Effects of menthol-based counterirritant on quadriceps motoneuron-pool excitability.
BACKGROUND
Motoneuron-pool facilitation after cryotherapy may be mediated by stimulation of thermoreceptors surrounding a joint. It is unknown whether menthol counterirritants, which also stimulate thermoreceptors, have the same effect on motoneuron-pool excitability (MNPE).


OBJECTIVE
To compare quadriceps MNPE after a menthol-counterirritant application to the anterior knee, a sham counterirritant application, and a control treatment in healthy subjects.


METHODS
A blinded, randomized controlled laboratory study.


METHODS
Laboratory.


METHODS
Thirty healthy subjects (16 m, 14 f; 24.1 +/- 3.9 y, 170.6 +/- 11.4 cm, 72.1 +/- 15.6 kg) with no history of lower extremity surgery volunteered for this study.


METHODS
Two milliliters of menthol or sham counterirritant was applied to the anterior knee; control subjects received no intervention.


METHODS
The average vastus medialis normalized Hoffmann reflex (Hmax:Mmax ratio) was used to measure MNPE. Measurements were recorded at 5, 15, 25, and 35 minutes postintervention and compared with baseline measures.


RESULTS
Hmax:Mmax ratios for all groups significantly decreased over time (F(4,108) = 10.52, P < .001; menthol: baseline = .32 +/- .20, 5 min = .29 +/- .18, 15 min = .27 +/- .18, 25 min = .28 +/- .19, 35 min = .27 +/- .18; sham: baseline = .46 +/- .26, 5 min = .36 +/- .20, 15 min = .35 +/- .19, 25 min = .35 +/- .20, 35 min = .34 +/- .18; control: baseline = .48 +/- .32, 5 min = .37 +/- .27, 15 min = .37 +/- .27, 25 min = .37 +/- .29, 35 min = .35 +/- .28). No significant Group x Time interaction or group differences in Hmax:Mmax were found.


CONCLUSIONS
Menthol did not affect quadriceps MNPE in healthy subjects.
Department of Kinesiology, Texas A&M University, Corpus Christi, TX, USA.
Daniel H
DH
Huffman
Brian G
BG
Pietrosimone
Terry L
TL
Grindstaff
Joseph M
JM
Hart
Susan A
SA
Saliba
Christopher D
CD
Ingersoll
D000704:Analysis of Variance; D000982:Antipruritics / Q000494:pharmacology / Q000627:therapeutic use*; D016001:Confidence Intervals; D004311:Double-Blind Method; D004576:Electromyography; D005260:Female; D006801:Humans; D007717:Knee / Q000294:innervation*; D007719:Knee Joint / Q000187:drug effects; D007866:Leg / Q000294:innervation*; D008297:Male; D008610:Menthol / Q000494:pharmacology / Q000627:therapeutic use*; D009046:Motor Neurons / Q000187:drug effects*; D052097:Quadriceps Muscle / Q000187:drug effects* / Q000294:innervation; D012021:Reflex, Abnormal; D055815:Young Adult
D000982:Antipruritics; D008610:Menthol