Determining The Electromyographic Fatigue Threshold Following a Single Visit Exercise Test

Summary

This protocol describes the electromyographic fatigue threshold which demarcates between nonfatiguing and fatiguing exercise workloads. This information could be used to develop a more individualized training program.

Abstract

Theoretically, the electromyographic (EMG) fatigue threshold is the exercise intensity an individual can maintain indefinitely without the need to recruit more motor units which is associated with an increase in the EMG amplitude. Although different protocols have been used to estimate the EMG fatigue threshold they require multiple visits which are impractical for a clinical setting. Here, we present a protocol for estimating the EMG fatigue threshold for cycle ergometry which requires a single visit. This protocol is simple, convenient, and completed within 15-20 min, therefore, has the potential to be translated into a tool that clinicians can use in exercise prescription.

Introduction

Surface electromyography (EMG) is a noninvasive approach of studying motor unit recruitment during isometric^1-3, isokinetic^4-6, or continuous^7-10 muscle action. The amplitude of the EMG signal represents muscle activation which consists of the number of motor units activated, the firing rate of the motor units, or both¹¹. The concept of the EMG fatigue threshold is used to indicate the highest workload in which an individual can exercise indefinitely without an increase in EMG amplitude⁸.

It is important to briefly discussion the origin of the EMG fatigue threshold. The original study b....

Protocol

All procedures were approved by the University Institutional Review Board for Human Subjects.

1. Preparation of the Participant’s Leg

1. Have the participant neatly roll up their shorts for the desired leg. Then tape the shorts so that the quadriceps femoris muscle group is exposed and draw a line around the area the participant needs to shave.
2. IMPORTANT: Have the participant shave their leg before the test rather than the previous day as this ensures that there are no stubbles which may interfere with the EMG signal.
3. Once the participant has finished shaving the desired area of the leg, clean the shaved a....

Results

As shown in Figure 1, for a single participant, each power output that is completed has six data points that represent the EMG amplitude for the vastus lateralis muscle. Therefore, in this example, the highest power output with a non-significant (p >0.05) slope is 200 watts, whereas the lowest power output with a significant (p <0.05) slope is 225 W. Therefore, for this participant the EMG fatigue threshold is 213 W. Once the EMG fatigue threshold is determined for each participan.......

Discussion

We here present a method for determining neuromuscular fatigue in the quadriceps femoris muscles for dynamic exercise. This method provides a straightforward and non-invasive approach to using surface EMG. Moreover, the versatility of this method is that researchers can adapt it to other modes of exercise such as the treadmill²⁰.

Theoretically, for intensities at or below the EMG fatigue threshold the participant should be able to sustain the exercise workbout indefinitely^12,13.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
839 E Monark cycle ergometer	Monark Exercise AB	839 E
Heart rate monitor	Polar	Polar H1
Laptop	Dell Inspiron	varies	any laptop computer with USB slots should work.
EMG amplifiers	BioPac Systems, Inc.	100B	100C are the latest version
Disposable EMG electrodes	BioPac Systems, Inc.	EL-500
Sandpaper	Home Depot	9 inch x 11 inch 60 Grit course no-slip grip Advanced Sandpaper (3-Pack)