Concentric and eccentric torque in COPD patients

It has been shown that skeletal muscle strength of COPD patients is reduced (Kim H.C., 2008) and eccentric contraction resulted greater compared to control subjects, when normalized for lean body mass (Mathur S., 2007). The aim of the study is to access if eccentric and concentric peaks torque are correlated with disease severity.Thirty-four males with COPD (mean FEV1=66.9±19.1% of predicted and FEV1/FVC=55.4±14.1% of predicted, age 66.35±4.6 years, lean body mass at DXA 55.54±9.55 Kg) performed an isokinetic concentric and eccentric torque of the knee extensors on dynamometer at 30 and 210 deg/s. Pearson coefficient was used to detect correlation between independent and dependent variables.Both concentric and eccentric peak torque at 30 deg/s were correlated with FEV1 (0.470 p<0.01; 0.391 p<0.05) and FEV1/FVC (0.518 p<0.01; 0.424 p<0.05). Same results were observed at 210 deg/s: both concentric and eccentric peak torque were correlated with FEV1 (0.380 p<0.05 and 0.391 p<0.05) and FEV1/FVC (0.409 p<0.05 and 0.360 p<0.05). The ratio between eccentric and concentric peak torque was significantly correlated with FEV1 (-0.366 p<0.05) and FEV1/FVC (-0.436 p<0.05).Our results confirm that muscle strength in COPD is correlated with severity disease both in concentric and eccentric torque at different angular velocities. Moreover, the eccentric peak torque showed less decrease than concentric one. Eccentric contraction is characterized by unique neural mechanisms, involving fast twitch motor units (Duchateau J., 2008). Also, it has been shown that COPD hypoxemic condition leads fiber type shift towards fast twitch fibers (Gosker H.R., 2002). In conclusion, COPD patients seem to develop favorable profile to minimize strength loss.