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- Forward trunk lean with arm support affects the activity of accessory respiratory muscles and thoracoabdominal movement in healthy individualsPublication . Mesquita Montes, António; Tam, Carolina; Crasto, Carlos; Melo, Cristina; Carvalho, Paulo; Santos, Rita; Vilarinho, Rui; Vilas-Boas, João PauloDespite the reported benefits of postures involving leaning the trunk forward with arm support for relieving dyspnea, how those postures influence the mechanics of breathing remains unclear. In response, the aim of the study reported here was to evaluate how posture (i.e., standing and sitting) and leaning the trunk forward with arm support affect the activity of accessory respiratory muscles and thoracoabdominal movement in healthy individuals. Thirty-five volunteers (15 males and 20 females) aged 18-29 years breathed with the same rhythm in standing and sitting positions while upright and while leaning the trunk forward with arm support. Surface electromyography was performed to assess the activity of accessory inspiratory (i.e., during inspiration) and abdominal (i.e., during inspiration and expiration) muscles, and a motion capture system was used to assess thoracoabdominal movement. Results revealed that upper trapezius activity was significantly lower in forward-leaning postures than in upright ones (P = 005; ηp2 = 0.311), although the activity of the sternocleidomastoideus and scalenus (P < 0.001; ηp2 = 0.427-0.529), along with the anterior-to-posterior movement of the upper ribcage (P < 0.001; ηp2 = 0.546), were significantly greater in forward-leaning postures than in upright ones. The activity of the external oblique and transversus abdominis/internal oblique was significantly lower in sitting than in standing postures (P < 0.050; ηp2 = 0.206-0.641), and though the activity of the transversus abdominis/internal oblique was significantly lower in forward-leaning than in upright postures (P ≤ 0.001; ηp2 = 0.330-0.541), a significantly greater anterior-to-posterior movement of the abdomen was observed (P < 0.001; ηp2 = 0.662). However, the magnitude of the lower ribcage's medial-to-lateral movement was significantly lower in forward-leaning than in upright postures (P = 0.039; ηp2 = 0.149). Leaning the trunk forward with arm support not only increased the use of accessory inspiratory muscles but also decreased the use of the transversus abdominis/internal oblique, which improved thoracoabdominal movement.
- Abdominal muscle activity during breathing with and without inspiratory and expiratory loads in healthy subjectsPublication . Mesquita Montes, António; Baptista, João; Crasto, Carlos; Melo, Cristina; Santos, Rita; Vilas-Boas, João PauloCentral Nervous System modulates the motor activities of all trunk muscles to concurrently regulate the intra-abdominal and intra-thoracic pressures. The study aims to evaluate the effect of inspiratory and expiratory loads on abdominal muscle activity during breathing in healthy subjects. Twenty-three higher education students (21.09±1.56years; 8males) breathed at a same rhythm (inspiration: two seconds; expiration: four seconds) without load and with 10% of the maximal inspiratory or expiratory pressures, in standing. Surface electromyography was performed to assess the activation intensity of rectus abdominis, external oblique and transversus abdominis/internal oblique muscles, during inspiration and expiration. During inspiration, transversus abdominis/internal oblique activation intensity was significantly lower with inspiratory load when compared to without load (p=0.009) and expiratory load (p=0.002). During expiration, the activation intensity of all abdominal muscles was significantly higher with expiratory load when compared to without load (p<0.05). The activation intensity of external oblique (p=0.036) and transversus abdominis/internal oblique (p=0.022) was significantly higher with inspiratory load when compared to without load. Transversus abdominis/internal oblique activation intensity was significantly higher with expiratory load when compared to inspiratory load (p<0.001). Transversus abdominis/internal oblique seems to be the most relevant muscle to modulate the intra-abdominal pressure for the breathing mechanics.
- Abdominal muscle activity during breathing in different postural sets in healthy subjectsPublication . Mesquita Montes, António; Gouveia, Sara; Crasto, Carlos; Melo, Cristina; Carvalho, Paulo; Santos, Rita; Vilas-Boas, João PauloThis study aims to evaluate the effect of different postural sets on abdominal muscle activity during breathing in healthy subjects. Twenty-nine higher education students (20.86 ± 1.48 years; 9 males) breathed at the same rhythm (inspiration: 2 s; expiration: 4 s) in supine, standing, tripod and 4-point-kneeling positions. Surface electromyography was performed to assess the activation intensity of rectus abdominis, external oblique and transversus abdominis/internal oblique muscles during inspiration and expiration. During both breathing phases, the activation intensity of external oblique and transversus abdominis/internal oblique was significantly higher in standing when compared to supine (p ≤ 0.001). No significant differences were found between tripod position and 4-point-kneeling positions. Transversus abdominis/internal oblique activation intensity in these positions was higher than in supine and lower than in standing. Postural load and gravitational stretch are factors that should be considered in relation to the specific recruitment of abdominal muscles for breathing mechanics.