title: Radial bone size and strength indices in male road cyclists, mountain bikers and controls.
abstract: Mountain biking (MB), unlike road cycling (RC) involves exposure to ground impact bone strain and requires upper-body muscle forces to maintain stability over uneven terrain and therefore may have differential effects on radial bone structure and strength. This study aimed to compare serum bone turnover marker concentration, 1-repetition maximum muscle strength and the radial proximal (diaphysis) and distal (metaphysis) bone structure [bone mineral content, total and cortical area (CoA), density and thickness, diameter and circumference], strength strain indices and muscle cross-sectional area (MCSA) using peripheral quantitative computed tomography (pQCT) between 30 male cyclists (18-34 years) MB (n = 10), RC (n = 10) and non-athletes controls (CON, n = 10). Differences were assessed by ANOVA and an ANCOVA (adjusting for body mass and height) where appropriate. MB radii were characterised by significantly stronger (14-16%), denser (9-27%) and larger (10%) metaphyses and stronger (22-23%) and larger (11-13%) diaphyses compared to RC and CON. RC had significantly 7% higher strength indices and 4% greater CoA and thickness than CON at the diaphysis, with no differences for other bone measurements. Serum C-terminal telopeptides of type-1 collagen concentration (bone resorption marker) was higher in RC than MB (p < 0.05) and above the age-reference range. MCSA and strength were greater in MB than RC (p < 0.05). Muscle forces generated during RC appear to produce an osteogenic stimulus to increase radial bone strength indices with minimal improvement in bone structure. However greater resorptive activity in RC suggests inadequate loading to support bone maintenance. In conclusion, bone loading, muscle size and strength of MB are superior to RC.
authors.affiliation: a Exercise Laboratory, School of Physiology, Faculty of Health Sciences , University of Witwatersrand , Johannesburg , South Africa.
authors.forename: Joanne A
authors.initials: JA
authors.lastname: Mcveigh
authors.forename: Rebecca
authors.initials: R
authors.lastname: Meiring
authors.forename: Alessandra
authors.initials: A
authors.lastname: Cimato
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Micklesfield
authors.forename: Tanja
authors.initials: T
authors.lastname: Oosthuyse
mesh_terms: D000328:Adult; D015519:Bone Density; D024042:Collagen Type I / Q000097:blood; D018483:Diaphyses / Q000033:anatomy & histology; D006132:Growth Plate / Q000033:anatomy & histology; D006801:Humans; D008297:Male; D009049:Motorcycles; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D010455:Peptides / Q000097:blood; D011859:Radiography; D011884:Radius / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D055815:Young Adult
chemical_list: D024042:Collagen Type I; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide
keywords: bone strength; cyclists; pQCT