Post-exercise rehydration in man: effects of volume consumed and drink sodium content

Abstract

The interaction between the volume and composition of fluids ingested was investigated in terms of rehydration effectiveness. Twelve male volunteers, dehydrated by 2.06 +/- 0.02% (mean +/- SE) of body mass by intermittent cycle exercise, consumed a different drink volume on four separate weeks; six subjects received drink L (23 mmol.l-1 Na+) in each trial and six were given drink H (61 mmol.l-1 Na+). Volumes consumed were equivalent to 50%, 100%, 150%, and 200% of body mass loss (trials A, B, C, and D, respectively). Blood and urine samples were obtained before exercise and for 7.5 h after exercise. Less urine was excreted following rehydration in trial A than in all other trials. Cumulative urine output (median ml) was less in trial B (493, range 181-731) than D (1361, range 1014-1984), which was not different from trial C (867, range 263-1191) in group L. In group H, the volume excreted in trial B (260, range 137-376) was less than trials C (602, range 350-994) and D (1001, range 714-1425), and the volume in trial C was less than in trial D. These results suggest that both sodium concentration and fluid volume consumed interact to affect the rehydration process. A drink volume greater than sweat loss during exercise must be ingested to restore fluid balance, but unless the sodium content of the beverage is sufficiently high this will merely result in an increased urinary output.

Effect of whey protein isolate on rehydration after exercise

“…This suggests that the increased drink retention observed by Seifert et al (2006) might be related to the lower drink volume ingested. Ingesting a lower drink volume produces a less pronounced dieresis after drink ingestion (Shirreffs et al 1996) and it is possible that if the effects of whey protein on rehydration are only subtle, the volume induced diuresis caused by ingestion of 150% of sweat losses over 1 h in the present study and that of James et al (2012) might have masked any beneficial effects of the added whey protein. Furthermore, the very low energy density of the drinks used in the present study would lead to rapid gastric emptying (Vist and Maughan 1994) and consequently a rapid appearance in the peripheral circulation and a larger diuresis compared to if carbohydrate was included in the drink (Osterberg et al 2010).…”

“…It seems that when rehydration drinks are ingested in a volume equivalent to 150% of sweat losses over 1 h, the addition of carbohydrate (Evans et al 2009), protein (James et al 2012) or potassium (Shirreffs et al 2007a) might not sufficiently reduce urine production to prevent fluid balance from becoming negative in the hours after drinking. In contrast, the addition of sodium to a rehydration drink has been shown to consistently influence urine production in a dosedependent manner (Maughan and Leiper 1995;Shirreffs et al 1996;Merson et al 2008). …”

The effect of post-exercise drink macronutrient content on appetite and energy intake

“…Following exercise, the consumption of fluid helps restore any plasma volume losses (Nose,59 Mack, Shi, & Nadal, 1988; Shirreffs, Taylor, & Leiper, 1996), and the addition of protein to 60 post-exercise drinks might aid post-exercise rehydration (James, 2012), as well as being 61 critically important for myofibrillar and mitochondrial protein synthesis (Wilkinson et al,62 2008). From a weight management perspective, it is also important to consider whether 63 consuming energy in a post-exercise recovery drink will weaken the energy deficit induced 64 by the exercise session, and how accurately the energy contained in the drink will be 65 compensated for during subsequent feeding.…”

Guidelines for Bystander First Aid 2016

“…First aid measures include rest, cooling of the body with water or drinking a carbohydrate-electrolyte solution (such as juice, milk or a commercial drink) and icing or stretching of the affected muscles. (48)(49)(50)(51)(52)(53)(54)(55)(56)(57) Potable water may be used if carbohydrate-electrolyte solutions are not readily available. (9) Casualties with heat exhaustion may present with nausea, dizziness, muscle cramps, headache, fatigue and heavy sweating.…”