VENTILATORY DEMANDS OF SWIMMING AT AND BELOW RESPIRATORY MUSCLE FATIGUE PACE

Ventilatory Demands of Swimming at and below Respiratory Muscle Fatigue Pace

Ventilatory Demands of Swimming at and below Respiratory Muscle Fatigue Pace

Introduction

The study protocol was approved by the Human Subjects Institutional Review Board. Informed consent was obtained from the subjects prior to enrollment in the study. This study compared the effects resistance respiratory muscle training (RRMT) performed 3 days per week with RRMT ?ve days per week, for 4 weeks, on respiratory and ?n swimming performance in trained scuba divers. In addition, the potential usefulness of a two day per week RRMT (maintenance RRMTM), after RRMT-3, was evaluated over a three month period.

Pre- and Post-RMT Testing

Pulmonary function testing

A Morgan Spiro?ow Spirometer Model #131 (PK Morgan Ltd., Rainham, Gillingham, Kent, UK) was used to obtain maximal voluntary ventilation in 15 seconds (MVV), slow vital capacity (SVC), forced vital capacity (FVC), and forced expiratory volume in one second (FEV1 ). All of these variables were recorded in accordance with ATS standards and are reported at BTPS (Alberty 2008, 1191-1200). Respiratory muscle strength was estimated from measurements of maximal inspiratory pressure (P Imax ) at residual volume (RV) and expiratory pressure (P Emax ) exerted at total lung capacity (TLC). These pressures were measured with a manometer connected to the mouthpiece. A small hole in the manometer system generated a leak that prevented the use of buccal muscles to generate false pressure readings. A timed, isocapnic respiratory muscle endurance test (RET) was also performed. Using a tidal volume of approximately 50% SVC and a frequency determined by dividing 60% of the MVV value by the tidal volume, subjects breathed into a mouthpiece and rebreathing bag (to maintain normocapnia) until they were unable to maintain the target ventilation presented to each subject on the computer display (Craig 1985, 625-634).



Maximal VO2 determined during surface swimming

Paced surface V O2max tests were conducted prior to and after RRMT. Using ?ns, subjects swam at the surface following a monitoring platform that paced swimming speed and on which data were collected. The velocity was increased from 0.4 m/s in 0.1 m/sec increments every three minutes until the diver could no longer maintain the speed (Cardelli 1999, 51-74). Via a two-hose mouth piece expired gases were collected in “Douglas” bags during the last minute of each speed segment for determination of V O2 , a venous blood sample was taken 5-7 min postswim for lactate (anaerobic metabolism). Expired gas volume was measured with a dry gas meter (Harvard Model#AH-50-6164) and CO2 and O2 concentrations were analyzed with the previously calibrated mass spectrometer (MGA1100, Perkin-Elmer, Pomona, CA). Standard equations were used to calculate V O2 and VCO2 and values were expressed at standard temperature, pressure dry gas (STPD) (Cardelli 2000, 979-987).

Subjects

Thirty experienced male swimmers were recruited as subjects from University Club. Informed consent was obtained from each subject prior to enrollment into the study. The physical characteristics of the subjects were: age 18-27 years, height ...