3.3 Exercise economy

Being more economical during endurance exercise should lead to a reduction in the amount of energy used for a given power output, and therefore postpone the onset of fatigue. In running, for example, if two athletes have the same VO2 max but one has a better running economy, that athlete would use less energy when running at the same speed and should therefore be able to run for longer, or faster, for the same power output. In Activity 3 you’ll investigate running economy further and how you can improve it.

Activity 3

Timing: Allow 15 minutes for this activity

Watch Video 1, which explains the factors that determine running economy and how these may be improved. While you watch Video 1, note down the factors that you as an athlete or coach may be able to influence – for example, if working with a marathon runner, how could you improve their running economy?

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Transcript: Video 1 Improve your running economy

NARRATOR

VO2 max is the maximal amount of oxygen that can be consumed and utilised during maximal exercise. Economy refers to how much oxygen is consumed for a given speed and is, arguably, a more important measure.

The problem with VO2 max as the holy grail of performance is that most athletes don't perform maximally the entire duration of their events. In fact, it has been found that elite marathon runners operate between 80% to 90% of their VO2 max for the duration of their event.

Economy in sports can be likened to fuel economy in a car. What we want to know is how much fuel that car uses per kilometre, or in this case, how much oxygen the athlete consumes at a given pace. An athlete's economy is affected by many factors including genetics, fibre-type distribution, and in particular, biomechanics and anthropometry.

A 2004 review article on running economy suggested that the following factors are important for running economy. Height-- on general, the smaller, the better for men and taller for women. Somatotype-- ectomorphs, or those with long limbs relative to height with lean bodies, narrow hips, and shoulders, are likely to have higher economy. Narrow pelvis and legs with weight distributed close to the hips and small feet-- less mass at the end of the limb reduces the moment of inertia and improves economy.

Light shoes with good cushioning to reduce rotating mass but absorb force and cushion the landing. A freely chosen stride length that is neither too short nor too long. Minimal movement of the arms, but at least some movement. A more acute knee angle during the swing phase at higher speeds-- i.e., a more flexed knee in the leg that is not planted but is swinging through with the next step-- and low vertical oscillation of the centre of mass-- essentially, the area surrounding the hips has to stay level.

Obviously, some of these factors are inherited and cannot be changed while others can be modified. In general, Kenyan and Ethiopian runners tend to have more of the unmodifiable factors such as relatively long legs compared to height, low body fat, narrow hips, and small calves.

Any athlete's economy can be improved by reducing body fat, choosing correct footwear that is light and shock-absorbent, and by improving running technique. By far, the most effective way to improve economy seems to be by undertaking resistance training, and in particular, plyometric training.

While running and just before landing your foot, the body pre-activates the muscles in order to absorb force and reduce the amount of eccentric or lengthening contraction encountered. This pre-activation leads to an increased concentric contraction to propel the runner forward. This is known as the stretch-shortening cycle. In general, strength training has been shown to improve the function of the neuromuscular system and enhances recruitment of motor units that will assist in these pre-activation.

The most effective method of training to improve running economy appears to be plyometric training. Plyometric exercises are commonly characterised by jumping and bounding and include examples such as depth jumps, weighted landings, skips, and hops. This training is designed to maximise the use of the stretch-shortening cycle. Numerous articles have shown that this type of training improves running economy by improving musculotendinous stiffness which, in effect, creates more elastic return and, ultimately, higher running speeds.

In summary, economy is vitally important in running performance and has been shown to be a major determinant of running performance in prolonged endurance events. Very little can be done to alter the anthropometric characteristics in an individual, but economy can be improved by technique training, choosing your correct footwear, and by incorporating plyometric training into your routine. Thanks for watching.

End transcript: Video 1 Improve your running economy

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Discussion

Running economy is determined by multiple predetermined factors. However, there are some factors that can be trained for. A marathon runner may improve their running economy by reducing body fat (if they need to), wearing lighter shoes with good cushioning, and improve their biomechanics (in terms of freely chosen stride length, minimal movement at the arms, more acute knee angle, and low bouncing when running). Additionally, by including resistance and plyometric training in their training programme they can enhance their running economy by improving the function of her neuromuscular system.

For longer-duration events where fatigue plays a relatively larger role, lactate threshold and running economy become relatively more important. However, in shorter-duration endurance events (such as a 5 km run), where fatigue plays a smaller role, the VO2 max and anaerobic capacity of athletes should correlate more accurately with performance.