What is new in musculoskeletal interactions? Lateral force transmission, botox, calcium and bone strength, and osteoccyte apoptosis.
Year: 2010
Type: article
Abstract: Muscular adaptations to resistance training: the case for lateral force transmission An increase in force of human skeletal muscle following resistance training is generally ascribed to changes in muscle mass and architecture, and in neural activation capacity. While these phenomena have been extensively studied in the past, a number of methodological limitations precluded an exhaustive examination of the relationships between the increase in strength and other training-induced adaptations. By using latest technology for the assessment of muscle structure and function, Erskine et al. 1 circumvented these limitations and delivered one of the most comprehensive estimations of in vivo muscular adaptations to heavy resistance training. By combining measurements of isometric torque, agonist (interpolated twitch technique) and antagonist (electromyography) neural activation, muscle architecture (ultrasound), muscle volume and patellar tendon moment arm (magnetic resonance imaging), the authors estimated the specific tension of the whole quadriceps muscle, calculated as the ratio of the patellar tendon force by the summated physiological cross section areas of each head of the quadriceps. Importantly, apart from muscle volume, all measurements were obtained near optimum sarcomeric length, during maximal voluntary contraction at a knee joint angle enabling maximal torque production. One might - rightly - argue that despite this unprecedented level of complexity for a training study, the validity of the outcome is not perfect, for most of these variables still rely on necessary assumptions/approximations. Nevertheless, the findings from this study are surprising: an increase in quadriceps specific tension, largely independent from changes in neural factors. The authors quote a number of possible factors to explain their results, including changes in myofilaments packing density, increase in the proportion of type IIX fibres, or the possible role of lateral force transmission. An elevation of force per cross sectional area of single muscle fibres and a shift in fibre-type composition towards type IIX have indeed both been reported in the extreme case of bodybuilders, following years of heavy resistance loading 2 . However, such adaptations are unlikely in young humans subjected to short term resistance training 3 , leaving the controversial hypothesis of lateral force transmission.
Source: PubMed
Authors: O R Seynnes, J Rittweger
Institution: Manchester Metropolitan University
Language: English
Subfield: Orthopedics and Sports Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W1569437812