RESUMO
The purpose of this study was to examine the relationship between smoking and cardiopulmonary function, and the effect of smoking habit on exercise tolerance after discharge from the hospital, focusing on CPX test data of patients hospitalized for acute myocardial infarction, and on CPX test data at 6 months after discharge. A total of 123 male patients hospitalized for acute myocardial infarction between April 2014 and December 2020 were included. Laboratory and CPX data were compared between smokers and non-smokers. CPX data of smokers, ex-smokers and non-smokers were also compared in 24 patients who underwent CPX examination 6 months after discharge. HDL-C was significantly decreased (p < 0.05) and τON was significantly prolonged (p < 0.05) during hospitalization in smokers. τON was significantly shorter only in ex-smokers (p < 0.05) 6 months after discharge compared to during hospitalization. These results suggest that τON, which reflects the oxygen uptake kinetics of peripheral tissues, is shortened by smoking cessation.
RESUMO
A study was performed to clarify the relationships between oxygen uptake (VO<SUB>2</SUB>) kinetics on recovery from incremental maximal exercise and blood lactate, glucose and alanine metabolism. Eight healthy males aged 21.6±3.3 years were studied. The incremental exercise test was performed using a modified version of Bruce's protocol until 30 min after exhaustion. The VO<SUB>2</SUB> responses on recovery were fitted by a two-component exponential model. Blood lactate concentration in the recovery phase was fitted by a bi-exponential time function to assess the velocity constant of the slowly decreasing component (γ2) expressing the rate of blood lactate removal. Both blood lactate and plasma alanine concentration were significantly increased from rest to maximal exercise, and were significantly decreased thereafter, but remained above resting values for 30 min after the maximal stage. Blood glucose concentration was significantly decreased following maximal exercise and returned to the pre-exercise value by 30 min after the maximal stage. Concentrations of plasma branched-chain amino acids (valine, leucine and isoleucine) were significantly decreased from the maximal stage until 30 min after exhaustion. The time constant of the slow component on recovery VO<SUB>2</SUB> [τVO<SUB>2</SUB> (s) ] was correlated with neither γ2 nor the degree of change in blood lactate from the maximal stage until 30 min after exhaustion (Δlactate) . However, τVO<SUB>2</SUB> (s) was significantly correlated with both Δ blood glucose and Δ alanine. In addition, Δ alanine was significantly correlated with Δ blood glucose. From these results, we conclude that oxygen uptake kinetics after exhaustive maximal exercise is related to glucose resynthesis through alanine metabolism, as compared with that from lactate metabolism.
RESUMO
Circadian rhythms (diurnal variations) in many physiological parameters have been reported. However, there are no data on gas exchange kinetics at the onset of exercise. The purpose of this study was to establish whether there are circadian rhythms in gas exchange kinetics at the onset of exercise.<BR>Six male subjects performed 120W exercise on a cycle ergometer for 7 min in the morning (AM; 7: 30-8: 30) and evening (PM; 16: 30-17: 30) . Rectal temperature (Tr) and mean skin temperature (T<SUB>sk</SUB>) at rest were significantly higher PM than AM, the differences being 0.9±0.2°C and 0.7±0.2°C, respectively. Respiratory and circulatory parameters at rest and during exercise were not different between AM and PM. The time constants of oxygen uptake (Vo<SUB>2</SUB>), carbon dioxide output (Vco<SUB>2</SUB>), minute ventilation (V<SUB>E</SUB>), heart rate (HR), and oxygen pulse (Vo<SUB>2</SUB>/HR) showed the same results. There was no relationship between temperature parameters (Tr, T<SUB>sk</SUB>) and the time constants.<BR>It is suggested that circadian rhythms reflected by the change in body temperature do not have any effect on gas exchange kinetics at the onset of moderate bicycle exercise.