Endurance Rides
One aspect of training that I have never been 100% happy about is how we prescribe endurance rides. These rides are crucial to the development of your aerobic and metabolic fitness, whatever cycling discipline you take part in. There has been a lot written about endurance or zone 2 rides and whether they are worth it, especially for time crunched athletes. My opinion has been, and will always be, that progressive, moderate intensity riding is a cornerstone to building the deep aerobic fitness that is the foundation of high performance on a bike. For those of you taking part in long Gran Fondos, Races and Sportives, it is the essential component of your training and normally generates the most weekly training load. Numerous studies have shown that there is a significant increase in efficiency (energy in vs energy out) to be gained from endurance riding and the building of more and better slow twitch muscle fibres.
How do we set endurance rides? Our rides have either been set with power or with heart rate, and I have never been satisfied with either. Riding to a constant power is impractical, unenjoyable and turns you into a neurotic screen gazer. Riding to heart rate is more stable, but introduces all the variables that go with how our heart rate responds to exercise on a day-to-day basis. There are other physiological issues at play here too, which we will dig into.
Added to this, there are way too many methods of prescribing heart rate zones which makes training to heart rate confusing at best. Using different systems, the top of my zone 2 heart rate can be anything from 115bpm to 144bpm. Clearly, this is not helpful.
So I set about to find out more about the physiology of endurance riding by reading some rather dry research papers and also listening to a few podcasts, including one by Kolie more at Empirical Cycling, who takes a very physiological approach to training.
Riding at constant Heart Rate
Lets go for a 3hr ride and aim to keep a constant heart rate of 135bpm+/-5bpm, which we assume is zone 2. At this level of intensity you will be using predominantly your type 1 slow twitch muscles fibres. Muscle fibres are connected with nerves. The fibres and nerves combine to make motor units which contract to produce power. Slow twitch fibres have small motor units, produce less force, are slow to contract and are pretty resistant to fatigue. During the course of a long ride, however, these muscle fibres do fatigue and produce less power. The muscle fibres need energy via oxygenated blood from carbohydrate, fat and protein. As the fibres tire, they need an increasing amount of fuel from oxygen and hence a higher heart rate to transport and deliver it. By riding at a constant heart rate, you are limiting the supply of oxygen to these fatigued muscles and stopping the recruitment of more muscle fibres. If you allow heart rate to increase, you will both increase the supply of oxygen to the fatigued muscles and start to recruit the next largest types of motor unit (the size principle). These larger motor units will produce more force but will need a greater percentage of fuel from carbohydrate. The consumption of carbohydrate is also necessary for more efficient slow twitch muscle fibre function and can be the main reason why heart rate and power decouple on an aerobic ride.
Take Away: Riding at constant heart rate may be limiting the adaption of a more diverse set of muscle motor units and could be limiting adaption, and performance increases.
Riding at constant Power
Lets go for a 3hr ride and aim to keep a constant power of 175w+/-10w which we assume is zone 2. At the start of the ride this might feel like quite a high wattage to stick to but it is the ‘target’ so you stick at it. As the ride progresses, the wattage becomes harder and harder to maintain and your head becomes scrambled with the constant gear changes to keep wattage between 170-180w. You hit some steep hills and you have to stop and get off as the power needed to get over the hill is 250w and something bad will happen if you exceed 180w!
Take Away: Riding at a constant power is impractical for most people and will make you hate cycling!
Riding at constant heart rate may be limiting the adaption of a more diverse set of muscle motor units and could be limiting adaption, and performance increases.
So what to do?
The research suggests that riding to perceived effort might the best way to regulate endurance rides. This is how I have been riding my endurance rides since I started training for Mont Blanc. The pattern of my rides is very predictable. I start out easy at a perceived effort of around 3/10 for the first 20-60 minutes until I feel good, then I build to around 5/10 for the rest of the ride. As my slow twitch muscle fibres fatigue, my heart rate elevates to provide more oxygen to the muscles and the larger motor units start to turn on. From a fuelling point of view, this makes sense as we all experience a need for greater carbohydrate as we ride for longer periods of time. The larger motor units require more CHO and you can also delay slow twitch muscle fatigue with regular CHO intake.
I have now introduced these rides into our coached riders' plans. There are two versions, one where you ride at a constant perceived effort and one where we aim to ride a negative split, riding the first half easier than the second. The key to the success of these rides is to ride with no heart rate or power data on your screen. Personally, I have the map page on and have only ride time data on my screen. By riding to perceived effort, you will be more in tune with how your body feels, will develop better pacing, improve your average speeds and simply enjoy the rides more.
This might all seem to be taking a step backwards to a time when we did not have heart rate monitors and power meters, and it is. We have become too fixated on numbers and have lost some of the art of cycling and gauging efforts. The human body is massively complex and although adaptions are somewhat predictable, they do not happen because you are pushing a precise power number or holding an exact heart rate. Endurance adaptions happen through progressive training consistency in roughly the right areas over the long term.
Q. How much endurance training do I need to do to adapt more and improve?
A. More than you are doing now!
So do yourself a favour and turn the data screen off, go ride at an effort level that feels comfortable, ride for 30 minutes more than normal and enjoy yourself!
I will wager that you will be pleasantly surprised and pleased with the results.
Rob Wakefield / Founder and Level 3 Coach
rob@propello.bike / 07779 136 840 www.propello.bike
