Two-a-day practices can remove fluid through sweat faster than most athletes replace it, and the urine concentrates in the same hours that the body is under the most stress. Add the teenage pattern of under-drinking — many athletes simply do not carry water between sessions — and the afternoon practice often starts with urine already dark. For a young athlete with a family history of stones, that pattern is the exact setup for a first stone.
The fix is not less training; it is a hydration and recovery structure that matches the training load.
A practical two-a-day hydration plan: pre-hydrate with two glasses in the hour before the first practice; drink a full bottle during each session; rehydrate between sessions with a full bottle plus a salted snack; and finish the day with water at dinner. The urine-color check is the honest gauge — pale straw means the plan is working, dark amber means tomorrow's intake goes up. Weighing before and after practice, where available, gives the precise number: roughly one liter of fluid per kilogram lost.
Recovery nutrition matters as much as the hydration. The post-practice meal should carry protein, calcium, and low-oxalate carbohydrates: milk or chocolate milk (calcium plus fluid), a turkey or chicken wrap, fruit, and a vegetable. Milk is the standout recovery drink — it replaces fluid, adds protein, and delivers the calcium that binds oxalate. The table below shows the measured values.
| Food | Oxalate (mg) | Serving | Rating |
|---|---|---|---|
| Milk, cow's | 0 | 1 cup | Safe |
| Chocolate milk | 0 | 1 cup | Safe |
| Chicken wrap | 0 | 1 wrap | Safe |
| Banana | 6 | 1 medium | Safe |
| Trail mix with almonds | 60 | 1/4 cup | Caution |
| Protein bar (peanut) | 72 | 1 bar | Caution |
The athlete snack bag is where the measured check matters most. Peanut-based protein bars measure 72 mg of oxalate per bar — caution range — and trail mix with almonds climbs higher. The friendlier athlete snacks are milk, yogurt, string cheese, fruit, and pretzels. For athletes who genuinely need a protein bar after practice, portioning and pairing with milk keeps the load manageable. The goal is recovery without stacking oxalate on top of a dehydration-heavy day.
Not by themselves, but they concentrate urine and increase stone risk if hydration does not keep pace. The protective plan is pre-hydration, water during both sessions, rehydration between, and a urine-color check each evening. Athletes with a stone history should have a fluid plan set with their clinician before camp.
Excellent. Milk replaces fluid, adds protein for recovery, and delivers calcium at zero oxalate — a combination no sports drink matches. Chocolate milk is the athlete classic and carries the same profile.
In portions, yes — but peanut-based bars measure about 72 mg of oxalate each (caution range). Milk, yogurt, and string cheese deliver the same recovery protein at near-zero oxalate. If a bar is needed, pair it with milk and choose it occasionally, not daily.
Parents and coaches should know the warning signs that a young athlete's hydration is failing: dark urine by midday, dizziness or headache in the second session, cramping, and a marked drop in performance. None of these is a stone emergency by itself, but they are signals that the fluid plan is not keeping pace, and the same failure that causes heat issues is the one that concentrates urine. A stone-history athlete should have a clinician-approved fluid target before camp, and any symptom beyond simple thirst should be checked rather than pushed through.
For the athlete with a known stone history, the preseason visit matters: the clinician sets the fluid target, reviews the last urine test, and flags any medications or supplements that interact with hydration. Teen athletes are often reluctant to slow down, which makes the parent's role structural — the water bottle is packed, the break is scheduled, and the plan is non-negotiable without being dramatic. The measured structure does the protecting, and the athlete stays in the game.
High school and college athletic departments are increasingly staffing nutrition support, and the stone-aware athlete should use it. The athletic trainer or team dietitian can review the hydration plan, adjust the recovery meals, and flag the snack-bag items that concentrate oxalate. For the athlete with a stone history, the nutrition staff becomes part of the care team — the person who translates the clinician's urine numbers into a practical training diet. The request is normal and increasingly expected, not a special case.
Parents can do the same from home: a pre-camp note to the athletic trainer with the stone history and the fluid target, and a post-practice check-in that includes the urine-color question. The athlete trains, the staff supports, and the parent monitors — three roles, one plan, and the kidneys protected through the hardest weeks of the season.
A family history of stones changes the two-a-day math. An athlete whose parent or sibling has formed stones carries a higher baseline risk, and the camp plan should reflect it: a clinician-approved fluid target, a lower threshold for stopping practice to hydrate, and a preseason urine test where the clinician recommends it. The conversation is not about fear — it is about structure. The athlete with a known family history trains with the same intensity, protected by a plan that accounts for the biology. The parent's role is to raise the history early, before the first practice, so the plan is in place before the heat is.
And a closing word to the athlete: hydrating is not a sign of weakness — it is part of training, as essential as the warm-up and the recovery work. The athlete who drinks on schedule trains harder, recovers faster, and protects the kidneys that the sport needs. The measured plan is a competitive advantage, not a limitation.
And the parent's closing reminder: the two-a-day season is short, but the hydration habit it builds lasts. The athlete who learns the water schedule in August carries it into the school year, the winter sport, and the rest of life — one more reason the preseason plan is worth the effort.
Research on heat-illness prevention in athletes suggests that scheduled hydration outperforms thirst-based drinking — the same finding that underlies the stone plan.
See how oxalate values are measured and verified on our data methodology page.