Why I Peed So Much at 28km Into My 50kmUltra (and What My Swollen Hands Had to Do With It)

Completing my first 50km ultramarathon at Lake Tekapo was one of the biggest physical and mental challenges I have ever taken on.

The views were incredible, the atmosphere was supportive, and the whole day felt like a mix of excitement, grit, pain, and pure determination. Tekapo delivered everything you want from an ultra, stunning scenery, tough kilometres, and that unique feeling of being completely out of your comfort zone.

But one part of the race caught me completely off guard.

At around 28km, I suddenly needed multiple toilet stops within a short period of time.

Not one.

Multiple.

And this was not just the typical runner “urgency” where you feel like you need to pee but barely anything comes out. This was genuine. Each stop involved a large volume of urine, which made it clear that my body was actively filtering and producing more urine than expected mid race.

Around the same time, I also noticed something else.

My hands and arms started swelling.

My fingers felt puffy, my rings felt tighter, and my upper limbs felt heavy and uncomfortable. It was subtle at first, but it became obvious as the km's went on.

As a runner, it was inconvenient.

As a pelvic health physiotherapist, it was fascinating.

Because it highlighted something many runners forget.

Running is not just about your legs.

It is about your entire system, including your kidneys, electrolytes, fluid balance, circulation, and pelvic floor.

Why would you need to pee repeatedly during an ultra?

Toilet stops during running are common. Many runners experience bladder urgency, especially during high impact activities.

But frequent stops with a full bladder and large urine output is a different situation entirely.

This points less towards bladder sensitivity and more towards hydration and kidney filtration changes.

Your kidneys are responsible for filtering your blood and deciding what to keep and what to excrete. During endurance events, this system can become unpredictable because your body is under prolonged stress and working hard to maintain balance.

Your kidneys are constantly responding to:

• how much fluid you are drinking

• how much sodium you are taking in

• sweat loss

• temperature changes

• inflammation and muscle breakdown

• stress hormones such as adrenaline and cortisol

In other words, your kidneys are doing a huge amount of behind the scenes work during an ultra.

The role of electrolytes

One of the biggest takeaways from my experience was how important electrolytes are.

Many runners focus heavily on hydration and understandably so. Nobody wants dehydration, cramps, headaches, or fatigue.

But drinking a lot of water without adequate electrolytes can cause your sodium levels to become diluted. This can affect how your body holds onto fluid.

When sodium becomes diluted, your body may respond by shifting fluid around the body and trying to regain balance.

This can lead to symptoms like:

• increased urination

• swelling in the hands and arms

• bloating

• feeling heavy or waterlogged

• nausea or fatigue

This is why electrolytes are not just an optional extra. They are often essential in long distance running.

The swelling in my arms was the clue

The upper limb swelling was a surprising part of the race.

Most people associate swelling with lower limbs, but swelling in the hands and arms is actually quite common during long endurance events. Some runners notice their fingers become puffy, their rings feel tight, or their hands feel uncomfortable.

This can occur due to a combination of:

• fluid retention and shifting

• electrolyte imbalance

• inflammation

• prolonged repetitive movement

• changes in circulation and venous return

• temperature and environmental factors

When the body is under stress for hours, it is constantly redistributing fluid. Sometimes it holds fluid in the tissues, and sometimes it dumps it via the kidneys.

In my case, the combination of swollen hands and frequent large urine output strongly suggested my body was struggling to find its normal fluid and electrolyte equilibrium.

What does this have to do with pelvic health?

This is where things get interesting.

When we talk about running and pelvic health, most people think about leaking urine, prolapse, or pelvic floor weakness. And yes, those are common concerns, particularly for women postpartum.

But pelvic health is also about understanding what is happening in the body as a whole.

If you are stopping repeatedly to pee during long runs, it is worth considering the bigger picture.

Is it a pelvic floor coordination issue?

Or is it an endurance fuelling and hydration issue?

Sometimes it is both.

The pelvic floor is part of the pressure management system of the body. It responds to fatigue, impact, breathing, and intra abdominal pressure. And during a long event like a 50km ultra, the pelvic floor can fatigue just like your calves or glutes.

Even if bladder filling is due to kidney filtration, the pelvic floor still has to manage the pressure of a fuller bladder, repeated stops, and the physical strain of running.

It is all connected.

What I learned from the Tekapo 50km

Ultra running teaches you a lot about your body, and this experience was no exception.

Here are my main takeaways.

1. Hydration is not just about water

In long endurance events, hydration needs to be balanced with electrolytes. Drinking more is not always better.

2. The body can change mid race

Everything can feel fine early on, then suddenly at 28km your body decides to throw in a curveball.

3. Swelling can be a sign of fluid imbalance

Swollen hands and arms may be normal, but they are also worth paying attention to, especially if paired with excessive urination.

4. Your pelvic floor still matters

Even if the bladder issue is driven by kidney filtration, the pelvic floor is still working hard in the background to manage impact and pressure for hours.

What should runners do if this happens?

If you experience repeated large urine output during long runs or races, it may be worth reflecting on:

• your fluid intake before and during the run

• whether you are taking in enough electrolytes

• whether you are drinking out of habit rather than thirst

• the weather conditions

• whether you are over compensating due to fear of dehydration

It can also be helpful to trial electrolyte strategies during training, rather than experimenting on race day.

When should you seek help?

Toilet stops during long runs are common, but it is worth seeking advice if you notice:

• excessive urination repeatedly during endurance events

• bladder symptoms that interfere with training

• pelvic heaviness, pressure, or discomfort

• leaking during running

• difficulty fully emptying

• pain in the pelvic region

• fear of running due to toilet access

These symptoms are common but they are not something you have to accept as normal.

How pelvic health physiotherapy can support runners

Pelvic health physiotherapy is not only for postpartum women or those with incontinence.

It is also valuable for runners wanting to understand how their body responds to load and endurance.

A pelvic health physio can assess:

• pelvic floor strength and endurance

• pelvic floor relaxation and coordination

• bladder habits and triggers

• breathing and pressure management

• core and hip strength

• return to running readiness

For runners doing longer distances, pelvic floor endurance and coordination becomes increasingly important, particularly under fatigue.

My first 50km ultra at Lake Tekapo was an unforgettable experience. It pushed me physically, mentally, and emotionally.

But the unexpected part of the day was learning how dramatically the body can shift during endurance exercise, particularly around fluid balance.

At 28km, my kidneys clearly decided to increase filtration and output, and the swelling in my upper limbs was a reminder that hydration and electrolyte balance is a complex system.

It is not just about drinking water.

It is about supporting your whole body.

And if you are a runner who struggles with toilet stops, leaking, or pelvic pressure, know that there are answers and support available.