Myofiber Permeability and Force Production of Rat Muscles Following Eccentric Contractions: The Repeated Bout Effect Depends on the Interval

Past eccentric contraction (ECC)-induced muscle injury reduces the severity of symptoms of subsequent muscle injury;this phenomenon is known as a repeated bout effect (RBE). It has been reported that increases in the duration of the interval between the first and second bouts are linked to weakening of the RBE. However, the histology following the attenuation of the RBE remains unclear. We examined the sustained effects of the second bout with regard to myofiber permeability and muscle force. Sixty-four male rats were randomly assigned to eight groups that varied in the number of exercise sessions and the duration of the interval between the first and second bouts: the non-ECC (Control);the single-injury (Post 1st bout);groups that were allowed to recover for 1, 2, and 4 weeks after a single injury (Pre 2nd bout_1w, Pre 2nd bout_2w, and Pre 2nd bout_4w);and groups that were subjected to second injuries 1, 2, and 4 weeks after the first (Post 2nd bout_1w, Post 2nd bout_2w, and Post 2nd bout_4w). The tibialis anterior was electrically stimulated in each ECC group. Twenty-four hours before muscle sampling, Evans blue dye (EBD) (a marker of myofiber damage) was administered. The maximal isometric contraction tension was measured immediately before sampling. The number of EBD-positive (+) fibers was determined via histological analysis. An RBE was revealed by functional examination at the 1- and 2-week and histological examination at the 1-, 2-, and 4-week time points (P < 0.05). In terms of myofiber permeability, prolongation of the interval before the second bout weakened this effect (P < 0.05). Experiments with 1-, 2-, and 4-week intervals indicated that prolongation of the interval before the second bout weakened the RBE with regard to myofiber permeability.

The Effects of 5 Weeks of Leg-Drive Training on Bench Press Performance in Recreationally-Trained,College-Age Men

Introduction The bench press is commonly used to measure upper-body strength.While much emphasis has been placed on the upper-body,little is known about how the lower-body can play a role in bench press performance.Leg-drive is a technique that includes flexing the knee so the feet line up posterior to the knee joint,while simultaneously contracting the knee extensors isometrically during the lift.The purpose of this study was to compare strength characteristics of lifters in a standard bench press versus a leg-drive bench press over the course of 5-weeks of training.Methods Twenty-three recreationally active males(age:22.4±2.1 years,height:175.0±5.9 cm,mass:78.4±9.5 kg)were randomized into a standard bench or leg-drive bench press group.Participants performed four sets to failure,two times per week for five weeks.Variables of interests were training volume and 1-repetition maximum(1RM)strength.For training volume,a 2×5(group×week)repeated measures analysis of variance(RMANOVA)was used.For the 1RM’s,a 2×2×2(group×press type×time)RMANOVA was used.A priori alpha levels were set to 0.05.Results Over time,both groups showed an approximate 6%increase in 1RM strength.Training volume for week 4 was 5.6%less than week 5,but was not different from weeks 1 through 3.No between-group differences were observed for 1RM strength or training volume.Conclusion This results of this work indicates that 5 weeks of leg-drive training is effective in increasing 1RM strength,but was not more effective than standard bench press training.Practically,lifters should choose either lifting style based on personal preference.