Issue No. 12
Sometimes in life you need to read between the lines or gather up all the throwaway comments and see what you end up with. So it is with respiratory muscle training (RMT) devices and freediving.
Of the three units reviewed here only the PowerLung is both an inspiratory and expiratory trainer – resistance on both ‘suck and blow’. PowerBreathe and Ultrabreathe are inspiratory trainers only. All claim to improve athletic performance through strengthening the muscles involved in breathing. And all reference research into the effects of RMT on anaerobic and aerobic activity.
On the one hand freediving is an anaerobic activity – no oxygen due to the absence of breathing. On the other hand it can be viewed as an aerobic activity – high efficiency in the use of the available oxygen is required.
But RMT research views anaerobic activity as exercise of high intensity. Hardly a fitting description of the almost meditative sport of freediving. And RMT research looks at aerobic activity in light of prolonged submaximal exercise. In breathhold, seven minutes is an eternity, in submaximal exercise it isn’t even a warm-up.
Despite these discrepancies, there are a nuggets of information to be extracted from the reading. Suzuki, Suzuki and Okubu (1991) note a reduction in fatigue in both inspiratory and expiratory muscles after expiratory resistance training.
By contrast, O’ Kroy and Coast (1993) conclude that non-resisted hyperventilation and resisted inspiratory training are more effective than resisted expiratory training in eliciting improved strength and endurance of the breathing muscles.
Work by Cain and McConnell (1998) shows a significant increase in breathing muscle fatigue resistance and improved whole body performance when tested on stationary bicycles following respiratory training. A very recent study by Amonette and Dupler (2001) confirm previous findings.
So, let us accept that the training devices do actually work to improve the ‘fitness’ of the breathing muscles. But does it apply to freediving? On a purely mechanical basis there is evidence (Yan, 1999) to suggest that increased inspiratory strength may allow for greater ‘packing’, as the freediver prepares for immersion. Increased packing means higher total volume of oxygen pre-dive.
Physiologically, Yan (1999) also indicates that weak expiration both increases carbon dioxide and reduces oxygen after subsequent inspiration. Incomplete expiration leaves a high residual volume of ‘stale air’ in the lungs. This means the next inhalation is smaller, thereby reducing potential oxygen intake and the carbon dioxide reservoir is larger.
Amonette and Dupler (2001) observed that as “the treatment subjects developed stronger respiratory muscles they were able to move more air with fewer breaths” strongly supporting the mechanical and physiological benefits suggested by Yan (1999)
This is where the neurological and/or psychological effects of the RMT devices come into play. Boutellier (1998), Gorman McKenzie and Gandevia’s testing group had “discomfort” related to carbon dioxide accumulation and “sensations’ generated by increased lung pressures. Yan confirms that these “perceived inspiratory difficulty” can be limited through increased respiratory muscular strength and endurance. Which takes us, full circle, back to the RMT devices.
This is all well and good and may explain how RMT devices can increase the time to the first “involuntary contraction” – which is remarkably unvaried between individuals and is strongly related to the oxygen/carbon dioxide balance in the blood – but only deals with the first half of a typical breath-hold.
But how does the conscious mind stop the body from taking the next breath?
I have been led to believe my old training partner, the PowerBreathe, is no longer available. Of the two inspiratory trainers I felt that the PowerBreathe was the more “substantial” – a more robust unit with a comfortable “pistol grip.”
The second inspiratory trainer, the Ultrabreathe, is light, compact and washes up easily; hygiene is an important consideration with these devices. The Ultrabreathe is very popular with runners in particular. This unit has the advantage of being the least expensive available. This alone scores its third star to bring it level with the PowerBreathe.
The PowerLung is a late entry into the market and it is a gem. Heavy-duty build. Comfy grip. Easy to clean. Less “clinical” look. And, the real selling feature, independently adjustable inspiratory and expiratory pressures. An excellent product supported by excellent customer service. Four stars. Would have been five but for the price.