Efficacy Of A Novel Method For Inspiratory Muscle Training In Chronic Obstructive Pulmonary Disease Patients
Authors: D. Langer, N. Charususin, C. Jacome, M. Hoffman, A. McConnell, M. Decramer and R. Gosselink
DOI / Source: https://doi.org/10.2522/ptj.20140245
Date: September 2015
Reading level: Intermediate
Why This Matters for Freedivers
Even though this study is in COPD patients (not freedivers), it supports a useful idea: very short, consistent IMT sessions can measurably improve inspiratory muscle strength and endurance, and devices that manage the load more intelligently may let you train harder with the same perceived effort. For freedivers, that’s potentially relevant for comfort during ventilation, recovery breathing, and respiratory muscle “resilience” during heavy training blocks—just treat it as supportive evidence, not direct proof of performance gains in apnea.
Synopsis
Breathing muscles can be trained just like legs and arms — and for some people, that training can change how “hard breathing feels” during effort. This study looked at inspiratory muscle training (IMT) in people with COPD who had weak breathing muscles, and tested a very practical question: can a short, mostly home-based IMT routine work well, and does a newer “smart” device work better than the classic one? 
Twenty stable COPD patients in a pulmonary rehab program were randomized to 8 weeks of IMT using either a traditional mechanical threshold loading device (MTL) or an electronic tapered flow resistive loading device (TFRL). The routine was short but frequent: two sessions per day, each just 30 breaths (about 3–5 minutes), plus twice-weekly supervised sessions. Training intensity was set at the highest tolerable load, and the researchers tracked both strength (max inspiratory mouth pressure, Pi,max) and endurance (how long they could sustain a loaded breathing task, T,lim). 
Both approaches worked: people completed over 90% of sessions, and inspiratory muscle function improved. But the TFRL device had an edge: patients could tolerate higher training loads in the final weeks while feeling similar effort, and they achieved larger improvements in both Pi,max and T,lim than the traditional device group. The authors note an important limitation: there wasn’t a sham (placebo) IMT group, so the comparison is device-vs-device rather than “IMT vs no IMT.”
Abstract
Background: Most inspiratory muscle training (IMT) interventions in patients with COPD have been implemented as fully supervised daily training for 30 minutes with controlled training loads using mechanical threshold loading (MTL) devices. Recently, an electronic tapered flow resistive loading (TFRL) device was introduced that has a different loading profile and stores training data during IMT sessions.
Objective: We aimed to compare the effectiveness of a brief, largely unsupervised IMT protocol, conducted using either traditional MTL or TFRL, on inspiratory muscle function in patients with COPD.
Design: Twenty clinically stable patients with inspiratory muscle weakness, participating in a pulmonary rehabilitation program, were randomly allocated to perform eight weeks of either MTL-IMT or TFRL-IMT.
Methods: Patients performed two daily home-based IMT sessions of 30 breaths (3–5 minutes per session) at the highest tolerable intensity, supported by twice-weekly supervised sessions. Compliance, progression of training intensity, and increases in maximal inspiratory mouth pressure (Pi,max) and endurance capacity of inspiratory muscles (T,lim) were evaluated.
Results: More than 90% of IMT sessions were completed in both groups. The TFRL group tolerated higher loads during the final three weeks of the IMT program (all p < 0.05) with similar effort scores on a Borg CR-10 scale, and achieved larger improvements in Pi,max (p = 0.02) and T,lim (p = 0.02) than the MTL group.
Limitation: Absence of a study arm involving a sham-IMT intervention.
Conclusion: The short and largely home-based IMT protocol was effective in both groups and is an alternative to traditional IMT protocols in this population. Patients in the TFRL group tolerated higher training loads and achieved larger improvements in inspiratory muscle function than patients in the MTL group.