The impact of static muscle tension on total respiratory
resistance (TRR) was examined. Participants (24 healthy,
24 asthmatic) performed biofeedback-assisted sequences
of tensing (15 s) and relaxing (20 s) forehead and forearm
muscles. Muscle tension levels were 40% or 80% of the maximum
individual force. Oscillatory TRR, electromyograms, ventilation,
heart period, and respiratory sinus arrhythmia were recorded.
Baseline TRR did not change over the session as a whole.
Decreases in TRR during forehead tension in both groups
were accompanied by increases in end-expiratory volume,
which could have mediated TRR changes. During forearm tension,
decreases in TRR with minimal ventilation changes were
only observed in healthy participants, whereas asthmatic
patients revealed marked increases in respiratory volume
and flow. These results indicate that static muscle activity
and TRR are negatively related. Ventilatory changes can
exaggerate or diminish evidence for this relationship.