# Two synergistic types of muscles were detected during forearm rotation exercise by T2 cumulative frequency curves using 0.2 T magnetic resonance imaging

## TL;DR

This study used MRI to identify two types of synergistic muscles involved in forearm rotation exercises, revealing how different muscles work together during movement.

## Contribution

The study introduces a novel method using T2 cumulative frequency curves to detect and classify synergistic and co-contracting muscles during forearm exercises.

## Key findings

- Two types of synergistic muscles were identified during supination and pronation exercises.
- One muscle type was activated in a strength-dependent manner, while the other was only active in a subset of participants.
- Co-contraction was observed during supination, highlighting the complexity of muscle coordination.

## Abstract

The purpose of this study was the detection and characterization of synergistic muscle activity. Using T2-map MRI, T2 values for 10 forearm muscles in 11 healthy adult volunteers were obtained in the resting state and after isotonic forearm supination and pronation exercises with the elbow extended. T2 was normalized by Z = (T2e–T2r)/SDr, where T2e was T2 after exercise, while T2r and SDr were the reference values of 34 ms and 3 ms, respectively. Using the cumulative frequency curves of Z values (CFZ), we detected 2 and 3 synergistic muscles for supination and pronation, respectively, and divided these into 2 types, one activated by exercise strength dependently, and the other, independent of exercise strength, activated by only a smaller fraction of the participants. We also detected co-contraction for the supination. Thus, CFZ is a useful visualization tool to detect and characterize not only synergistic muscle, but also co-contraction muscle.