title: Identical twins are discordant for markers of eccentric exercise-induced muscle damage.
abstract: This study investigated whether the variability observed in the markers of exercise-induced muscle damage (EIMD) has a genetic etiology. Sixteen pairs of identical twins performed 24 maximal eccentric contractions (24MAX) using the elbow flexors. EIMD indicators were measured pre-24MAX and three days post-24MAX and included: post-exercise force deficit, maximal isometric force (ISO), plasma creatine kinase (CK), myoglobin (Mb), and joint range of motion. Force-time curves were recorded throughout the 24MAX. Twin siblings were alike for pre-exercise ISO (intraclass R = 0.89) and CK (R = 0.76) (p < 0.001), but were discordant for post-exercise force deficit (R = 0.29), CK (R = 0.15), and Mb (R = 0.17) (p > 0.05). In comparison with individuals minimally affected by the 24MAX, those who experienced the greatest force deficit 3 days post-exercise (> 50 %) were characterised by the greater application of eccentric force at longer muscle lengths (23.1 % vs 17.3 %) (p < 0.05). This study demonstrates that twins do not experience the same level of EIMD following identical exercise bouts. This suggests that the individual variability following high-force eccentric exercise cannot be attributed to genetic differences, refuting the idea that an inherited subclinical predisposition is responsible. From these results, a potential mechanism for the repeated bout effect is discussed.
authors.affiliation: Division of Sports Sciences/Sports Medicine, Australian Institute of Sport, Bruce, Australia. gulbinj@ausport.gov.au
authors.forename: J P
authors.initials: JP
authors.lastname: Gulbin
authors.forename: P T
authors.initials: PT
authors.lastname: Gaffney
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001134:Arm Injuries / Q000503:physiopathology*; D003402:Creatine Kinase / Q000097:blood; D004551:Elbow Joint / Q000502:physiology; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000293:injuries* / Q000502:physiology; D009211:Myoglobin / Q000097:blood; D016059:Range of Motion, Articular; D014430:Twins, Monozygotic / Q000235:genetics*
chemical_list: D009211:Myoglobin; D003402:Creatine Kinase