By Sarah Dawkins u2014 BBC Sport Senior Journalist
Every long-distance runner will relate to the relief of a hydration station appearing in the distance. The trail they leave behindu2014a sea of thousands of discarded cups and bottlesu2014is however less idyllic.
Litter-strewn courses are synonymous with marathons, but could that be about to change?
All eyes in the running world will be on the French capital this weekend as single-use cups and plastic bottles will not be available at the Paris Marathon on Sundayu2014the first time it has happened at a mass participation event.
Instead, runners will be required to carry their own hydration containeru2014whether thatu2019s a soft flask, collapsible cup, or hydration pack on their backu2014that they will be able to refill at water points along the course.
The decision has divided the road-running community, with some runners abandoning their personal best attempts and others celebrating the shift towards sustainability. Organisers say the decision will not affect performance and this is the future of mass participation events.
BBC Sport understands representatives from the London, New York and Chicago marathons, which are all on a similar scale to Paris, will be on the ground to observe how the system works.
u2018Itu2019s going to impact my timeu2019
Cari Brown is hooked on marathons and is preparing to compete in her 11th on Sunday. After learning of the changes, she felt forced to abandon her plans to run a personal best in Paris and entered a different race to chase her goal.
u201cUnfortunately, itu2019s not going to be my goal marathon. Any runner who has to stop and start to get water, itu2019s going to affect your time and itu2019s going to affect your cadence,u201d Brown said.
Her biggest disappointment, though, is the decision to allow pre-filled personal water bottles on the course for runners targeting a time under two hours and 50 minutes. It is a common practice in elite races to avoid athletes losing time at hydration stations, but generally not a luxury extended to those in the wider event.
u201cThat is a massive advantage to generally younger male runners, as on average their marathon times are quicker. It also gives recognition to the fact that it [stopping for water] does affect your time,u201d Brown adds.
The IT manager from Woking will be running the streets of Paris with a hydration backpack. It is a tried-and-tested method for trail runners, but is less familiar for road runners who generally prefer to keep their kit as light as possible and rely on water provided along the course.
That causes concern for Brown who, while acknowledging plastic waste is an issue, believes having no water available at all in single-use paper cups on a potentially warm day is a big u201crisk factoru201d, with runners likely to skip stations if they are busy and put themselves at risk of dehydration.
Organisers insist this will not be the case, with the number of aid stations increased from eight to 13 and water spray systems in operation in case of hot weather.
Thomas Delpeuch, director of the Paris Marathon, told BBC Sport that while the system is a u201csignificant changeu201d, it is u201csuccessful and efficientu201d after a trial at the cityu2019s half marathon last month.
Prompted by a city-wide ban two years ago on single-use plastics at all Parisian races, it is hoped this change to the marathon will eliminate waste equivalent to 660,000 plastic bottles.
u201cPlastic is everywhere in our life and we need strong decisions to break free. Runners have appreciated bottles and cups for years for their practicality, but things are changing now,u201d Delpeuch adds.
u2018Individual choices can make a big differenceu2019
Tina Muir is a runner on a mission. After the high of representing Great Britain at the World Half Marathon Championships in 2016, she fell out of love with running. Now, the 37-year-old has returned with what she describes a u201cnew purposeu201d to promote more sustainable practices in running and this move by Paris organisers is exactly what she has been hoping for.
u201cI had a feeling this was coming and I was so excited to see a race as big as Paris be so bold to do it,u201d Muir said.
Since establishing campaign group u2018Racing for Sustainabilityu2019 last year, she has worked with organisers of some of the biggest races in the world to try to eliminate the cups used at these events, which is estimated to be between one and two million in number.
Muir has lived in the USA since her college years and is now famous for running in skirts made of rubbish. After overhauling her habits as a runner, she now wants others to follow suit and take u201cpersonal accountabilityu201d by embracing these changes.
u201cI come from a place of imperfect attempts, imperfect action. Iu2019m not saying u2018never use a gel again because it comes in a plastic containeru2019,u201d Muir said.
u201cThis is a small step that we can all takeu2014I think if it is given a chance, runners will find itu2019s actually not as bad as they think, or maybe even better than they think,u201d she adds. u201cThis could be easily adapted and taken on by other races. I think it can be a blueprint. We just have to get runners to trust that change is okay.u201d