Short-term recovery from prolonged constant pace running in a warm environment: The effectiveness of a carbohydrate-electrolyte solution

Recovery from prolonged exercise involves both rehydration and replenishment of endogenous carbohydrate stores. This study examined the influence of drinking a carbohydrate-electrolyte solution on short-term recovery and subsequent exercise capacity in a warm environment. Thirteen healthy male volunteers completed two trials, at least 7 days apart. On each occasion subjects performed an initial treadmill run at 60% of maximal oxygen uptake (VO(2max)), for 90 min or until volitional fatigue (T1), in a warm environment (35 °C, 40% relative humidity, RH). Volitional ingestion of water was permitted during each of the exercise trials. During a subsequent 4-h recovery period (REC) subjects consumed either a 6.9% carbohydrate-electrolyte solution (CES) or a sweetened placebo (P), in a volume equivalent to 140% of body mass loss. Following REC, subjects ran to exhaustion at the same % VO(2max) in order to assess their endurance capacity (T2). Mean (SEM) run times during T1 did not differ between the CES [74.8 (4.6) min] and P [72.5 (5.2) min] trials. Body mass was reduced (P < 0.01) by 1.9 (0.2)% (CES) and 1.7 (0.2)% (P), and plasma volume (P < 0.01) by 6.0 (0.9)% (CES) and 5.4 (1.0)% (P) during the T1 trials. During REC 2006 (176) ml and 1830 (165) ml of fluid was ingested, providing 138 (12) g and 0 g of carbohydrate in the CES and P trials, respectively. Prior to T2, plasma volume and net fluid balance were similarly restored [CES + 58 (26) g; P -4 (68) g] in both trials. During T2 the exercise duration was longer (P < 0.01) in the CES compared to the P trial [CES 60.9 (5.5) min; P 44.9 (3.0) min]. Thus, provided that an adequate hydration status is maintained, inclusion of carbohydrate within an oral rehydration solution will delay the onset of fatigue during a subsequent bout of prolonged submaximal running in a warm environment.