Run Well by Juliet McGrattan (reading books for 5 year olds .TXT) 📕

pressure is falling then angiotensin will constrict the blood vessels, to increase pressure and also trigger release of a hormone called aldosterone from the adrenal glands, which are located just above each kidney. Aldosterone messages the kidneys to reabsorb more sodium and water from its tubules, which increases the blood volume and restores the balance again. If blood pressure is too high then the blood vessels are dilated and the kidneys take back less sodium and water to reduce the blood volume and pressure.

The ureters transport urine from the kidneys to the bladder where it’s stored until you want to have a wee. The bladder is actually a muscular bag which can expand and then shrink back down again. It can hold about 500mls of urine and when it’s getting stretched, it sends messages to your brain that it would be a good idea to find a toilet. When the time is right, the bladder muscle (called the detrusor muscle) contracts, forcing the urine out. At the same time, the sphincters and pelvic floor muscles, which keep urine in, relax and allow the urine to flow.

It’s a complex system with many functions which are crucial to us as runners. Let’s look at some questions related to the urinary system to further help us understand how it all works and to make sure we can run healthily.

Q I know that hydration is important for runners, but how much should I drink when I run?

A How much fluid you need when running depends on many variables, including your weight, the air temperature, your fitness, how much you sweat, your intensity and duration of exercise, what you’ve eaten… the list goes on and on. If you want to get very technical about it then you can follow the steps below to see how much fluid you’ve lost during a run. You do need to remember that there will be day-to-day variation so you can’t assume this amount is what you need every time. It’s just a guide. The simple answer is to just be directed by your thirst. You may have heard of the concept that if you’re thirsty you’re already dehydrated, but your thirst mechanism is well-designed and very sensitive. It will let you know when taking on water would be a good idea and it will tell you well ahead of time. You just need to tune into it. If you’ve had a drink before you exercise then you might not need one at all during activity unless it’s a very hot day, your effort level is intense or you’re running for over an hour. There are plenty of experienced runners doing ten-mile weekend runs without drinking while they’re on the move. We can sometimes get too hung up on the whole water issue. It’s sensible to take water with you on longer runs and drink to thirst. What you drink is important too, because replacing fluids lost through running means replacing salts as well as water.

Did you know?

Sweating is our body’s way of cooling us down. Heat is lost when sweat evaporates from our skin. We have millions of sweat glands in our skin with more in areas such as our armpits, forehead and palms. Sweat contains mostly water, but also lactic acid and urea. Minerals such as sodium, potassium, calcium and magnesium are lost in sweat, as are tiny amounts of trace metals such as iron, copper and zinc.

Q What is hyponatraemia and how can I avoid it?

A Hyponatraemia means low blood sodium levels. Sodium is a mineral which the body’s nerves and muscles need to function properly, but it also plays a crucial role in fluid balance in the body. Have you heard of osmosis, the process by which water is drawn across a membrane from a less concentrated solution to a more concentrated one? The kidney uses sodium to enable osmosis. Ions such as sodium are initially filtered out of the blood by the kidney, and into the tubule, to make urine. The kidney then selectively reabsorbs sodium back into the blood. By doing this it increases the concentration of sodium in the blood and water is then drawn in too. By moving sodium and regulating blood concentration, the kidney can move water back into the system to maintain fluid balance and blood pressure. If you ingest excess salt, then high sodium levels can mean that more water is drawn into your bloodstream and high blood pressure can result.

Sweat contains large amounts of sodium, so over a run of marathon distance or longer, you can lose significant amounts. At the same time, ingesting large quantities of water will literally dilute your blood. The result can be hyponatraemia – potentially dangerous low sodium levels, where cells begin to swell with water and malfunction. Hyponatraemia can present as weakness, confusion, cramps, nausea, headaches and, in severe cases, seizures and even death. This is why long-distance runners need to pay attention to their hydration and not drink large quantities of water at every drink station. Drinking to thirst is better and also making sure that some of what is consumed contains electrolytes (minerals), which include sodium. You can use specifically designed sports rehydration drinks or you can make your own using fruit squash and a pinch of salt. Sodium can also be replaced through eating salty foods such as pretzels or taking salt tablets. The longer and hotter the race, the bigger the risk. Being aware of the potential of hyponatraemia is important, but at the same time don’t limit your fluid intake because you are scared of it, because you’ll be at risk of harmful dehydration instead! Use your common sense, adapt to race conditions and practise your fuelling to minimise your risks.

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Running hydration

If you’re concerned about your hydration or simply curious about how much fluid you’re losing during a run, then you can try this simple test. This will give you a good idea about how much you sweat,