Eccentric exercise per se does not affect muscle damage biomarkers: early and late phase adaptations

Abstract

Purpose Acute high-intensity unaccustomed eccentric exercise performed by naive subjects is accompanied by disturbances in muscle damage biomarkers. The aim of the study was to investigate whether a causal relationship indeed exists between eccentric exercise and muscle damage. Methods Twenty-four men randomly assigned into a concentric only or an eccentric-only training group and performed 10 weeks of isokinetic resistance exercise (one session/week of 75 maximal knee extensors actions). Physiological markers of muscle function and damage (i.e., range of motion, delayed onset muscle soreness, isometric, concentric and eccentric peak torque) were assessed prior to and 1-3 and 5 days post each session. Biochemical markers of muscle damage (creatine kinase) and inflammation (C-reactive protein) were measured prior and 2 days post each session. Results After the first bout, eccentric exercise induced greater muscle damage compared to concentric exercise; however, during the nine following sessions, this effect progressively diminished, while after the 10th week of training, no alterations in muscle damage biomarkers were observed after either exercise protocol. Additionally, strength gains at the end of the training period were comparable between the two groups and were mode-specific. Conclusion (1) eccentric exercise per se does not affect muscle damage biomarkers; (2) muscle damage occurs as a result of muscle unaccustomedness to this action type; (3) exercise-induced muscle damage is not a prerequisite for increased muscle strength. Collectively, we believe that muscle unaccustomedness to high-intensity eccentric exercise, and not eccentric exercise per se, is the trigger for muscle damage as indicated by muscle damage biomarkers.

The role of exercise selection in regional Muscle Hypertrophy: A randomized controlled trial

“…These authors proposed that the time spent in each phase of an exercise change the torque at the knee joint and thus, this could be responsible for this regional response of growth. As strength gains are mode dependent (Paschalis et al, 2011;Margaritelis et al, 2021) it seems reasonable to think that muscle hypertrophy would also follow a mode dependent growth pattern. However, there may be other unknown factors playing a role in the regional hypertrophy responses of a muscle.…”

The Effects of High-Intensity Interval Exercise on Skeletal Muscle and Cerebral Oxygenation during Cycling and Isokinetic Concentric and Eccentric Exercise

“…It is known that HIIT can be performed using a wide range of exercise activities such as cycling, running, rowing, and swimming which, in turn, may cause numerous physiological adaptations in health and disease [3][4][5][6][7][8][9][10][11][12][13][14][15][16]67]. High-intensity interval training has also been used during pure eccentric and pure concentric muscle actions using an isokinetic dynamometer, causing beneficial effects in health and performance parameters [19][20][21]. In the present investigation, we compared a traditional type of HIIE (i.e., cycling) with HIIE performed during isokinetic eccentric and concentric exercise in relation to skeletal muscle and cerebral oxygenation.…”

“…In these activities, muscles work in a continuous shortening and a lengthening cycle, i.e., concentric and eccentric muscle contraction, respectively [18]. Recently, high-intensity interval training was also performed during pure concentric (muscle shortening) and pure eccentric (muscle stretching) muscle contractions using isokinetic dynamometers [19][20][21]. It is known that different modes of muscle contraction exhibit diverse molecular, metabolic, mechanical, and neural characteristics [22,23].…”

Acute and Delayed Effects of Time-Matched Very Short “All Out” Efforts in Concentric vs. Eccentric Cycling

“…Two familiarization sessions with the eccentric ergometer (Cyclus2 Eccentric Trainer, RBM Elektronik-Automation GmbH, Leipzig, Germany) in a standard seated position were deemed sufficient for obtaining reliable mechanical responses in "sprint" eccentric cycling at 80 rpm [10], and probably providing some protection to avoid a exacerbate EIMD as observed in pilot testing, based on the repeated bout effect (RBE) [15]. The initial session took place 5 min after cessation of the ramp test.…”

“…Most commonly, eccentric cycling is accompanied by exercise-induced muscle damaged (EIMD) which is characterized by muscle soreness, inflammation, and loss of functional capacity, such as strength loss and decreased proprioceptive function [14]. It is well accepted that eccentric contractions are more prone to inducing EIMD than concentric work, however recent evidence suggest that this may be attributed to muscle unaccustomedness and not to eccentric exercise per se [15]. In this regard, there are a number of confounding factors other than mechanical stress that may be associated to the etiology of EIMD after eccentric contractions, including the relative exercise intensity [16] and the metabolic milieu [17,18].…”