# A Systematic Review of the Effects of Nutrient Intake in Handball Players on Exercise Performance
## 4 Discussion  
### Hydration  
The need for a state of euhydration and normal plasma electrolyte levels during sport is clear because of its influence on exercise performance and the development of fatigue [62; 63]. Fluid replacement guidelines before, during and after exercise are necessary to promote this state of euhydration in the athlete. Before exercise, there is no universal agreement on optimal hydration status. Slow intakes of 5-7 mL/kg of sodium-containing beverages (20-50 mEq/L) and/or salt-containing foods or meals at least 4 h before may be appropriate to start physical activity euhydrated and with adequate plasma electrolyte levels [63]. Analysing the colour or frequency of the athlete's urine may be a practical tool to determine if previous hydration practices are correct [64], with an additional 3-5 mL/kg of fluids recommended if the individual does not produce urine or has dark or highly concentrated urine [63; 65]. Although handball athletes appear to comply with daily fluid AIs [18; 19], no studies have assessed fluid and electrolyte intake in the pre-sport period. Only [PERSON] et al. [24] assessed the previous hydration status of Brazilian track handball players by BIA with mean values of 71 \(\pm\) 0.65% of total body water, although confounding factors and the lack of precision and accuracy of the method limit its use for monitoring hydration [65]. During exercise, the amount and rate of fluid replacement depends on individual sweat rate, duration and drinking opportunities [63]. As a general rule, during high-intensity physical activity and adverse environmental conditions, intakes of 0.6-1 L/h with frequent intakes (150-250 mL) every 15-20 min and sodium concentrations of 0.5-0.7 g/L are recommended [66], amounts achieved by most female handball athletes (200-800 mL and 1.38 \(\pm\) 0.64 L) [20; 22]. In addition, losses below approximately 2% of body weight when environmental conditions are warm and humid appear to compromise cognitive, skill and physical domains in team sports [67]. No included study observed losses greater than 2 kg during training and competition in track handball players [22; 24]. This may be due to the greater number of drinking opportunities offered by the sport of both beach and court handball, and the lower risk of dehydration compared to other team sports [68]. However, there is a need for personalised hydration strategies during handball given the wide variability in sweat rates of athletes, with particular interest in contexts that compromise a state of euhydration such as young athletes [69], and/or matches/training of longer duration [22] with more time at high intensities (>90% FCmax) [23]. Furthermore, the results obtained in sweat tests must be correctly interpreted as being applicable to the specific samples and conditions under which the test was performed and under the same methods [70]. More studies are needed that relate fluid intakes to the individualised needs of handball athletes, rather than isolated intakes [20; 21], as well as studies that reflect the water demands of handball, especially beach handball, where environmental conditions, clothing, playing time, etc., can have a significant influence on the water balance of athletes and thus on their performance and health [62; 71]. After exercise, the goal is to replace any fluid and electrolyte deficits. Athletes seeking rapid and complete recovery from dehydration may employ intakes of 1.5 L of fluid per kilogram of body weight lost with sufficient sodium to balance inter-individual losses, help retain fluid ingested and stimulate thirst, while if recovery time is sufficient, the inclusion of normal meals and snacks with enough water and sodium may be sufficient to replace sweat losses [63]. In this review, we observed losses of 0.19 \(\pm\) 2.03 kg [22], and 38 \(\pm\) 10 mmol Na/L in sweat in female athletes during matches of different competitions [23], values of sodium loss similar to other team sports such as football or basketball [72].