title: Influence of concentric and eccentric resistance training on architectural adaptation in human quadriceps muscles.
abstract: Studies using animal models have been unable to determine the mechanical stimuli that most influence muscle architectural adaptation. We examined the influence of contraction mode on muscle architectural change in humans, while also describing the time course of its adaptation through training and detraining. Twenty-one men and women performed slow-speed (30 degrees /s) concentric-only (Con) or eccentric-only (Ecc) isokinetic knee extensor training for 10 wk before completing a 3-mo detraining period. Fascicle length of the vastus lateralis (VL), measured by ultrasonography, increased similarly in both groups after 5 wk (Delta(Con) = +6.3 +/- 3.0%, Delta(Ecc) = +3.1 +/- 1.6%, mean = +4.7 +/- 1.7%; P < 0.05). No further increase was found at 10 wk, although a small increase (mean approximately 2.5%; not significant) was evident after detraining. Fascicle angle increased in both groups at 5 wk (Delta(Con) = +11.1 +/- 4.0%, Delta(Ecc) = +11.9 +/- 5.4%, mean = 11.5 +/- 3.2%; P < 0.05) and 10 wk (Delta(Con) = +13.3 +/- 3.0%, Delta(Ecc) = +21.4 +/- 6.9%, mean = 17.9 +/- 3.7%; P < 0.01) in VL only and remained above baseline after detraining (mean = 13.2%); smaller changes in vastus medialis did not reach significance. The similar increase in fascicle length observed between the training groups mitigates against contraction mode being the predominant stimulus. Our data are also strongly indicative of 1) a close association between VL fascicle length and shifts in the torque-angle relationship through training and detraining and 2) changes in fascicle angle being driven by space constraints in the hypertrophying muscle. Thus muscle architectural adaptations occur rapidly in response to resistance training but are strongly influenced by factors other than contraction mode.
authors: Centre for Sports Medicine and Human Performance, School of Sport and Education, Brunel Univ., Uxbridge UB8 3PH, UK. anthony.blazevich@brunel.ac.uk
authors: Anthony J
authors: AJ
authors: Blazevich
authors: Dale
authors: D
authors: Cannavan
authors: David R
authors: DR
authors: Coleman
authors: Sara
authors: S
authors: Horne
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D048429:Cell Size; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007717:Knee / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D009119:Muscle Contraction; D018485:Muscle Fibers, Skeletal / Q000000981:diagnostic imaging / Q000502:physiology*; D053580:Muscle Strength; D052097:Quadriceps Muscle / Q000033:anatomy & histology* / Q000166:cytology / Q000000981:diagnostic imaging / Q000502:physiology*; D016059:Range of Motion, Articular; D013997:Time Factors; D019415:Torque; D014463:Ultrasonography