Exercise Physiology Laboratory at Toledo, University of Castilla-La Mancha, Avda. Carlos III, s/n., 45071 Toledo, Spain.
Eur J Appl Physiol. 2010 May;109(2):213-9. doi: 10.1007/s00421-009-1333-x. Epub 2010 Jan 8.
To determine if athletes' muscle mass affects the usefulness of urine specific gravity (U(sg)) as a hydration index. Nine rugby players and nine endurance runners differing in the amount of muscle mass (42 +/- 6 vs. 32 +/- 3 kg, respectively; P = 0.0002) were recruited. At waking during six consecutive days, urine was collected for U (sg) analysis, urine osmolality (U(osm)), electrolytes (U[Na+], U[K+] and U[Cl-]) and protein metabolites (U([Creatinine]), U([Urea]) and U([Uric acid])) concentrations. In addition, fasting blood serum osmolality (S(osm)) was measured on the sixth day. As averaged during 6 days, U(sg) (1.021 +/- 0.002 vs. 1.016 +/- 0.001), U(osm) (702 +/- 56 vs. 554 +/- 41 mOsmol kg(-1) H(2)O), U([Urea]) (405 +/- 36 vs. 302 +/- 23 mmol L(-1)) and U([Uric acid]) (2.7 +/- 0.3 vs. 1.7 +/- 0.2 mmol L(-1)) were higher in rugby players than runners (P < 0.05). However, urine electrolyte concentrations were not different between groups. A higher percentage of rugby players than runners (56 vs. 11%; P = 0.03) could be cataloged as hypohydrated by U(sg) (i.e., >1.020) despite S (osm) being below 290 mOsmol kg(-1) H(2)O in all participants. A positive correlation was found between muscle mass and urine protein metabolites (r = 0.47; P = 0.04) and between urine protein metabolites and U(sg) (r = 0.92; P < 0.0001). In summary, U(sg) specificity to detect hypohydration was reduced in athletes with large muscle mass. Our data suggest that athletes with large muscle mass (i.e., rugby players) are prone to be incorrectly classified as hypohydrated based on U(sg).
为了确定运动员的肌肉质量是否会影响尿比重（U(sg)）作为水合指数的有用性。招募了 9 名橄榄球运动员和 9 名耐力跑步者，他们的肌肉质量不同（分别为 42 +/- 6 公斤和 32 +/- 3 公斤；P = 0.0002）。在连续六天的早晨醒来时，收集尿液进行 U(sg)分析、尿渗透压（U(osm)）、电解质（U[Na+]、U[K+]和 U[Cl-]）和蛋白质代谢物（U([Creatinine])、U([Urea])和 U([Uric acid])）浓度。此外，第六天还测量了空腹血清渗透压（S(osm)）。六天平均，U(sg)（1.021 +/- 0.002 对 1.016 +/- 0.001）、U(osm)（702 +/- 56 对 554 +/- 41 mOsmol kg(-1) H(2)O）、U([Urea])（405 +/- 36 对 302 +/- 23 mmol L(-1)）和 U([Uric acid])（2.7 +/- 0.3 对 1.7 +/- 0.2 mmol L(-1)）在橄榄球运动员中高于跑步者（P < 0.05）。然而，两组之间的尿液电解质浓度没有差异。尽管所有参与者的 S(osm)均低于 290 mOsmol kg(-1) H(2)O，但橄榄球运动员中比跑步者有更高比例的人（56%对 11%；P = 0.03）可通过 U(sg)（即>1.020）被归类为低血容量。肌肉质量与尿液蛋白质代谢物之间存在正相关（r = 0.47；P = 0.04），尿液蛋白质代谢物与 U(sg)之间存在正相关（r = 0.92；P < 0.0001）。总之，肌肉质量较大的运动员中 U(sg)检测低血容量的特异性降低。我们的数据表明，肌肉质量较大的运动员（即橄榄球运动员）可能会错误地被归类为低血容量，这是基于 U(sg)的。
