Effects Of Respiratory Muscle Work On Cardiac Output And Its Distribution During Maximal Exercise.

Harms, Craig A.; Wetter, Thomas J.; McClaran, Steven R.; Pegelow, David F.; Nickele, Glenn A.; Nelson, W. Bradley; Hanson, Peter; Dempsey, Jerome A.

doi:10.1097/01823246-199809040-00009

Cited by 110 publications

(209 citation statements)

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“…Harms et al showed that minor tiredness in respiratory muscles, which can be experimentally obtained by mechanical unloading of these muscles, allows for a reduction of respiratory muscles _ VO 2 and blood flow and that this phenomenon is associated with more than 10% leg blood flow increase (Harms et al 1995;Harms et al 1997). Moreover, the same Authors suggested that the reduction of respiratory muscles workload and the increase in peripheral muscles flow, delays the feeling of dyspnoea, allowing a more advanced exercise load (Harms et al 1998).…”

Section: Discussionmentioning

confidence: 95%

“…However, a lower hyperventilation and the consequent higher P a CO 2 can, per se, affect maximal exercise performance. Indeed, a reduced hyperventilation could determine lower respiratory muscles work allowing for a lower blood flow towards respiratory muscles and a gain of up to 10%, in leg blood flow (Harms et al 1997(Harms et al , 1998(Harms et al , 2000. This mechanism delays the onset of leg fatigue and permits greater exercise performance.…”

Section: Introductionmentioning

confidence: 97%

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End-tidal pressure of CO2 and exercise performance in healthy subjects

et al. 2008

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High arterial CO(2) pressure (P(a)CO(2)) measured in athletes during exercise suggests inadequate hyperventilation. End-tidal CO(2) pressure (P (ET)CO(2)) is used to estimate P(a)CO(2.) However, P(ET)CO(2) also depends on exercise intensity (CO(2) production, .VCO2) and ventilation efficiency (being P(ET)CO(2) function of respiratory rate). We evaluated P(ET)CO(2) as a marker, which combines efficiency of ventilation and performance. A total of 45 well-trained volunteers underwent cardiopulmonary tests and were grouped according to P(ET)CO(2) at respiratory compensation (RC): Group 1 (P(ET)CO(2) 35.1-41.5 mmHg), Group 2 (41.6-45.7) and Group 3 (45.8-62.6). At anaerobic threshold, RC and peak exercise, ventilation (.VE) was similar, but in Group 3, a greater tidal volume (Vt) and lower respiratory rate (RR) were observed. Peak exercise workload and .VO2 were lowest in Group 1 and similar between Group 2 and 3. Group 3 subjects also showed high peak .VCO2 suggesting a greater glycolytic metabolism. In conclusion, a high P(ET)CO(2) during exercise is useful in identifying a specific respiratory pattern characterized by high tidal volume and low respiratory rate. This respiratory pattern may belong to subjects with potential high performance.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 97%

End-tidal pressure of CO2 and exercise performance in healthy subjects

et al. 2008

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“…Therefore, VM was considered to be more effective in competing for blood flow and O 2 availability than LM in VML. Moreover, Harms et al (1997Harms et al ( , 1998 showed that the blood flow in LM was compromised with VM loading during maximal exercise where a further increase in total cardiac output was limited. The considerable O 2 availability, reduced in LM under the VM loaded breathing condition, was used to compensate the augmented O 2 demand in VM to work against the increased inspiratory impedance.…”

Section: Metabolic Stressmentioning

confidence: 97%

Increased sensations of intensity of breathlessness impairs maintenance of intense intermittent exercise

Tong

Chow

et al. 2003

Eur J Appl Physiol

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To identify the reserve of an individual's tolerance of the sensation of breathlessness and metabolic stress in maintaining intense intermittent exercise at exhaustion under conditions of normal breathing, the contribution of the effect of modest inspiratory load on these two responses to the change in the exercise sustainability (Ex(sus)) were examined. Seven men repeatedly performed 12 s exercise at 160% maximal aerobic power output followed by passive recovery for 18 s under normal and ventilatory muscle loaded (VML) breathing conditions until exhaustion. In the VML trial, ventilatory muscle work at exhaustion was double that of the normal control. The control Ex(sus) was reduced [mean (SEM)] [31.7 (6.6)%] while the slope of the time course for the rating of the perceived magnitude of breathing effort (RPMBE/Time), which reflected the intensity of breathlessness, was increased [164.8 (32.2)%] from control and the RPMBE at exhaustion was higher than corresponding control value [144.4 (21.8)%]. Moreover, increases in plasma ammonia and uric acid concentrations, which indicated metabolic stress, were increased [168.1 (28.0)% and 251.7 (57.4)%, respectively], with no change in total oxygen uptake from control when the control exercise was repeated with an identical duration of VML exercise. It was found that the reduction in Ex(sus) in the VML trial was correlated to the increase in their sensations of the intensity of breathlessness (RPMBE/Time: r=0.81; RPMBE at exhaustion: r=0.97, P<0.05). The reduction in Ex(sus), however, was not correlated to the increase in metabolite concentrations. These findings implied that there was no substantial reserve of tolerance of the sensation of breathlessness relative to that of metabolic stress in subjects maintaining intense intermittent exercise at exhaustion under normal conditions of breathing.

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“…Several studies have reported that decreasing the work of breathing leads to significantly longer exercise tolerance which is associated with a reduced rate of oxygen uptake ( _ V O 2 ), ventilation and reduced perceptions of respiratory and limb discomfort (Harms et al 1998(Harms et al , 2000. This suggests that the work of breathing normally encountered during sustained heavy exercise has a significant influence on exercise performance, possibly due to diaphragmatic fatigue or a higher distribution of blood flow to the working muscles as a consequence of enhanced respiratory efficiency (Harms et al 1997;Johnson et al 1993;Mador et al 1993).…”

Section: Introductionmentioning

confidence: 99%

Oxygen uptake kinetics and maximal aerobic power are unaffected by inspiratory muscle training in healthy subjects where time to exhaustion is extended

Edwards

Cooke

2004

Eur J Appl Physiol

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The aim of this study was to determine whether 4 weeks of inspiratory muscle training (IMT) would be accompanied by alteration in cardiopulmonary fitness as assessed through moderate intensity oxygen uptake (V(.)O(2)) kinetics and maximal aerobic power (V(.)O(2max)). Eighteen healthy males agreed to participate in the study [training group (Tra) n=10, control group (Con) n=8]. Measurements of spirometry and maximal static inspiratory mouth pressure ( PI(max)) were taken pre- and post-training in addition to: (1) an incremental test to volitional exhaustion, (2) three square-wave transitions from walking to running at a moderate intensity (80% ventilatory threshold) and (3) a maximal aerobic constant-load running test to volitional fatigue for the determination of time to exhaustion ( T(lim)). Training was performed using an inspiratory muscle trainer (Powerbreathe). There were no significant differences in spirometry either between the two groups or when comparing the post- to pre-training results within each group. Mean PI(max) increased significantly in Tra ( P<0.01) and showed a trend for improvement ( P<0.08) in Con. Post-training T(lim) was significantly extended in both Tra [232.4 (22.8) s and 242.8 (20.1) s] ( P<0.01) and Con [224.5 (19.6) and 233.5 (12.7) s] ( P<0.05). Post-training T(lim) was significantly extended in Tra compared to Con ( P<0.05). In conclusion, the most plausible explanation for the stability in V(.)O(2) kinetics and V(.)O(2max) following IMT is that it is due to insufficient whole-body stress to elicit either central or peripheral cardiopulmonary adaptation. The extension of post-training T(lim) suggests that IMT might be useful as a stratagem for producing greater volumes of endurance work at high ventilatory loads, which in turn could improve cardiopulmonary fitness.

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Effects Of Respiratory Muscle Work On Cardiac Output And Its Distribution During Maximal Exercise.

Cited by 110 publications

References 0 publications

End-tidal pressure of CO2 and exercise performance in healthy subjects

End-tidal pressure of CO2 and exercise performance in healthy subjects

Increased sensations of intensity of breathlessness impairs maintenance of intense intermittent exercise

Oxygen uptake kinetics and maximal aerobic power are unaffected by inspiratory muscle training in healthy subjects where time to exhaustion is extended

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