EGB Magazine 1 Fuel efficiency

This is the first in a series of articles I wrote for the EGB endurance magazine in 2023. I have added it as a blog as well for you to enjoy and use 

I (well, really hubby and me 😉 ) bought a new car. Our older (very fuel-efficient) diesel needed replacing and we got a hybrid. Not one of those plug-in ones, but one that will load up its own battery when you are driving and braking. You will even drive electric at times when you are not too heavy-footed on the accelerator. So it is cheap when using the battery, and not so cheap when it is using the petrol. I had already become a little obsessed with driving the diesel as efficiently as possible (competitive at all Esther?) but now it has become a sport on its own to drive electric as much as possible and I'm utterly disappointed in myself when the economy goes down (winter days were particularly bad… bring back summer I say, for loads of reasons!)

I know, this is an endurance magazine, not a car magazine! So why do I start yapping about my car when I should be telling to something useful about endurance?

I'll tell you why, whilst driving and thinking (as you do on autopilot) about writing my coaching tutorials about how muscles are utilising fuel, I realised there are quite some links between the fuel efficiency of a hybrid car and that of an endurance horse. There actually are loads of links between fuel use of cars and horses, so you'll have to stick with this metaphor I'm afraid.
Like the hybrid car the horse has 2 (main) types of energy sources: "expensive" glycogen and "cheap" fatty acids, you can sort of see it as the equivalent of petrol and electric driving on the battery. Like petrol, we actively need to add glycogen (which is really the animal equivalent of starch) into our horse by feeding it higher energy foods. The carbs and glucose in the food will either be used in daily work, but the access will be stored in muscles (and liver) to use when there is a higher demand in higher intensity work. And like petrol, we can run empty if we have depleted our resources.

Another source of energy in the horse is fatty acids, these are derived mostly from digesting fibres (from grass and hay) by the bacteria in the gut and a horse has stored loads of these fatty acids in its body. So many it will never really run out, even when a horse is super skinny! We can compare the stored energy in the battery and driving electrically to these fatty acids, both are used for low-intensity work. These are pretty much non-depletive systems, both in the (hybrid) car and the horse. Who needs petrol (or glycogen!) you might think, we'll all just use the fatty acids and have that non-depletable cheap fuel!

But this is where it gets a bit tricky, I'll try to keep it as clear as possible. Like different brands and models of cars have different fuel efficiency (both petrol/diesel as the hybrid battery) so do different breeds(or individual) horses. Each horse has a different ability to use their fuel based on their genetic athletic makeup. Some horses will be able to do a lot on their battery (fatty acids) and can go for long distances at moderate to even reasonably high speeds. Yes, you guessed it, the top-level Arabs would fall into this category. Other horses would be able to do a good bit on fatty acids but would need to top up more (and quicker) with glycogen, but they should still be able to have plenty in the tank at the end of a ride. A lot of part-bred Arabs and sporty warmbloods or lighter native types would fall into this range of slightly less fuel-efficient types.

But some horses (and breeds) struggle more with using fatty acids as energy, either because they can only use them when they go very slow (our heavier types that tend to be more cold-blooded in origin) or when they are really bred for high-speed gaz guzzling work like racing. These horses will default to using glycogen a lot more and will risk running low much quicker than horses that can run well on fatty acids. 

Now, there is good and bad news. Let me start with the bad as I always like to finish on a positive note. The bad news is that the deeper we press that accelerator and the more often we press it the less fuel efficient we will be, both in our car and our horse. When we ask higher intensity work of our horse it will always need more fuel. So when we go for a faster canter a lot of horses will start using their glycogen resources. Going up a hill is also higher intensity work, which will have nearly all horses fueling their muscles on glycogen, especially at the beginning of the hill and at increases in incline. And like any car will use more petrol when it is just starting and not warmed up, and so will our "equine engines". Poor warm-up gives poor fuel use. And we all know that stopping and starting a lot with our car is less fuel-efficient. Again, the same goes for our horse, with every upward transition the horse has to fire up its glycogen pathway for a moment to give the muscles the extra power they need.
So if higher intensity work like a fast canter or a gallop will use a lot of glycogen and going uphill does as well… You can imagine what going up a hill fast can do to our fuel efficiency? But I see sooo many riders do just that! 

This is actually where we see a very important difference between our cars and our horses. If we go up a hill fast with our car all we do is use a lot of petrol, besides a lot of noise from the engine and a dent in our bank balance we have no ill effects. But the horse does!

Going up a hill at speed is depleting the glycogen stores fast. We cannot top them up fast as we do with our car either, it takes a few days to have all the glycogen back. But when there is a very high demand for fuel for the muscles, the horse will have to switch to anaerobic fuel use: extremely inefficient as we use loads of glycogen and only get a little energy in return. But it is also creating lactic acid which will make the muscles acidic and fatigued, sometimes even stopping them from working properly for a while (if you have had that vague lameness at the end of a ride that has disappeared after about an hour, there is a good chance there was some muscle fatigue happening).

So the positive message then? We can optimise fatty acid energy pathways in every horse! By training them correctly for their type of breed and for their required work, we can increase the intensity of work within the "battery mode". And we delay the moment the horse needs to tap into the glycogen. If we add a good warm-up to that, and sensible riding like keeping a nice steady pace throughout the ride and slowing down when we have to go up hills we can save valuable fuel for when we really need it.

In our cars we have lovely displays that show us what is happening, this is a little more difficult in our horses unfortunately, so we need to invest some time and effort into knowing what is happening inside of them. Logging can certainly help you become aware of what you are doing. And we have an indicator for intensity: a heart rate monitor. A good few of you use one, but do you use them to their full potential? In the next articles, I will tell you more about how to gauge the effort your horse is making in its work and about optimising the use of your heart rate monitor to learn about your horse's individual boundaries.