To determine the effectiveness of 3 commonly used beverages in restoring fluid and electrolyte balance, 8 volunteers dehydrated by 1.94% ± 0.17% of body mass by intermittent exercise in the heat, then ingested a carbohydrate-electrolyte solution (Gatorade), carbonated water/apple-juice mixture (Apfelschorle), and San Benedetto mineral water in a volume equal to 150% body-mass loss. These drinks are all are perceived to be effective rehydration solutions, and their effectiveness was compared with the rehydration effectiveness of Evian mineral water, which is not perceived in this way by athletes. Four hours after rehydration, the subjects were in a significantly lower hydration status than the pretrial situation on trials with Apfelschorle (–365 ± 319 mL, P = 0.030), Evian (–529 ± 319 mL, P < 0.0005), and San Benedetto (–401 ± 353 mL, P = 0.016) but were in the same hydration status as before the dehydrating exercise on Gatorade (–201 ± 388 mL, P = 0.549). Sodium balance was negative on all trials throughout the study; only with Apfelschorle did subjects remain in positive potassium balance. In this scenario, recovery of fluid balance can only be achieved when significant, albeit insufficient, quantities of sodium are ingested after exercise. There is a limited range of commercially available products that have a composition sufficient to achieve this, even though the public thinks that some of the traditional drinks are effective for this purpose.
Susan M. Shirreffs, Luis F. Aragon-Vargas, Mhairi Keil, Thomas D. Love and Sian Phillips
Stephen Heung-Sang Wong and Yajun Chen
This study examined the rehydration achieved by drinking different beverages during a short-term recovery period (REC) after exercise-induced dehydration.
Thirteen well-trained men (age 22.1 ± 3.3 yr, body mass 61.2 ± 9.1 kg, VO2max 64.9 ± 4.0 ml · kg−1 · min−1, maximum heart rate 198 ± 7 beats/min) ran for 60 min on 3 occasions on a level treadmill at 70% VO2max. All trials were performed in thermoneutral conditions (21 °C, 71% relative humidity) and were separated by at least 7 d. During 4 hr REC, the subjects consumed either a volume of a carbohydrate-electrolyte beverage (CE), lemon tea (LT), or distilled water (DW) equal to 150% of the body weight (BW) lost during the previous run. The fluid was consumed in 6 equal volumes at 30, 60, 90, 120, 150, and 180 min of REC.
After the completion of the 60-min run, the subjects lost ~2.0% of their preexercise BW in all trials, and no differences were observed in these BW changes between trials. At the end of REC, the greatest fraction of the retained drink occurred when the CE drink was consumed (CE vs. LT vs. DW: 52% ± 18% vs. 36% ± 15% vs. 30% ± 14%, p < .05). The CE drink also caused the least diuretic effect (CE vs. LT vs. DW: 638 ± 259 vs. 921 ± 323 vs. 915 ± 210 ml, p < .05) and produced the optimal restoration of plasma volume (CE vs. LT vs. DW: 11.2% ± 2.0% vs. –3.1% ± 1.8% vs. 0.2% ± 2.1%, p < .05).
The results of this study suggest that CE drinks are more effective than DW or LT in restoring fluid balance during short-term REC after exercise-induced dehydration.
Kelsey Dow, Robert Pritchett, Karen Roemer and Kelly Pritchett
forms of carbohydrate may be more practical and appealing for meeting post-exercise nutrition recommendations ( Dziedzic & Higham, 2014 ). Rehydration is another critical aspect of recovery between exercise bouts when recovery periods are limited to a few hours, such as during intermittent sport
Ben Desbrow, Danielle Cecchin, Ashleigh Jones, Gary Grant, Chris Irwin and Michael Leveritt
The addition of 25 mmol·L−1 sodium to low alcohol (2.3% ABV) beer has been shown to enhance post exercise fluid retention compared with full strength (4.8% ABV) beer with and without electrolyte modification. This investigation explored the effect of further manipulations to the alcohol and sodium content of beer on fluid restoration following exercise. Twelve male volunteers lost 2.03 ± 0.19% body mass (mean ± SD) using cycling-based exercise. Participants were then randomly allocated a different beer to consume on four separate occasions. Drinks included low alcohol beer with 25 mmol·L−1 of added sodium [LightBeer+25], low alcohol beer with 50 mmol·L−1 of added sodium [LightBeer+50], midstrength beer (3.5% ABV) [Mid] or midstrength beer with 25 mmolL−1 of added sodium [Mid+25]. Total drink volumes in each trial were equivalent to 150% of body mass loss during exercise, consumed over a 1h period. Body mass, urine samples and regulatory hormones were obtained before and 4 hr after beverage consumption. Total urine output was significantly lower in the LightBeer+50 trial (1450 ± 183 ml) compared with the LightBeer+25 (1796 ± 284 ml), Mid+25 (1786 ± 373 ml) and Mid (1986 ± 304 ml) trials (allp < .05). This resulted in significantly higher net body mass following the LightBeer+50 trial (-0.97 ± 0.17kg) compared with all other beverages (LightBeer+25 (-1.30 ± 0.24 kg), Mid+25 (-1.38 ± 0.33 kg) and Mid (-1.58 ± 0.29 kg), all p < .05). No significant changes to aldosterone or vasopressin were associated with different drink treatments. The electrolyte concentration of low alcohol beer appears to have more significant impact on post exercise fluid retention than small changes in alcohol content.
Eva M.R. Kovacs, Regina M. Schmahl, Joan M.G. Senden and Fred Brouns
The effect of a high (H) and a low (L) rate of post-exercise fluid consumption on plasma volume and fluid balance restoration was investigated. Eight well-trained cyclists were dehydrated at 3% of body weight (BW) by cycling at 28 °C. During the recovery period, they ingested a carbohydrate-electrolyte solution in a volume equivalent to 120% of BW loss. Randomly, they ingested 60%, 40%, and 20% in the 1 st, 2nd, and 3rd hours of the recovery period, respectively (H), or 24% · h−1 during 5 hours (L). BW loss was similar for both trials and resulted in a total drink intake of 2.6 ± 0.1 kg. Urine output in H exceeded significantly that of L in the 2nd and 3rd hours. This was reversed in the 5th and 6th hours. Plasma volume and fluid balance increased more rapidly in H compared to L. After 6 hours this difference disappeared. It is concluded that H results in a faster rate of plasma volume and fluid balance restoration compared to L, despite a temporary large urine output.
Lawrence E. Armstrong, Jorge A. Herrera Soto, Frank T. Hacker Jr., Douglas J. Casa, Stavros A. Kavouras and Carl M. Maresh
This investigation evaluated the validity and sensitivity of urine color (Ucol), specific gravity (Usg), and osmolality (Uosm) as indices of hydration status, by comparing them to changes in body water. Nine highly trained males underwent a 42-hr protocol involving dehydration to 3.7% of body mass (Day 1, −2.64 kg), cycling to exhaustion (Day 2, −5.2% of body mass, −3.68 kg), and oral rehydration for 21 hr. The ranges of mean (across time) blood and urine values were Ucol, 1-7; Usg, 1.004-1.029; U08m, 117-1,081 mOsm • kg−1; and plasma osmolality (Posm), 280-298 mOsm ⋅ kg−1. Urine color tracked changes in body water as effectively as (or better than) Uosm, Usg, urine volume, Posm, plasma sodium, and plasma total protein. We concluded that (a) Ucol, Uosm, and Usg are valid indices of hydration status, and (b) marked dehydration, exercise, and rehydration had little effect on the validity and sensitivity of these indices.
Paola Rodriguez-Giustiniani and Stuart D.R. Galloway
state and replacing lost fluids on cessation of exercise is recommended; however, most of the research on this field has been done in males due to the uncertainty of including females in relation to menstrual cycle phase effects on fluid balance. Many factors affect fluid balance and rehydration, such
Timothy P. Scheett, Michael J. Webster and Kent D. Wagoner
On two occasions, 8 male subjects completed a dehydration protocol, immediately followed by a 180-min rehydration protocol, then a subsequent exercise bout. During each dehydration session, subjects lost 3.1 ± 0.4% body weight (BW) following discontinuous exercise in the heat (40 °C, 33 % rh). During the first 30 min of rehydration, subjects ingested either 1.0-g glycerol · kg body weight−1 + 30% of the total rehydration water volume (GLY), or 30% of the total rehydration water volume without glycerol (CON). The five remaining ingestions (every 30 min) were equal to 14% of the remaining fluid volume and were identical in nature. Fluid volume ingested equaled fluid volume lost during dehydration. Following the 180 min rehydration period, subjects cycled (~50% V̇O2peak) in the heat (40 °C, 33% rh) until volitional exhaustion. Three observations were made: (a) Following glycerol-induced rehydration, time to volitional exhaustion was greater during the subsequent exercise bout in the heat (CON: 38.0 ± 2.0, GLY 42.8 ± 1.0 min, p < .05); (b) glycerol-induced rehydration significantly increased plasma volume restoration within 60 min and at the end of the 180-min rehydration period; and (c) total urine volume was lower and percent rehydration was greater following GLY, but neither was significantly different.
João C. Dias, Melissa W. Roti, Amy C. Pumerantz, Greig Watson, Daniel A. Judelson, Douglas J. Casa and Lawrence E. Armstrong
Dieticians, physiologists, athletic trainers, and physicians have recommended refraining from caffeine intake when exercising because of possible fluid-electrolyte imbalances and dehydration.
To assess how 16-hour rehydration is affected by caffeine ingestion.
59 college-age men.
Subjects consumed a chronic caffeine dose of 0 (placebo), 3, or 6 mg · kg−1 · day−1 and performed an exercise heat-tolerance test (EHT) consisting of 90 minutes of walking on a treadmill (5.6 km/h) in the heat (37.7 °C).
There were no between-group differences immediately after and 16 hours after EHT in total plasma protein, hematocrit, urine osmolality, specific gravity, color, and volume. Body weights after EHT and the following day (16 hours) were not different between groups (P > .05).
Hydration status 16 hours after EHT did not change with chronic caffeine ingestion.
Eric J. Jones, Phil A. Bishop, James M. Green and Mark T. Richardson
This study compared the effects of a rapid bolus and a slower metered water-consumption rate on urine production and postexercise rehydration. Participants (n = 8) dehydrated by 2% body weight through moderate exercise in an environmentally controlled chamber (35 °C, 55% relative humidity). Breakfast and lunch were standardized for all participants during each 8-hr data-collection period. Rehydration was performed using a volume of water equal to that lost during exercise either as bolus consumption (100% of volume consumed in 1hr; BOL) or metered consumption (12.5% of volume every 30 min for 4 hr; MET). Urine volume was used to assess hydration efficiency (water retained vs. water lost) and net fluid balance at 8 hr. Mean urine outputs were 420 ml (MET) and 700 ml (BOL). A paired-samples t test showed that hydration efficiency was greater for MET (75%) than for BOL (55%; p = .018). These data suggest that metered administration was more effective in maintaining fluid balance. These findings suggest that rehydration rate is a factor in fluid-balance response. For situations in which available fluid volume is restricted, greater hydration efficiency is highly desirable.