Attenuation of eccentric exercise-induced muscle damage conferred by maximal isometric contractions: a mini review

Abstract

Although, beneficial in determined contexts, eccentric exercise-induced muscle damage (EIMD) might be unwanted during training regimens, competitions and daily activities. There are a vast number of studies investigating strategies to attenuate EIMD response after damaging exercise bouts. Many of them consist of performing exercises that induce EIMD, consuming supplements or using equipment that are not accessible for most people. It appears that performing maximal isometric contractions (ISOs) 2-4 days prior to damaging bouts promotes significant attenuation of EIMD symptoms that are not related to muscle function. It has been shown that the volume of ISOs, muscle length in which they are performed, and interval between them and the damaging bout influence the magnitude of this protection. In addition, it appears that this protection is not long-lived, lasting no longer than 4 days. Although no particular mechanisms for these adaptations were identified, professionals should consider applying this non-damaging stimulus before submitting their patients to unaccustomed exercised. However, it seems not to be the best option for athletes or relatively trained individuals. Future, studies should focus on establishing if ISOs protect other populations (i.e., trained individuals) or muscle groups (i.e., knee extensors) against EIMD, as well as investigate different mechanisms for ISO-induced protection.

Keywords: exercise-induced muscle damage; isometric contractions; pre-conditioning; prevention strategy; repeated bout effect.

Figure 1

Schematic illustration of the hypothetical relationship between the number of maximal isometric contractions (ISOs), attenuation of exercise-induced muscle damage (EIMD), and duration of the conferred protection according to the data from Chen et al. (2012b,c, 2013). Note that muscle groups that are not frequently exposed to EIMD (e.g., untrained and/or upper limb muscles) might benefit from the protective effect conferred by ISOs without the manifestation of EIMD (i.e., before the onset of EIMD). Based on data obtained from maximal eccentric contractions (Chen et al., ; Lima and Denadai, 2011), we also speculate that muscle groups that are highly exposed to EIMD (e.g., trained and/or lower limb muscles) require a greater number of ISOs in order to benefit from a protective effect with lesser magnitude and duration and that EIMD is required for it to manifest. The “?” represents that this assumption is hypothetical and based on studies that did not use ISOs as a preconditioning activity.