Hydration for climbers, at the gym and on the crag

Climbers rarely think of themselves as endurance athletes, so hydration often gets ignored. But a three-hour gym session in summer, or a full day at a sunny crag with a long approach, can easily leave you more dehydrated than you realise. Thirst, fatigue and poor focus creep in, and your last few attempts suffer.

This article is general information. If you have a medical condition that affects fluid balance, or you are unsure how much to drink, please ask a doctor or a qualified sports dietitian.

Why it matters

Water helps regulate body temperature, keeps blood volume up and supports concentration. When you lose a meaningful amount of fluid through sweat, exercise feels harder and decision-making can suffer.

The American College of Sports Medicine position stand on exercise and fluid replacement notes that losing more than about 2% of body mass through sweat can impair performance, especially in the heat. For a climber who weighs 60 kilograms, that is a little over a kilogram of fluid, which is quite achievable on a hot day.

The same position stand also warns against drinking far more than you lose. Over-drinking during long activities can be dangerous too. The goal is to replace losses sensibly, not to drink as much as possible.

Drink to stay comfortable and clear-headed. More is not always better.

How much do you lose?

Sweat losses vary enormously between people and conditions. Heat, humidity, sun exposure, effort and approach walks all matter. A cool winter bouldering session might cost very little; a summer multi-pitch day could cost a lot.

A simple way to learn your own pattern is to weigh yourself before and after a typical session, without clothes or with the same clothes, and account for anything you drank. A noticeable drop tells you that you lost more than you replaced. Do this a few times in different conditions rather than obsessing over a single measurement.

Practical habits

At the gym

1. Start hydrated. Drink normally through the day, and have a drink with your pre-session meal or snack.
2. Keep a bottle by your mat. Sipping between attempts and during rests is easy when the bottle is in sight.
3. Pay attention in summer. Many gyms get warm, and long sessions add up.

At the crag

1. Carry more than you think. There is often no water at the base. Factor in the approach and the walk out.
2. Drink before the approach. It is easier to carry water inside you than on your back.
3. Seek shade between routes. Sitting in the sun while belaying adds to sweat losses.
4. Consider electrolytes on long, hot days. When you sweat a lot for hours, replacing some salt as well as water can help. Salty snacks often do the job.

After climbing

Rehydrate with your next meal and drinks. Food contains water and salt, which help you retain fluid.

Simple checks

• Thirst is a reasonable guide for most people in moderate conditions.
• Urine colour: pale yellow generally suggests you are well hydrated; dark yellow suggests you could drink more.
• Headache, unusual fatigue or dizziness on a hot day are signals to stop, rest in the shade and drink.

Young climbers and hot conditions

Children and teenagers may not notice thirst as readily when absorbed in climbing. Coaches and parents can build in regular drink breaks, especially at outdoor sessions and competitions.

In Train Climb

• Use the notes field when you log a session to record heat, approach length or how much you drank. Patterns become clear over time.
• If you felt drained, say so in how you felt. It helps your coach interpret a high effort rating.
• Coaches: add a reminder to bring water to calendar events for outdoor days and competitions.
• Hydration is one piece of recovery. Read Proper rest and Energy availability and RED-S for the bigger picture.