title: The electromyographic threshold in boys and men.
abstract: BACKGROUND
  Children have been shown to have higher lactate (LaTh) and ventilatory (VeTh) thresholds than adults, which might be explained by lower levels of type-II motor-unit (MU) recruitment. However, the electromyographic threshold (EMGTh), regarded as indicating the onset of accelerated type-II MU recruitment, has been investigated only in adults.
  
  
  OBJECTIVE
  To compare the relative exercise intensity at which the EMGTh occurs in boys versus men.
  
  
  METHODS
  Participants were 21 men (23.4 ± 4.1 years) and 23 boys (11.1 ± 1.1 years), with similar habitual physical activity and peak oxygen consumption (VO2pk) (49.7 ± 5.5 vs. 50.1 ± 7.4 ml kg(-1) min(-1), respectively). Ramped cycle ergometry was conducted to volitional exhaustion with surface EMG recorded from the right and left vastus lateralis muscles throughout the test (~10 min). The composite right-left EMG root mean square (EMGRMS) was then calculated per pedal revolution. The EMGTh was then determined as the exercise intensity at the point of least residual sum of squares for any two regression line divisions of the EMGRMS plot.
  
  
  RESULTS
  EMGTh was detected in 20/21 of the men (95.2 %) and only in 18/23 of the boys (78.3 %). The boys' EMGTh was significantly higher than the men's (86.4 ± 9.6 vs. 79.7 ± 10.0 % of peak power output at exhaustion; p < 0.05). The pattern was similar when EMGTh was expressed as percentage of VO2pk.
  
  
  CONCLUSIONS
  The boys' higher EMGTh suggests delayed and hence lesser utilization of type-II MUs in progressive exercise, compared with men. The boys-men EMGTh differences were of similar magnitude as those shown for LaTh and VeTh, further suggesting a common underlying factor.
authors.affiliation: Applied Physiology Laboratory, Faculty of Applied Health Sciences, Brock University, 500 Glenridge Ave, St. Catharines, ON, L2T 2Y1, Canada.
authors.forename: Brynlynn
authors.initials: B
authors.lastname: Pitt
authors.forename: Raffy
authors.initials: R
authors.lastname: Dotan
authors.forename: Jordan
authors.initials: J
authors.lastname: Millar
authors.forename: Devon
authors.initials: D
authors.lastname: Long
authors.forename: Craig
authors.initials: C
authors.lastname: Tokuno
authors.forename: Thomas
authors.initials: T
authors.lastname: O'Brien
authors.forename: Bareket
authors.initials: B
authors.lastname: Falk
mesh_terms: D000328:Adult; D015308:Anaerobic Threshold; D002648:Child; D015444:Exercise; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000254:growth & development / Q000502:physiology*