Vis sammendrag
HIGH METABOLIC RESERVE CAPACITY IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) PATIENTS B. Rud1, C. C. Christensen2, M. Ryg2, S. Skumlien2 and J. Hallén1 1Norwegian University of Sport and Physical Education, Oslo, Norway; 2The Glittre Clinic, Norway In COPD patients exercise capacity is markedly reduced compared to healthy aged-matched controls. This is due to pulmonary and cardiovascular dysfunctions. However, COPD patients also have alteration in the muscles, such as low levels of oxidative enzymes, low capillary density, low fraction of type I fibres and decreased fiber cross-sectional area (Jakobsson et al., 1990; Whittom et al., 1998). This probably leads to reduced metabolic capacity and whether these peripheral changes limit the exercise capacity has being discussed (Richardson, 1999). In this study we attempted to test if skeletal muscle limits exercise capacity in COPD patients. Eight COPD patients and eight healthy sedentary controls (mean+/-SD 596yr, FEV1 35+/-8% of predicted and 51+/-8yr, FEV1 103+/-12% of predicted, respectively) performed three different exercise tests with stepwise increments of intensity until exhaustion (defined as inability to maintain pedal frequency, normally lasting 9-12 min): single-legged knee extension (SLE), two legged knee extension (TLE) and bicycling. All tests were performed in one day with at least 1 hour’s rest in between. Pulmonary oxygen uptake (VO2), heart rate (HR) and arterial blood pressure (BP) were measured continuously before, during and 6 min after the exercise tests. VO2 at rest, sitting on the ergometers, was (mean+/-SE) 321+/-25 and 352+/-34 ml.min-1 in controls and COPD patients, respectively (ns). At SLE VO2peak increased by 667+/-66 (controls) and 452+/-71 mlxmin-1 (COPD). The increase in VO2peak from SLE to TLE was 73+/-10 % of the increase from rest to SLE in the controls while the corresponding value in COPD was only 34+/-13 %. With bicycling VO2peak was 249+/-6 and 145+/-4 % of SLE VO2peak in controls and COPD patients, respectively. From anthropometrical measures quadriceps muscle mass can be calculated to 2.0+/-0.2 and 1.7+/-0.3 kg in controls and COPD. Peak VO2 per kg muscle mass during SLE was calculated to 348+/-25 and 241+/-26 in the two groups, respectively. During bicycling, the exercising muscles of controls utilized 30% per kg active muscle mass (set to 25% of body weight) of the SLE mass specific VO2peak while COPD patients utilized only 19%. The COPD patients showed lower HR and higher BP than controls during exercise. In conclusion, COPD patients have larger metabolic reserve capacity than controls during whole body exercise. The muscles of COPD patients are not as seriously detrained as previously suggested. REFERENCES Jakobsson, P., Jorfeldt, L., & Brundin, A. (1990). Eur.Respir.J. 3, 192-196. Richardson, R. S. (1999). J Appl.Physiol 86, 1751-1753. Whittom, F., Jobin, J., Simard, P. M., Leblanc, P., Simard, C., Bernard, S., Belleau, R., & Maltais, F. (1998). Med.Sci.Sports Exerc. 30, 1467-1474