ABSTRACT
Six trained male cyclists and triathletes participated in a double blind study to determine the effects of phosphate loading on maximal and endurance exercise performance. Subjects ingested either 1 gm of tribasic sodium phosphate or a glucose placebo four times daily for 3 days prior to performing either an incremental maximal cycling test or a simulated 40-km time trial on a computerized race simulator. They continued the supplementation protocol for an additional day and then performed the remaining maximal or performance exercise test. Subjects observed a 17-day washout period between testing sessions and repeated the experiment with the alternate supplement regimen in identical fashion. Metabolic data were collected at 15-sec intervals while venous blood samples and 2D-echocardiographic data were collected during each stage of exercise during the maximal exercise test and at 8-km intervals during the 40-km time trial. Results indicate that phosphate loading attenuated anaerobic threshold, increased myocardial ejection fraction and fractional shortening, increased maximal oxidative capacity, and enhanced endurance performance in competitive cyclists and triathletes.
Subject(s)
Exercise/physiology , Heart/physiology , Metabolism/drug effects , Phosphates/administration & dosage , Physical Endurance/physiology , Adult , Bicycling , Double-Blind Method , Echocardiography , Heart/drug effects , Hematocrit , Hemodynamics , Hemoglobins/metabolism , Humans , Male , Oxygen Consumption , Phosphates/blood , Phosphates/pharmacology , Placebos , Random AllocationABSTRACT
Triathletes typically train each triathlon event separately. Therefore, to determine the cardiovascular and thermal differences between training and triathlon performance, nine male triathletes performed a simulated 75-min (40 km) control bike and a 40-min (10 km) control run at 70% of maximal oxygen uptake. Control data were compared to data derived from a simulated triathlon (0.8-km swim, 75-min bike, and 40-min run). Results demonstrated that prior swimming significantly decreased (P less than 0.05) triathlon cycling work output (191 +/- 4.2 to 159 +/- 7.6 W) producing mean differences (P less than 0.05) in oxygen uptake (3.18 +/- 0.1 to 3.01 +/- 0.11.min-1), ventilation (84.7 +/- 4 to 80.4 +/- 4.21.min-1), stroke volume (128 +/- 7.1 to 118 +/- 3.5 ml.min-1), cardiac output (20.7 +/- 1.2 to 18.9 +/- 0.8 l.min-1), mean arterial pressure (105 +/- 3.8 to 96 +/- 7.9 mm Hg) and rectal temperature (38.2 +/- 0.2 to 38.4 +/- 0.3 degrees C). Triathlon running, while performing identical control work output, elicited significant increases (P less than 0.05) in oxygen uptake (3.41 +/- 0.1 to 3.85 +/- 0.1 l.min-1), ventilation (91.3 +/- 3.3 to 104.2 +/- 2.8 l.min-1), heart rate (161 +/- 3.1 to 174 +/- 3.6 beats.min-1), arteriovenous oxygen difference (15.3 +/- 0.2 to 17.2 +/- 0.3 ml.100 ml-1) and rectal temperature (38.3 +/- 0.2 and 39.2 +/- 0.3 degrees C) with significantly lower (P less than 0.05) stroke volume (138 +/- 2.4 to 129 +/- 3.6 ml.min-1) and mean arterial pressure (102 +/- 11.2 to 89 +/- 5.5 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)
