EFFECTS OF STATIC FOREHEAD AND FOREARM MUSCLE TENSION ON TOTAL RESPIRATORY RESISTANCE IN HEALTHY AND ASTHMATIC PARTICIPANTS

The impact of static muscle tension on total respiratory resistance (T RR) was examined. Participants (24 healthy, 24 asthmatic) performed bi ofeedback-assisted sequences of tensing (15 s) and relaxing (20 s) for ehead and forearm muscles. Muscle tension levels were 40% or 80% of th e maximum individual force. Oscillatory TRR, electromyograms, ventilat ion, heart period, and respiratory sinus arrhythmia were recorded. Bas eline 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. Durin g forearm tension, decreases in TRR with minimal ventilation changes w ere only observed in healthy participants, whereas asthmatic patients revealed marked increases in respiratory volume and flow. These result s indicate that static muscle activity and TRR are negatively related. Ventilatory changes can exaggerate or diminish evidence for this rela tionship.