# Effects of Performing Eccentric Contractions to Failure After Concentric Muscle Failure in Resistance Training Sessions: Protocol for a Within-Participant Randomized Trial

## TL;DR

This study tests if adding extra eccentric exercises after reaching muscle failure improves strength and muscle growth in women.

## Contribution

The study introduces a novel resistance training protocol combining concentric and eccentric contractions to enhance muscle adaptations.

## Key findings

- Evaluating if additional eccentric contractions after concentric failure improve neuromuscular adaptations.
- Using a within-subject design to compare traditional and enhanced resistance training protocols.
- Assessing muscle function and composition changes over 10 weeks of training.

## Abstract

Resistance training is a well-established strategy to promote muscle hypertrophy and strength gains. Performing sets to concentric muscle failure (MFCON) is commonly used to maximize neuromuscular adaptations. However, after reaching MFCON, there is a remaining capacity for eccentric contractions that could be used. Increasing eccentric contraction volume may represent a promising and practical alternative to enhance training volume load and optimize adaptations, although its effectiveness in this specific application has not yet been tested.

This study aims to investigate whether performing additional eccentric contractions to eccentric muscle failure (MFEXC), after the occurrence of MFCON, enhances neuromuscular and morphological adaptations beyond those promoted by a traditional protocol to MFCON.

In a randomized within-subject design, untrained young adult females will perform 2 upper-limb resistance training protocols over 10 weeks, including traditional (TRAD) training to MFCON and a training protocol (ECC+) consisting of sets to MFCON followed by eccentric-only contractions to MFEXC. Each arm will be assigned to one of the protocols. Sessions (twice per week) will consist of 6 sets of unilateral elbow flexion with a load between 9 and 12 repetition maximum, with 2-minute rest intervals. Muscle function (isometric, concentric, and eccentric strength) and body composition (biceps brachii and brachialis muscle thickness and dual-energy x-ray absorptiometry [DXA]–based analysis) will be assessed pre and post intervention. Comparisons between limbs and across time will be analyzed using 2-way ANOVA. The level of significance will be set at P<.05.

As of July 2024, a total of 7 participants have completed the intervention. Data collection was conducted between March and July 2024, with a new phase planned for the first half of 2025. Manuscript submission is expected in the second half of 2025.

If the hypothesis is confirmed, the ECC+ protocol may represent a practical, simple, and low-cost strategy to increase training volume and optimize strength and hypertrophy outcomes. This study may contribute to evidence-based resistance training prescriptions, particularly for women, and support the use of additional eccentric contractions as an effective tool to enhance localized muscle adaptations.

DERR1-10.2196/67537