IIn a hot June tournament, I took almost an hour longer on the back nine than the front nine. My score went up by seven strokes. I thought I was tired. In reality, I was dehydrated – and didn't realize it because I wasn't thirsty. Three weeks later, I did it right: two water bottles, a sip every two holes, even without thirst. The score collapse disappeared.

Hydration is one of those topics that seems self-explanatory. Drink when you're thirsty, and everything will be fine. This doesn't apply to people over 60. The part of the brain that signals thirst becomes less sensitive with age. You can accumulate a deficit of a liter without receiving any signal.

What makes dehydration measurable

Even a deficit of two percent of body weight (1.6 liters for an 80 kg player) reduces cognitive performance by 10 to 20 percent. Reaction times become longer, attention spans shorter, and decision quality decreases.

On the green, this means: Putt reading becomes less accurate. On the fairway: Club selection becomes less certain. During the swing: Stability decreases, the last ten percent of speed is lost — distance gone. This isn't „being tired.” It's a measurable, biological deficit.

−15 % cognitive performance with a 2 % body weight deficit — exactly what happens during a 4-hour summer run without drinking.

Why seniors are particularly at risk

Three biological changes occur together after age 60: The kidneys concentrate urine less effectively (more fluid loss), the perception of thirst decreases, and the body's water reserve diminishes. While a 30-year-old has 60 percent water content, a 70-year-old often has only 50 percent. This means the same fluid loss has a greater relative effect.

Hydration is the simplest, cheapest, and most underestimated performance measure in senior sports. It costs two Euros per lap, works immediately, and nobody does it consistently.

— German Sport University Cologne, Senior Sports Study 2024

Four mistakes build up the deficit without you noticing. They are all easy to avoid—if you know them.

Coffee in the morning

A double espresso before the round has a diuretic effect — approximately 1.5 times the amount of fluid goes through the kidney. Those who get up early and start right away already have a deficit on the first [hole].

Drink only when you're thirsty

The classic mistake. For older adults, the sensation of thirst often doesn’t set in until there is a 3 % deficit—that is, after their performance has already declined. Hydration must be proactive.

Only refill at the halfway house

Drinking two large glasses of water on the 9th hole is too late and too much. The stomach can only process about 200 ml of water every 15 minutes. The rest just goes right through.

What happens when you drink too much

Hyponatremia—the dangerous dilution of blood sodium—occurs in senior sports. Drinking three liters of pure water on a run risks cramps, confusion, and in extreme cases, unconsciousness. The solution: add a pinch of salt or an electrolyte powder. Clear water alone is not enough for more than two hours of exertion.