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Time-efficient, high-resistance inspiratory muscle strength training increases exercise tolerance in midlife and older adults
Craighead DH, Freeberg KA, Heinbockel TC, Rossman MJ, Jackman RA, McCarty NP, Jankowski LR, Nemkov T, Reisz JA, D' Alessandro A, Chonchol M, Bailey EF, Seals DR
Medicine and Science in Sports and Exercise 2023 Sep;56(2):266-276
clinical trial
5/10 [Eligibility criteria: No; Random allocation: Yes; Concealed allocation: No; Baseline comparability: Yes; Blind subjects: No; Blind therapists: No; Blind assessors: No; Adequate follow-up: Yes; Intention-to-treat analysis: No; Between-group comparisons: Yes; Point estimates and variability: Yes. Note: Eligibility criteria item does not contribute to total score] *This score has been confirmed*

PURPOSE: To determine if time-efficient, high-resistance inspiratory muscle strength training (IMST), comprising 30 inhalation-resisted breaths per day, improves cardiorespiratory fitness, exercise tolerance, physical function and/or regional body composition in healthy midlife and older adults. METHODS: We performed a double-blind, randomized, sham-controlled clinical trial (NCT03266510) testing 6 weeks of IMST (30 breaths/day, 6 days/week, 55% to 75% maximal inspiratory pressure) versus low-resistance sham training (15% maximal inspiratory pressure) in healthy men and women aged 50 to 79 years. Subjects performed a graded treadmill exercise test to exhaustion, physical performance battery (eg, handgrip strength, leg press), and body composition testing (dual x-ray absorptiometry) at baseline and after 6 weeks of training. RESULTS: Thirty-five participants (17 women, 18 men) completed high-resistance IMST (n = 17) or sham training (n = 18). Cardiorespiratory fitness (VO2peak) was unchanged, but exercise tolerance, measured as treadmill exercise time during a graded exercise treadmill test, increased with IMST (baseline: 539 +/- 42 s, end-intervention: 606 +/- 42 s; p = 0.01) but not sham training (baseline: 562 +/- 39 s, end-intervention: 553 +/- 38 s; p = 0.69). IMST increased peak respiratory exchange ratio (baseline: 1.09 +/- 0.02, end-intervention: 1.13 +/- 0.02; p = 0.012), peak ventilatory efficiency (baseline: 25.2 +/- 0.8, end-intervention: 24.6 +/- 0.8; p = 0.036) and improved submaximal exercise economy (baseline: 23.5 +/- 1.1 ml/kg/min, end-intervention: 22.1 +/- 1.1 ml/kg/min; p < 0.001); none of these factors were altered by sham training (all p > 0.05). Changes in plasma acylcarnitines (targeted metabolomics analysis) were consistently positively correlated with changes in exercise tolerance following IMST but not sham training. IMST was associated with regional increases in thorax lean mass (+4.4%; p = 0.06) and reductions in trunk fat mass (-4.8%; p = 0.04); however, peripheral muscle strength, muscle power, dexterity and mobility were unchanged. CONCLUSIONS: These data suggest that high-resistance IMST is an effective, time-efficient lifestyle intervention for improving exercise tolerance in healthy midlife and older adults.

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