Concentric and eccentric torque in COPD patients vs. healthy control

Background Presence of muscle wasting is common in COPD patients across all disease stages (Seymour J.M, 2010) and eccentric contraction resulted greater compared to control subjects (Mathur S., 2007). The aim of our study is to outline a description of COPD strength performances as a function of contraction modalities and velocities. Methods Thirty-five COPD males (mean FEV1=64.76±20.08% of pred.; FEV1/FVC= 57.35±13.56% of pred.; age 67.21±4.7 years) and 25 healthy males (FEV1= 115.06±17.43% of pred.; FEV1/FVC=101.87±6.62% of pred.; age 65.15±5.69 years) performed an isokinetic concentric and eccentric torque of the knee extensors on dynamometer at 30 and 210 deg/s. Also, measurements of fascicle length, thickness and pennation angle of Vastus lateralis, 6MWT, 1RM at Leg press, Biceps curl and Chest press, and lifestyle data with Sensewear® were assessed. Analysis of variance (ANOVA) and Pearson coefficient were used to detect significant differences between groups and correlation between independent and dependent variables. Results Significant differences were found between groups and FEV1 (p<0.001), FEV1/FVC (p<0.001), 6MWT (p<0.001) 1RM Leg press (p<0.05), Chest Press (p<0.00), Biceps Curl (p<0.001), n°steps (p<0.001), 3METs energy expenditure (p<0.01) and concentric 30deg/s contraction (p<0.05). Moreover, significant differences were found between groups and both eccentric/concentric peak torque ratio (30 deg/sec p<0.001; 210 deg/sec p<0.01). No significant differences were found in muscle architecture, fast concentric and both eccentric contraction. Significant correlations were found between FEV1 and 6MWT (0.719 p<0.001), 1RM Leg press (0.449 p<0.001), Chest Press (0.384 p<0.05), n°steps (0.472 p<0.001), 3METs energy expenditure (0.329 p<0.05), both peak torque contraction at 30 deg/sec (0.427 p<0.01; 0.280 p<0.05), at 210 deg/sec (0.285 p<0.05; 0.276 p<0.05) and eccentric/concentric peak torque ratio at both velocities (-0.562 p<0.001; -0.292 p<0.05). Same results were observed between FEV1/FVC and parameters assessed. Conclusions According with literature, COPD patients showed lower health related parameters. Moreover, they performed a slow concentric contraction compared with healthy controls, while preserving eccentric contractions and fast concentric torque. Eccentric contraction is characterized by unique neural mechanisms, involving fast twitch motor units (Duchateau J., 2008). Also, COPD hypoxemic condition leads fiber type shift towards fast twitch fibers (Gosker H.R., 2002). Therefore, COPD patients seem to develop favorable profile to minimize strength loss and no finding of muscle architecture differences’ lead us to speculate in a neural-muscular modifications. References Mathur S. et al. Preservation of eccentric torque of the knee extensors and flexors in patients with COPD; J Cardiopulm Rehabil Prev. 2007; 27:411–6; Duchateau J et al. Neural control of shortening and lengthening contractions: influence of task constraints; Physiol. 2008; 586:5853-64; Gosker H.R. et al. Skeletal Muscle fibre-type shifting and metabolic profile in patients with chronic obstructive pulmonary disease. Eur Respir J. 2002; 19:617-25. Seymour J.M. et al. The prevalence of quadriceps weakness in COPD and relationship with disease severity; Eur Respi J. 2010; 36: 81-88.