[Relationship between anaerobic threshold and breathlessness during exercise].
We studied the possibility that during incremental exercise anaerobic threshold (AT) is associated with an increase in breathlessness in subjects with increased impedance or respiratory system. Six patients with chronic lung diseases (CLD) and six healthy subjects performed cycle ergometer exercise under two conditions; with free resistive loading and with 9 cmH2O/l/sec of inspiratory resistive loading (IRL). Ventilation, respiratory pattern, VO2, VCO2, were measured every 15 sec by a metabolic cart, Minato Respiromonitor RM 300. AT was determined by V-slope method. Mouth occlusion pressure (P0.1) was also measured in six subjects during exercise. The subjects selected a number of modified Borg scale (psi) to express their breathlessness during exercise by pushing a electrically potentiated remote button. Slopes of changes in psi with increasing work-load, delta psi/delta watt-slope, were calculated before and after V-slope AT, and each inflection point of VE, respiratory rate, VT/Ti, and VCO2. In order to evaluate which parameters are the most responsible for a change in psi, statistical significance (P-value) in changes of slope of each parameters were compared. The delta psi-slope increased with the highest significance after AT point. Under IRL the significance was more pronounced. There was a highly significant linear correlation between P0.1 and psi during exercise both under free resistive loading and IRL. In addition the increase of P0.1 with incremental exercise was characterized by a presence of inflection at a workload of V-slope AT in most of the subjects. From these results it was concluded that anaerobic threshold was closely associated with an increase of breathlessness during exercise via enhancing respiratory motor command.(ABSTRACT TRUNCATED AT 250 WORDS)
Kurihara
N
N
First Department of Internal Medicine, Osaka City University Medicine School, Japan.
Matsushita
H
H
Wakayama
K
K
Fujimoto
S
S
Nakano
N
N
Hirata
K
K
Ohta
K
K
Takeda
T
T
D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology*; D004417:Dyspnea / Q000209:etiology* / Q000503:physiopathology; D015444:Exercise; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000503:physiopathology; D008875:Middle Aged