Gender differences in the fatigability of the inspiratory muscles.
OBJECTIVE
The purpose of the present study was to determine whether gender differences are present in the fatigability of the inspiratory muscles of humans. Based on evidence for a gender difference in the oxygen cost of breathing, we hypothesized that females would result in a greater magnitude and/or faster rate of inspiratory muscle fatigue than males.


METHODS
Eleven females and males (N = 22) performed resistive breathing at a target pressure of 70% of maximal inspiratory pressure (PImax). Rate of inspiratory muscle fatigue was calculated from measures of PImax taken every 2 min during resistive breathing, and recovery of inspiratory muscle strength was assessed up to 45 min following task failure.


RESULTS
Resting PImax was found to be lower for females than males (F:137.0 +/- 7.6 cm H2O; M:172.5 +/- 9.8 cm H2O, mean +/- SE, P </= 0.05). During resistive breathing, females exhibited a slower absolute and relative rate of muscle fatigue than males (F: 1.5 +/- 0.4 cm H2O.min(-1); M: -2.9 +/- 0.3 cm H2O.min(-1); P </=0.05). Females and males resulted in a similar decrease in PImax at task failure (15%), and no gender difference was found for recovery of inspiratory muscle strength. Separate analyses were performed in a subgroup of females and males that were matched for resting PImax. Females demonstrated a slower rate of fatigue and less muscle fatigue at task failure than males. No gender difference was found in time to task failure or the recovery of inspiratory muscle strength.


CONCLUSIONS
The results provide some evidence that the fatigability of the inspiratory muscles is different between genders. Females demonstrated a slower rate of fatigue during resistive breathing than males, a finding independent of muscle strength.
Gonzales
Joaquin U
JU
Cardiopulmonary and Metabolism Research Laboratory, Department of Kinesiology, University of Toledo, Toledo, OH, USA.
Scheuermann
Barry W
BW
D000328:Adult; D015444:Exercise; D005260:Female; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012119:Respiration; D012132:Respiratory Muscles / Q000502:physiology*; D012737:Sex Factors; D014481:United States