Effect of whey protein isolate on rehydration after exercise

Fluid and electrolyte balance following consumption of skimmed milk and a plant-based soya beverage at rest in euhydrated males

PURPOSE

Cow's milk is one of the most hydrating beverages, but many individuals choose not to consume dairy in their diet due to intolerance, allergy, or dietary preference. Milk is commonly replaced with plant-based beverages, including soya which has the most comparable protein content, but little is known about their hydration potential. This study compared fluid and electrolyte balance responses between a soya beverage and skimmed cow's milk.

METHODS

Ten healthy males [age 27 (6) y; body mass index 24.6 (2.3) kg/m2] completed two randomised counterbalanced trials, involving consuming 1000 mL water from approximately isocaloric amounts of skimmed cow's milk (MILK) or a sweetened soya beverage (SOYA), in four aliquots over 30 min in a euhydrated fasted state. Volume, specific gravity, and electrolyte (sodium, potassium, chloride) concentrations were determined in total-void urine samples collected pre-/post-beverage ingestion, and hourly for 180 min thereafter. Hunger, thirst, nausea and stomach fullness were rated proximal to urine samples.

RESULTS

Total urine mass (MILK, 986 ± 254 g; SOYA, 950 ± 248 g; P = 0.435) and urine specific gravity (P = 0.156) did not differ between trials. Potassium balance was greater in SOYA 0-180 min post-beverage (P ≤ 0.013), whilst chloride balance was greater in MILK 0-120 min post-beverage (P ≤ 0.036). Sodium balance (P = 0.258), total electrolyte balance (P = 0.258), and subjective measures (P ≥ 0.139) were not different between trials.

CONCLUSION

Replacing cow's milk with a soya beverage did not negatively impact fluid balance in healthy young males, making it a viable option for those who choose not to consume dairy in their diet.

Compositional Aspects of Beverages Designed to Promote Hydration Before, During, and After Exercise: Concepts Revisited

Hypohydration can impair aerobic performance and deteriorate cognitive function during exercise. To minimize hypohydration, athletes are recommended to commence exercise at least euhydrated, ingest fluids containing sodium during long-duration and/or high-intensity exercise to prevent body mass loss over 2% and maintain elevated plasma osmolality, and rapidly restore and retain fluid and electrolyte homeostasis before a second exercise session. To achieve these goals, the compositions of the fluids consumed are key; however, it remains unclear what can be considered an optimal formulation for a hydration beverage in different settings. While carbohydrate-electrolyte solutions such as sports drinks have been extensively explored as a source of carbohydrates to meet fuel demands during intense and long-duration exercise, these formulas might not be ideal in situations where fluid and electrolyte balance is impaired, such as practicing exercise in the heat. Alternately, hypotonic compositions consisting of moderate to high levels of electrolytes (i.e., ≥45 mmol/L), mainly sodium, combined with low amounts of carbohydrates (i.e., <6%) might be useful to accelerate intestinal water absorption, maintain plasma volume and osmolality during exercise, and improve fluid retention during recovery. Future studies should compare hypotonic formulas and sports drinks in different exercise settings, evaluating different levels of sodium and/or other electrolytes, blends of carbohydrates, and novel ingredients for addressing hydration and rehydration before, during, and after exercise.

Post-exercise rehydration: Comparing the efficacy of three commercial oral rehydration solutions

Introduction

This study compared the efficacy of three commercial oral rehydration solutions (ORS) for restoring fluid and electrolyte balance, after exercise-induced dehydration.

Method

Healthy, active participants (N = 20; ♀ = 3; age ∼27 y, V˙O₂peak ∼52 ml/kg/min) completed three randomised, counterbalanced trials whereby intermittent exercise in the heat (∼36°C, ∼50% humidity) induced ∼2.5% dehydration. Subsequently, participants rehydrated (125% fluid loss in four equal aliquots at 0, 1, 2, 3 h) with a glucose-based (G-ORS), sugar-free (Z-ORS) or amino acid-based sugar-free (AA-ORS) ORS of varying electrolyte composition. Urine output was measured hourly and capillary blood samples collected pre-exercise, 0, 2 and 5 h post-exercise. Sodium, potassium, and chloride concentrations in urine, sweat, and blood were determined.

Results

Net fluid balance peaked at 4 h and was greater in AA-ORS (141 ± 155 ml) and G-ORS (101 ± 195 ml) than Z-ORS (-47 ± 208 ml; P ≤ 0.010). Only AA-ORS achieved positive sodium and chloride balance post-exercise, which were greater for AA-ORS than G-ORS and Z-ORS (P ≤ 0.006), as well as for G-ORS than Z-ORS (P ≤ 0.007) from 1 to 5 h.

Conclusion

when provided in a volume equivalent to 125% of exercise-induced fluid loss, AA-ORS produced comparable/superior fluid balance and superior sodium/chloride balance responses to popular glucose-based and sugar-free ORS.

European Resuscitation Council Guidelines 2021: First aid

The European Resuscitation Council has produced these first aid guidelines, which are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. The topics include the first aid management of emergency medicine and trauma. For medical emergencies the following content is covered: recovery position, optimal positioning for shock, bronchodilator administration for asthma, recognition of stroke, early aspirin for chest pain, second dose of adrenaline for anaphylaxis, management of hypoglycaemia, oral rehydration solutions for treating exertion-related dehydration, management of heat stroke by cooling, supplemental oxygen in acute stroke, and presyncope. For trauma related emergencies the following topics are covered: control of life-threatening bleeding, management of open chest wounds, cervical spine motion restriction and stabilisation, recognition of concussion, cooling of thermal burns, dental avulsion, compression wrap for closed extremity joint injuries, straightening an angulated fracture, and eye injury from chemical exposure.

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.

Selected In-Season Nutritional Strategies to Enhance Recovery for Team Sport Athletes: A Practical Overview

Team sport athletes face a variety of nutritional challenges related to recovery during the competitive season. The purpose of this article is to review nutrition strategies related to muscle regeneration, glycogen restoration, fatigue, physical and immune health, and preparation for subsequent training bouts and competitions. Given the limited opportunities to recover between training bouts and games throughout the competitive season, athletes must be deliberate in their recovery strategy. Foundational components of recovery related to protein, carbohydrates, and fluid have been extensively reviewed and accepted. Micronutrients and supplements that may be efficacious for promoting recovery include vitamin D, omega-3 polyunsaturated fatty acids, creatine, collagen/vitamin C, and antioxidants. Curcumin and bromelain may also provide a recovery benefit during the competitive season but future research is warranted prior to incorporating supplemental dosages into the athlete's diet. Air travel poses nutritional challenges related to nutrient timing and quality. Incorporating strategies to consume efficacious micronutrients and ingredients is necessary to support athlete recovery in season.

Role of Functional Beverages on Sport Performance and Recovery

Functional beverages represent a palatable and efficient way to hydrate and reintegrate electrolytes, carbohydrates, and other nutrients employed and/or lost during physical training and/or competitions. Bodily hydration during sporting activity is one of the best indicators of health in athletes and can be a limiting factor for sport performance. Indeed, dehydration strongly decreases athletic performance until it is a risk to health. As for other nutrients, each of them is reported to support athletes' needs both during the physical activity and/or in the post-workout. In this study, we review the current knowledge of macronutrient-enriched functional beverages in sport taking into account the athletes' health, sports performance, and recovery.

Fluid, energy, and nutrient recovery via ad libitum intake of different commercial beverages and food in female athletes

This study investigated the effect of consuming different commercial beverages with food ad libitum after exercise on fluid, energy, and nutrient recovery in trained females. On 4 separate occasions, 8 females (body mass (BM): 61.8 ± 10.7 kg; maximal oxygen uptake: 46.3 ± 7.5 mL·kg^-1·min^-1) lost 2.0% ± 0.3% BM cycling at ∼75% maximal oxygen uptake before completing a 4-h recovery period with ad libitum access to 1 of 4 beverages: Water, Powerade (Sports Drink), Up & Go Reduced Sugar (Lower Sugar (LS)-MILK) or Up & Go Energize (Higher Protein (HP)-MILK). Participants also had two 15-min opportunities to access food within the first 2 h of the recovery period. Beverage intake, total water/nutrient intake, and indicators of fluid recovery (BM, urine output, plasma osmolality), gastrointestinal tolerance and palatability were assessed periodically. While total water intake (from food and beverage) (Water: 1918 ± 580 g; Sports Drink: 1809 ± 338 g; LS-MILK: 1458 ± 431 g; HP-MILK: 1523 ± 472 g; p = 0.010) and total urine output (Water: 566 ± 314 g; Sports Drink: 459 ± 290 g; LS-MILK: 220 ± 53 g; HP-MILK: 230 ± 117 g; p = 0.009) differed significantly by beverage, the quantity of ingested water retained was similar across treatments (Water: 1352 ± 462 g; Sports Drink: 1349 ± 407 g; LS-MILK: 1238 ± 400 g; HP-MILK: 1293 ± 453 g; p = 0.691). Total energy intake (from food and beverage) increased in proportion to the energy density of the beverage (Water: 4129 ± 1080 kJ; Sports Drink: 5167 ± 643 kJ; LS-MILK: 6019 ± 1925 kJ; HP-MILK: 7096 ± 2058 kJ; p = 0.014). When consumed voluntarily and with food, different beverages promote similar levels of fluid recovery, but alter energy/nutrient intakes. Providing access to food and understanding the longer-term dietary goals of female athletes are important considerations when recommending a recovery beverage.

Bolus Ingestion of Whey Protein Immediately Post-Exercise Does Not Influence Rehydration Compared to Energy-Matched Carbohydrate Ingestion

Whey protein is a commonly ingested nutritional supplement amongst athletes and regular exercisers; however, its role in post-exercise rehydration remains unclear. Eight healthy male and female participants completed two experimental trials involving the ingestion of 35 g of whey protein (WP) or maltodextrin (MD) at the onset of a rehydration period, followed by ingestion of water to a volume equivalent to 150% of the amount of body mass lost during exercise in the heat. The gastric emptying rates of the solutions were measured using ¹³C breath tests. Recovery was monitored for a further 3 h by the collection of blood and urine samples. The time taken to empty half of the initial solution (T_1/2) was different between the trials (WP = 65.5 ± 11.4 min; MD = 56.7 ± 6.3 min; p = 0.05); however, there was no difference in cumulative urine volume throughout the recovery period (WP = 1306 ± 306 mL; MD = 1428 ± 443 mL; p = 0.314). Participants returned to net negative fluid balance 2 h after the recovery period with MD and 3 h with WP. The results of this study suggest that whey protein empties from the stomach at a slower rate than MD; however, this does not seem to exert any positive or negative effects on the maintenance of fluid balance in the post-exercise period.

Effects of whey protein in carbohydrate-electrolyte drinks on post-exercise rehydration

The purpose of this study was to examine the effects of different amounts of whey protein in carbohydrate-electrolyte (CE) drinks on post-exercise rehydration. Ten males completed 5 trials in a randomised cross-over design. A 4-h recovery was applied after a 60-min run at 65% VO_2peak in each trial. During recovery, the participants ingested a high-carbohydrate CE drink (CE-H), a low-carbohydrate CE drink (CE-L), a high-whey-protein (33 g·L^-1) CE drink (CW-H), a medium-whey-protein (22 g·L^-1) CE drink (CW-M) or a low-whey-protein (15 g·L^-1) CE drink (CW-L) in a volume equivalent to 150% of their body mass (BM) loss. The drinks were provided in six equal boluses and consumed by the participants within 150 min in each trial. After exercise, a BM loss of 2.15% ± 0.05% was achieved. Urine production was less in the CW-M and CW-H trials during recovery, which induced a greater fluid retention in the CW-M (51.0% ± 5.7%) and CW-H (55.4% ± 3.8%) trials than in any other trial (p < .05). The plasma albumin content was higher in the CW-H trial than in the CE-H and CE-L trials at 2 h (p < .05) and 3 h (p < .01) during recovery. The aldosterone concentration was lower in the CE-H trial than in the CW-M and CW-H trials after recovery (p < .05). It is concluded that the rehydration was improved when whey protein was co-ingested with CE drinks during a 4-h recovery after a 60-min run. However, this additive effect was only observed when whey protein concentration was at least 22 g·L^-1 in the current study.

Values for digestible indispensable amino acid scores (DIAAS) for some dairy and plant proteins may better describe protein quality than values calculated using the concept for protein digestibility-corrected amino acid scores (PDCAAS)

An experiment was conducted to compare values for digestible indispensable amino acid scores (DIAAS) for four animal proteins and four plant proteins with values calculated as recommended for protein digestibility-corrected amino acid scores (PDCAAS), but determined in pigs instead of in rats. Values for standardised total tract digestibility (STTD) of crude protein (CP) and standardised ileal digestibility (SID) of amino acids (AA) were calculated for whey protein isolate (WPI), whey protein concentrate (WPC), milk protein concentrate (MPC), skimmed milk powder (SMP), pea protein concentrate (PPC), soya protein isolate (SPI), soya flour and whole-grain wheat. The PDCAAS-like values were calculated using the STTD of CP to estimate AA digestibility and values for DIAAS were calculated from values for SID of AA. Results indicated that values for SID of most indispensable AA in WPI, WPC and MPC were greater (P<0·05) than for SMP, PPC, SPI, soya flour and wheat. With the exception of arginine and tryptophan, the SID of all indispensable AA in SPI was greater (P<0·05) than in soya flour, and with the exception of threonine, the SID of all indispensable AA in wheat was less (P<0·05) than in all other ingredients. If the same scoring pattern for children between 6 and 36 months was used to calculate PDCAAS-like values and DIAAS, PDCAAS-like values were greater (P<0·05) than DIAAS values for SMP, PPC, SPI, soya flour and wheat indicating that PDCAAS-like values estimated in pigs may overestimate the quality of these proteins.

Optimizing the restoration and maintenance of fluid balance after exercise-induced dehydration

Hypohydration, or a body water deficit, is a common occurrence in athletes and recreational exercisers following the completion of an exercise session. For those who will undertake a further exercise session that day, it is important to replace water losses to avoid beginning the next exercise session hypohydrated and the potential detrimental effects on performance that this may lead to. The aim of this review is to provide an overview of the research related to factors that may affect postexercise rehydration. Research in this area has focused on the volume of fluid to be ingested, the rate of fluid ingestion, and fluid composition. Volume replacement during recovery should exceed that lost during exercise to allow for ongoing water loss; however, ingestion of large volumes of plain water results in a prompt diuresis, effectively preventing longer-term maintenance of water balance. Addition of sodium to a rehydration solution is beneficial for maintenance of fluid balance due to its effect on extracellular fluid osmolality and volume. The addition of macronutrients such as carbohydrate and protein can promote maintenance of hydration by influencing absorption and distribution of ingested water, which in turn effects extracellular fluid osmolality and volume. Alcohol is commonly consumed in the postexercise period and may influence postexercise rehydration, as will the coingestion of food. Future research in this area should focus on providing information related to optimal rates of fluid ingestion, advisable solutions to ingest during different duration recovery periods, and confirmation of mechanistic explanations for the observations outlined.

A metered intake of milk following exercise and thermal dehydration restores whole-body net fluid balance better than a carbohydrate–electrolyte solution or water in healthy young men

Appropriate rehydration and nutrient intake in recovery is a key component of exercise performance. This study investigated whether the recovery of body net fluid balance (NFB) following exercise and thermal dehydration to −2 % of body mass (BM) was enhanced by a metered rate of ingestion of milk (M) compared with a carbohydrate–electrolyte solution (CE) or water (W). In randomised order, seven active men (aged 26·2 (sd 6·1) years) undertook exercise and thermal dehydration to −2 % of BM on three occasions. A metered replacement volume of M, CE or W equivalent to 150 % of the BM loss was then consumed within 2–3 h. NFB was subsequently measured for 5 h from commencement of rehydration. A higher overall NFB in M than CE (P=0·001) and W (P=0·006) was observed, with no difference between CE and W (P=0·69). After 5 h, NFB in M remained positive (+117 (sd 122) ml) compared with basal, and it was greater than W (−539 (sd 390) ml, P=0·011) but not CE (−381 (sd 460) ml, P=0·077, d=1·6). Plasma osmolality (Posm) and K remained elevated above basal in M compared with CE and W. The change in Posm was associated with circulating pre-provasopressin (rs 0·348, P<0·001), a biomarker of arginine vasopressin, but could not account fully for the augmented NFB in M compared with CE and W. These data suggest that a metered approach to fluid ingestion acts in synergy with the nutrient composition of M in the restoration of NFB following exercise and thermal dehydration.

Comparison of energy supplements during prolonged exercise for maintenance of cardiac function: carbohydrate only versus carbohydrate plus whey or casein hydrolysate

Cardiac function is often suppressed following prolonged strenuous exercise and this may occur partly because of an energy deficit. This study compared left ventricular (LV) function by 2-dimensional echocardiography and tissue Doppler imaging (TDI) before and after ∼2.5 h of cycling (2-h steady-state 60% peak aerobic power output plus 16 km time trial) in 8 male cyclists when they ingested either placebo, carbohydrate-only (CHO-only), carbohydrate-casein hydrolysate (CHO-casein), or carbohydrate-whey hydrolysate (CHO-whey). No treatment-by-time interactions occurred, but pre-to-postexercise time effects occurred selectively. Although diastolic function measured by pulsed-wave Doppler early-to-late (E/A) transmitral blood flow velocity was suppressed in all trials from pre- to postexercise (mean change post-pre exercise: -0.53 (95% CI -0.15 to -0.91)), TDI early-to-late (e'/a') tissue velocity was significantly suppressed pre- to postexercise only with placebo, CHO-only, and CHO-whey (septal and lateral wall e'/a' average change: -0.62 (95% CI -1.12 to -0.12); -0.69 (95% CI -1.19 to -0.20); and -0.79 (95% CI -1.28 to -0.29), respectively) but not with CHO-casein (-0.40 (95% CI -0.90 to 0.09)). LV contractility was, or tended to be, significantly reduced pre- to postexercise with placebo, CHO-only, and CHO-whey (systolic blood pressure/end systolic volume change, mm Hg·mL(-1): -0.8 (95% CI -1.2 to -0.4), p = 0.0003; -0.5 (95% CI -0.9 to -0.02), p = 0.035; and -0.4 (95% CI -0.8 to 0.04), p = 0.086, respectively), but not with CHO-casein (-0.3 (95% CI -0.8 to 0.1), p = 0.22). However, ejection fraction (EF) and ventricular-arterial coupling were significantly reduced pre- to postexercise only with placebo (placebo change: EF, -4.6 (95% CI -8.4 to -0.7)%; stroke volume/end systolic volume, -0.3 (95% CI -0.6 to -0.04)). Despite no treatment-by-time interactions, pre-to-postexercise time effects observed with specific beverages may be meaningful for athletes. Tentatively, the order of beverages with least-to-most variables displaying a time effect indicating suppression of LV function following exercise was CHO-casein < CHO-only and CHO-whey < placebo, and calls for further verification.

Differential acute effects of carbohydrate- and protein-rich drinks compared with water on cardiac output during rest and exercise in healthy young men

The acute effects of drinks rich in protein (PRO) versus carbohydrate (CHO) on cardiovascular hemodynamics and reactivity are uncertain. A randomized crossover design was used to compare 400-mL isoenergetic (1.1 MJ) drinks containing whey protein (PRO; 44 g) or carbohydrate (CHO; 57 g) versus 400 mL of water in 14 healthy men. The primary and secondary outcomes were changes in cardiac output, blood pressure, systemic vascular resistance (SVR) and digital volume pulse measured prior to and 30 min following consumption at rest, during 12 min of multi-stage bicycle ergometry, and 15 min postexercise. The mean change (95% confidence interval (CI)) in resting cardiac output at 30 min was greater for CHO than for PRO or water: 0.7 (0.4 to 1.0), 0.1 (-0.2 to 0.40), and 0.0 (-0.3 to 0.3) L/min (P < 0.001), respectively; the higher cardiac output following CHO was accompanied by an increase in stroke volume and a lower SVR. The mean increments (95% CI) in cardiac output during exercise were CHO 4.7 (4.4 to 5.0), PRO 4.9 (4.6 to 5.2), and water 4.6 (4.3 to 4.9) L/min with the difference between PRO versus water being significant (P < 0.025). There were no other statistically significant differences. In summary, a CHO-rich drink increased cardiac output and lowered SVR in the resting state compared with a PRO-rich drink or water but the effect size of changes in these variables did not differ during or after exercise between CHO and PRO. Neither protein nor carbohydrate affected blood pressure reactivity to exercise.

Post-Exercise Protein Trial: Interactions between Diet and Exercise (PEPTIDE): study protocol for randomized controlled trial

BACKGROUND

Performing regular exercise is known to manifest a number of health benefits that mainly relate to cardiovascular and muscular adaptations to allow for greater oxygen extraction and utilization. There is increasing evidence that nutrient intake can affect the adaptive response to a single exercise bout, and that protein feeding is important to facilitate this process. Thus, the exercise-nutrient interaction may potentially lead to a greater response to training. The role of post-exercise protein ingestion in enhancing the effects of running-based endurance exercise training relative to energy-matched carbohydrate intervention remains to be established. Additionally, the influence of immediate versus overnight protein ingestion in mediating these training effects is currently unknown. The current protocol aims to establish whether post-exercise nutrient intake and timing would influence the magnitude of improvements during a prescribed endurance training program.

METHODS/DESIGN

The project involves two phases with each involving two treatment arms applied in a randomized investigator-participant double-blind parallel group design. For each treatment, participants will be required to undergo six weeks of running-based endurance training. Immediately post-exercise, participants will be prescribed solutions providing 0.4 grams per kilogram of body mass (g · kg(-1)) of whey protein hydrolysate plus 0.4 g · kg(-1) sucrose, relative to an isocaloric sucrose control (0.8 g · kg(-1); Phase I). In Phase II, identical protein supplements will be provided (0.4 + 0.4 g · kg(-1) · h(-1) of whey protein hydrolysate and sucrose, respectively), with the timing of ingestion manipulated to compare immediate versus overnight recovery feedings. Anthropometric, expired gas, venous blood and muscle biopsy samples will be obtained at baseline and following the six-week training period.

DISCUSSION

By investigating the role of nutrition in enhancing the effects of endurance exercise training, we will provide novel insight regarding nutrient-exercise interactions and the potential to help and develop effective methods to maximize health or performance outcomes in response to regular exercise.

TRIAL REGISTRATION

Current Controlled Trials registration number: ISRCTN27312291 (date assigned: 4 December 2013). The first participant was randomized on 11 December 2013.