Quadriceps and ankle dorsiflexor strength in chronic obstructive pulmonary disease



Introduction: Quadriceps strength and size are commonly reduced in chronic obstructive pulmonary disease (COPD). We wished to assess volitional and nonvolitional ankle dorsiflexor strength in COPD. Methods: Quadriceps and ankle dorsiflexor strength were measured by maximum voluntary contraction (MVC) and by twitch responses to supramaximal femoral and fibular nerve stimulation. Cross-sectional areas of the tibialis anterior (TACSA) and rectus femoris muscles (RFCSA) were measured by ultrasound. Results: Eighteen elderly subjects and 20 COPD patients [mean(SD) %predictedFEV1 50(20)%] participated. No significant difference in fat-free mass index, ankle dorsiflexor strength, or TACSA were observed in the presence of reduced quadriceps strength and size in COPD [mean MVC difference: −10.9 kg (95% confidence interval {CI}: −17.1 kg to −4.8 kg, P < 0.01; mean RFCSA difference −119 mm2, 95% CI: −180 mm2 to −58 mm2, P < 0.01)]. Conclusions: Ankle dorsiflexor strength is less attenuated than quadriceps strength in COPD patients with moderate airflow obstruction. Direct quadriceps assessment may be more relevant than measurement of lower limb fat-free mass. Muscle Nerve 46: 548–554, 2012