Summary
Damien Roos of the Semi-Pro Cycling Podcast delivers a detailed breakdown of inspiratory muscle training (IMT) for cycling endurance, drawing from a presentation by Dr. Peter Brown at the World Congress of Cycling Science. He traces IMT research from the 1960s to Jerome Dempsey's breakthrough discovery that breathing muscles fatigue like any other muscles, with diaphragm force dropping significantly after exercise and remaining depressed for up to two days. The episode distinguishes between three training approaches: expiratory muscle training (found to inhibit performance), respiratory muscle training (hyperventilation into a bag, which can trigger asthma), and inspiratory muscle training (the most effective approach). Key studies showed 3.5% and 2.7% improvements in 20-40km time trial performance after 6 weeks of IMT. Professor Alison McConnell's functional IMT concept is highlighted, where athletes train breathing while in race positions. Roos concludes that IMT offers small single-digit gains best suited for well-trained athletes seeking a competitive edge.
Key Points
- Breathing muscles fatigue like any other muscles -- diaphragm force drops after exercise and can stay depressed for days
- Expiratory muscle training inhibits performance; respiratory muscle training (hyperventilation) can trigger asthma
- IMT focuses specifically on strengthening inhalation muscles and has the best evidence base
- Rowe et al. 2002 showed 3.5% improvement in 20-40km time trials after 6 weeks of IMT
- Johnson et al. 2007 showed 2.7% improvement in 25km time trial performance
- IMT improved maximum inspiratory pressure, reduced heart rate, blood lactate, RPE, and respiratory muscle fatigue
- IMT does not improve VO2max or lactate threshold -- the mechanism of performance improvement is unclear
- Functional IMT (training in race position) is the latest approach, pioneered by Professor Alison McConnell
- Base protocol: 2x30 breaths daily for 4-6 weeks, then sports-specific exercises for 4-6 weeks
Key Moments
Breathing muscles fatigue like any other muscles and stay depressed for days
Jerome Dempsey's breakthrough discovery showed that breathing muscles fatigue just like any other muscles, with diaphragm force dropping significantly after exercise and staying depressed for up to an hour or even days.
"It really started to gain momentum after a guy called Jerome Dempsey from the Wisconsin University had a breakthrough discovery when he found that breathing muscles fatigue just like any other muscles."
Key studies show 2.7-3.5% time trial improvements with 6 weeks of IMT
Two landmark studies showed real performance improvements from IMT. Rowe et al. 2002 found 3.5% improvement in 20-40km time trials, and Johnson et al. 2007 found 2.7% in 25km time trials after six weeks of training.
"The first one, Roma et al., 2002, where there was a 3.5 improvement in performance of 20 and 40 kilometer time trials with six weeks of IMT. The second one, Johnson et al., in 2007, where there was a 2.7 improvement in performance in a 25 kilometer time trial."
Functional IMT trains breathing in race position for sport-specific gains
Professor Alison McConnell pioneered functional IMT, where athletes use breathing devices while in sport-specific positions like the time trial aero position. This trains respiratory muscles under the mechanical constraints they face during racing.
"So examples of functional IMT, off the bike stuff, an ab crunch where you're actually standing and bending over like you're in a time trial position while you have the device in your mouth."
IMT does not improve VO2max or lactate threshold
Despite performance improvements, IMT does not change standard laboratory markers like VO2max or lactate threshold. This leaves researchers speculating on the actual mechanisms of benefit.
"What is clear is that respiratory muscles training does not result in improvements in the standard laboratory markers of endurance performance such as VO2 max or lactate threshold."
