Abstract
Respiratory endurance test (RET) is characterized by considerable differences in the recruitment of respiratory muscles, energy/metabolic demands, and changes in chest wall kinematics. We aimed to study the development of fatigue and recovery of ribcage inspiratory muscles during normocapnic hyperpnea (HN) and inspiratory pressure threshold loads (IPTL) endurance tests. Spirometry, respiratory muscle strength was measured. The protocol consisted of 10 sniff test (to calculate relaxation rates) before and after RET. The subjects were simultaneous monitored by optoelectronic plethysmography, surface electromyography (sternocleidomastoid-SCM, scalene-SC and parasternal-PARA) and NIRS (SCM) during RET (HN protocol: bag size at 50–60% VC and minute ventilation at 70% of MVV; IPTL protocol: load at 80% of PImax). We studied 22 subjects (11M), aged 24.36±2.06 years. The subjects showed a decrease in the peak of pressure generated in the sniff test after both RET protocols (p <0.05), besides a decrease in the maximum relaxation rate (MRR) and an increase in the decay time constant (τ) only after the IPTL protocol (p<0.05). There was a decrease in the shortening velocity and mechanical power of the inspiratory rib cage muscles (p<0.05) and a linear drop in the median frequency of sEMG (-0.047 r2 = 0.495) in the IPTL protocol. The two RET protocols determine different changes in ribcage inspiratory muscles and ventilation. The IPTL protocol induces fatigue of ribcage inspiratory muscles, selectively or together, evidenced by non-invasive techniques as chest wall kinematics, the power spectrum of sEMG, and relaxation rates.
Footnotes
Cite this article as: European Respiratory Journal 2020; 56: Suppl. 64, 3218.
This abstract was presented at the 2020 ERS International Congress, in session “Respiratory viruses in the "pre COVID-19" era”.
This is an ERS International Congress abstract. No full-text version is available. Further material to accompany this abstract may be available at www.ers-education.org (ERS member access only).
- Copyright ©the authors 2020