Reviewed by John Baur, PT, DPT, OCS, CSCS, FAAOMPT
Why train the breathing muscles?
The authors argue that conventional sport training does not sufficiently stress the respiratory musculature to drive meaningful adaptation. In elite endurance athletes, the respiratory system—particularly the muscles of breathing—can become a relative limiter because the ventilatory work and oxygen cost rise steeply at race intensities. At V̇O₂max, respiratory muscles may demand ~15–20% of total oxygen consumption and cardiac output in trained athletes (vs ~8–10% in untrained), making fatigue of these muscles a plausible constraint on whole‑body performance. A key mechanism is the respiratory metaboreflex: metabolite accumulation and fatigue in the inspiratory muscles evoke sympathetic vasoconstriction in the locomotor limbs, reducing their blood flow and hastening peripheral fatigue. Improving the efficiency and fatigue resistance of respiratory muscles can therefore blunt this reflex and support better endurance performance.
What improves with respiratory muscle training (RMT)?
Synthesizing recent reviews and trials, the paper concludes that RMT can (1) improve time‑trial and constant‑load performance, (2) increase respiratory muscle strength and endurance, and (3) lower perceived exertion or dyspnea. Benefits extend to hypoxic exercise where RMT reduces respiratory fatigue and helps maintain oxygen saturation.
How to train the breathing muscles—methods and devices.
Three methods have robust support in sport settings:
– Inspiratory Pressure Threshold Loading (IPTL): breaths against a constant pressure load (often 50–80% of maximal inspiratory pressure), typically 30 forceful inspirations, twice daily.
– Tapered Flow Resistive Loading (TFRL): resistance decreases during the inspiratory phase to allow full vital‑capacity inspirations while maintaining substantial load.
Voluntary Isocapnic Hyperpnea (VIH): sustained hyperventilation (≈60–90% of maximal voluntary ventilation) for 15–40 minutes with a rebreathing circuit to keep CO₂ constant; this primarily targets endurance of the respiratory muscles.
Key visuals.
Table 1 (p. 6) catalogs commonly used devices and price points, from basic mechanical trainers (e.g., Philips Threshold IMT ≈$26; POWERbreathe Plus ≈$65) to electronic systems (e.g., POWERbreathe K4 ≈$675; Airofit PRO 2.0 ≈$349) and hyperpnea devices (e.g., Idiag/SpiroTiger P100 ≈$1,639). This table also lists inspiratory/expiratory resistance ranges, useful when matching device capability to athlete needs.
Table 2 (p. 6) summarizes protocols that improved performance across sports: e.g., rowing with IPTL (30 inspirations, twice daily, 4–11 wks); cycling with VIH (30 min, 5×/wk, 4–6 wks) or IPTL (30 inspirations, twice daily, 6 wks); swimming with IPTL (various 4–8‑wk protocols); and running with VIH (30 min, 5×/wk, 4 wks) or TFRL (36 inspirations, 3×/wk, 6 wks).
Figures 1–2 (p. 5) illustrate IPTL with a POWERbreathe device and VIH with an Isocapnic BWB system; Figure 3 (p. 10) shows real‑time S‑Index testing output for inspiratory strength.
Programming principles.
Respiratory muscles adapt like other striated muscles, so apply progressive overload, specificity, periodization, and reversibility. Many athletes plateau in RMT gains at ~6–9 weeks, after which altering method or loading is advised (e.g., switch from VIH to IPTL every ~8 weeks or alternate high‑resistance/low‑repetition and lower‑resistance/higher‑repetition phases). Detraining over 2–4 weeks produces minimal loss, but more substantial decline appears by 8–12 weeks—yet values may remain above pre‑training baselines. Practical “classic” protocols include 30 fast forceful inspiratory efforts twice per day, 5–6 days per week (resistance devices) or 3–5 VIH sessions of 15–40 minutes per week.
Sport‑specific applications.
Rowing. Extreme ventilatory demands, constrained body positions, and entrainment between stroke and breathing load the inspiratory muscles heavily. Trials show inspiratory training improves inspiratory strength (e.g., ~34–45% over 11 weeks) and produces small but decisive gains: ~3.5% greater distance in a 6‑min test and ~3.1% faster 5000 m vs placebo. The literature favors inspiratory‑only training for performance gains; adding expiratory work may improve pulmonary function but not race outcomes. An IPTL‑based respiratory warm‑up can also acutely improve maximal rowing performance.
Cycling. Both IPTL and VIH can raise ventilatory capacity (~12–16%) and improve time‑trial outcomes by ~2.1–4.75% over 4–6 weeks (not always statistically significant). Benefits appear larger as event duration increases, suggesting particular utility for longer time trials or stage racing. RMT may also help riders sustain aero positions by improving comfort and the efficiency of locomotor‑respiratory coupling.
Swimming. Among studied sports, swimmers exhibit the greatest inspiratory fatigue after single race‑pace efforts (≈17–21% drop in inspiratory strength), likely due to breath timing constraints, resisting hydrostatic pressure, and potential co‑contraction patterns. RMT has produced performance gains of ~1.2–7.3% over 50–200 m in several studies; even when inspiratory strength does not rise in highly trained swimmers (whose base programs already strengthen respiratory muscles), performance may still improve via reduced fatigue and a delayed metaboreflex. Divers and finswimmers also benefit; disabled swimmers show marked improvements in pulmonary function and ventilation disorders resolution.
Triathlon. Wetsuits increase chest/abdominal resistance to breathing, and bike‑to‑run transitions elevate respiratory fatigue relative to running alone; fatigue can persist >24 h post‑race. RMT can be particularly helpful in multi‑race formats where recovery windows are short.
Hypoxia. In 4–8‑week pre‑exposure protocols, RMT reduces respiratory fatigue, delays metaboreflex activation, improves buffering/clearance of anaerobic metabolites, and helps preserve oxygenation and limb blood flow during hypoxic exercise. Use caution layering RMT on top of altitude/cold training loads due to heightened systemic stress and infection risk.
Assessment and technique.
Before RMT, assess respiratory muscle strength/endurance and (where regulations permit) pulmonary function. In practice, many coaches use device‑embedded tests such as the POWERbreathe S‑Index—8 dynamic inspirations from residual volume to full capacity after a brief warm‑up—to quantify inspiratory strength and to track pre‑ vs post‑session decrements as a field estimate of fatigue (a 10–15% drop is often used as a working threshold). As with any strength work, emphasize movement quality first: teach an efficient breathing pattern and thoracic mobility. Evidence does not conclusively favor a particular breathing technique (e.g., nasal vs diaphragmatic) during exercise, though diaphragmatic breathing may reduce psychological/physiological stress; still, technique instruction is a sensible foundation before loading. RMT is generally safe, with occasional transient headache or dizziness reported. It integrates easily into warm‑ups, recoveries, or brief standalone sessions.
- The back extensors. (The three groups are diaphragm, rib‑cage muscles, abdominal muscles; back extensors are not one of them; see p. 4.)
- Inspiratory muscles. (They expand the lungs during inhalation; primary muscle is the diaphragm; p. 4.)
- Hypertrophied inspiratory muscles. (Benefits stem from enhanced mechanical efficiency and fatigue resistance—not hypertrophy per se; p. 4.)
- Flow volume loop tracing. (Proven training methods are IPTL, TFRL, and VIH; p. 4–5.)
- 6–9 weeks. (Benefits tend to plateau after about 6–9 weeks, prompting periodization; p. 5.)
- Inspiratory training. (Preferred for rowing performance; expiratory or combined approaches improve lung function but not rowing results; p. 7.)
- Swimming. (Shows the most substantial respiratory muscle fatigue among studied sports; p. 8.)
- Women. (The respiratory system may limit performance to a greater extent in women; p. 9.)
- 10–15%. (No universal consensus, but thresholds of ~10–15% decline are commonly used to mark inspiratory fatigue; p. 10.)
- Scientific evidence is inconclusive. (No clear advantage for specific techniques like nasal or diaphragmatic breathing during exercise; p. 10–11.)
References:
Kowalski T, Granda D, Klusiewicz A. Practical Application of Respiratory Muscle Training in Endurance Sports. Strength Cond J. 2024;46(6):686‑695.