Harrison, Micheal F.

Assessments of electrocardiographic (ECG) responses during swimming activities are impossible without mobile waterproof recording units and rarely completed. This preliminary study characterized changes in the ventricular diastolic, PR‐, QT‐, and RR‐intervals that occurred during a 1 km indoor swim in 78°F water with a waterproof Actiwave ECG recording system (CamNtech Inc., Boerne, TX) and the .epf data files were analyzed with software from ADInstruments Inc. (Colorado Springs CO). Values within times expressed as mean ± SE with significance evaluated using ANOVA and repeated measures. Competitive club swimmers (3 male, 1 female) with an age, height, and weight of 51 ± 3 years, 175 ± 4 cm, and 83 ± 8 kg, with a BMI of 27 ± 2 completed the 1 km swim (44 laps × 75 foot laps) using a standard crawl in 17.9 ± 1.3 minutes using 10.5 ± 0.50 arm cycles/second. A continuous ECG with waveform was obtained and measurements were performed 120 and 30 seconds before swim, during the swim (at end of lap‐1, ‐22 and ‐43), and at 30 and 300 seconds post‐completion. Heart rate (from RR‐interval) −120, and −30 seconds prior to the swim, at end of swim lap 1, 22 and 43, and during recovery 30 and 300 seconds post swim was 68 ± 5, 73 ± 6, 107 ± 3, 142 ± 4, 147 ± 5, 132 ± 8 and 89 ± 3 beats/minute (P<0.0001). Respective QT‐intervals were 392 ± 14, 374 ± 13, 307 ± 38, 259 ± 15, 254 ± 2, 255 ± 14, and 338 ± 6 msec (n = 2 at lap‐1, and n = 3 at lap‐22) (P<0.0001). Respective ventricular diastole time was 509 ± 61, 468 ± 61, 253 ± 45, 166 ± 10, 166 ± 7, 204 ± 25 and 339 ± 26 msec (P<0.0001). Respective PR‐Intervals were 130 ± 12, 127 ± 12, 111 ± 18, 111 ± 2, 105 ± 14, 107 ± 15 and 125 ± 18 msec (P<0.094). Heart rate increased and duration of ventricular diastole decreased between lap 1 and 22, and was relatively stable between lap 22 and the end of lap 43. This study determined that with appropriate waterproof equipment a continuous ECG record can be collected from swimming athletes and used to provide an accurate assessment swim‐associated changes in cardiac function. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .