Effects of Inspiratory Muscle Strength Training on Cardiorespiratory Fitness in Middle‐Aged to Older Adults

Abstract

BackgroundCardiorespiratory fitness declines with aging and is a strong independent risk factor for future morbidity and mortality. Conventional aerobic exercise improves cardiorespiratory fitness in middle‐aged and older (MA/O) adults, but is associated with relatively low adherence, due, in part, to significant time requirements (150 min/week). High‐resistance, short‐duration inspiratory muscle strength training (IMST) requires only 30 min/week and is associated with excellent adherence, but effects on cardiorespiratory fitness are unknown. We assessed whether high‐resistance, short‐duration IMST improves cardiorespiratory fitness assessed under maximal exercise (VO2max, exercise tolerance) and standardized submaximal exercise conditions.MethodsHealthy, recreationally active MA/O adults (50–79 years) were recruited. Subjects were randomly assigned to perform 6‐weeks of IMST (30 breaths/day; 6 days/week; 75% maximum inspiratory pressure [PIMAX]) (n=7 age: 68 ± 2 years) or sham (15% PIMAX) training (n=7; age: 67 ± 3 years) in a randomized, double‐blind, placebo‐controlled study. Oxygen uptake (VO2) and other responses were measured throughout incremental treadmill exercise to exhaustion using a modified Balke Protocol pre‐ and post‐intervention.ResultsAdherence, defined as percentage of prescribed training sessions completed, was high in both the IMST (100%) and sham (98%) groups. PIMAX increased in the IMST group (pre: 57 ± 5, post: 70 ± 4 mmHg; p=0.048) but not sham group (pre: 54 ± 2, post: 60 ± 1 mmHg; p=0.5). VO2max did not change with training in either group (p>0.05), but exercise time to exhaustion increased by 15% in the IMST group (pre: 629 ± 64, post: 726 ± 50 seconds; p=0.009) and decreased in the sham group (pre: 583 ± 74, post: 500 ± 77 seconds; p=0.02). At maximal exercise, most markers of voluntary effort (minute ventilation, VE, heart rate, HR, and rating of perceived exertion, RPE) were unchanged pre vs. post training in both groups (all p>0.05), but peak respiratory exchange ratio, a measure of hyperventilation, was higher in the IMST group after training (pre: 1.08 ± 0.03, post: 1.14 ± 0.03; p=0.05; sham group: pre: 1.06 ± 0.02, post: 1.05 ± 0.04; p=0.96). At a fixed submaximal workload (~80% of initial VO2max), VO2 (pre: 23.3 ± 1.8, post: 21.3 ± 1.5 ml/kg/min; p=0.01) and HR (pre: 131 ± 7, post: 127 ± 7; p=0.07) were lower after vs. before IMST, but unchanged with sham training. VE and RPE during submaximal exercise were unchanged with training in both groups (all p>0.05).ConclusionHigh‐resistance short‐duration IMST increases exercise time to exhaustion (exercise tolerance), improves submaximal exercise economy, and lowers HR during submaximal exercise in healthy, recreationally active, MA/O adults. Thus, high resistance, short‐duration IMST improves exercise performance in healthy MA/O adults, and may hold even greater promise for older adults with functional limitations and/or chronic disease.Support or Funding InformationAHA 18POST33990034, T32 DK007135, UL1 TR002535This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.