Lin J-S1, Lee C-T1, Lin H-C1, Wang L-Y1,2
1National Taiwan University, School and Graduate Institute of Physical Therapy, Taipei, Taiwan, 2National Taiwan University Hospital, Physical Therapy Center, Taipei, Taiwan
Background: Inspiratory muscle training (IMT) usually performed in the upright sitting position. In healthy individuals, sternocleidomastoid (SCM) is rarely recruited during tidal breathing, but previous studies have demonstrated SCM activation during inspiratory threshold loading (ITL) tasks in upright sitting position. Whether minimizing SCM activation in supine position would increase diaphragm activation during ITL tasks remains to be determined.
Purpose: To exam diaphragm and SCM activation during ILT tasks in sitting and supine position in healthy adults.
Methods: Diaphragm and SCM activation were simultaneously recorded using surface electromyography (sEMG), during quiet breathing, maximal inspiratory pressure test, and ITL with 30% maximal inspiratory pressure (PImax) intensity in sitting and supine positions. Diaphragm and SCM activation (%EMGDia and %EMGSCM) were calculated using mean root mean square (RMS) values from 10 breaths during each test condition normalized to RMS values measured during maximal inspiratory pressure test. Median frequency of diaphragm and SCM (MFDia and MFSCM) were analyzed and averaged from 10 breaths of each test conditions to exam muscle fatigue. Generalized Estimating Equation was used to detect between- and within-group differences among variables in different task conditions. Patterns of SCM activation were examined using group-based trajectory modeling. Significance α level was set at 0.05.
Results: A total of 14 healthy adults with a mean (±SD) age of 23.6 (±1.0) years and PImax of 98.6 (±31.6) cmH2O were recruited for the study. In sitting position, compared to quiet breathing, %EMGDia and %EMGSCM significantly increased by 29.5% and 48.4% during ILT at 30% PImax (both p 0.001). Compared to sitting position, significantly more diaphragm activation (11.2%, p = 0.001) and less SCM activation (14.9%, p = 0.007) was noted during ITL at 30% PImax in supine position. Trajectory remodeling identified two distinct patterns of diaphragm and SCM activation during ITL at 30% PImax in different body positions. A small numbers of subjects (n=4) showed relatively high SCM and low diaphragm activation in both testing positions. In addition, from sitting to supine, SCM activation decreased by 20.3% and diaphragm activation increased by 18.2% during ITL in this group of subjects.
Conclusion(s): Healthy adults demonstrated increased diaphragm and SCM activation during ITL in both sitting and supine position. ITL task, when performed in supine position yielded more diaphragm activation and less SCM activation than that of in sitting position.
Implications: The body position should be taken into consideration on how IMT is
performed if diaphragm is the target muscle for training.
Keywords: Inspiratory threshold loading, Electromyography, Body position
Funding acknowledgements: No specific funding was received for this study.
Purpose: To exam diaphragm and SCM activation during ILT tasks in sitting and supine position in healthy adults.
Methods: Diaphragm and SCM activation were simultaneously recorded using surface electromyography (sEMG), during quiet breathing, maximal inspiratory pressure test, and ITL with 30% maximal inspiratory pressure (PImax) intensity in sitting and supine positions. Diaphragm and SCM activation (%EMGDia and %EMGSCM) were calculated using mean root mean square (RMS) values from 10 breaths during each test condition normalized to RMS values measured during maximal inspiratory pressure test. Median frequency of diaphragm and SCM (MFDia and MFSCM) were analyzed and averaged from 10 breaths of each test conditions to exam muscle fatigue. Generalized Estimating Equation was used to detect between- and within-group differences among variables in different task conditions. Patterns of SCM activation were examined using group-based trajectory modeling. Significance α level was set at 0.05.
Results: A total of 14 healthy adults with a mean (±SD) age of 23.6 (±1.0) years and PImax of 98.6 (±31.6) cmH2O were recruited for the study. In sitting position, compared to quiet breathing, %EMGDia and %EMGSCM significantly increased by 29.5% and 48.4% during ILT at 30% PImax (both p 0.001). Compared to sitting position, significantly more diaphragm activation (11.2%, p = 0.001) and less SCM activation (14.9%, p = 0.007) was noted during ITL at 30% PImax in supine position. Trajectory remodeling identified two distinct patterns of diaphragm and SCM activation during ITL at 30% PImax in different body positions. A small numbers of subjects (n=4) showed relatively high SCM and low diaphragm activation in both testing positions. In addition, from sitting to supine, SCM activation decreased by 20.3% and diaphragm activation increased by 18.2% during ITL in this group of subjects.
Conclusion(s): Healthy adults demonstrated increased diaphragm and SCM activation during ITL in both sitting and supine position. ITL task, when performed in supine position yielded more diaphragm activation and less SCM activation than that of in sitting position.
Implications: The body position should be taken into consideration on how IMT is
performed if diaphragm is the target muscle for training.
Keywords: Inspiratory threshold loading, Electromyography, Body position
Funding acknowledgements: No specific funding was received for this study.
Topic: Cardiorespiratory
Ethics approval required: Yes
Institution: National Taiwan University Hospital
Ethics committee: Research Ethics Committee (REC) of National Taiwan University Hospital
Ethics number: 201807021RINA
All authors, affiliations and abstracts have been published as submitted.
