Abstract
BackgroundQuantifying the improvements in lower limb or quadriceps muscle mass following resistance training (RT), is an important outcome measure in COPD. Ultrasound is a portable, radiation free imaging technique that can measure the size of superficial muscles belonging to the quadriceps group such as the rectus femoris, but has not been previously used in COPD patients following RT. We compared the responsiveness of ultrasound derived measures of quadriceps mass against dual energy x-ray absorptiometry (DEXA), in patients with COPD and healthy controls following a programme of high intensity knee extensor RT.MethodsPortable ultrasound was used to assess the size of the dominant quadriceps in 45 COPD patients and 19 healthy controls-before, during, and after 8 weeks of bilateral high intensity isokinetic knee extensor RT. Scanning was performed at the mid-thigh region, and 2 indices of quadriceps mass were measured-rectus femoris cross-sectional area (RFcsa) and quadriceps muscle thickness (Qt). Thigh lean mass (Tdexa) was determined by DEXA.ResultsTraining resulted in a significant increase in Tdexa, RFcsa and Qt in COPD patients [5.7%, 21.8%, 12.1% respectively] and healthy controls [5.4%, 19.5%, 10.9 respectively]. The effect size for the changes in RFcsa (COPD= 0.77; Healthy=0.83) and Qt (COPD=0.36; Healthy=0.78) were greater than the changes in Tdexa (COPD=0.19; Healthy=0.26) following RT.ConclusionsSerial ultrasound measurements of the quadriceps can detect changes in muscle mass in response to RT in COPD. The technique has good reproducibility, and may be more sensitive to changes in muscle mass when compared to DEXA.Trial registrationhttp://www.controlled-trials.com (Identifier: ISRCTN22764439)
Highlights
Reduced lower limb skeletal muscle mass and strength is an important systemic feature of Chronic Obstructive Pulmonary Disease (COPD) which has a significant impact on mortality, morbidity and healthcare utilisation [1,2,3,4]
quadriceps isometric maximum voluntary contraction (QMVC) was significantly lower in patients compared with controls, but ultrasound and dual energy x-ray absorptiometry (DEXA) indices of thigh muscle mass did not differ between the groups at baseline
For the group as a whole, a significant linear relationship was observed between ultrasound and DEXA measured indices of quadriceps size [rectus femoris cross-sectional area (RFcsa) vs. Tdexa: r=0.68, p
Summary
Reduced lower limb skeletal muscle mass and strength is an important systemic feature of Chronic Obstructive Pulmonary Disease (COPD) which has a significant impact on mortality, morbidity and healthcare utilisation [1,2,3,4]. Ultrasound is an imaging technique that can determine thickness and crosssectional areas of superficial muscles such as the rectus femoris muscle It has the advantage of being portable, and involves no ionizing radiation. Quantifying the improvements in lower limb or quadriceps muscle mass following resistance training (RT), is an important outcome measure in COPD. Ultrasound is a portable, radiation free imaging technique that can measure the size of superficial muscles belonging to the quadriceps group such as the rectus femoris, but has not been previously used in COPD patients following RT. We compared the responsiveness of ultrasound derived measures of quadriceps mass against dual energy x-ray absorptiometry (DEXA), in patients with COPD and healthy controls following a programme of high intensity knee extensor RT
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