This project was funded by, in part, by start-up funds from Wayne State University to M.H. Malek.

All procedures were approved by the University Institutional Review Board for Human Subjects.
1. Preparation of the Participant&#8217;s Leg
<ol>
	<li>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.</li>
	<li>IMPORTANT: Have the participant shave their leg before the test rather than the previous day as this ensures that there are no...

<ol>
	<li>Hendrix, C. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+critical+force+to+EMG+fatigue+thresholds+during+isometric+leg+extension.">Comparison of critical force to EMG fatigue thresholds during isometric leg extension.</a> Medicine and science in sports and exercise. 41, 956-964 (2009).</li><li>Herda, T. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantifying+the+effects+of+electrode+distance+from+the+innervation+zone+on+the+electromyographic+amplitude+versus+torque+relationships.">Quantifying the effects of electrode distance from the innervation zone on the electromyographic amplitude versus torque relationships.</a> Physiological measurement. 34, 315-324 (2013).</li><li>Ryan, E. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inter-individual+variability+among+the+mechanomyographic+and+electromyographic+amplitude+and+mean+power+frequency+responses+during+isometric+ramp+muscle+actions.">Inter-individual variability among the mechanomyographic and electromyographic amplitude and mean power frequency responses during isometric ramp muscle actions.</a> Electromyography and clinical neurophysiology. 47, 161-173 (2007).</li><li>Beck, T. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+electrode+placement+over+the+innervation+zone+on+electromyographic+amplitude+and+mean+power+frequency+versus+isokinetic+torque+relationships.">The influence of electrode placement over the innervation zone on electromyographic amplitude and mean power frequency versus isokinetic torque relationships.</a> Journal of neuroscience. 162, 72-83 (2007).</li><li>Beck, T. W., Stock, M. S., DeFreitas, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Time-frequency+analysis+of+surface+electromyographic+signals+during+fatiguing+isokinetic+muscle+actions.">Time-frequency analysis of surface electromyographic signals during fatiguing isokinetic muscle actions.</a> Journal of strength and conditioning research / National Strength, &amp; Conditioning Association. 26, 1904-1914 (2012).</li><li>Evetovich, T. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mean+power+frequency+and+amplitude+of+the+mechanomyographic+signal+during+maximal+eccentric+isokinetic+muscle+actions.">Mean power frequency and amplitude of the mechanomyographic signal during maximal eccentric isokinetic muscle actions.</a> Electromyography and clinical neurophysiology. 39, 123-127 (1999).</li><li>Blaesser, R. J., Couls, L. M., Lee, C. F., Zuniga, J. M., Malek, M. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparing+EMG+amplitude+patterns+of+responses+during+dynamic+exercise:+polynomial+versus+log-transformed+regression.">Comparing EMG amplitude patterns of responses during dynamic exercise: polynomial versus log-transformed regression.</a> Scandinavian journal of medicine, &amp; science in sports. In press, (2015).</li><li>Briscoe, M. J., Forgach, M. S., Trifan, E., Malek, M. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Validating+the+EMGFT+from+a+single+incremental+cycling+testing.">Validating the EMGFT from a single incremental cycling testing.</a> International journal of sports medicine. 35, 566-570 (2014).</li><li>Zuniga, J. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuromuscular+and+metabolic+comparisons+between+ramp+and+step+incremental+cycle+ergometer+tests.">Neuromuscular and metabolic comparisons between ramp and step incremental cycle ergometer tests.</a> Muscle. 47, 555-560 (2013).</li><li>Mastalerz, A., Gwarek, L., Sadowski, J., Szczepanski, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+the+run+intensity+on+bioelectrical+activity+of+selected+human+leg+muscles.">The influence of the run intensity on bioelectrical activity of selected human leg muscles.</a> Acta of bioengineering and biomechanics / Wroclaw University of Technology. 14, 101-107 (2012).</li><li>Basmajian, J. V., De Luca, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Muscles alive, their functions revealed by electromyography. , (1985).</li><li>Vries, H. A., Moritani, T., Nagata, A., Magnussen, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relation+between+critical+power+and+neuromuscular+fatigue+as+estimated+from+electromyographic+data.">The relation between critical power and neuromuscular fatigue as estimated from electromyographic data.</a> Ergonomics. 25, 783-791 (1982).</li><li>Vries, H. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+method+for+estimating+physical+working+capacity+at+the+fatigue+threshold+(PWCFT).">A method for estimating physical working capacity at the fatigue threshold (PWCFT).</a> Ergonomics. 30, 1195-1204 (1987).</li><li>Vries, H. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+affecting+the+estimation+of+physical+working+capacity+at+the+fatigue+threshold.">Factors affecting the estimation of physical working capacity at the fatigue threshold.</a> Ergonomics. 33, 25-33 (1990).</li><li>Astrand, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+physical+work+capacity+of+workers+50-64+years+old.">The physical work capacity of workers 50-64 years old.</a> Acta physiologica Scandinavica. 42, 73-86 (1958).</li><li>Hettinger, T., Birkhead, N. C., Horvath, S. M., Issekutz, B., Rodahl, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+physical+work+capacity.">Assessment of physical work capacity.</a> Journal of Applied Physiology. 16, 153-156 (1961).</li><li>Smith, J. L., Karwowsk, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> International encyclopedia of ergonomics and human factors. , (2006).</li><li>Kenny, G. P., Yardley, J. E., Martineau, L., Jay, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physical+work+capacity+in+older+adults:+implications+for+the+aging+worker.">Physical work capacity in older adults: implications for the aging worker.</a> American journal of industrial medicine. 51, 610-625 (2008).</li><li>Matsumoto, T., Ito, K., Moritani, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relationship+between+anaerobic+threshold+and+electromyographic+fatigue+threshold+in+college+women.">The relationship between anaerobic threshold and electromyographic fatigue threshold in college women.</a> European journal of applied physiology. 63, 1-5 (1991).</li><li>Guffey, D. R., Gervasi, B. J., Maes, A. A., Malek, M. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimating+electromygraphic+and+heart+rate+fatigue+threshold+from+a+single+treadmill+test.">Estimating electromygraphic and heart rate fatigue threshold from a single treadmill test.</a> Muscle. 46, 577-581 (2012).</li><li>Camic, C. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+the+muscle+fiber+pennation+angle+and+innervation+zone+on+the+identification+of+neuromuscular+fatigue+during+cycle+ergometry.">The influence of the muscle fiber pennation angle and innervation zone on the identification of neuromuscular fatigue during cycle ergometry.</a> Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology. 21, 33-40 (2011).</li></ol>

The authors have nothing to disclose.

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 indefinitely12,13...

Surface electromyography (EMG) is a noninvasive approach of studying motor unit recruitment during isometric1-3, isokinetic4-6, or continuous7-10 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 by deVries et al.12 involved a protocol that consisted of multiple (usually 3 to 4) discontinuous work bouts, where the EMG amplitude was plotted versus time for each work bout. The power output was then plotted versus the slope coefficients from the EMG amplitude versus time relationship, and then extrapolated to zero slope (the y-intercept)12. The authors12 originally termed that protocol the physical working capacity at the fatigue threshold (PWCFT). In a another study, deVries et al.13 used discontinuous work bouts, but used linear regression to find the first power output that resulted in a significant slope for the EMG amplitude versus time relationship. The authors13 also termed that protocol the PWCFT, creating some confusion in the literature. In a subsequent article, deVries et al.14 modified their earlier protocol13 and developed a continuous incremental protocol. The EMG amplitude was plotted against time for each power output and the PWCFT was defined as the average of the highest power output that resulted in no change in EMG amplitude over time and the lowest power output that resulted in an increase in EMG amplitude over time14.
It should be noted that the term PWC was originally introduced in the late 1950s15,16 and is synonymous with a plethora of literature (past, present, and across different countries) examining aerobic capacity at a given workload17. Moreover, the term is used in the ergonomic and industrial literature which focus on day-to-day productivity of workers performing repetitive action during 8 hour work days such as individuals in an assembly plant18.
The term EMG fatigue threshold was initially used by Matsumoto and colleagues19 after they modified the deVries12 protocol where the power output versus slope coefficients of the EMG amplitude versus time relationship are plotted and extrapolated to the point of zero slope. More recently, Guffey et al.20 and Briscoe et al.8 used the method of deVries et al.14 and the terminology of Matsumoto et al.19 to operationally define the EMG fatigue threshold. Moving forward, we recommend that the term EMG fatigue threshold be used. Thus, the EMG amplitude versus time relationship is plotted for each power output and then analyzed using linear regression analyses (Figure 1). To estimate the EMG fatigue threshold, the highest power output with a non-significant (p &#62;0.05) slope and the lowest power output with a significant (p &#60;0.05) slope is identified and then the average is calculated14. This protocol is simple, convenient, and completed within 15-20 min. Moreover, the incremental rate can be modulated based on the individual&#8217;s level of habitual physical activity, and therefore has potential applications in clinical settings.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>839 E Monark cycle ergometer&#160;</td>
			<td>Monark Exercise AB</td>
			<td>839 E</td>
			<td></td>
		</tr>
		<tr>
			<td>Heart rate monitor</td>
			<td>Polar</td>
			<td>Polar H1</td>
			<td></td>
		</tr>
		<tr>
			<td>Laptop</td>
			<td>Dell Inspiron</td>
			<td>varies</td>
			<td>any laptop computer with USB slots should work.</td>
		</tr>
		<tr>
			<td>EMG amplifiers</td>
			<td>BioPac Systems, Inc.</td>
			<td>100B</td>
			<td>100C are the latest version</td>
		</tr>
		<tr>
			<td>Disposable EMG electrodes</td>
			<td>BioPac Systems, Inc.</td>
			<td>EL-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Sandpaper</td>
			<td>Home Depot</td>
			<td>9 in. x 11 in. 60 Grit course no-slip grip Advanced Sandpaper (3-Pack)</td>
			<td></td>
		</tr>
	</tbody>
</table>

determining the electromyographic fatigue threshold following a single visit exercise test

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.

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 &#62;0.05) slope is 200 watts, whereas the lowest power output with a significant (p &#60;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 particip...

Watch this Scientific Journal Video about Determining The Electromyographic Fatigue Threshold Following a Single Visit Exercise Test at JoVE.com

Determining The Electromyographic Fatigue Threshold Following a Single Visit Exercise Test

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.

Theoretically, the electromyographic (EMG) fatigue threshold is the exercise intensity an individual can maintain indefinitely without the need to recruit ...

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12.4K ビュー.  Wayne State University. 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.