Cross-country skiing is, without a doubt, an endurance sport, and long distance skiing is an extreme form of endurance sport. For skiers, endurance is a term that we are all very familiar with, or are we? Have we ever taken time to think about it in more detail? Perhaps not, but no worries as this article will tell you the true meaning of endurance in sports. 

In sport, endurance is the ability to sustain a specific activity, such as running, cycling, swimming, rowing, and cross-country skiing, for a prolonged period. The fundamental requirement for any endurance sport is the ability to sustain a submaximal work rate for a prolonged period. Naturally, psychology plays a pivotal part in success in endurance sports. 

The primary factor that limits endurance exercise is fatigue. When fatigue reaches a certain point, an athlete’s work rate decreases. The exact point where fatigue limits performance (tolerance level) varies, and some athletes can endure much greater levels of fatigue than others. While genetics and mental toughness contribute to fatigue tolerance, it is highly trainable.

Fatigue is affected by a number of factors such as cardiovascular endurance, muscular endurance, aerobic endurance, anaerobic endurance, muscle strength and mental toughness. All factors are certainly no strangers to anyone doing endurance sports, and in our case long distance skiing.

Cardiovascular endurance refers to the capacity of our lungs, heart, and circulatory system to transport oxygen during prolonged exercise. Muscular endurance is the ability of a muscle, or a group of muscles, to exert a force for a prolonged period. An athlete with good muscular endurance can repeat a series of muscular contractions without fatiguing. These two types of endurance are key components of fitness.

Muscles produce energy through aerobic (requiring oxygen) and anaerobic (not requiring oxygen) metabolism. During endurance sports, we meet most of our energy needs through aerobic metabolism. However, as exercise intensity rises (such as during high-intensity interval training) anaerobic metabolism becomes proportionally more important. At low intensities we recruit primarily slow twitch muscle fibers. However, as exercise intensity increases, there’s a shift towards increased recruitment of fast twitch muscle fibers. 

Aerobic endurance refers to the capacity to produce energy using aerobic metabolism. The limiting factor here is the ability to absorb, transport and utilize oxygen for energy production. The aerobic capacity can be measured by the efficiency of the lungs to inhale and absorb oxygen, the efficiency of our muscles, and specifically the mitochondria, to produce energy via aerobic metabolism, the efficient transportation of oxygenated blood around our body via our heart and circulatory systems and the ability of the muscles to absorb oxygen from the blood.

Anaerobic endurance refers to our ability to perform work in situations where anaerobic energy systems are playing an increased role in energy metabolism. The term anaerobic means “without oxygen”. When exercise intensity increases, the additional energy requirements (force production) are met by fast twitch muscle fibers, which leads to an increase in anaerobic metabolism.

Although anaerobic metabolism can supply energy at much faster rates, there is a trade-off. First, it leads to a buildup of hydrogen ions. This increases muscle acidity and can interfere with exercise performance. Second, it rapidly diminishes the key stores of muscle glycogen. Despite this, the development of anaerobic endurance is important in many endurance events such as skiing. In fact, it is necessary for maximizing performance potential in endurance events, even where aerobic metabolism is the principal energy system.

Muscle strength is our ability to exert force during a single maximal effort. It differs from muscular power because it is not time dependent – power refers to force exerted over time, whereas muscular strength relates to the maximum force you can exert. An athlete with greater strength will find it easier to work at the sub-maximal intensities required during endurance sport. The key is to improve strength without significantly affecting bodyweight.

Mental toughness – often referred to as ‘grit’ – is another key area that influences performance. Endurance athletes need the ability to resist the sensation of fatigue that cries out to us “slow down” or “stop” during endurance events or challenging training sessions. We develop mental toughness over time, through exposure to fatigue during training sessions.

All athletes require a level of general endurance. They also need to develop event specific endurance. General endurance is essential for long-term development. It involves training all the components that affect performance. Event specific endurance refers to the development of the specific endurance requirements for the athlete’s chosen event.