{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,27]],"date-time":"2026-03-27T13:18:47Z","timestamp":1774617527918,"version":"3.50.1"},"reference-count":33,"publisher":"Oxford University Press (OUP)","issue":"5","license":[{"start":{"date-parts":[[2000,11,1]],"date-time":"2000-11-01T00:00:00Z","timestamp":973036800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/pages\/standard-publication-reuse-rights"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2000,11,1]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>The mechanism responsible for diminished exercise performance in cystic fibrosis (CF) is not clear. We hypothesized that reduced muscle size, rather than an intrinsic muscle defect, was the primary factor in such diminished exercise performance. Twenty-two subjects with CF (14 females and eight males, aged 6.5 to 17.7 yr, with FEV1 of 46% to 111% predicted) participated in a study of this hypothesis, and were compared with healthy children tested in the same laboratory. Muscle size was estimated from midthigh muscle cross-sectional area (CSA) obtained by magnetic resonance imaging, and fitness was determined by progressive cycle ergometer exercise testing with breath-by-breath measurements of gas exchange. Peak oxygen consumption (V\u02d9o2) was reduced in CF subjects (956 \u00b1 81 [mean \u00b1 SEM] ml\/min, as compared with 1,473 \u00b1 54 ml\/min in controls; p &amp;lt; 0.00001). Surprisingly, CF subjects had a lower peak V\u02d9o2 per CSA (mean for CF subjects 70 \u00b1 3% predicted, p &amp;lt; 0.0001) than did controls, whereas muscle CSA in CF subjects was not significantly smaller than in controls. The scaling parameters of peak V\u02d9o2 and muscle CSA did not differ significantly between healthy controls (0.80 \u00b1 0.16) and CF subjects (1.03 \u00b1 0.12). Indexes of aerobic function that are less effort-dependent than peak V\u02d9o2 were also lower in the CF subjects (e.g., the slope of V\u02d9o2 versus work rate [WR] (\u0394V\u02d9o2\/\u0394 WR) was 68 \u00b1 2% predicted; p &amp;lt; 0.005). The study data did not support the initial hypothesis, and suggest a muscle-related abnormality in oxygen metabolism in patients with CF.<\/jats:p>","DOI":"10.1164\/ajrccm.162.5.2003057","type":"journal-article","created":{"date-parts":[[2013,4,4]],"date-time":"2013-04-04T14:25:08Z","timestamp":1365085508000},"page":"1823-1827","source":"Crossref","is-referenced-by-count":88,"title":["Muscle Size and Cardiorespiratory Response to Exercise in Cystic Fibrosis"],"prefix":"10.1093","volume":"162","author":[{"given":"CHUANPIT","family":"MOSER","sequence":"first","affiliation":[{"name":"Department of Pediatrics, University of California Irvine Medical Center, Irvine; and Division of Pediatric Pulmonology, Miller Children's at Long Beach Memorial Medical Center, Long Beach, California"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"PORNCHAI","family":"TIRAKITSOONTORN","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, University of California Irvine Medical Center, Irvine; and Division of Pediatric Pulmonology, Miller Children's at Long Beach Memorial Medical Center, Long Beach, California"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"ELIEZER","family":"NUSSBAUM","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, University of California Irvine Medical Center, Irvine; and Division of Pediatric Pulmonology, Miller Children's at Long Beach Memorial Medical Center, Long Beach, California"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"ROBERT","family":"NEWCOMB","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, University of California Irvine Medical Center, Irvine; and Division of Pediatric Pulmonology, Miller Children's at Long Beach Memorial Medical Center, Long Beach, California"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"DAN M.","family":"COOPER","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, University of California Irvine Medical Center, Irvine; and Division of Pediatric Pulmonology, Miller Children's at Long Beach Memorial Medical Center, Long Beach, California"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"286","published-online":{"date-parts":[[2000,11,1]]},"reference":[{"key":"2026032708325919000_B1","doi-asserted-by":"crossref","first-page":"1785","DOI":"10.1056\/NEJM199212173272504","article-title":"The prognostic value of exercise testing in patients with cystic fibrosis.","volume":"327","author":"Nixon","year":"1992","journal-title":"N Engl J Med"},{"key":"2026032708325919000_B2","doi-asserted-by":"crossref","first-page":"1145","DOI":"10.1164\/ajrccm.157.4.9705023","article-title":"Determinants of aerobic and anaerobic exercise performance in cystic fibrosis.","volume":"157","author":"Shah","year":"1998","journal-title":"Am J Respir Crit Care Med"},{"key":"2026032708325919000_B3","first-page":"R720","article-title":"Calf muscle cross sectional 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