Water and sodium intake habits and status of ultra-endurance runners during a multi-stage ultra-marathon conducted in a hot ambient environment: an observational field based study

Table 4 Plasma (P _Osmol ) and urine (U _Osmol ) osmolality, and U _Osmol /P _Osmol ratio of UER along MSUM competition

	Stage 1		Stage 2		Stage 3		Stage 4		Stage 5
	Pre	Post	Pre	Post	Pre	Post	Pre	Post	Pre	Post
Plasma Osmolality (mOsmol/kg)
UER	281 (16)	287 (14)^*	283 (16)	297 (17)^*	272 (13)	291 (16)^**	271 (12)	298 (10)^**	283 (15)	296 (10)^**
CON	287 (13)				276 (14)				270 (9)
SR	280 (18)	286 (17)^*	282 (17)	294 (16)^*	273 (15)	287 (16)^**	270 (10)	298 (6)^**	286 (13)	294 (10)^*
FR	282 (12)	289 (9)^*	285 (11)	302 (18)^**	271 (9)	297 (14)^**	273 (14)	299 (14)^**	278 (17)	298 (11)^**
Urine Osmolality (mOsmol/kg)
UER	535 (278)	811 (261)^**	673 (311)	914 (367)^**	792 (306)^††b	997 (352)^**†	750 (293)^††	898 (333)^**	834 (343)^††	1050 (402)^**††
CON	577 (197)				545 (78)				608 (349)
SR	514 (295)	840 (226)^**	702 (326)	969 (393)^**	849 (294)^††	1075 (356)^**††	770 (301)^††	939 (323)^**	846 (355)^††	1086 (400)^**††
FR	562 (256)	775 (298)^**	636 (293)	844 (324)^**	722 (311)	899 (326)^**c	724 (285)	847 (344)^**	818 (334)^†	1004 (406)^**
Urine to Plasma Osmolality ratio
UER	2.0 (0.6)	2.7 (0.9)^**	2.6 (1.0)	3.3 (1.1)^**	3.3 (1.0)^††bb	3.9 (1.2)^††**	3.1 (1.0)^††	3.3 (1.0)^**	3.5 (1.1)^††bb	4.2 (1.3)^††**
CON	2.0 (0.3)				2.0 (1.0)				2.2 (1.2)
SR	2.0 (0.7)	2.8 (0.9)^**	2.8 (1.0)	3.7 (1.3)^**cc	3.5 (0.9)^††	4.2 (1.1)^††**	3.2 (1.0)^††	3.3 (1.0)^**	3.6 (1.1)^††	4.4 (1.2)^††**
FR	2.1 (0.6)	2.6 (0.9)^**	2.1 (1.0)	2.8 (1.3)^**	3.1 (1.0)^†	3.5 (1.1)^**	3.1 (1.0)^†	3.3 (0.9)^**	3.4 (1.3)^††	4.0 (1.5)^††**
Individual UER response range (U_Osmol/P_Osmol ratio)
	0.6 to 2.9	0.9 to 4.0	0.4 to 4.6	0.5 to 6.1	1.3 to 4.8	1.6 to 6.1	1.1 to 4.7	1.1 to 5.0	0.9 to 5.4	1.1 to 6.6

Mean (SD): UER (U_Osmo n = 72, P_Osmol n = 28); Control (CON, n = 12); slow runners (SR; MSUM mean speed <8 km/h, U_Osmo n = 40, P_Osmol n = 17); fast runners (FR; MSUM mean speed ≥8 km/h, U_Osmo n = 32, P_Osmol n = 11). †† p < 0.01 and † p < 0.01 vs. Stage 1; ^** p < 0.01 and ^* p < 0.05 vs. pre-stage; ^bb p < 0.01 and ^b p < 0.05 vs. CON; ^cc p < 0.01 and ^c p < 0.05 vs. SR.

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