Skeletal Muscle Remodeling in Response to Eccentric vs. Concentric Loading: Morphological, Molecular, and Metabolic Adaptations

Abstract

Skeletal muscle contracts either by shortening or lengthening (concentrically or eccentrically, respectively); however, the two contractions substantially differ from one another in terms of mechanisms of force generation, maximum force production and energy cost. It is generally known that eccentric actions generate greater force than isometric and concentric contractions and at a lower metabolic cost. Hence, by virtue of the greater mechanical loading involved in active lengthening, eccentric resistance training (ECC RT) is assumed to produce greater hypertrophy than concentric resistance training (CON RT). Nonetheless, prevalence of either ECC RT or CON RT in inducing gains in muscle mass is still an open issue, with some studies reporting greater hypertrophy with eccentric, some with concentric and some with similar hypertrophy within both training modes. Recent observations suggest that such hypertrophic responses to lengthening vs. shortening contractions are achieved by different adaptations in muscle architecture. Whilst the changes in muscle protein synthesis in response to acute and chronic concentric and eccentric exercise bouts seem very similar, the molecular mechanisms regulating the myogenic adaptations to the two distinct loading stimuli are still incompletely understood.Thus, the present review aims to, (a) critically discuss the literature on the contribution of eccentric vs. concentric loading to muscular hypertrophy and structural remodeling, and, (b) clarify the molecular mechanisms that may regulate such adaptations.We conclude that, when matched for either maximum load or work, similar increase in muscle size is found between ECC and CON RT. However, such hypertrophic changes appear to be achieved through distinct structural adaptations, which may be regulated by different myogenic and molecular responses observed between lengthening and shortening contractions.

Isometric training and long‐term adaptations: Effects of muscle length, intensity, and intent: A systematic review

“…Unlike muscle volume, which is highly dependent on total training volume, there are demonstrable differences between contraction type and alteration in fascicle length and pennation angle . To date, very few studies have compared the effect of isometric resistance training variations on muscle architecture; of those that have, results are equivocal.…”

Eccentric cycling is more efficient in reducing fat mass than concentric cycling in adolescents with obesity

“…Although the impact of ECC training on lean mass (LM) has been extensively studied, the findings are too varied to clearly affirm the superiority of ECC training . Recent meta‐analyses demonstrated that when matched for load or work, changes between ECC and CON training were found similar in regard to muscle hypertrophy . Considering fat mass (FM), the impact of ECC training remains poorly studied, without direct comparisons between ECC and CON training.…”

Topology optimization of fusiform muscles with a maximum contraction

“… However, skeletal muscles may not necessarily grow to be the optimized shaped of the numerical examples because the complicated boundary condition is not taken into consideration in Section 3.1, and the difference of the contractile properties between different fusiform shapes is small as shown in Table . Skeletal muscles may grow to be some other fusiform shapes to pursue a better dynamic performance, eg, the dynamic performance in high‐power movements, eccentric loading, and concentric loading but not the static performance in proposed in Equation .…”