Four ideas do most of the heavy lifting in hydration science. Get them right and you'll make better decisions for yourself and the athletes you support.
Roughly 60% of the human body is water, and every physical and cognitive system depends on it. Blood volume, joint lubrication, temperature regulation, nutrient transport, and nerve signaling all rely on adequate fluid.
Even small losses matter. Research has repeatedly shown that fluid losses of just 1–2% of body weight can measurably impair endurance, reaction time, and decision-making.
Dehydration is rarely dramatic. It's usually quiet — a slight drop in performance, a slower recovery, a heavier feeling at practice. That's what makes it so easy to miss.
Hydration is a performance input, not just a safety concern. Treating it that way changes how you plan practice.
Electrolytes are charged minerals — primarily sodium, potassium, and magnesium — that regulate how fluid moves in and out of cells. Sweat pulls them out, and replacing them helps the body absorb and hold on to the fluid you're drinking. When losses are substantial and go unreplaced, that process becomes less efficient.
Sodium is the electrolyte lost in the greatest quantity in sweat, and the one most closely tied to fluid balance. When sodium and glucose are consumed together, they activate a transporter in the gut wall that moves water into the bloodstream more efficiently than water alone.
This mechanism — sodium-glucose co-transport — is the foundation of oral rehydration science, and the reason a well-formulated sports drink can be a more effective choice than plain water during longer or more demanding activity.
As sweat losses increase, replacing electrolytes, particularly sodium, can become increasingly important. The aim is to replace what you lose without going overboard — which is why intake works best when it's matched to the athlete and the session.
For longer, harder, or hot-weather sessions, athletes tend to accumulate substantial sweat and sodium losses and often benefit from electrolyte replacement. Individual needs vary.
Reaction time, decision speed, and executive function are all sensitive to hydration status. Studies of athletes and soldiers have shown measurable declines in tasks like target identification and reaction time at just 2% fluid loss.
That matters because most sports are decision-heavy. A wide receiver reading coverage, a shortstop reacting to a line drive, a defender picking up an off-ball run — these are cognitive tasks under physical load.
Acuity was built with this in mind. Beyond fluid and electrolytes, the formula contains 200 mg of Suntheanine® L-theanine and zero caffeine — the stimulant was left out of the design so athletes can choose caffeine separately, based on their age, tolerance, timing, and individual needs.
Late-game mistakes are often blamed on 'losing focus.' Sometimes they're blamed on the wrong thing — the athlete is dehydrated.
The 30 minutes after activity is the most productive window for rehydration. Sodium drives fluid retention, so the drink you use matters — plain water passes through faster and does less to restore balance.
A pound of body-mass loss is roughly 16 ounces of water-equivalent mass — but full rehydration can require roughly 100–150% of calculated losses when the recovery window is short, because some of what you drink is subsequently lost. Weigh in, weigh out, and rehydrate based on your losses, your thirst, and the time before your next session.
Recovery isn't just about the current session. It's about the next one. Athletes who rehydrate well after practice show up better prepared for tomorrow.
A five-minute post-practice hydration routine is one of the highest-leverage habits a program can build.
A curated list of the studies we lean on most, with plain-language takeaways for coaches, athletes, and parents. Updated regularly.