On training days you lose more fluid and sodium than on rest days—not only through sweat, but through heavier breathing and higher core temperature. Under-hydrating shows up as higher heart rate at the same pace, early fatigue, headaches, and slower recovery.
Over-hydrating plain water without replacing salt can dilute sodium during long hot sessions. The goal is not a fixed liter target; it is matching intake to your session length, heat, and how salty your sweat runs.
Before you start
Arrive well hydrated, not chugging right at the door. Pale yellow urine and no thirst are simple pre-session checks. In the two to three hours before training, drink steadily with meals—roughly 400–600 ml (about 14–20 oz) total is enough for many people, more if you train in heat or had a salty or high-fiber meal. Right before start, small sips (150–250 ml) are fine; large boluses can slosh in your stomach during intervals or heavy lifts.
If the session will exceed 60–75 minutes or you are a heavy sweater, include sodium in pre-hydration: salted breakfast, broth, or an electrolyte drink—not salt pills on an empty stomach. Caffeine is fine for most people if you tolerate it; just pair coffee with water so you are not starting dry.
During the session
Sessions under 45–60 minutes in cool conditions often need only water if you started hydrated. Longer efforts, heat, humidity, or high sweat rate call for electrolytes—especially sodium—so absorption keeps pace with losses. Sip every 10–15 minutes instead of guzzling at the end; your gut empties better with steady intake.
Strength training in air-conditioned gyms may need little beyond your bottle at hand; a 90-minute summer run may need 500–1000 ml per hour with 300–600 mg sodium per liter, adjusted to taste and tolerance. Thirst is a lagging signal—on hot long days, use a loose schedule (every mile or every 15 minutes) rather than waiting until you are parched.
After you finish
Recovery hydration replaces what you lost and supports glycogen storage with your post-workout meal. Weigh yourself before and after once, in similar conditions, to estimate sweat rate: each 0.5 kg (1 lb) drop is roughly 500 ml fluid to replace, plus a little extra over the next few hours. Pair fluids with food so sodium and potassium come from meals—yogurt, eggs, fruit, potatoes, or a normal dinner often beat a sweet sports drink alone after a standard gym session.
Spread rehydration over two to four hours. If urine stays dark or you feel light-headed, keep sipping; if you feel bloated or nauseated, slow down—forcing liters rarely helps. Talk with your clinician if you have heart, kidney, or blood-pressure limits that affect fluid or salt intake.
Two checks that actually help
- Weigh-in test: Same scale, minimal clothing, before and after one hard session. Repeat in heat and cool weather; your needs are not one number year-round.
- Urine color: Pale straw by the next morning is a decent recovery sign; tea-colored urine after training means keep fluids (and food-sourced electrolytes) coming.
Example: You have a 70-minute lunch-break run at 28°C (82°F). You drink 500 ml water with breakfast, sip 600 ml with electrolytes during the run, and weigh 0.6 kg less afterward. You have pasta with vegetables and chicken at dinner and water through the afternoon—no need to force another liter if urine lightens by evening.
Example: You lift legs for 55 minutes in a cool gym and sweat lightly. One bottle (750 ml) through the session plus your usual lunch is enough; you skip sports drink and still hit protein and carbs without cramping the next day.
Build a personal baseline over two weeks: note session type, temperature, fluids, and how you felt the next morning. Adjust up for heat waves and down for easy days—hydration should flex like training load, not stay frozen at eight glasses regardless of context. Ohga can nudge fluid and sodium targets when your logged workouts, weather, and post-session weight trends show repeated dehydration—so you fix patterns instead of guessing from a generic chart.
