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. 2022 Dec 7;17(12):e0277131.
doi: 10.1371/journal.pone.0277131. eCollection 2022.

Non-invasive assessment of fatigue and recovery of inspiratory rib cage muscles during endurance test in healthy individuals

Thiago Bezerra Wanderley E Lima  1   2 , Antonio Sarmento  1   2 , Rayane Grayce da Silva Vieira  1   2 , Esmívany Lhara de Freitas Castro  1   2 , Francesca Pennati  3 , Andrea Aliverti  3 , Vanessa Regiane Resqueti  1   2 , Guilherme Augusto de Freitas Fregonezi  1   2
Affiliations

Non-invasive assessment of fatigue and recovery of inspiratory rib cage muscles during endurance test in healthy individuals

Thiago Bezerra Wanderley E Lima et al. PLoS One. .

Abstract

Introduction: Fatigue is defined as loss of capacity to develop muscle force and/or velocity that is reversible at rest. We assessed non-invasively the fatigue and recovery of inspiratory rib cage muscles during two respiratory endurance tests in healthy individuals.

Methods: The sniff nasal inspiratory pressure (SNIP) was assessed before and after two respiratory endurance tests: normocapnic hyperpnea (NH) and inspiratory pressure threshold loading (IPTL). Contractile (maximum rate of pressure development and time to peak pressure) and relaxation parameters (maximum relaxation rate [MRR], time constant of pressure decay [τ], and half relaxation time) obtained from sniff curves and shortening velocity and mechanical power estimated using optoelectronic plethysmography were analyzed during SNIP maneuvers. Respiratory muscle activity (electromyography) and tissue oxygenation (near-infrared spectroscopy-NIRS) were obtained during endurance tests and SNIP maneuvers. Fatigue development of inspiratory rib cage muscles was assessed according to the slope of decay of median frequency.

Results: Peak pressure during SNIP decreased after both protocols (p <0.05). MRR, shortening velocity, and mechanical power decreased (p <0.05), whereas τ increased after IPTL (p <0.05). The median frequency of inspiratory rib cage muscles (i.e., sum of sternocleidomastoid, scalene, and parasternal) decreased linearly during IPTL and exponentially during NH, mainly due to the sternocleidomastoid.

Conclusion: Fatigue development behaved differently between protocols and relaxation properties (MRR and τ), shortening velocity, and mechanical power changed only in the IPTL.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Flowchart of participant selection.
Fig 2
Fig 2. Time courses of normalized median frequency of inspiratory rib cage muscles.
Mean of 22 subjects; inspiratory rib cage muscles (Panel A), sternocleidomastoid (Panel B), scalene (Panel C) and parasternal (Panel D) during endurance test and recovery. Each point during the test is the average of 5 seconds; during recovery, each point represents data extracted from one SNIP maneuver. In each muscle, starting point at time zero (white symbols) corresponds to the last point of endurance test.
Fig 3
Fig 3. Time courses of tissue oxygenation variables of sternocleidomastoid muscle during endurance test.
Each point during the test is the average of every 10% of test duration until time limit. Abbreviations: O2Hb = Oxyhemoglobin; HHb: deoxyhemoglobin; tHb: total hemoglobin. %: percentage.
Fig 4
Fig 4
Changes in maximum relaxation rate (MRR-panel A), time constant (tau) of relaxation curve (τ-panel B), and time to reach half of relaxation curve (½ RT-panel C). Comparison of values during recovery from endurance test and pre-test (gray band). Data presented as mean ± SE. Abbreviation: ms: milliseconds. *Statistically significant intragroup difference between pre-test and recovery p <0.05 **Statistically significant intragroup difference between pre-test and recovery p <0.01.
Fig 5
Fig 5
Changes in peak pressure of SNIP (panel A), maximum rate of pressure development (MRPD-panel B), contraction time (CT-panel C), and time to reach MRPD (TPS-panel D). Comparison of values during recovery from endurance test and pre-test (gray band). Data presented as mean ± SE. Abbreviations: cmH2O: centimeters of water; ms: milliseconds. *Statistically significant intragroup difference between pre-test and recovery p <0.05.
Fig 6
Fig 6
Changes in shortening velocity of global inspiratory muscles (ΔVCW / Ti- panel A), inspiratory rib cage muscles (ΔVRCp / Ti- panel B), and diaphragm (ΔVAB / Ti- panel C). Comparison of values during recovery of endurance test and pre-test (gray band). Data presented as mean ± SE. Abbreviation: L.s-1: liters per second. *Statistically significant intragroup difference between pre-test and recovery p <0.05.
Fig 7
Fig 7
Changes in mechanical power of global inspiratory muscles (Winsp−panel A), inspiratory rib cage muscles (Wrcm−panel B), and diaphragm (Wdi−panel C). Comparison of values during recovery of endurance test and pre-test (gray band). Data presented as mean ± SE. Abbreviations: cmH2O: centimeters of water; L.s: liters per second. *Statistically significant intragroup difference between pre-test and recovery. p <0.05.
Fig 8
Fig 8
Changes in activation (RMS) of sternocleidomastoid (panel A), scalene (panel B), and parasternal muscles (panel C) compared with pre-test values. Data presented as mean ± SE. *p <0.05 #: intergroup difference (p <0.05).
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