Effects of Age and Sex on Inspiratory Muscle Activation Patterns during Exercise

Purpose To characterize the effects of age, sex, and their interaction on inspiratory muscle activation patterns during exercise. Methods Twenty younger (20–30 yr, n = 10 women) and 20 older (60–80 yr, n = 10 women) subjects performed an incremental cycle exercise test. Electromyography (EMG) of the scalene (EMGsca) and EMG of the sternocleidomastoid (EMGscm) muscles were measured using skin surface electrodes, whereas diaphragm EMG (EMGdi) and esophageal and transdiaphragmatic pressures were measured using an esophageal catheter. Electromyography data were transformed into root mean square with a 100-ms time constant. Esophageal and diaphragmatic pressure–time products were used as indices of total inspiratory muscle pressure production and diaphragmatic pressure production, respectively. Results At absolute minute ventilations (V˙E), women and older subjects had greater EMGdi than men and younger subjects, respectively (all P 0.05). Women had greater EMGsca activity than men at absolute and relative levels of V˙E (all P 0.05). At absolute and relative levels of V˙E, women and older subjects had greater EMGscm than men and younger subjects, respectively (all P 0.05). No significant interactions between age and sex were noted (all P > 0.05). Conclusions Age and sex significantly affect inspiratory muscle activation patterns during exercise; however, the extent of the effects depends on whether comparisons are made at absolute or relative V˙E.

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