Cross-country skiing is undoubtedly an endurance sport, with long-distance skiing being one of its extremes. For skiers, endurance is a term we all know well, but do we really understand it? Have we ever taken the time to think about what the word “endurance” actually means? No worries, because this article explains what endurance means physiologically.

Skiing is an endurance sport, but what does the concept of endurance entail?

Endurance in sports refers to the ability to sustain a specific activity for a prolonged period, such as running, cycling, swimming, rowing, and cross-country skiing, where submaximal effort must be maintained for as long as possible. Naturally, psychology plays a crucial role in the success of endurance sports.

According to Maastohiihto.com, the primary factor limiting endurance exercise is fatigue. When fatigue reaches a certain point, the athlete’s pace slows down. The precise point at which fatigue limits performance (tolerance level) varies, and some athletes can endure much more fatigue than others. Although genetics and mental toughness contribute to fatigue tolerance, it can also be trained.

Fatigue is influenced by several factors, such as cardiovascular endurance (heart and vascular efficiency), muscular endurance, aerobic endurance, anaerobic endurance, muscle strength, and mental resilience. These factors are not unfamiliar concepts to those who practice endurance sports and skiing.

Cardiovascular endurance refers to the ability of our lungs, heart, and circulatory system to transport oxygen during prolonged exercise. Muscular endurance is the ability of a muscle or group of muscles to sustain force over time. An athlete with good muscular endurance can repeat muscle contractions without fatigue. These two fundamental aspects of endurance are the main components of an endurance athlete.

Muscles produce energy through aerobic (requires oxygen) and anaerobic (does not require oxygen) metabolism. During endurance sports, we meet most of our energy needs through aerobic metabolism. However, as exercise intensity increases (such as in races or during power and interval training), anaerobic metabolism becomes relatively more important. At low intensities, we primarily recruit slow-twitch muscle fibres. As exercise intensity increases, activation of fast-twitch muscle fibres accelerates.

Aerobic endurance refers to the ability to produce energy through aerobic metabolism. The limiting factor here is the ability to absorb, transport, and utilize oxygen in energy production. Aerobic capacity can be measured by lung efficiency in inhaling oxygen and absorbing it, muscle efficiency, and especially the efficiency of mitochondria in producing energy through aerobic metabolism, efficient oxygen transport through our bloodstream via the heart, and our circulatory system and muscles’ ability to extract oxygen from the blood.

Anaerobic endurance refers to our ability to work in situations where anaerobic energy systems play an increased role in energy metabolism. The term anaerobic means “without oxygen.” As exercise intensity increases, the additional energy demand (power output) is met by fast-twitch muscle fibres, leading to an increase in anaerobic metabolism.

Although anaerobic metabolism can produce energy much faster, we always compromise when using it. Firstly, it leads to an increase in hydrogen ions in our body, increasing muscle acidity and potentially disrupting exercise performance. Secondly, it rapidly depletes muscle glycogen stores. Nevertheless, developing anaerobic endurance is paramount in endurance sports like skiing. In fact, it is essential for maximizing performance potential in competitions, even though aerobic metabolism is our primary energy system.

Muscle strength is our ability to exert force during a single maximal effort. It differs from muscular endurance because muscle strength is not time dependent. Muscular endurance refers to sustained force over time, whereas muscle strength relates to maximal force that can be exerted in a single effort. An athlete with greater maximal force finds it easier to work at the maximal intensities required in endurance sports. Developing muscle strength is crucial without lifting weight, which is a disadvantage in the performance itself.

Mental resilience – known in Finnish as “sisu” – is a key component influencing overall performance. Endurance athletes have the ability to resist feelings of fatigue, which would otherwise require them to slow down or stop during tough races or challenging training sessions. Mental resilience develops over time as we repeatedly expose ourselves to fatigue during training, although it is also partly an innate characteristic.

All athletes require some level of aerobic endurance. They also need to develop sport-specific endurance. Sufficient endurance base is essential for long-term development regardless of the sport. It involves training all components affecting performance. Sport-specific endurance refers to developing specific targets required by the athlete’s chosen sport.

It goes without saying that a skier’s basic endurance training, especially during summer, includes a lot of low-intensity, aerobic training for many hours to develop capillaries and increase muscular endurance. As fitness improves and with a solid aerobic foundation, speeds can also be increased during basic runs and varied to avoid excessive stagnation – especially in sport-specific training with roller skis.

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