title: Relationship of skeletal muscle mass, muscle strength and bone mineral density in adults with cystic fibrosis.
abstract: Few studies have investigated peripheral muscle strength and quality in patients with cystic fibrosis (CF). The present study tested the isometric and isokinetic strength of the quadriceps and hamstrings using an isokinetic dynamometer and a strength-testing chair in 25 CF adults and 25 controls. Total body and leg muscle mass were determined by dual-energy X-ray absorptiometry, and bone mineral density (BMD) was also measured. Both muscle strength and muscle mass (total body and leg) were decreased in the CF group. In both groups there was a highly significant relationship between quadriceps strength and leg muscle mass (CF, r=0.7, P=0.0002; controls, r=0.6, P=0.0013). When strength was normalized for muscle size, there was no significant difference between the two groups. Total body and leg BMD were significantly reduced in CF subjects compared with controls. However, when corrected for height, the differences disappeared. There was a significant relationship found between leg muscle mass and leg BMD. We conclude that CF adults are significantly weaker than controls. This is due to lower muscle mass, and not to a reduced force-generating capacity of the muscle, implying that there is no decrease in the quality of CF muscle. BMD is also reduced in CF subjects, and this appears to be related to shorter stature in this group.
authors.affiliation: Department of Cystic Fibrosis at the Royal Brompton Hospital, Imperial College School of Medicine, Sydney Street, London SW3 6NP, UK. s.elkin@ic.ac.uk
authors.forename: S L
authors.initials: SL
authors.lastname: Elkin
authors.forename: L
authors.initials: L
authors.lastname: Williams
authors.forename: M
authors.initials: M
authors.lastname: Moore
authors.forename: M E
authors.initials: ME
authors.lastname: Hodson
authors.forename: O M
authors.initials: OM
authors.lastname: Rutherford
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D001696:Biomechanical Phenomena; D001827:Body Height; D015519:Bone Density; D016022:Case-Control Studies; D003550:Cystic Fibrosis / Q000150:complications / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007866:Leg; D008297:Male; D018908:Muscle Weakness / Q000000981:diagnostic imaging / Q000209:etiology; D018482:Muscle, Skeletal / Q000473:pathology* / Q000503:physiopathology