Hydration Status and Fluid Replacement Strategies of High-Performance Adolescent Athletes: An Application of Machine Learning to Distinguish Hydration Characteristics

Abstract

There are limited data on the fluid balance characteristics and fluid replenishment behaviors of high-performance adolescent athletes. The heterogeneity of hydration status and practices of adolescent athletes warrant efficient approaches to individualizing hydration strategies. This study aimed to evaluate and characterize the hydration status and fluid balance characteristics of high-performance adolescent athletes and examine the differences in fluid consumption behaviors during training. In total, 105 high-performance adolescent athletes (male: 66, female: 39; age 14.1 ± 1.0 y) across 11 sports had their hydration status assessed on three separate occasions—upon rising and before a low and a high-intensity training session (pre-training). The results showed that 20–44% of athletes were identified as hypohydrated, with 21–44% and 15–34% of athletes commencing low- and high-intensity training in a hypohydrated state, respectively. Linear mixed model (LMM) analyses revealed that athletes who were hypohydrated consumed more fluid (F (1.183.85)) = 5.91, (p = 0.016). Additional K-means cluster analyses performed highlighted three clusters: “Heavy sweaters with sufficient compensatory hydration habits,” “Heavy sweaters with insufficient compensatory hydration habits” and “Light sweaters with sufficient compensatory hydration habits”. Our results highlight that high-performance adolescent athletes with ad libitum drinking have compensatory mechanisms to replenish fluids lost from training. The approach to distinguish athletes by hydration characteristics could assist practitioners in prioritizing future hydration intervention protocols.

Trends and Missing Links in (De)Hydration Research: A Narrative Review

“…When intake strategy was based on the percentage of body weight lost (15%), studies averaged an amount of fluid corresponding to 112% (range: 50-150%) of body weight lost, with 100% (k = 13, 62% of the studies using body weight loss as parameter for fluid intake) being the most common amount (Table 2). Hypohydration can impair athletic performance [11,13]. However, contrary to common belief, hyperhydration can cause electrolyte imbalance, such as hyponatremia, also leading to a decline in performance or even life-threatening or fatal complications (when plasma sodium ≤ 120 mEq/L) [221,228].…”

“…Prolonged exercise leads to the loss of body fluid related to elevated sweat [ 12 ]. Thus, during sports competitions, water reaches its utmost importance, as maintaining fluid homeostasis is fundamental to optimizing athletic performance [ 13 ]. Body temperatures (core and skin) will significantly increase during exercise, depending on the environmental conditions (temperature, humidity, altitude, wind exposure, etc.)…”

“…Then, the excess heat produced by the body temperature elevation or absorbed from the environment is dissipated through sweat evaporation [ 14 , 15 ]. Considering that sweat is typically hypotonic, exercise-induced sweat losses lead to hypertonic hypovolemia, contributing to an increment in cardiovascular and thermoregulatory strain, an elevated perception of effort, and a decrement in muscle blood flow and aerobic reserve, especially in hot conditions [ 13 , 15 , 16 , 17 ]. In parallel, body water and electrolyte stores are reduced, which must be counterbalanced by consuming fluids during the exercise or, to a lesser contribution, by hyperhydration hours before the event [ 15 , 17 , 18 ].…”

“…These athletes incur a body fluid deficit where dehydration (loss of ≥2% of body mass) and hyponatremia (blood sodium < 135 mEq/L) are achieved, adversely impacting athletic performance and potentially their health, mainly when core and skin temperatures are concomitantly high [ 14 , 15 , 19 ]. Such a fluid deficit is exacerbated when athletes start exercising in a hypohydrated state [ 13 ]. Conversely, hyperhydration may also be problematic during prolonged exercise by increasing the risk of hyponatremia [ 19 , 20 , 21 ].…”

Nutritional Recommendations for the Young Athlete

“…38 Fluid deficiency is common, with one study finding 20-44% of athletes are underhydrated even at the beginning of their training sessions. 39 To combat dehydration, fluids should be readily available for consumption before, during, and after activity sessions, and contrary to the routines of many youth athletes, activity sessions need to be separated further to maintain their normal level of hydration. [40][41][42][43] Moreover, drinking fluids ad libitum during practices is insufficient to prevent further dehydration.…”