title: Change in body mass accurately and reliably predicts change in body water after endurance exercise.
abstract: This study tested the hypothesis that the change in body mass (DeltaBM) accurately reflects the change in total body water (DeltaTBW) after prolonged exercise. Subjects (4 men, 4 women; 22-36 year; 66 +/- 10 kg) completed 2 h of interval running (70% VO(2max)) in the heat (30 degrees C), followed by a run to exhaustion (85% VO(2max)), and then sat for a 1 h recovery period. During exercise and recovery, subjects drank fluid or no fluid to maintain their BM, increase BM by 2%, or decrease BM by 2 or 4% in separate trials. Pre- and post-experiment TBW were determined using the deuterium oxide (D(2)O) dilution technique and corrected for D(2)O lost in urine, sweat, breath vapor, and nonaqueous hydrogen exchange. The average difference between DeltaBM and DeltaTBW was 0.07 +/- 1.07 kg (paired t test, P = 0.29). The slope and intercept of the relation between DeltaBM and DeltaTBW were not significantly different from 1 and 0, respectively. The intraclass correlation coefficient between DeltaBM and DeltaTBW was 0.76, which is indicative of excellent reliability between methods. Measuring pre- to post-exercise DeltaBM is an accurate and reliable method to assess the DeltaTBW.
authors.affiliation: Noll Laboratory, Kinesiology Department, Pennsylvania State University, University Park, PA 16802-6900, USA. lindsay.baker@gatorade.com
authors.forename: Lindsay B
authors.initials: LB
authors.lastname: Baker
authors.forename: James A
authors.initials: JA
authors.lastname: Lang
authors.forename: W Larry
authors.initials: WL
authors.lastname: Kenney
mesh_terms: D000284:Administration, Oral; D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D015992:Body Mass Index; D001834:Body Water / Q000502:physiology*; D001944:Breath Tests; D017666:Deuterium Oxide / Q000008:administration & dosage / Q000097:blood / Q000652:urine; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D010807:Physical Endurance / Q000502:physiology*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012420:Running / Q000502:physiology*; D013046:Specific Gravity; D013542:Sweat / Q000378:metabolism
chemical_list: D015415:Biomarkers; D017666:Deuterium Oxide