Abstract
Few studies have quantified lower limb muscle activity over 24 h using electromyographic signals (EMG). None have described the changes in EMG duration and intensity when data are analyzed with different thresholds. Continuous bilateral EMG recordings were made from vastus lateralis (VL) in 10 subjects (20-48 yr) for 24 h. Before and after this recording, voluntary quadriceps forces and VL EMG at 25%, 50%, 75%, and 100% of the maximal voluntary contraction (MVC), percentage voluntary activation (twitch interpolation), and compound action potentials (Mwaves) were recorded. Offline, the 24-h EMG integrals (IEMG, 10-ms time constant) were normalized to the MVCIEMG. Total EMG duration and mean IEMG ranged from 1-3 h and 3.2-12.1% MVC, respectively, when the data were analyzed using the baseline (+3 SD) as threshold. When analysis was done with progressively higher thresholds, from baseline up to 4% MVC, the total EMG duration, declined curvilinearly. In some cases the decline in duration was 50-60% for a 1% MVC threshold increment. The mean 24-h IEMG increased by 1.5-2% MVC for each 1% MVC threshold increment. Hence, a small change in the analysis threshold may result in large changes in 24-h EMG duration, but moderate changes in mean IEMG. Our findings suggest that VL was active for a short amount of time and at low intensities over 24 h.
| Original language | English |
|---|---|
| Pages (from-to) | 655-661 |
| Number of pages | 7 |
| Journal | Journal of Applied Physiology |
| Volume | 108 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 1 2010 |
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Keywords
- Electromyogram
- Electromyogram threshold
- Long-term electromyogram recording
- Maximal voluntary contraction
- Voluntary activation
ASJC Scopus subject areas
- Physiology
- Physiology (medical)
Cite this
Sensitivity of 24-h EMG duration and intensity in the human vastus lateralis muscle to threshold changes. / Klein, Cliff S.; Peterson, Lillian B.; Ferrell, Sean; Thomas, Christine K.
In: Journal of Applied Physiology, Vol. 108, No. 3, 01.03.2010, p. 655-661.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Sensitivity of 24-h EMG duration and intensity in the human vastus lateralis muscle to threshold changes
AU - Klein, Cliff S.
AU - Peterson, Lillian B.
AU - Ferrell, Sean
AU - Thomas, Christine K
PY - 2010/3/1
Y1 - 2010/3/1
N2 - Few studies have quantified lower limb muscle activity over 24 h using electromyographic signals (EMG). None have described the changes in EMG duration and intensity when data are analyzed with different thresholds. Continuous bilateral EMG recordings were made from vastus lateralis (VL) in 10 subjects (20-48 yr) for 24 h. Before and after this recording, voluntary quadriceps forces and VL EMG at 25%, 50%, 75%, and 100% of the maximal voluntary contraction (MVC), percentage voluntary activation (twitch interpolation), and compound action potentials (Mwaves) were recorded. Offline, the 24-h EMG integrals (IEMG, 10-ms time constant) were normalized to the MVCIEMG. Total EMG duration and mean IEMG ranged from 1-3 h and 3.2-12.1% MVC, respectively, when the data were analyzed using the baseline (+3 SD) as threshold. When analysis was done with progressively higher thresholds, from baseline up to 4% MVC, the total EMG duration, declined curvilinearly. In some cases the decline in duration was 50-60% for a 1% MVC threshold increment. The mean 24-h IEMG increased by 1.5-2% MVC for each 1% MVC threshold increment. Hence, a small change in the analysis threshold may result in large changes in 24-h EMG duration, but moderate changes in mean IEMG. Our findings suggest that VL was active for a short amount of time and at low intensities over 24 h.
AB - Few studies have quantified lower limb muscle activity over 24 h using electromyographic signals (EMG). None have described the changes in EMG duration and intensity when data are analyzed with different thresholds. Continuous bilateral EMG recordings were made from vastus lateralis (VL) in 10 subjects (20-48 yr) for 24 h. Before and after this recording, voluntary quadriceps forces and VL EMG at 25%, 50%, 75%, and 100% of the maximal voluntary contraction (MVC), percentage voluntary activation (twitch interpolation), and compound action potentials (Mwaves) were recorded. Offline, the 24-h EMG integrals (IEMG, 10-ms time constant) were normalized to the MVCIEMG. Total EMG duration and mean IEMG ranged from 1-3 h and 3.2-12.1% MVC, respectively, when the data were analyzed using the baseline (+3 SD) as threshold. When analysis was done with progressively higher thresholds, from baseline up to 4% MVC, the total EMG duration, declined curvilinearly. In some cases the decline in duration was 50-60% for a 1% MVC threshold increment. The mean 24-h IEMG increased by 1.5-2% MVC for each 1% MVC threshold increment. Hence, a small change in the analysis threshold may result in large changes in 24-h EMG duration, but moderate changes in mean IEMG. Our findings suggest that VL was active for a short amount of time and at low intensities over 24 h.
KW - Electromyogram
KW - Electromyogram threshold
KW - Long-term electromyogram recording
KW - Maximal voluntary contraction
KW - Voluntary activation
UR - http://www.scopus.com/inward/record.url?scp=77949597064&partnerID=8YFLogxK
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U2 - 10.1152/japplphysiol.00757.2009
DO - 10.1152/japplphysiol.00757.2009
M3 - Article
C2 - 20007856
AN - SCOPUS:77949597064
VL - 108
SP - 655
EP - 661
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
SN - 8750-7587
IS - 3
ER -