Endurance Training

Endurance training is quite a broad sweeping term. It’s often used interchangeably with terms like “aerobic”, “anaerobic”, “strength” and “speed”. This section of the website focuses primarily on aerobic endurance conditioning and the various training methods that have been developed to help athletes reach peak aerobic fitness.

Endurance training is important for many sports – not just the pure distance events like running, swimming and cycling for example. While the type and amount of endurance training will change according to the specific demands of the sport, even some traditional strength and power based games demand a solid aerobic base.


Central to the study of Exercise Physiology is determining the limiting factors in a particular event or activity. In endurance sports those limiting factors are based predominantly around the causes of fatigue. Unfortunately, fatigue is a complex issue and one that is likely to consist of both physical and psychological factors. However, exercise scientists have identified several major causes of exhaustion and research has shown that they can all be manipulated (some to a greater extent than others) with proper training:

VO2 Max
It’s difficult to talk about endurance performance and endurance training without mentioning VO2 max or maximal oxygen uptake. Elite endurance athletes typically have a high VO2 max and for the most part it seems to be genetically determined (1). However, in untrained individuals VO2 max can be improved by as much as 20% (2). A goal of any endurance training program is to help the athlete reach thier genetic upper limit for aerobic power. In athletes with the same or similar value for VO2 max, those who perform best tend to have a superior…

Lactate Threshold
If VO2 max can be seen as an upper limit for aerobic exercise, the lacate threshold determines how much of that ‘aerobic’ upper limit can be used. Numerous terms have been proposed to describe the relationship between blood lactate accumulation and increasing exercise intensity and it’s a subject that generates much debate. what is agreed upon is that training can have a favorable effect on lactate accumulation and when it occurs (3,4), which is associated with improved endurance performance.

Exercise Economy
Two athletes may have the same VO2 max expressed in ml/kg/min and they may have the same lactate threshold expressed as a percentage of their VO2 max. Yet what is far more relevant is the speed or workload at which the athlete is exercising when they reach these two markers. Athletes with a high exercise economy expend less energy (consume less oxygen) at any given workload. As such many researchers believe economy of exercise – be it stride length, swimming technique or body position on a bicycle – is an important contributor to endurance performance (5,6,7).

Substrate Utilization
The oxidative energy system can utilize either fat or carbohydrate to produce energy. However, when exercise intensity is higher (>70% VO2 max), there is a greater reliance on carbohydrate than fat for fuel (8). If and when carbohydrate stores are depleted exercise intensity must reduce accordingly. With training, a greater percentage of fat is used as fuel at any given work rate (8,9,10). This has a sparing effect on carbohydrate allowing a higher intensity to be maintained for longer.

Muscle Fiber Characteristics
Elite endurance athletes exhibit a high proportion of type I muscle fibers (11,12). Type I fibers have a high mitochondrial density and oxidative enzyme capacity which allows the majority of energy production to come from aerobic metabolism. While endurance training doesn’t seem to change fiber types (i.e. type II fibers to type I), the metabolic characteristics of muscle fibers can be altered so that aerobic energy production becomes more efficient (13,14).

Aside from these changes within skeletal muscle what other adaptations does aerobic endurance training elicit?

Other Adaptations to Endurance Training
Following suitable training, the body becomes better able to produce ATP via aerobic metabolism. The adaptations that occur improve oxygen delivery and oxygen utilization, increase the rate of aerobic energy production and the utilization of fat fuel and reduce disturbances in the acid-base balance (13,15,16,17,18).

More specific adaptations are summarized in the table below:



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