What are the main limiting factors for endurance athletes?

We explain why heart function is more important than lung capacity, and what other factors like technique and genetics might also be holding you back on race day

Coach Joe Beer riding hard

Although a large lung capacity isn’t a bad thing, it’s not considered to be a major determinant of performance.

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The heart is more important, with endurance athletes developing larger, stronger and more efficient hearts through training, which enables them to pump more blood to the working muscles. This cardiac output is a function of stroke volume and heart rate. Obviously, there’s a point where the heart can’t adapt any further and a ceiling in oxygen delivery is reached.

In addition to a high cardiac output, endurance athletes have well-developed circulatory systems, muscle cells that are greater in volume and size, and high aerobic enzyme activity. All of these cardiovascular adaptations result in a high VO2max. Cardiac output is the largest limiting factor in VO2max and all the other factors are smaller limiters with less impact. Ultimately, however, performance is judged by finishing time, not VO2max. Therefore, we need to consider factors that affect speed and resistance to fatigue.

These include biomechanical factors, neuromuscular fatigue and how all the systems of the body interact together. All these factors are influenced by race distance and each of the triathlon disciplines. They’re too complex to address here so perhaps answering the following question will be more helpful: what are the limiting factors in your performance?

What limits on your performance will be influenced by your unique genetics, physiology, training history and technical ability. For example, if you can’t swim 1.5km in under 20mins, then you’ll find that technique is the major limiting factor. The efficiency of your muscles becomes more important in longer races, which is why athletes with poorer efficiency are more suited to shorter races.

Ironman ability: is it in your genes?

Triathlon training and racing is mentally tough though, and in my experience the mind and behaviour of an athlete ultimately determines whether they’ll realise their full physical potential or not. This means being able to keep going and pushing through the pain barrier when the suffering begins. It also means having the focus to avoid time penalties or silly mistakes in the heat of the race.

Discipline in training is critical, which means sticking to the correct pace, taking the prescribed rests and not racing teammates (unless that’s the intention). Only by understanding the psychological factors that limit your performance, will you come close to discovering what your physical ones are too.

(Image: Jonny Gawler)

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