Written by Chrystal Moulton, Staff Writer. 6-week high resistance inspiratory muscle strength training (IMST) significantly improved blood pressure in healthy adults (p<0.05).
In a double-blind, randomized, sham-controlled study 1, researchers wanted to establish the safety, efficacy, and adherence to high resistance inspiratory muscle strength training (IMST). Inspiratory muscle strength training is a form of physical therapy using the diaphragm and accessory respiratory muscles to inhale repeatedly against resistance. Sixty-four participants aged 50-79 years old with a baseline systolic blood pressure of 120 mmHg were recruited for this trial. Participants were excluded if plasma glucose was ≥126 mg/dL, total cholesterol was ≥240 mg/dL, if they were severely obese, had alcohol dependence, or uncontrolled thyroid disease. The study was six weeks long and contained an optional follow-up exam six weeks after completion of the assessment. Subjects were randomly assigned to inspiratory muscle strength training (IMST) or sham training using the block randomization method in which subjects were stratified by age, sex, and systolic blood pressure. Both groups used the same inspiratory muscle training device and performed 30 inspiratory maneuvers 6 days per week for six weeks. However, subjects in the IMST group trained at 55% maximal inspiratory pressure (PI-Max) at week one, 65% maximum inspiratory pressure (PI-Max) at week 2 and 75% maximum inspiratory pressure (PI-Max) weeks three to six. Individuals in the sham group trained at 15% PI-Max weeks 1-6. Adherence was defined as a number and quality of completed versus prescribed training sessions. All outcome measures were obtained after a 12 hour fast from food and caffeine and at 24-hour abstinence from physical activity, alcohol, supplements, and over the counter medications. Subjects on anti-hypertensive medication only refrained from taking all prescription medications in the morning until after completing the experimental visit. Blood samples and ambulatory blood pressure were taken at baseline and week 6. Casual systolic blood pressure and diastolic blood pressure was measured as an average of 6 blood pressure recordings taken two days (3 times/day) during the six weeks of the trial. Researchers also measured vascular endothelial function, plasma metabolomics, and arterial stiffness.
Of the 64 participants recruited for this trial, 36 subjects were included in the final analysis (IMST group n=18, sham group n=18). No differences were observed between groups across the intervention. In the IMST group, PI-Max significantly increased from 64±5mmHg at baseline to 74±4mmHg at the end of week 6 (P<0.01). No significant change was observed in the sham group (P=0.33). The intervention group also experienced a significant decrease in casual systolic blood pressure from baseline to week 6 (baseline= 135±2 mmHg, week 6= 126±3mmHg [P<0.01]) and Casual diastolic blood pressure at week 6 (baseline= 79±2mmHg, week 6= 77±2mmHg [P=0.03]). No significant change in casual systolic blood pressure (P=0.07) or diastolic blood pressure was observed in the sham group. At 6-week follow up, casual systolic blood pressure among participants in the IMST group remained significantly lower than those in the sham group and compared to baseline IMST measures (128±4mmHg, P<0.01). Average 24-hour blood pressure measurements did not change significantly in the intervention group (P=0.52) but increased in the sham group (P=0.04). This was true also for average 24-hour diastolic blood pressure between the IMST group and sham group. Average 24-hour diastolic blood pressure was unchanged in the IMST group (P=0.63) but increased in the sham group (P=0.04). Flow mediated dilation of the brachial artery increased by 45% In the IMST group (P=0.05) but was unchanged in this sham group. However, after 6-week follow up, flow mediated dilation of the brachial artery returned to baseline levels in the IMST group. Plasma concentration of C-reactive protein was 30% lower after IMST training versus baseline (P=0.05) but was unchanged with sham training versus baseline (P=0.85). No significant differences were observed between group or within group for other circulating markers of inflammation and oxidative stress. Plasma metabolomics revealed three potential markers exhibiting cardiovascular effects that increased during IMST training but not sham training: L- ornithine (P= 0.01), indole (P= 0.03), and hexanoic acid (P= 0.04). No significant changes were observed for arterial stiffness between IMST group and sham group during the intervention period and at six weeks follow up. Participants in the IMST group had 94% adherence to treatment protocol with 2 reported adverse events (both minor). No adverse events occurred in the sham group.
Overall, IMST improved casual systolic blood pressure, flow mediated dilation of the brachial artery, and plasma C-reactive protein levels. Three metabolites were increased with IMST: L-ornithine (an amino acid which serves as a precursor to NO substrate l-arginine 2, hexanoic acid (a short chain fatty acid that mediates anti-inflammatory response 3, and indole (a microbial metabolite which acts on the central nervous systems to reduce blood pressure 4.The training was also tolerable and safe with a strong adherence among the participants. Further research is needed to validate these findings.
Source: Craighead, Daniel H., Thomas C. Heinbockel, Kaitlin A. Freeberg, Matthew J. Rossman, Rachel A. Jackman, Lindsey R. Jankowski, Makinzie N. Hamilton et al. “Time‐Efficient Inspiratory Muscle Strength Training Lowers Blood Pressure and Improves Endothelial Function, NO Bioavailability, and Oxidative Stress in Midlife/Older Adults With Above‐Normal Blood Pressure.” Journal of the American Heart Association 10, no. 13 (2021): e020980.
© 2021 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
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Posted October 11, 2021.
Chrystal Moulton BA, PMP, is a 2008 graduate of the University of Illinois at Chicago. She graduated with a bachelor’s in psychology with a focus on premedical studies and is a licensed project manager. She currently resides in Indianapolis, IN.
References:
- Craighead DH, Heinbockel TC, Freeberg KA, et al. Time-Efficient Inspiratory Muscle Strength Training Lowers Blood Pressure and Improves Endothelial Function, NO Bioavailability, and Oxidative Stress in Midlife/Older Adults With Above-Normal Blood Pressure. J Am Heart Assoc. 2021;10(13):e020980.
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