The human body is a complex piece of machinery, and as such, there continues to be vast research undertaken in an attempt to further understand how it functions. The processes in which the human body adapts to exercise is no different; we understand much of how this occurs, but there is still a lot of assumptions and unknowns to explore. The following series of articles in this blog will educate you on the current understandings of how we improve your endurance performance in any continuous, repetitive sport (such as running, riding, swimming, rowing, triathlon etc). We will delve into the current sport science literature to help you understand the processes which occur during endurance training, the best methods to improve your performances, and the core components which create an elite athlete compared to an amateur athlete.
The following components are essential for success in endurance sport. We will provide an overview of each, before exploring deeper into each individual category in subsequent blogs, including how to train each aspect to improve your performances.
1. VO₂ Max
VO₂ max is defined as “the maximum volume of oxygen that the body can take in, transport and utilise in one minute”. It is often referred to as your ‘aerobic capacity’ or ‘aerobic engine’. It encompasses the respiratory system (‘taking in’ oxygen), cardiovascular system (‘transporting’ oxygen) and muscular system (‘utilising’ oxygen).
Put simply, the higher your VO₂ max, the more aerobic energy you can produce without creating fatiguing metabolic by-products such as lactic acid. Athletes who can deliver high volumes of oxygen to their working muscles are able to produce high power outputs for long periods of time without fatiguing. We will further explore VO₂ max, including how to improve it, in our next blog.
2. Lactate Threshold
The Lactate Threshold (LT) is the exercise intensity in which lactate production exactly meets lactate removal, with any small increases of intensity above this point causing quick and significant fatigue. LT is often referred to as ‘Lactate Inflection Point’, ‘anaerobic threshold’, ‘anaerobic capacity’, or ‘functional threshold power’. These terms are used interchangeably and all mean the same thing. Your LT is defined as “the maximum intensity you can exercise at for 45-60 minutes”. Your LT is important because it is the functional component of endurance performance. Nobody can withstand exercise at 100% of their VO₂ max for any length of time, but those who can hold a high percentage of their VO₂ max will be successful in endurance sport.
The average athlete reaches their LT at around 70% of their VO₂ max, whereas elite athletes generally reach LT between 88-94% of their VO₂ max. Even if an amateur and elite athlete both had a VO₂ max of 70ml/kg/min, the average athlete can only hold 49ml/kg/min at LT (70% VO₂ max), whereas the elite can hold 65.8ml/kg/min at LT (94% of VO₂ max). The elite athlete has a much higher functional threshold power, and will be much more successful than the average athlete.
3. Economy of Movement
Movement economy refers to how efficiently the body moves from point A to point B. It encompasses both biomechanics and bioenergetics. Biomechanics is the study of mechanical laws relating to human movement, whereas bioenergetics is the study of the transformation of energy in human movement.
Do you ever notice those athletes who seem to effortlessly glide through the air while they’re running, or smoothly cut through the water while they’re swimming? They have fantastic movement economy. Athletes who have optimal biomechanics during their sport save significant amounts of energy. An efficient runner, for example, may be able to run at 3:30min/km pace using only 55ml/kg/min of oxygen to fuel their performance, where as a fit but inefficient runner may use closer to 65ml/kg/min of oxygen to run at the same pace.
It doesn’t take a scientist to figure out who will win a 5km race if we have two athletes with identical VO₂ max values and identical Lactate Thresholds, one of whom runs efficiently, and one of whom doesn’t. The more efficient runner can hold higher paces at LT because they require less oxygen to fuel performance due to better biomechanics than their opposition.
4. Muscle Fibre Type
There are two types of muscle fibres found in skeletal muscle: slow twitch and fast twitch. Slow twitch fibres are called type I fibres, and are the preferred fibre type for endurance performances.
When compared to fast twitch fibres, slow twitch fibres are:
- Resistant to fatigue
- Have a high oxidative capacity
- Have a high number of aerobic adaptations (mitochondrial density, capillarisation, myoglobin content etc) which help fuel aerobic performance
- Contract slowly but for long periods
Fast twitch fibres, on the other hand, can be split into two categories: Type IIA and Type IIB (type IIB is often referred to as type IIX in some texts).
Type IIB fibres are the explosive, but quickly fatigued, fibres which have a high prevalence in elite sprinters. IIB and type I slow twitch fibres are largely genetically determined, so you are somewhat ‘stuck’ with what your parents hand down to you.
IIA fibres, however, elicit properties from both type I fibres and IIB fibres. These fibres are manipulated by the type of exercise you complete and adapt in accordance. If you complete a lot of endurance training, these fibres become closer to type I slow twitch fibres. If you complete a lot of sprint training, these fibres elicit type IIB characteristics.
Although there is limited room to change your fibre type, performing endurance work will both strengthen your current slow twitch fibres, and adapt your type IIA fibres to elicit slow twitch fibre characteristics. These two training outcomes allow endurance athletes to perform long distances without muscular fatigue, and are crucial in the longer endurance events lasting more than 2 hours.
5. Heat Load and Dehydration
Heat load is the effect of internal and external factors on your core body temperature. The obvious external factor is the ambient temperature caused by weather conditions and the sun. You will overheat quicker on a 40⁰C than a 20⁰C day. The major internal factor is the heat produced as a result of energy production and muscular contraction. Humans are very inefficient organisms, and upwards of 70% of our energy production is lost as heat.
Dehydration contributes to heat load stress and is extremely detrimental to performance. A loss of 2% body weight as a result of fluid content loss will negatively affect your performance. Hydration is responsible for thermoregulation (‘cooling’ the body), blood plasma volume (the blood’s water content), and muscular contraction (via the use of electrolytes), just to name a few.
As a result, some of the effects of dehydration include:
- Heat stress
- Blood thickening
- Muscle cramp
- Inhibited sweating, causing core body temperature to rise further
- Heat exhaustion
Athletes who have increased core body temperature will re-divert blood to the surface of the skin to initiate sweating. If blood is being sent to the skin instead of the muscles, we have less oxygen available at the muscles for aerobic energy production, resulting in us relying more on anaerobic energy pathways which cause lactic acid and fatigue. Heart rate increases to counteract this deficit by circulating more oxygen, but it can only do so much.
Athletes who stay hydrated and acclimatise properly to weather conditions will perform better than athletes who don’t, particularly when the length of the event becomes longer.
The body needs food like a car needs petrol. Nutrients can be split into macronutrients and micronutrients. Macronutrients include carbohydrate, fat and protein, which make up the majority of our diet and provide us with usable energy. Micronutrients include everything else (such as vitamins and minerals) and are required in smaller doses.
Consuming enough calories, and with an appropriate proportion of macronutrients, will affect your endurance performance, particularly during events lasting longer than 2 hours. Carbohydrates are the body’s preferred fuel source above around 65% of VO₂ max, as they require less oxygen to break down to produce energy compared to fat or protein. This means carbohydrates can produce energy more quickly. As a result, athletes who consume adequate carbohydrates and implement an appropriate carbohydrate loading program prior to a long distance event, as well as consuming appropriate nutrition during training/race day, will be able to work harder for longer than those who do not. Ever wonder why you ‘bonk’ or hit the wall after 2-3 hours of hard exercise? You have depleted your muscle glycogen stores (carb stores) and are now resorting to fat stores for energy production. As mentioned above, fat requires MORE OXYGEN to break down to release energy, so your body has to slow down to give it adequate time to fuel performance. Athletes who consume adequate carbohydrate avoid bonking and will not have to slow down during a race or training.
Recovery is often the forgotten component of endurance performance. We constantly see sub-standard performances from athletes because they are overtrained and do not recover adequately. Let me say this once: ALL of your training adaptations occur AFTER your session, during the recovery stage. Training is necessary to elicit the protein and gene expression required to stimulate aerobic adaptations, but it takes time and recovery for this expression to create new organelles responsible for improving your aerobic capacity. If you do back-to-back-to-back hard sessions, you WILL NOT elicit any more gene or protein expression, and you will in fact hinder your body’s ability to adapt and grow new organelles. You can’t grow a flower overnight, regardless of how much you water it. Over-watering it, however, can slow and inhibit its ability to grow. You also can’t grow new mitochondria (the organelle solely responsible for aerobic energy production) overnight, regardless of how many training sessions you complete. Overtraining, however, will slow the adaptation process. Be patient and stick to a progressive training program which includes adequate recovery.
This is not even mentioning the obvious and well-known effects of overtraining, which include muscle breakdown, illness, injury, psychological burnout and poor performance.
Athletes (or their coaches) who understand this science are guaranteed to perform better than their less educated counterparts.
Thanks for reading and please stay tuned for next week’s blog which will discuss everything you need to know about VO₂ max and how to improve it!
Written by Luke McIlroy – Director of Sport Science at METS Performance Consulting
BEx&SpSci, ESSAM, AES