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Camilla Care

How science can help runners avoid hitting the wall

Vaseline 4 weeks ago

The 2024 TCS London Marathon is almost here and the 26.2 mile distance often feels like a puzzle for runners to solve. While each training run may present a different component, most runners are wise to think about how they will use fuel and hydration that day so that it all fits together.

Dream finish times are often left painfully out of reach when runners neglect this crucial part of the equation, which makes matters worse considering the amount of research and information available to help runners avoid hitting the dreaded wall.

I ran the London Marathon in 2021 and 2022, finishing in 3:04 both times, and while I felt proud, there was still an element of disappointment after coming agonizingly close to that magical three-hour mark.

On both occasions I suffered a series of hamstring cramps, which forced me to stumble in the last five to six miles and even stop several times.

So a priority for attempt three this year was to execute a better strategy both before and during the race, and that’s where Precision Fuel & Hydration came in and a drastically different approach. With experience working with top endurance athletes in running and triathlon, their assistance has proven fascinating. So part of my confidence in a sub-three-hour performance is relying on the science for this year’s race, including a sweat test conducted by Stuart Anderson of Precision.

Sweat rate can vary up to 15 times between apparently similar individuals; from 200 mg per liter of sweat to as much as 2,000 mg/l, with that percentage largely determined genetically.

Fortunately, the test did not include a blood sample or any variation on the painful beep test. In fact, it was quite nice to sit with Stuart’s help for about 45 minutes. An electrical current was delivered to my arm via a strap, similar to a watch, with beads of sweat, which eventually filled the space between my skin and a transparent disc. The liquid eventually turned blue before a reading appeared on the monitor.

This number told me exactly how much sodium I lose in sweat during exercise.

The conclusion from my test? I’m officially a “salty sweater,” which I’m told presents a series of tricky hurdles to overcome over 26.2 miles, namely making sure my sodium or glycogen stores don’t drop drastically at any point.

By calculating that I lose 1,146 mg of sodium per liter of sweat, I now know exactly what to consume on race day to avoid bonking: the point of exhaustion due to the functional depletion of glycogen.

Armed with the science, Precision advised me to supplement my marathon and those heavy training runs with 75 g of carbohydrates per hour (high intake), 1,000 mg of sodium per liter of sweat (high intake) and to drink 450 ml of water per day. hours (moderate intake). Ultimately, this led to me consuming and sometimes enforcing the following: an electrolyte capsule every 30 minutes and then 2.5 PF 30 gels per hour. The advice therefore concludes that I should use a rather difficult seven to eight gels during the marathon.

But instead of experimenting with fuel and hydration throughout the training block, Precision has now taken the guesswork out of the equation and developed an efficient strategy. I know exactly what to gather before each training session and what to bring on race day. In fact, the race day plan starts from the night before and then from 60-90 minutes before the start.

Years previously I would fill up on fuel when craving water or flagging after a test section of the course, but this now feels like a more effective and comprehensive approach and ensures that a crucial factor in endurance performance is not left to chance.

There have been good signs so far too, including a half marathon personal best and successful 16 and 20 mile races, mainly designed to test my race day routine including fuel and hydration.

But ultimately the proof will be in the race and how far I can go without feeling those nagging cramps in the back of my legs.

Read more about Precision Fuel & Hydration and the benefits of a sweat test here