Previously it was demonstrated that mineralization and alkalization properties of mineral water are important factors influencing acid-base balance and hydration status in athletes.
The purpose of this study was to investigate the effects of drinking different types of water on urine pH, specific urine gravity, and post-exercise lactate utilization in response to strenuous exercise. Thirty-six male soccer players were divided into three intervention groups, consuming around 4.0 l/day of different types of water for 7 days:
The athletes performed an exercise protocol on two occasions (before and after intervention). The exercise protocol consisted of 5 bouts of intensive 60-s (120% VO2max) cycling separated by 60 s of passive rest. Body composition, urinalysis and lactate concentration were evaluated – before (t0), immediately after (t1), 5’ (t2), and 30’ (t3) after exercise.
Total body water and its active transport (TBW – total body water / ICW – intracellular water / ECW – extracellular water) showed no significant differences in all groups, at both occasions.
In the post-hydration state we found a significant decrease of specific urine gravity in HM (1021±4.2 vs 1015±3.8 g/L) and LM (1022±3.1 vs 1008±4.2 g/L). We also found a significant increase of pH and lactate utilization rate in LM.
In conclusion, the athletes hydrated with alkaline, low mineralized water demonstrated favorable changes in hydration status in response to high-intensity interval exercise with a significant decrease of specific urine gravity, increased urine pH and more efficient utilization of lactate after supramaximal exercise.
A good hydration state, regardless of the sport discipline and training intensity, provides the opportunity to achieve an optimal physical and mental state .
Hydration protocols during training and competition are a basic part of athletic training .
The hydration strategy should consider in detail the type and properties of administered fluids, and their volume in relation to the type of physical activity, its intensity and duration .
The American College of Sports Medicine, The National Athletic Trainer’s Association and other institutions of sport and science present their recommendations to optimize performance, and to reduce the probability of injuries and overtraining due to dehydration .
The optimal hydration state is determined by monitoring urine specific gravity .
Acid-base equilibrium within the body is tightly maintained through the interaction of three complementary mechanisms:
blood and tissue buffering systems (e.g., bicarbonate), the diffusion of carbon dioxide from the blood to the lungs via respiration, and the excretion of hydrogen ions from the blood to the urine by the kidneys .
The most widely used fluid during exercise includes water. Different properties and especially the mineral content, the proportions between SO4 2- and HCO3 – as well as the pH determine hydration status and other therapeutic properties. This has been documented in numerous experiments and clinical trials [7, 8].
Mineral water has a significant impact on acid-base balance, which determines anaerobic exercise capacity . Many researchers have suggested that water rich in Ca is characterized by this specific quality .
Even subtle changes in blood and tissue pH have significant metabolic consequences, including the response to oxidative stress [11, 12].
During supramaximal exercise, there is a significant increase in reactive oxygen species (ROS) and reactive nitrogen species (RNS). In trained individuals the antioxidant system is more efficient due to the adaptation to exercise [13, 14, 15, 16].
The neutralization of ROS may promote the use of water rich in hydrogen ions. This action is explained by the stimulation of numerous antioxidant proteins [17, 18].
The results of long-term research show that the use of hydrogen-rich water is helpful in preventing metabolic diseases , including diabetes .
Alkaline mineral water with a high pH, through the effect on acid-base balance can increase the rate of lactate utilization following anaerobic exercise .
Many studies have shown that the consumption of alkalizing supplements can have a significant effect on the body’s acid-base balance using surrogate markers of urine and blood pH .
It is possible that the regular consumption of alkaline water could have an effect similar to nutritional supplements on markers of acid-base balance, yet this has not been evaluated in a controlled manner.
The aim of this study was to investigate the effects of water intake with different mineralization and alkalization properties on the state of hydration and the rate of lactate utilization in athletes following high-intensity interval exercise.
Many studies have focused on the maintenance of proper hydration during prolonged aerobic exercise , whereas inadequate data have been presented regarding rehydration procedures and benefits during short-term anaerobic exercise. During high-intensity exercise water loss is minimal and other aspects of recovery should be taken into account.
Fluid-electrolyte balance and hydration affect the mental and physical state of athletes. Hydration can have a significant influence on both aerobic and anaerobic performance .
The results of our study indicate that the use of water with alkalizing properties exhibits a significant potential for hydration. It reduces fluid-electrolyte disturbances and accelerates the rate of lactate utilization following intensive anaerobic interval exercises.
Skeletal muscle fatigue is caused by numerous mechanisms, including accumulation of metabolites, such as potassium, or H+ .
To a large extent, the structural damage to the myocytes and inflammation depend on the exercise ROS production .
Analysis of urine osmolality, specific urine gravity and colour may suggest the state of hydration .
Consumption of alkaline water following a dehydrating bout of cycling exercise has previously been shown to rehydrate cyclists faster and more completely than the consumption of placebo water.
Following the consumption of alkaline water, the cyclists demonstrated lower total urine output, their urine was more concentrated (higher specific gravity), and total blood protein concentration was lower, all of which are expected observations for improved hydration status .
Heil  reported that water retention at the end of a 3-hour recovery period was 79.2 ± 3.9% when subjects drank alkaline water versus 62.5 ± 5.4% when drinking a placebo (p < 0.05).
Thus, the present study has shown that the habitual consumption of mineralized bottled water can actually improve indicators of hydration status. The test procedures included in the study determined urine specific gravity and urine pH before and after exercise, in the pre- and post-hydration state. In both pre-hydration and the post-hydration states, the urine specific gravity decreased.
However, in the LM group after hydration the changes were more significant (HM 1015 ± 3.8 g/L vs LM 1008± 4.2 g/L, LM 1008± 4.2 g/L vs Con. 1014± 4.1; p< 0.001).
The specific gravity of urine is dependent on the amount and weight of the solutes, including electrolytes. Improved water absorption causes a lower concentration of soluble particles and suggests stronger water retention, as observed in the LM group.
Simultaneously, we recorded an exercise-induced increase in urinary pH. This change could be the result of drinking large amounts of alkaline water with aforementioned mineralization properties.
Consumption of alkaline water in the present study was associated with an increase in urine pH, while the dietary composition remained stable.
Previous research by Welch et al.  demonstrated that urinary pH from 24-hour collection samples could function as an effective surrogate marker for changes in acid-base balance when evaluating differences in dietary intake.
A study conducted by Konig et al.  suggested that drinking water rich in minerals causes an increase in urine pH (5.94 to 6.57). Numerous experiments confirm the benefits of alkalizing additives in water.
Heil  described the effects of highly alkalized water on the state of hydration and improved acid-base balance. Similarly, Berardi et al.  reported that urinary pH increased from 6.07 to 6.21 and 6.27 following one and two weeks of ingestion, respectively, of a plant-based supplement.
The observations from these studies [6, 11] are consistent with the changes in urine pH (6.00 to 6.51) observed by the present study for group 2. Our study confirms the possible effect on hydration and accelerated recovery.
Group 2 hydrating with alkaline water had much more efficient lactate utilization following the high-intensity interval training protocol (5.83±0.25 p<0.05). This result can be attributed to the specific properties of the alkaline water used for hydration in this group of athletes.
There are a few well-recognized activating factors at the cellular level: ATP, inorganic phosphate and H+ ions. Skeletal muscle has a large capacity for ammonia production, which is usually revealed by its high blood accumulation during exercise above 60 VO2max.
It is clear that an increase in lactate production mirrors recruitment and activity of type II muscle fibres, and this process starts at exercise intensity reaching the anaerobic threshold.
Rapid adenosine triphosphate hydrolysis during high-intensity exercise builds up adenosine di-phosphate and adenosine monophosphate (AMP).
In the further metabolic degeneration cascade known as the purine nucleotide cycle, AMP is deaminated into inosinomono-phosphate, with the parallel formation of ammonia (NH3).
Because ammonia is correlated with the number of fast switch muscle fibres, an increase in lactate and efficacy of oxidative metabolism, this may suggest that ammonia might be an important player in modulation of central fatigue .
Dehydration in athletes may also lead to fatigue, poor performance, decreased coordination, and muscle cramping. Although further studies are absolutely warranted, drinking highly alkaline water seems an effective fluid hydration strategy for high-intensity interval training.
Drinking alkaline water in amounts of 4.0 l per day shows a positive effect on hydration status after anaerobic exercise with a significant decrease of specific urine gravity.
Intake of alkaline water also shows a positive effect on urine pH during the anaerobic test protocol, and much more efficient lactate utilization after the high-intensity interval exercise.
The consumption of alkaline water was associated with improved acid-base balance and hydration status. In contrast, subjects who consumed table water showed no changes over the same period of time. These results indicate that the habitual consumption of alkaline water may be a valuable nutritional vector influencing both acid-base balance and hydration status in active healthy adults.
These preliminary data demonstrated that consumption of alkaline water can improve anaerobic performance and post-exercise recovery.