The Electromyographic Threshold in Girls and Women

Devon Long, Raffy Dotan, Brynlynn Pitt, Brandon McKinlay, Thomas D. O'Brien, Craig Tokuno, Bareket Falk
2017 Pediatric Exercise Science  
27 Background: The electromyographic threshold (EMGTh) is thought to reflect increased high-28 threshold/type-II motor-unit (MU) recruitment and was shown higher in boys than in men. Women 29 differ from men in muscular function. Purpose: Establish whether females' EMGTh and 30 girls-women differences are different than males'. Methods: Nineteen women (22.9±3.3yrs) and 31 20 girls (10.3±1.1yrs) had surface EMG recorded from the right and left vastus lateralis muscles 32 during ramped
more » ... g ramped cycle-ergometry to exhaustion. EMG root-mean-squares were averaged per pedal 33 revolution. EMGTh was determined as the least residual sum of squares for any two regression-line 34 data divisions, if the trace rose ≥3SD above its regression line. EMGTh was expressed as % final 35 power-output (%Pmax) and %VO2pk power (%PVO2pk). Results: EMGTh was detected in 13 (68%) 36 of women, but only 9 (45%) of girls (p<0.005) and tended to be higher in the girls (%Pmax= 37 88.6±7.0 vs. 83.0±6.9%, p=0.080; %PVO2pk= (101.6±17.6 vs. 90.6±7.8%, p=0.063). When EMGTh 38 was undetected it was assumed to occur at 100%Pmax or beyond. Consequently, EMGTh values 39 turned significantly higher in girls than in women (94.8±7.4 vs. 88.4±9.9 %Pmax, p=0.026; and 40 103.2±11.7 vs. 95.2±9.9 %PVO2pk, p=0.028). Conclusions: During progressive exercise, girls 41 appear to rely less on higher-threshold/type-II MUs than do women, suggesting differential muscle 42 activation strategy. 43
doi:10.1123/pes.2016-0056 pmid:27427951 fatcat:mcn4r4vtp5fk7h3gzkos4vqlya