser University. Eight male subjects undertook two, 2 h experiments. In the first they were immersed, naked, to the xiphoid process in 20°C water. Low (L, average oxygen consumption (Vo2) 0-49 1 min-), low-moderate (LM, average Vo2 0-61 lmin-) and moderate (M, average Vo02 0-9 1 min-) intensity shivering was elicited from the subjects by cooling and stirring the water, and spraying the neck and shoulders. During the second experiment, the V02 measured during shivering was reproduced in each subject by bicycle ergometry. During both experiments V02 was recorded every 10 s using on-line sampling and a computer-based data acquisition system. The rates of hepatic glucose output (HGO) and utilization (Rd) were determined using radioimmunoassay following primed constant infusions of sterile, pyrogen-free [3-3H] glucose. Arterialized blood samples were taken every 10 min from a vein in the dorsum of the hand from which plasma free fatty acid (FFA) and ,-hydroxybutyrate (,-HBA) concentrations were determined. The Wilcoxon signed ranks test was used to analyse the data.None of the variables recorded differed between the two conditions at rest. The shivering and exercise V02 of the subjects were closely matched, the highest average (2 S.D.)variation observed being 0f02 (0 03) 1 min-'. HGO (,rIE) has been shown to be reduced in humans by procedures designed to augment peripheral chemosensitivity, such as acute hypoxaemia (Griffiths et al. 1986) and chronic metabolic acidaemia (Oren et al. 1982). However, as these conditions are not normally encountered during exercise at sea level, we wished to examine whether an endogenously induced, acute metabolic acidaemia (which is commonly encountered) might have a similar effect.Six healthy subjects performed an incremental cycle ergometer test to estimate the lactate threshold (6L) and peak V02. Subsequently (on different days), they completed two tests, each consisting of two consecutive, 6 min exercise bouts separated by 6 min at '0' Watts. In both instances, the second (or 'test') bout was at a work rate equivalent to 90 % of 6L; the initial (or 'conditioning') bout was also sub-9L (90% 6L) in one case, and supra-OL (at a work rate halfway between OL and peak fo2) in the other (i.e. to generate an acute metabolic acidaemia). Pulmonary gas exchange variables were derived breath-by-breath from continuous monitoring of respiratory volumes (turbine) and gas concentrations (mass spectrometer). During minute 6 of each exerc...

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“…By contrast, after contractions of the quadriceps at 40% MVC there was an apparent surge of carbon dioxide from the exercising muscle, resulting in a rapid rise in PET,CO2 (Fig. 7B) similar to that observed by Poole et al (1988). Ventilation was no higher in those subjects with elevated carbon dioxide levels, and the usual relationship between alveolar Pco2 and ventilation was again absent.…”

Section: Alveolar Pco2mentioning

confidence: 78%

“…Alveolar Pco , whether low or high, is apparently ineffective as a controller in this situation. The levels of lactate present in the blood during and after contraction (Poole et al 1988) are insufficient to stimulate ventilation.…”

Section: Alveolar Pco2mentioning

confidence: 99%

“…Firstly, increases of plasma lactate concentration are small and fall slowly after exercise (Poole et al 1988) and only small quantities of oxygen will be required for metabolism of lactate. Since the proportion of the cardiac output going to active muscle is small, there will be only a small fall of mixed venous oxygen saturation RESPIRATION DURING ISOMETRIC EXERCISE which will require little additional oxygen to replenish it.…”

Section: Alveolar Pco2mentioning

confidence: 99%

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Respiratory responses to sustained isometric muscle contractions in man: the effect of muscle mass.

Imms

Mehta

1989

The Journal of Physiology

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SUMMARY1. Respiratory responses to sustained isometric contractions of a small mass of muscle (the finger flexors) during handgripping, and of a larger mass of muscle (the quadriceps) during extension of the leg at the knee, have been studied in man.2. For both masses of muscle the increases of ventilation and of oxygen consumption were greater for contractions at 40 % maximum voluntary contraction (MVC) than for contractions at 20 % MVC.3. The increase of ventilation was not related to the mass of muscle involved. 4. At 20% MVC oxygen consumption during contraction of the quadriceps was greater than that during handgripping. At 40 % MVC the oxygen consumptions were similar. The oxygen debts following both handgrip and knee extensor contractions at 20 % MVC were negligible. Following 40 % MVC contractions of the quadriceps a significant oxygen debt was recorded but no debt was apparent following 40 % MVC contractions of the finger flexors.5. The increases of ventilation during isometric exercise were generally inappro-

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Control of blood‐gas and acid‐base status during isometric exercise in humans.

Cited by 22 publications

References 34 publications

Oxygen uptake kinetics during treadmill running across exercise intensity domains

Oxygen uptake kinetics during treadmill running across exercise intensity domains

Human Physiology

Respiratory responses to sustained isometric muscle contractions in man: the effect of muscle mass.

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