2007, Piran, Slovenia

Altitude Physiology
ENDURANCE RESPIRATORY MUSCLE TRAINING: DOES IT
AFFECT NORMOXIC OR HYPOXIC EXERCISE
PERFORMANCE?
Michail E. Keramidas 1,2 , Mojca Amon 1 , Tadej Debevec 1 , Boštjan Šimunič 3 , Rado
Pišot 3 , Pietro E. di Prampero 4 and Igor B. Mekjavic 1
1 Jozef Stefan Institute, Ljubljana, Slovenia;
2 National and Kapodistrian University of Athens, Greece;
3 MATI Centro di Eccellenza - Università di Udine, Udine, Italy;
4 Institute for Kinesiology Research, University of Primorska, Koper, Slovenia;
INTRODUCTION
Recent studies have shown that fatigue of respiratory muscles is one of the main
limitations of intense exercise and cause of reduced exercise performance. However,
there are controversial findings regarding the effect of specific training protocols of
respiratory muscles. Specifically, the training mode of voluntary isocapnic
hyperpnoea has been shown to improve endurance performance.
The aim of the present study was to evaluate the effect of respiratory muscle training
on endurance performance in normoxic and hypoxic conditions.
METHODS
Fourteen healthy young males were recruited, stratified for age and aerobic capacity,
and randomly assigned to either a control (CON), or respiratory muscle training
(RMT) group (CON: n = 7, age = 21.43 ± 4.35 yrs, height = 178.24 ± 5.13 cm, mass =
72.11 ± 11.05 kg, and VO2max = 47.41 ± 6.16 ml/kg - /min; RMT: n = 7, age = 22.00 ±
3.56 yrs, height = 178.83 ± 4.85 cm, mass = 70.74 ± 9.42 kg, and VO2max = 47.60 ±
5.80 ml/kg/min).
Two incremental tests to exhaustion (VO2max tests), two constant power (CP) tests
until exhaustion and a standard pulmonary function test (PFT) were completed pre
and post training. In particular, the VO2max and the CP tests were performed on two
occasions: in one the subjects inspired normal room air (FIO2 0.21) (VO2maxNor and
CP Nor, respectively), and on the other a hypoxic gas mixture (FIO2 0.12)
(VO2maxHypo and CP Hypo, respectively). The intensity of CP tests in both conditions
was 80% VO2maxNor, and they were repeated each time at the same absolute intensity
as before training. PFT was used to obtain forced vital capacity (FVC), forced
expiratory volume in 1 sec (FEV1), peak expiratory flow (PEF), slow vital capacity
(SVC), and maximum voluntary ventilation (MVV).
The training protocol of RMT group comprised 30 min of endurance training of
respiratory muscles with a specific device (SpiroTiger ® , Italy) and 60 min of cycling
at 50% of peak power output (PPO). The training device for respiratory muscles
consisted of a nose clip, mouthpiece, a hand-held device with sensors (breathing
frequency, ventilation, etc.) and a respiratory-bag connected to a tube equipped with
one-way inlet and outlet valves. The valves permitted the addition of fresh inspired air
into the rebreathing bag with each breath, thus maintaining end-tidal CO2 constant
(isocapnic). The volume of the bag was initially set at approximately 55% of the
subjects’ SVC. The breathing frequency (fb) was then determined by dividing 50% of
MVV by the bag volume. In each session, the participants were instructed to increase
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