Effects of work Intensity on the Dynamics of Pulmonary Gas Exchange During Execise in Humans

Tez Türü: Doktora

Tezin Yürütüldüğü Kurum: University of London, Birleşik Krallık

Tez Danışmanı: Brian J Whipp

Tezin Onay Tarihi: 2000

Tezin Dili: İngilizce

Desteklendiği Program: YÖK 100/2000 Programı

Özet:

Pulmonary oxygen uptake () kinetics below the lactate-threshold (q_L), is adequately described as a mono-exponential function of time. At higher intensities (> q_L) however, the profile is more complex, because of a delayed-onset slow component (“excess” ). We were interested in studying ventilatory and pulmonary gas exchange kinetics in different intensity domains using step and ramp work rate forcings, and also the intra-muscular oxygenation profile in both leg and arm muscles.

After an incremental work test (IWT) to the limit of tolerance (peak), subjects performed constant-load exercise tests at four intensity domains: 90% of q_L, 40 and 80% of D (the difference between the q_L and ), and 110 % of . They also performed step-decremental ramps (SDR) from both peak and 50% of peak power. Gas exchange variables were derived breath-by-breath from continuous monitoring of respiratory volumes (turbine) and gas concentrations (mass spectrometer), and the temporal oxygenation profile of the vastus lateralis and biceps brachii was assessed by near infrared spectroscopy.

The sub-q_L on-transient kinetics were mono-exponential, whereas at 40 and 80% of D they were better characterised by a double-exponential model with a slow component of delayed onset. For supra-maximal exercise the response was again mono-exponential. There was no delay term in the slow component at high work rates at the off-transient. The slope for the SDR was significantly greater than for the IWT, but only for the peak test. Endurance-type athletes were able to exercise at their for an average of 5 min, whereas for sprint-type athletes the average was less than half min. The intra-muscular oxygenation profile of the arm during leg exercise suggests that additional work done by the arm muscles to stabilise the body at high work rates may play an important role in the slow component of kinetics.