Impact of beverage acceptability on fluid intake during exercise

Sports Diet and Oral Health in Athletes: A Comprehensive Review

Food and fluid supply is fundamental for optimal athletic performance but can also be a risk factor for caries, dental erosion, and periodontal diseases, which in turn can impair athletic performance. Many studies have reported a high prevalence of oral diseases in elite athletes, notably dental caries 20-84%, dental erosion 42-59%, gingivitis 58-77%, and periodontal disease 15-41%, caused by frequent consumption of sugars/carbohydrates, polyunsaturated fats, or deficient protein intake. There are three possible major reasons for poor oral health in athletes which are addressed in this review: oxidative stress, sports diet, and oral hygiene. This update particularly summarizes potential sports nutritional effects on athletes' dental health. Overall, sports diet appropriately applied to deliver benefits for performance associated with oral hygiene requirements is necessary to ensure athletes' health. The overall aim is to help athletes, dentists, and nutritionists understand the tangled connections between sports diet, oral health, and oral healthcare to develop mitigation strategies to reduce the risk of dental diseases due to nutrition.

Hydration Is More Important Than Exogenous Carbohydrate Intake During Push-to-the-Finish Cycle Exercise in the Heat

Dehydration ≥2% loss of body mass is associated with reductions in performance capacity, and carbohydrate (CHO)-electrolyte solutions (CES) are often recommended to prevent dehydration and provide a source of exogenous carbohydrate during exercise. It is also well established that performance capacity in the heat is diminished compared to cooler conditions, a response attributable to greater cardiovascular strain caused by high skin and core temperatures. Because hydration status, environmental conditions, and carbohydrate availability interact to influence performance capacity, we sought to determine how these factors affect push-to-the-finish cycling performance. Ten young trained cyclists exercised at a moderate intensity (2.5 W·kg^-1) in a hot-dry condition [40°C, 20% relative humidity (RH)] until dehydration of ~2% body mass. Subjects then consumed either no fluid (NF) or enough fluid (water, WAT; Gatorade®, GAT; or GoodSport™, GS) to replace 75% of lost body mass over 30 min. After a 30-min light-intensity warm-up (1.5 W·kg^-1) in a 35°C, 20% RH environment, subjects then completed a 120-kJ time trial (TT). TT time-to-completion, absolute power, and relative power were significantly improved in WAT (535 ± 214 s, 259 ± 99 W, 3.3 ± 0.9 W·kg^-1), GAT (539 ± 226 s, 260 ± 110 W, 3.3 ± 1.0 W·kg^-1), and GS (534 ± 238 s, 262 ± 105 W, 3.4 ± 1.0 W·kg^-1) compared to NF (631 ± 310 s, 229 ± 96 W, 3.0 ± 0.9 W·kg^-1) all (p < 0.01) with no differences between WAT, GAT, and GS, suggesting that hydration is more important than carbohydrate availability during exercise in the heat. A subset of four subjects returned to the laboratory to repeat the WAT, GAT, and GS treatments to determine if between-beverage differences in time-trial performance were evident with a longer TT in thermoneutral conditions. Following dehydration, the ambient conditions in the environmental chamber were reduced to 21°C and 20% RH and subjects completed a 250-kJ TT. All four subjects improved TT performance in the GS trial (919 ± 353 s, 300 ± 100 W, 3.61 ± 0.86 W·kg^-1) compared to WAT (960 ± 376 s, 283 ± 91 W, 3.43 ± 0.83 W·kg^-1), while three subjects improved TT performance in the GAT trial (946 ± 365 s, 293 ± 103 W, 3.60 ± 0.97 W·kg^-1) compared to WAT, highlighting the importance of carbohydrate availability in cooler conditions as the length of a push-to-the-finish cycling task increases.

Sensory Perception of an Oral Rehydration Solution during Exercise in the Heat

Prolonged exercise in the heat elicits a number of physiological changes as glycogen stores are low and water and electrolytes are lost through sweat. However, it is unclear whether these changes provoke an increase in liking of saltiness and, therefore, palatability of an oral rehydration solution (ORS). Twenty-seven recreationally active participants (n = 13 males; n = 14 females) completed sensory analysis of an ORS, a traditional sports drink (TS), and a flavored water placebo (PL) at rest and during 60 min (3 × 20-min bouts) of cycling exercise at 70% age-predicted maximum heart rate (HR_max) at 35.3 ± 1.4 °C and 41 ± 6% relative humidity. Before and after every 20 min of exercise, drinks were rated (using 20-mL beverage samples) based on liking of sweetness, liking of saltiness, thirst-quenching ability, and overall liking on a nine-point hedonic scale. Hydration status was assessed by changes in semi-nude body mass, saliva osmolality (S_Osm), and saliva total protein concentration (S_PC). After 60 min of exercise, participants lost 1.36 ± 0.39% (mean ± SD) of body mass and there were increases in S_Osm and S_PC. At all time points, liking of sweetness, saltiness, thirst-quenching ability, and overall liking was higher for the TS and PL compared to the ORS (p < 0.05). However, the saltiness liking and thirst-quenching ability of the ORS increased after 60 min of exercise compared to before exercise (p < 0.05). There was also a change in predictors of overall liking with pre-exercise ratings mostly determined by liking of sweetness, saltiness, and thirst-quenching ability (p < 0.001), whereas only liking of saltiness predicted overall liking post-exercise (R² = 0.751; p < 0.001). There appears to be a hedonic shift during exercise in which the perception of saltiness becomes the most important predictor of overall liking. This finding supports the potential use of an ORS as a valuable means of hydration during the latter stages of prolonged and/or intense exercise in the heat.

Primary, Secondary, and Tertiary Effects of Carbohydrate Ingestion During Exercise

The purpose of this current opinion paper is to describe the journey of ingested carbohydrate from 'mouth to mitochondria' culminating in energy production in skeletal muscles during exercise. This journey is conveniently described as primary, secondary, and tertiary events. The primary stage is detection of ingested carbohydrate by receptors in the oral cavity and on the tongue that activate reward and other centers in the brain leading to insulin secretion. After digestion, the secondary stage is the transport of monosaccharides from the small intestine into the systemic circulation. The passage of these monosaccharides is facilitated by the presence of various transport proteins. The intestinal mucosa has carbohydrate sensors that stimulate the release of two 'incretin' hormones (GIP and GLP-1) whose actions range from the secretion of insulin to appetite regulation. Most of the ingested carbohydrate is taken up by the liver resulting in a transient inhibition of hepatic glucose release in a dose-dependent manner. Nonetheless, the subsequent increased hepatic glucose (and lactate) output can increase exogenous carbohydrate oxidation rates by 40-50%. The recognition and successful distribution of carbohydrate to the brain and skeletal muscles to maintain carbohydrate oxidation as well as prevent hypoglycaemia underpins the mechanisms to improve exercise performance.

Ingestion of maple-based and other carbohydrate sports drinks: effect on sensory perceptions during prolonged exercise

Background

Taste and appreciation of sports drinks can affect perceived exertion during exercise. Anecdotal evidence shows that maple products are regularly consumed by recreational and professional athletes but very few studies have reported on their effects during exercise. The purpose of the current study is to report the taste, appreciation and perceived exertion following the ingestion of maple-based sports drinks and other carbohydrate drinks during prolonged exercise.

Methods

Recreationally and competitively active male subjects (n = 76, mass = 73.7 ± 10.3 kg, maximum oxygen consumption (VO₂max) = 4.4 ± 0.5 L/min, maximal aerobic power (MAP) = 309 ± 42 W) ingested one of four carbohydrate solutions (all at 60 g CHO/L): concentrated maple sap (MW), diluted maple syrup (MS), glucose (G), a commercial sports drink (CSD), or a placebo (P; water sweetened with stevia) at every 30 min during 120 min of steady-state exercise (SSE) on a cycle ergometer at 66% MAP. Ratings of perceived exertion (RPE, Borg CR-10) were recorded at each 30 min throughout SSE. A questionnaire was administered to assess sensory characteristics (sweetness, acidity, refreshing, and overall taste on a visual analogue scale, converted to decimals from 0 to 1) and appreciation (sweet, acid and overall on a 9-point hedonic scale) 30 min before (immediately after the first ingestion) and immediately after SSE.

Results

Sweetness was perceived to be higher for MW than G and P (pre: 0.60 ± 0.19, 0.51 ± 0.17 and 0.50 ± 0.17 and post: 0.69 ± 0.19, 0.34 ± 0.18 and 0.48 ± 0.22; p < 0.05, respectively) and MS was rated higher than MW for the appreciation of the sweet taste (pre: 6.5 ± 1.5 vs. 4.6 ± 1.8 and post: 6.8 ± 1.8 and 4.1 ± 1.8; p < 0.05, respectively). Furthermore, subjects that had ingested MW, reported a significantly lower RPE than those with P at 120 min (14.1 ± 2.2 vs. 16.0 ± 2.0, respectively).

Conclusions

A sports drink containing maple syrup is well appreciated during prolonged exercise and appears to be a viable alternatives to more common sources of carbohydrates.

Trial registration

NCT02880124. Registered on 26 August 2016.

Hydration Efficacy of a Milk Permeate-Based Oral Hydration Solution

Milk permeate is an electrolyte-rich, protein- and fat-free liquid with a similar carbohydrate and mineral content to that of milk. Its hydration efficacy has not been examined. The beverage hydration index (BHI) has been used to compare various beverages to water in terms of post-ingestion fluid balance and retention. Our purpose was to compare the BHI (and related physiological responses) of a novel milk permeate solution (MPS) to that of water and a traditional carbohydrate–electrolyte solution (CES). Over three visits, 12 young subjects consumed 1 L of water, CES, or MPS. Urine samples were collected immediately post-ingestion and at 60, 120, 180, and 240 min. BHI was calculated by dividing cumulative urine output after water consumption by cumulative urine output for each test beverage at each time point. The BHI for MPS was significantly higher at all time points compared to water (all p < 0.001) and CES (all p ≤ 0.01) but did not differ between CES and water at any time point. Drinking 1 L of MPS resulted in decreased cumulative urine output across the subsequent 4 h compared to water and CES, suggesting that a beverage containing milk permeate is superior to water and a traditional CES at sustaining positive fluid balance post-ingestion.

Effect of Drinking Rate on the Retention of Water or Milk Following Exercise-Induced Dehydration

This study investigated the effect of drinking rate on fluid retention of milk and water following exercise-induced dehydration. In Part A, 12 male participants lost 1.9% ± 0.3% body mass through cycle exercise on four occasions. Following exercise, plain water or low-fat milk equal to the volume of sweat lost during exercise was provided. Beverages were ingested over 30 or 90 min, resulting in four beverage treatments: water 30 min, water 90 min, milk 30 min, and milk 90 min. In Part B, 12 participants (nine males and three females) lost 2.0% ± 0.3% body mass through cycle exercise on four occasions. Following exercise, plain water equal to the volume of sweat lost during exercise was provided. Water was ingested over 15 min (DR15), 45 min (DR45), or 90 min (DR90), with either DR15 or DR45 repeated. In both trials, nude body mass, urine volume, urine specific gravity and osmolality, plasma osmolality, and subjective ratings of gastrointestinal symptoms were obtained preexercise and every hour for 3 hr after the onset of drinking. In Part A, no effect of drinking rate was observed on the proportion of fluid retained, but milk retention was greater (p < .01) than water (water 30 min: 57% ± 16%, water 90 min: 60% ± 20%, milk 30 min: 83% ± 6%, and milk 90 min: 85% ± 7%). In Part B, fluid retention was greater in DR90 (57% ± 13%) than DR15 (50% ± 11%, p < .05), but this was within test-retest variation determined from the repeated trials (coefficient of variation: 17%). Within the range of drinking rates investigated the nutrient composition of a beverage has a more pronounced impact on fluid retention than the ingestion rate.

Honey Supplementation and Exercise: A Systematic Review

Honey is a natural substance formed primarily of carbohydrates (~80%) which also contains a number of other compounds purported to confer health benefits when consumed. Due to its carbohydrate composition (low glycaemic index, mostly fructose and glucose), honey may theoretically exert positive effects when consumed before, during or after exercise. This review therefore appraised research examining the effects of honey consumption in combination with exercise in humans. Online database (PubMed, MEDLINE, SPORTDiscus) searches were performed, yielding 273 results. Following duplicate removal and application of exclusion criteria, nine articles were reviewed. Large methodological differences existed in terms of exercise stimulus, population, and the nutritional interventions examined. All nine studies reported biochemical variables, with four examining the effects of honey on exercise performance, whilst five described perceptual responses. Acute supplementation around a single exercise session appeared to elicit similar performance, perceptual, and immunological responses compared with other carbohydrate sources, although some performance benefit has been observed relative to carbohydrate-free comparators. When consumed over a number of weeks, honey may dampen immunological perturbations arising from exercise and possibly improve markers of bone formation. More well-controlled research is required to better understand the role for honey in a food-first approach to exercise nutrition.

Calorie-Containing Recovery Drinks Increase Recreational Runners' Voluntary Energy and Carbohydrate Intake, with Minimal Impact on Fluid Recovery

This study assessed voluntary dietary intake when different beverages were provided within a recovery area following recreational exercise. Participants completed two 10-km runs 1 week apart. Immediately after the first run, "beer drinkers" (n = 54; mean ± SD: age = 23.9 ± 5.8 years, body mass [BM] = 76 ± 13 kg) randomly received low-alcohol beer (Hahn Ultra^® [Lion Co.], 0.9% alcohol by volume) or sports drink (SD; Gatorade^® [PepsiCo]), whereas "nonbeer drinkers" (n = 78; age = 21.8 ± 2.2 years, BM = 71 ± 13 kg) received water or SD. Participants remained in a recovery area for 30-60 min with fluid consumption monitored. The following week, participants received the alternate beverage. Participants recorded all food/fluid consumed for the remainder of both trial days (diary and photographs). Fluid balance was assessed via BM change and urine specific gravity. Paired t tests were used to assess differences in hydration and dietary variables. No differences were observed in preexercise urine specific gravity (∼1.01) or BM loss (∼2%) between intervention groups (ps > .05). Water versus SD: No difference in acute fluid intake was noted (water = 751 ± 259 ml, SD = 805 ± 308 ml, p = .157). SD availability influenced total energy and carbohydrate intakes (water = 5.7 ± 2.5 MJ and 151 ± 77 g, SD = 6.5 ± 2.7 MJ and 187 ± 87 g, energy p = .002, carbohydrate p < .001). SD versus beer: SD availability resulted in greater acute fluid intake (SD = 1,047 ± 393 ml, beer = 850 ± 630 ml; p = .004), which remained evident at the end of trial days (SD = 3,337 ± 1,100 ml, beer = 2,982 ± 1,191 ml; p < .01). No differences in dietary variables were observed. Next day, urine specific gravity values were not different between water versus SD. However, a small difference was detected between SD versus beer (SD = 1.021 ± 0.009, beer = 1.016 ± 0.008, p = .002). Consuming calorie-containing drinks postexercise appears to increase daily energy and carbohydrate intake but has minimal impact on next-day hydration.

The influence of angiotensin converting enzyme and bradykinin receptor B2 gene variants on voluntary fluid intake and fluid balance in healthy men during moderate-intensity exercise in the heat

Angiotensin converting enzyme (ACE) and bradykinin receptor B2 (B2R) genetic variation may affect thirst because of effects on angiotensin II production and bradykinin activity, respectively. To examine this, 45 healthy Caucasian men completed 60 min of cycle exercise at 62% ± 5% peak oxygen uptake in a room heated to 30.5 ± 0.3 °C with ad libitum fluid intake. Blood samples were collected pre-, mid-, and immediately post-cycle. Fluid intake, body mass loss (BML), sweat loss (determined via changes in body mass and fluid intake), and thirst sensation were recorded. All participants were genotyped for the ACE insert fragment (I) and the B2R insert sequence (P). Participants were homozygous for the wild-type allele (WW or MM), heterozygous (WI or MP) or homozygous for the insert (II or PP). No differences between genotype groups were found in mean (±SD) voluntary fluid intake (WW: 613 ± 388, WI: 753 ± 385, II: 862 ± 421 mL, p = 0.31; MM: 599 ± 322, MP: 745 ± 374, PP: 870 ± 459 mL, p = 0.20), percentage BML or any other fluid balance variables for both the ACE and B2R genes, respectively. Mean thirst perception in the B2R PP group, however, was higher (p < 0.05) than both MM and MP at 30, 45, and 60 min. In conclusion, the results of this study suggest that voluntary fluid intake and fluid balance in healthy men performing 60 min of moderate-intensity exercise in the heat are not predominantly influenced by ACE or B2R genetic variation.

Optimal composition of fluid-replacement beverages

The objective of this article is to provide a review of the fundamental aspects of body fluid balance and the physiological consequences of water imbalances, as well as discuss considerations for the optimal composition of a fluid replacement beverage across a broad range of applications. Early pioneering research involving fluid replacement in persons suffering from diarrheal disease and in military, occupational, and athlete populations incurring exercise- and/or heat-induced sweat losses has provided much of the insight regarding basic principles on beverage palatability, voluntary fluid intake, fluid absorption, and fluid retention. We review this work and also discuss more recent advances in the understanding of fluid replacement as it applies to various populations (military, athletes, occupational, men, women, children, and older adults) and situations (pathophysiological factors, spaceflight, bed rest, long plane flights, heat stress, altitude/cold exposure, and recreational exercise). We discuss how beverage carbohydrate and electrolytes impact fluid replacement. We also discuss nutrients and compounds that are often included in fluid-replacement beverages to augment physiological functions unrelated to hydration, such as the provision of energy. The optimal composition of a fluid-replacement beverage depends upon the source of the fluid loss, whether from sweat, urine, respiration, or diarrhea/vomiting. It is also apparent that the optimal fluid-replacement beverage is one that is customized according to specific physiological needs, environmental conditions, desired benefits, and individual characteristics and taste preferences.

Ad libitum fluid consumption via self- or external administration

CONTEXT

During team athletic events, athletic trainers commonly provide fluids with water bottles. When a limited number of water bottles exist, various techniques are used to deliver fluids.

OBJECTIVE

To determine whether fluid delivered via water-bottle administration influenced fluid consumption and hydration status.

DESIGN

Crossover study.

SETTING

Outdoor field (22.2°C ± 3.5°C).

PATIENTS OR OTHER PARTICIPANTS

Nineteen participants (14 men, 5 women, age = 30 ± 10 years, height = 176 ± 8 cm, mass = 72.5 ± 10 kg) were recruited from the university and local running clubs.

INTERVENTION(S)

The independent variable was fluid delivery with 3 levels: self-administration with mouth-to-bottle direct contact (SA-DC), self-administration with no contact between mouth and bottle (SA-NC), and external administration with no contact between the mouth and the bottle (EA-NC). Participants warmed up for 10 minutes before completing 5 exercise stations, after which an ad libitum fluid break was given, for a total of 6 breaks.

MAIN OUTCOME MEASURE(S)

We measured the fluid variables of total volume consumed, total number of squirts, and average volume per squirt. Hydration status via urine osmolality and body-mass loss, and perceptual variables for thirst and fullness were recorded. We calculated repeated-measures analyses of variance to assess hydration status, fluid variables, and perceptual measures to analyze conditions across time.

RESULTS

The total volume consumed for EA-NC was lower than for SA-DC (P = .001) and SA-NC (P = .001). The total number of squirts for SA-DC was lower than for SA-NC (P = .009). The average volume per squirt for EA-NC was lower than for SA-DC (P = .020) and SA-NC (P = .009). Participants arrived (601.0 ± 21.3 mOsm/L) and remained (622.3 ± 38.3 mOsm/L) hydrated, with no difference between conditions (P = .544); however, the EA-NC condition lost more body mass than did the SA-DC condition (P = .001). There was no main effect for condition on thirst (P = .147) or fullness (P = .475).

CONCLUSIONS

External administration of fluid decreased total volume consumed via a decreased average volume per squirt. The SA-DC method requires fewer squirts within a specific time frame. Fluid breaks every 15 minutes resulted in maintenance of euhydration; however, loss of body mass was influenced by fluid administration. Athletic trainers should avoid external administration to promote positive hydration behaviors. When fluid is self-administered, individual bottles may be the best clinical practice because more volume can be consumed per squirt.

Comparing the rehydration potential of different milk-based drinks to a carbohydrate-electrolyte beverage

The aim of this study was to compare the rehydration potential of a carbohydrate-electrolyte beverage with several varieties of milk following exercise-induced fluid losses. Fifteen male participants (age 24.9 ± 5.5 years, height 179.3 ± 4.9 cm, body mass 75.8 ± 6.6 kg (mean ± SD)) lost 2.0% ± 0.2% body mass through intermittent cycling before consuming a different beverage on 4 separate occasions. Drinks included cow's milk (286 kJ·100 mL(-1)), soy milk (273 kJ·100 mL(-1)), a milk-based liquid meal supplement (Sustagen Sport (Nestle); 417 kJ·100 mL(-1)), and a sports drink (Powerade (Coca Cola Ltd); 129 kJ·100 mL(-1)). Beverages were consumed over 1 h in volumes equivalent to 150% of body mass loss. Body mass, blood and urine samples, and measures of gastrointestinal tolerance were obtained before and hourly for 4 h after beverage consumption. Net body mass at the conclusion of each trial was significantly less with Powerade (-1.37 ± 0.3 kg) than with cow's milk (-0.92 ± 0.48 kg), soy milk (-0.78 ± 0.37 kg), and Sustagen Sport (-0.48 ± 0.39 kg). Net body mass was also significantly greater for Sustagen Sport compared with cow's milk trials, but not soy milk. Upon completion of trials, the percentage of beverage retained was Sustagen Sport 65.1% ± 14.7%, soy milk 46.9% ± 19.9%, cow's milk 40.0% ± 24.9%, and Powerade 16.6% ± 16.5%. Changes in plasma volume and electrolytes were unaffected by drink treatment. Subjective ratings of bloating and fullness were higher during all milk trials compared with Powerade whereas ratings of overall thirst were not different between beverages. Milk-based drinks are more effective rehydration options compared with traditional sports drinks. The additional energy, protein, and sodium in a milk-based liquid meal supplement facilitate superior fluid recovery following exercise.

24-h fluid kinetics and perception of sweat losses following a 1-h run in a temperate environment

This study examined 24-h post-run hydration status and sweat loss estimation accuracy in college age runners (men=12, women=8) after completing a 1-h self-paced outdoor run (wet bulb globe temperature=19.9±3.0 °C). Sweat losses (1353±422 mL; 1.9%±0.5% of body mass) were significantly greater (p<0.001) than perceived losses (686±586 mL). Cumulative fluid consumption equaled 3876±1133 mL (218±178 mL during) with 37% of fluid ingested lost through urine voids (1450±678 mL). Fluid balance based on intake and urine production equaled +554±669 mL at 12 h and +1186±735 mL at 24 h. Most runners reported euhydrated (pre-run urine specific gravity (USG)=1.018±0.008) with no changes (p=0.33) at hours 12 or 24 when both genders were included. However, USG was higher (p=0.004) at 12 h post-run for men (1.025±0.0070 vs. 1.014±0.007), who consumed 171%±40% of sweat losses at 12 h vs. 268%±88% for women. Most runners do not need intervention concerning between bout hydration needs in temperate environments. However, repeated USG measurements were able to identify runners who greatly under or over consumed fluid during recovery. Practitioners can use multiple USG assessments as cheap method to detect runners who need to modify their hydration strategies and should promote assessment of sweat losses by change in body mass, as runners had poor perception of sweat losses.

Half-marathon and full-marathon runners' hydration practices and perceptions

CONTEXT

The behaviors and beliefs of recreational runners with regard to hydration maintenance are not well elucidated.

OBJECTIVE

To examine which beverages runners choose to drink and why, negative performance and health experiences related to dehydration, and methods used to assess hydration status.

DESIGN

Cross-sectional study.

SETTING

Marathon registration site.

PATIENTS OR OTHER PARTICIPANTS

Men (n = 146) and women (n = 130) (age = 38.3 ± 11.3 years) registered for the 2010 Little Rock Half-Marathon or Full Marathon.

INTERVENTION(S)

A 23-item questionnaire was administered to runners when they picked up their race timing chips.

MAIN OUTCOME MEASURE(S)

Runners were separated into tertiles (Low, Mod, High) based on z scores derived from training volume, expected performance, and running experience. We used a 100-mm visual analog scale with anchors of 0 (never) and 100 (always). Total sample responses and comparisons between tertile groups for questionnaire items are presented.

RESULTS

The High group (58±31) reported greater consumption of sport beverages in exercise environments than the Low (42 ± 35 mm) and Mod (39 ± 32 mm) groups (P < .05) and perceived sport beverages to be superior to water in meeting hydration needs (P < .05) and improving performance during runs greater than 1 hour (P < .05). Seventy percent of runners experienced 1 or more incidents in which they believed dehydration resulted in a major performance decrement, and 45% perceived dehydration to have resulted in adverse health effects. Twenty percent of runners reported monitoring their hydration status. Urine color was the method most often reported (7%), whereas only 2% reported measuring changes in body weight.

CONCLUSIONS

Greater attention should be paid to informing runners of valid techniques to monitor hydration status and developing an appropriate individualized hydration strategy.

Effects of rehydration fluid temperature and composition on body weight retention upon voluntary drinking following exercise-induced dehydration

The purpose of this study was to determine the effects of beverage temperature and composition on weight retention and fluid balance upon voluntary drinking following exercise induced-dehydration. Eight men who were not acclimated to heat participated in four randomly ordered testing sessions. In each session, the subjects ran on a treadmill in a chamber maintained at 37℃ without being supplied fluids until 2% body weight reduction was reached. After termination of exercise, they recovered for 90 min under ambient air conditions and received one of the following four test beverages: 10℃ water (10W), 10℃ sports drink (10S), 26℃ water (26W), and 26℃ sports drink (26S). They consumed the beverages ad libitum. The volume of beverage consumed and body weight were measured at 30, 60, and 90 min post-recovery. Blood samples were taken before and immediately after exercise as well as at the end of recovery in order to measure plasma parameters and electrolyte concentrations. We found that mean body weight decreased by 1.8-2.0% following exercise. No differences in mean arterial pressure, plasma volume, plasma osmolality, and blood electrolytes were observed among the conditions. Total beverage volumes consumed were 1,164 ± 388, 1,505 ± 614, 948 ± 297, and 1,239 ± 401 ml for 10W, 10S, 26W, and 26S respectively (P > 0.05). Weight retention at the end of recovery from dehydration was highest in 10S (1.3 ± 0.7 kg) compared to 10W (0.4 ± 0.5 kg), 26W (0.4 ± 0.4 kg), and (0.6 ± 0.4 kg) (P < 0.005). Based on these results, carbohydrate/electrolyte-containing beverages at cool temperature were the most favorable for consumption and weight retention compared to plain water and moderate temperature beverages.

Hydration profile and influence of beverage contents on fluid intake by women during outdoor recreational walking

This study examined hydration status, sweat losses, and the effects of flavoring and electrolytes on fluid intake for women (n = 27, age = 24 ± 4 years) walking at a self-selected pace for ~1 h on a 1 km outdoor path during summer mornings or evenings. Over five consecutive days, participants consumed ad libitum one non-caloric beverage containing: (1) water (W), (2) acidified water (AW), (3) acidified water with electrolytes (AWE), (4) acidified water with flavor (AWF), and (5) acidified water with flavor and electrolytes (AWFE) in a counter-balanced order during walks and a 1-h recovery period. Walk Wet bulb globe temperature (26.2 ± 1.8 °C) and pace (6.0 ± 0.5 km/h) did not differ among beverages (P > 0.05). Thirty-four percent of pre-walk urine specific gravity samples exceeded 1.020. Flavoring (AWF 700 ± 393 mL; AWFE 719 ± 405 mL) did not result in greater consumption (P > 0.05) over W (560 ± 315 mL), with all three beverages exceeding grand mean sweat losses (528 ± 208 mL). Addition of electrolytes did not influence (P > 0.05) the intake between AW versus AWE or AWF versus AWFE. The results of this study indicate that the majority of women will consume fluids in excess of their sweat losses within 1 h post-walk. Over half of consumption took place during walks, highlighting the importance of fluid availability during exercise. Great among-subjects variability in sweat losses and fluid intake support the need for promoting individualized hydration strategies based on the changes in body mass for athletic populations.

Effect of mouth-rinsing carbohydrate solutions on endurance performance

Ingesting carbohydrate-electrolyte solutions during exercise has been reported to benefit self-paced time-trial performance. The mechanism responsible for this ergogenic effect is unclear. For example, during short duration (≤1 hour), intense (>70% maximal oxygen consumption) exercise, euglycaemia is rarely challenged and adequate muscle glycogen remains at the cessation of exercise. The absence of a clear metabolic explanation has led authors to speculate that ingesting carbohydrate solutions during exercise may have a 'non-metabolic' or 'central effect' on endurance performance. This hypothesis has been explored by studies investigating the performance responses of subjects when carbohydrate solutions are mouth rinsed during exercise. The solution is expectorated before ingestion, thus removing the provision of carbohydrate to the peripheral circulation. Studies using this method have reported that simply having carbohydrate in the mouth is associated with improvements in endurance performance. However, the performance response appears to be dependent upon the pre-exercise nutritional status of the subject. Furthermore, the ability to identify a central effect of a carbohydrate mouth rinse maybe affected by the protocol used to assess its impact on performance. Studies using functional MRI and transcranial stimulation have provided evidence that carbohydrate in the mouth stimulates reward centres in the brain and increases corticomotor excitability, respectively. However, further research is needed to determine whether the central effects of mouth-rinsing carbohydrates, which have been seen at rest and during fatiguing exercise, are responsible for improved endurance performance.

Changes in sensory perception of sports drinks when consumed pre, during and post exercise

The aim of this study was to examine sensory perceptions towards different formulations of sports drinks when consumed before, at various points during, and following exercise. Following familiarization 14 recreational runners underwent four trials in a single blind counterbalanced design. Each trial utilised one of four different solutions: 7.5% carbohydrate, 421 mg L(-1) electrolyte (HiC-HiE); 7.5% carbohydrate, 140 mg L(-1) electrolyte (HiC-LoE); 1.3% carbohydrate, 421 mg L(-1) electrolyte (LoC-HiE) and water. Subjects were provided with 50-ml samples to ingest and then rate (using a 100-mm line scale) the intensity of sweetness, saltiness, thirst-quenching ability and overall liking before (-30 min), during (0, 30 and 60 min) and following (90 and 120 min) treadmill running exercise. Ratings of sweetness for all energy-containing drinks were higher during exercise relative to pre- and post-exercise conditions (P<0.05); ratings also increased with duration of exercise (P<0.001). Sweetness ratings for LoC-HiE increased during exercise (P<0.05) but remained the same for other beverages. Ratings of saltiness decreased for all energy-containing drinks during exercise relative to pre-exercise (P<0.05); ratings decreased with duration of exercise in these drinks (P<0.05). Ratings of thirst-quenching ability (P=0.039) and overall liking (P=0.013) increased with duration of exercise with all beverages. Significant changes in sensory perception occur when consuming sports drinks during exercise relative to non-exercise conditions. Temporal changes also occur during exercise itself which leads to enhanced liking of all beverages.

Fluid consumption and sweating in National Football League and collegiate football players with different access to fluids during practice

CONTEXT

Considerable controversy regarding fluid replacement during exercise currently exists.

OBJECTIVE

To compare fluid turnover between National Football League (NFL) players who have constant fluid access and collegiate football players who replace fluids during water breaks in practices.

DESIGN

Observational study.

SETTING

Respective preseason training camps of 1 National Collegiate Athletic Association Division II (DII) football team and 1 NFL football team. Both morning and afternoon practices for DII players were 2.25 hours in length, and NFL players practiced for 2.25 hours in the morning and 1 hour in the afternoon. Environmental conditions did not differ.

PATIENTS OR OTHER PARTICIPANTS

Eight NFL players (4 linemen, 4 backs) and 8 physically matched DII players (4 linemen, 4 backs) participated.

INTERVENTION(S)

All players drank fluids only from their predetermined individual containers. The NFL players could consume both water and sports drinks, and the DII players could only consume water.

MAIN OUTCOME MEASURE(S)

We measured fluid consumption, sweat rate, total sweat loss, and percentage of sweat loss replaced. Sweat rate was calculated as change in mass adjusted for fluids consumed and urine produced.

RESULTS

Mean sweat rate was not different between NFL (2.1 +/- 0.25 L/h) and DII (1.8 +/- 0.15 L/h) players (F(1,12) = 2, P = .18) but was different between linemen (2.3 +/- 0.2 L/h) and backs (1.6 +/- 0.2 L/h) (t(14) = 3.14, P = .007). We found no differences between NFL and DII players in terms of percentage of weight loss (t(7) = -0.03, P = .98) or rate of fluid consumption (t(7) = -0.76, P = .47). Daily sweat loss was greater in DII (8.0 +/- 2.0 L) than in NFL (6.4 +/- 2.1 L) players (t(7) = -3, P = .02), and fluid consumed was also greater in DII (5.0 +/- 1.5 L) than in NFL (4.0 +/- 1.1 L) players (t(7) = -2.8, P = .026). We found a correlation between sweat loss and fluids consumed (r = 0.79, P < .001).

CONCLUSIONS

During preseason practices, the DII players drinking water at water breaks replaced the same volume of fluid (66% of weight lost) as NFL players with constant access to both water and sports drinks.

Pregame urine specific gravity and fluid intake by National Basketball Association players during competition

CONTEXT

Urine specific gravity (USG) has been used to estimate hydration status in athletes on the field, with increasing levels of hypohydration indicated by higher USG measurements (eg, greater than 1.020). Whether initial hydration status based on a urine measure is related to subsequent drinking response during exercise or athletic competition is unclear.

OBJECTIVE

To determine the relationship between pregame USG and the volume of fluid consumed by players in a professional basketball game.

DESIGN

Cross-sectional study.

SETTING

Basketball players were monitored during Summer League competition.

PATIENTS OR OTHER PARTICIPANTS

Players (n = 29) from 5 teams of the National Basketball Association agreed to participate.

MAIN OUTCOME MEASURE(S)

Pregame USG was measured for each player on 2 occasions. Athletes were given ad libitum access to fluid during each game and were unaware of the purpose of the study. Volume of fluid intake was measured for each player. To assess sweat loss, athletes were weighed in shorts before and after each game.

RESULTS

Sweat loss ranged from 1.0 to 4.6 L, with a mean sweat loss of 2.2 +/- 0.8 L. Fluid intake ranged from 0.1 to 2.9 L, with a mean fluid intake of 1.0 +/- 0.6 L. Pregame USG was greater than 1.020 in 52% of the urine samples collected and was not correlated with fluid volume consumed during either of the games (r = 0.15, P = .48, and r = 0.15, P = .52, respectively).

CONCLUSIONS

Approximately half of the players began the games in a hypohydrated state, as indicated by USG. Fluid intake during the game did not compensate for poor hydration status before competition. Furthermore, sweat losses in these players during games were substantial (greater than 2 L in approximately 20 minutes of playing time). Therefore, both pregame and during-game hydration strategies, such as beverage availability and player education, should be emphasized.

The meta-volition model: organizational leadership is the key ingredient in getting society moving, literally!

This paper argues that substantive and sustainable population-wide improvements in physical activity can be achieved only through the large scale adoption and implementation of policies and practices that make being active the default choice and remaining inactive difficult. Meta-volition refers to the volition and collective agency of early adopter leaders who implement such changes in their own organizations to drive productivity and health improvements. Leaders, themselves, are motivated by strong incentives to accomplish their organizational missions. The meta-volition model (MVM) specifies a cascade of changes that may be sparked by structural integration of brief activity bouts into organizational routine across sectors and types of organizations. MVM builds upon inter-disciplinary social ecological change models and frameworks such as diffusion of innovations, social learning and social marketing. MVM is dynamic rather than static, integrating biological influences with psychological factors, and socio-cultural influences with organizational processes. The model proposes six levels of dissemination triggered by organizational marketing to early adopter leaders carried out by "sparkplugs," boisterous leaders in population physical activity promotion: initiating (leader-leader), catalyzing (organizational-individual), viral marketing (individual-organizational), accelerating (organizational-organizational), anchoring (organizational-community) and institutionalizing (community-individual). MVM embodies public-private partnership principles, a collective investment in the high cost of achieving and maintaining active lifestyles.

Biobehavior of the human love of salt

We are beginning to understand why humans ingest so much salt. Here we address three issues: The first is whether our salt appetite is similar to that in animals, which we understand well. Our analysis suggests that this is doubtful, because of important differences between human and animal love of salt. The second issue then becomes how our predilection for salt is determined, for which we have a partial description, resting on development, conditioning, habit, and dietary culture. The last issue is the source of individual variation in salt avidity. We have partial answers to that too in the effects of perinatal sodium loss, sodium loss teaching us to seek salt, and gender. Other possibilities are suggested. From animal sodium appetite we humans may retain the lifelong enhancement of salt intake due to perinatal sodium loss, and a predisposition to learn the benefits of salt when in dire need. Nevertheless, human salt intake does not fit the biological model of a regulated sodium appetite. Indeed this archetypal 'wisdom of the body' fails us in all that has to do with behavioral regulation of this most basic need.

Fighting cancer with fitness: dietary outcomes of a randomized, controlled lifestyle change intervention in healthy African-American women

OBJECTIVES

This study tested the efficacy of an 8-week, culturally targeted community-based nutrition and physical activity promotion intervention, Fight Cancer with Fitness! (FCF).

METHODS

A randomized, controlled trial was conducted in a black-owned commercial gym in a sample of 366 predominantly overweight or obese, healthy African-American women.

RESULTS

Dietary quality as indexed by fruit and vegetable intake improved significantly in the intervention group compared to the control group at 12-month follow-up, and proportion of calories consumed as fat decreased in both groups.

CONCLUSIONS

This individually targeted cancer prevention intervention produced beneficial effects on dietary quality that were sustained for at least 12 months.

Creating a robust public health infrastructure for physical activity promotion

The essential role of physical activity both as an independent protective factor against numerous common chronic diseases and as a means to maintain a healthy weight is gaining increasing scientific recognition. Although the science of physical activity promotion is advancing rapidly, the practice of promoting physical activity at a population level is in its infancy. The virtual absence of a public health practice infrastructure for the promotion of physical activity at the local level presents a critical challenge to control policy for chronic disease, and particularly obesity. To translate the increasing evidence of the value of physical activity into practice will require systemic, multilevel, and multisectoral intervention approaches that build individual capability and organizational capacity for behavior change, create new social norms, and promote policy and environmental changes that support higher levels of energy expenditure across the population. This paper highlights societal changes contributing to inactivity; describes the evolution and current status of population-based public health physical activity promotion efforts in research and practice settings; suggests strategies for engaging decision makers, stakeholders, and the general public in building the necessary infrastructure to effectively promote physical activity; and identifies specific recommendations to spur the creation of a robust public health infrastructure for physical activity.

Ambient-temperature beverages are consumed at a rate similar to chilled water in heat-exposed workers

Palatability of beverages has been shown to influence drinking patterns and hydration. Cool beverages are known to enhance palatability; however, situations exist in which cooling is not possible. The purpose of this study was to determine the palatability of a variety of flavors of ambient temperature beverages. Ten healthy males performed two work trials in a temperature-controlled environment (WBGT = 30 degrees C; wet = 25 degrees C, dry = 40 degrees C, globe = 41 degrees C). In one trial, the subjects had only chilled water to drink. In the second trial the subjects drank their choice (any or all) of five ambient temperature beverages (water, fruit punch, lemon-lime, orange, and cola). Repeated measures ANOVA showed no difference in absolute or relative fluid consumption between the two trials (chilled = 1730 +/- 316 mL and 21 +/- 5 mL/kg; ambient [all five beverages combined] = 1510 +/- 219 mL and 19 +/- 4 mL/kg). There was no difference in the rate of fluid consumption between the two trials (608 +/- 88 mL/30 min and 674 +/- 82 mL/30 min, p > 0.05). Additionally, when combining all ambient-temperature, flavored beverages, consumption was significantly greater than that of ambient temperature water (1245 +/- 206 vs. 255 +/- 86 mL, p < 0.05). These findings demonstrate that providing ambient temperature beverages in a hot condition results in fluid consumption values similar to chilled water. These findings are relevant to industry in that there may be times when workers are at risk for heat-related illness due to dehydration and chilled beverages are not available. By providing flavored beverages, fluid consumption may be maintained and degree of heat-illness may be lessened.

Nutritional considerations in triathlon

Triathlon combines three disciplines (swimming, cycling and running) and competitions last between 1 hour 50 minutes (Olympic distance) and 14 hours (Ironman distance). Independent of the distance, dehydration and carbohydrate (CHO) depletion are the most likely causes of fatigue in triathlon, whereas gastrointestinal (GI) problems, hyperthermia and hyponatraemia are potentially health threatening, especially in longer events. Although glycogen supercompensation may be beneficial for triathlon performance (even Olympic distance), this does not necessarily have to be achieved by the traditional supercompensation protocol. More recently, studies have revealed ways to increase muscle glycogen concentrations to very high levels with minimal modifications in diet and training. During competition, cycling provides the best opportunity to ingest fluids. The optimum CHO concentration seems to be in the range of 5-8% and triathletes should aim to achieve a CHO intake of 60-70 g/hour. Triathletes should attempt to limit body mass losses to 1% of body mass. In all cases, a drink should contain sodium (30-50 mmol/L) for optimal absorption and prevention of hyponatraemia.Post-exercise rehydration is best achieved by consuming beverages that have a high sodium content (>60 mmol/L) in a volume equivalent to 150% of body mass loss. GI problems occur frequently, especially in long-distance triathlon. Problems seem related to the intake of highly concentrated carbohydrate solutions, or hyperosmotic drinks, and the intake of fibre, fat and protein. Endotoxaemia has been suggested as an explanation for some of the GI problems, but this has not been confirmed by recent research. Although mild endotoxaemia may occur after an Ironman-distance triathlon, this does not seem to be related to the incidence of GI problems. Hyponatraemia has occasionally been reported, especially among slow competitors in triathlons and probably arises due to loss of sodium in sweat coupled with very high intakes (8-10 L) of water or other low-sodium drinks.

Fluids and hydration in prolonged endurance performance

Numerous studies have confirmed that performance can be impaired when athletes are dehydrated. Endurance athletes should drink beverages containing carbohydrate and electrolyte during and after training or competition. Carbohydrates (sugars) favor consumption and Na(+) favors retention of water. Drinking during competition is desirable compared with fluid ingestion after or before training or competition only. Athletes seldom replace fluids fully due to sweat loss. Proper hydration during training or competition will enhance performance, avoid ensuing thermal stress, maintain plasma volume, delay fatigue, and prevent injuries associated with dehydration and sweat loss. In contrast, hyperhydration or overdrinking before, during, and after endurance events may cause Na(+) depletion and may lead to hyponatremia. It is imperative that endurance athletes replace sweat loss via fluid intake containing about 4% to 8% of carbohydrate solution and electrolytes during training or competition. It is recommended that athletes drink about 500 mL of fluid solution 1 to 2 h before an event and continue to consume cool or cold drinks in regular intervals to replace fluid loss due to sweat. For intense prolonged exercise lasting longer than 1 h, athletes should consume between 30 and 60 g/h and drink between 600 and 1200 mL/h of a solution containing carbohydrate and Na(+) (0.5 to 0.7 g/L of fluid). Maintaining proper hydration before, during, and after training and competition will help reduce fluid loss, maintain performance, lower submaximal exercise heart rate, maintain plasma volume, and reduce heat stress, heat exhaustion, and possibly heat stroke.

Effects of mouth dryness on drinking behavior and beverage acceptability

In humans, the association between mouth dryness and thirst has been examined in a variety of contexts. Typically, drinking behavior produces a concomitant reduction in unpleasant dry mouth sensations. Evidence is reviewed for a mechanism that influences the termination of drinking behavior by metering this change. Drinking behavior causes a progressive increase in parotid saliva flow. Thus, one possibility is that satiety results from a decrease in the reward associated with mouth wetting during a drinking episode. Beverages can differ in their satiating ability. This variability may be related to their mouth-wetting characteristic, and may be reflected in a shift in their acceptability when the mouth becomes dry. Physically drying the mouth appears to increase the acceptability of beverages that are either cold or acidic. It may be significant that two important determinants of mouth wetting are temperature and acidity. Cold or acidic beverages are also likely to be regarded as 'thirst-quenching.' Thus, shifts in acceptability, 'thirst quenching' and satiety may all be related to the mouth-wetting properties of a beverage. The extent to which this coincidence is meaningful warrants further investigation. However, if a common underlying process exists, then this may help to elucidate reasons for voluntary dehydration and aberrant drinking behavior in the elderly.