I didn't do any.....
Do you need to do any speed training for Marathon des Sables? Good question. I would hesitantly say no, if your aim is to "just" get round. If you want a top 200 place then you probably need to incorporate some speed work into your training sessions.
But what on earth does speed training mean in the context of something like the Marathon des Sables? You can't tackle it like you would a 10km or even a marathon where the aim may be to get a pb.
I'm open to suggestions on this one, but here's what a bit of research told me:
It helps improve your running economy
This means how much oxygen you use during exercise. If you are economical, you will need less oxygen. Speed work helps improve your running economy.
It increases your maximal aerobic capacity (VO2 max)
Your VO2 max is the maximum amount of oxygen your body can use during exercise. So the higher yours is, the faster you can go without your body feeling stressed.
It helps you use lactate more effectively
Lactate is part of lactate acid. With speed training, it can be used as energy rather than converting to lactate acid.
It helps increase your flexibility
Done jointly with stretching exercises, speed work can help improve your flexibility as it works your muscles and joints through a greater range of motion.
So ultimately, speed work helps ultra runners run faster and more efficiently for longer. It helps improve your cardiovascular efficiency, muscle strength, flexibility and biomechanics. It also helps break up ultra training, which, lets be honest, can get dull plodding out those endless miles week after week.
How to include speed work into your ultra training?
Plan a speed workout the day before a long run. Your legs will be fatigued already, so training on already-tired legs will help you maintain form during multiday ultras where you will be doing this during the race.
Speed sessions should be centred on quality shorter runs (up to 10 miles), nothing longer. Start with fartlek workouts.
Then introduce speed drills e.g. 10s sprint up a hill. Rest 30s. Repeat 10 times.
High intensity training sessions are also recommended.