The Effects of Altitude on Cycling Performance
Picture this: you’re in your Lycra, sliding on your sunglasses past your helmet straps and about to clip into your pedals. You can see the mountain summits far away in the distance…it’s here…today is Etape du Tour 2019!
We’re sure that you know that riding in the mountains is different to riding at sea level. Other than noticeably longer climbs, there are many factors during the picturesque ascents and fierce descents that should be considered before you arrive and during the unforgettable ride. Within this blog post, we will cover most of the main factors to ensure that you enjoy the ups as well as the downs on the big day!
Firstly, the air when above 1500 m feels thinner and subsequently makes cycling feel a lot harder, predominantly due to the main difference of a lower oxygen pressure. Essentially there is an equivalent of a 25% loss in oxygen availability at the summit and race finish of Val Thorens (~2400 m) compared to sea level. Given that oxygen allows us to exercise aerobically, having less will make your legs and lungs demand it even more! For example, when climbing up a 7% gradient at 250 W (a similar power output you have been working at on your turbo trainer at home), you can expect your heart rate to be around 10–20 bpm higher even when still holding 250 W. Likewise, if you prefer to ride at a pre-determined heart rate, i.e., 160 bpm, you can achieve this with a power output 10–20% less than you would expect when not in the mountains (e.g. 225 W). If you are a fan of numbers, then take a look at one of our earlier blog posts to estimate potential differences in power as altitude increases.
Secondly, it is well known that just a 2% loss in body weight (through fluid loss) leads to negatively impacted performance. As you are likely to be working a lot harder during Etape than some of your local weekend loops, you are more likely to lose fluids through sweat as well as possibly forgetting to take on fluids from your bidon’s down below in your bottle cages. The loss in sweat will also include salt (not a good look on the jersey or bib shorts…), also known as sodium bicarbonate, which your legs will need to grind you up the big climbs and keep you ticking along the flats. Take a look at one of our previous research posts relating to this!
Thirdly, as well as hydration, your appetite may also be affected whilst you tackle the route. We’ve all heard of ghrelin before (the hormone that makes you feel hungry when increased), but did you know that this is suppressed when at altitude? During the many hours you’ll spend in the saddle, you’ll burn a lot of calories. Naturally the harder you push, the more calories you’ll burn. But due to a reduced appetite when at altitude, it may feel like a chore to take on energy gels, bars and drinks, or even your go-to snacks that you’re used to consuming! For example, during the first climb up to the Col du Meraillet (~1600 m), you’ll likely feel fresh and energised and not need much food or even fluids. However, come the next climb up to the Cormet de Roselend (~2000 m) shortly after, your energy stores may be running low and it will be tough task to prevent yourself entering the red.
By now you may feel a little fear or even panic, but no need…there are many benefits of cycling at altitude! Not only will this day make you stronger, but you’ll descend much quicker than normal! This is because of the first point made in this blog being a lower oxygen pressure at altitude, making the air thin! From this, even when you’re tucked into your aero position like Peter Sagan or even still spinning over 100 rpm like Chris Froome, you’ll still reach speeds faster than descents you’re used to. Watch them hairpins!
So you now know that you’re going to have to be careful with your efforts, but this doesn’t affect just you – the pro’s are just as cautious! Chris Froome believes that altitude will be a “significant factor” of the Tour in 2019, and some riders will respond better than others. Overall, Etape du Tour will be a tough ride and a great challenge. Going into the red will make it extremely difficult to get back to a comfortable intensity without further damage…but there are factors and methods that you can use to prepare come next summer…stay tuned!
The Altitude Centre, research post, How to prevent over-training at altitude.
Human Kinetics, research post, Dehydration and its effects on performance.
The Altitude Centre, research post, Should you change your diet when exercising at altitude?
Debevec (2017). Front. Physiol. https://doi.org/10.3389/fphys.2017.00366
Cycling News, website post, Chris Froome: High altitude will be a significant factor at 2019 Tour de France