AUTHOR=Barreto Renan Vieira , de Lima Leonardo Coelho Rabello , Greco Camila Coelho , Denadai Benedito Sérgio TITLE=Protective Effect Conferred by Isometric Preconditioning Against Slow- and Fast-Velocity Eccentric Exercise-Induced Muscle Damage JOURNAL=Frontiers in Physiology VOLUME=Volume 10 - 2019 YEAR=2019 URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2019.01203 DOI=10.3389/fphys.2019.01203 ISSN=1664-042X ABSTRACT=We investigated if the same isometric preconditioning protocol (IPP) attenuates the magnitude of muscle damage induced by different maximal eccentric exercise protocols in the elbow flexors. Sixty-four untrained men were assigned to either two experimental or two control groups. Participants in the experimental groups performed an IPP prior to either slow (60°·s-1 – ISO+ECC-S) or fast (180°·s-1 – ISO+ECC-F) maximal eccentric contractions (MaxECC). Subjects in the control groups performed slow (ECC-S) or fast (ECC-F) MaxECC without IPP. Maximal isokinetic concentric torque (MVC), muscle soreness (SOR) and muscle thickness (MT) were assessed before, immediately after, and 1-4 days following the MaxECC. Significant (p < 0.05) group vs time interactions were found for MVC (F = 4,517), SOR (F = 6,318), and MT (F = 1,863). The ECC-S group presented faster (p<0.05) recovery of MVC and MT and less (p<0.05) SOR at 96h post-MaxECC compared with ECC-F group. No significant differences in MVC and MT were found between ECC-S and ECC-F groups following MaxECC. The ISO+ECC-S group showed faster (p<0.05) recovery of MVC and SOR compared to the ECC-S group. No significant differences were evident between ISO+ECC-S and ECC-S in any variable. The ISO+ECC-F group showed faster (p<0.05) recovery of all assessed variables compared with the ECC-F group. MVC was greater (p<0.05) at 48-72h and SOR was less (p<0.05) at 48-96h in the ISO+ECC-F compared to the ECC-F group. No significant differences were evident between ISO+ECC-S and ISO+ECC-F for any variable. These results show that the IPP accelerated recovery of MVC and SOR for the slow-eccentric exercise condition and attenuated strength loss and SOR in addition to faster recovery of all assessed variables for the fast-eccentric exercise condition. Therefore, the IPP can be used as a strategy to attenuate and accelerate recovery of muscle damage induced by different-velocity eccentric exercises, resulting in greater protection against muscle damage induced by faster velocity.