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Rethinking Aerobic Development for 14U Swimmers: A Contrarian Approach

May 26, 20247 min read

Rethinking Aerobic Development for 14U Swimmers: A Contrarian Approach

In the world of youth swimming, conventional wisdom often emphasizes long, steady-state aerobic sets to build endurance. However, this approach may not be the most effective or sustainable way to develop young swimmers. As an expert swim coach and advocate for alternative training methods, I propose a contrarian view: developing aerobic capacity through short, fast repetitions, focusing on technique, and prioritizing speed development over long swim practices.

The Physiological Basis of Short, Fast Repetitions

Traditional aerobic training for youth swimmers typically involves long sets at moderate intensity, aimed at improving cardiovascular endurance. However, young swimmers can develop aerobic capacity more effectively through high-intensity interval training (HIIT), characterized by short but fast repetitions. This method leverages the principles of anaerobic metabolism, where the body operates at a high intensity, generating energy without relying on oxygen.

Muscle Fiber Recruitment

Short, fast repetitions engage fast-twitch muscle fibers, which are crucial for explosive movements. Over time, these fibers become more efficient at utilizing oxygen, enhancing both aerobic and anaerobic capacity. Research shows that high-intensity training can improve the oxidative capacity of fast-twitch fibers, leading to greater endurance performance (Burgomaster et al., 2008).

Increased Mitochondrial Density

High-intensity efforts stimulate mitochondrial biogenesis, increasing the number and efficiency of mitochondria in muscle cells. This boosts the body's ability to produce energy aerobically during both high-intensity and prolonged efforts. A study by Gibala et al. (2006) demonstrated that short bursts of intense exercise significantly increase mitochondrial content in skeletal muscles, enhancing overall aerobic capacity.

Enhanced Lactate Threshold

Frequent exposure to high-intensity efforts improves the body's ability to buffer and clear lactate, delaying the onset of fatigue and allowing swimmers to sustain higher intensities for longer periods. Studies have shown that high-intensity training can increase lactate threshold, improving performance in both short and long events (Weston et al., 1997).

Prioritizing Technique and Speed Development

For young swimmers, technique and speed are the foundations of successful performance. Ensuring swimmers can move efficiently through the water is paramount. Efficient technique reduces drag and energy expenditure, allowing swimmers to maintain higher speeds with less effort. This is particularly crucial for younger swimmers who are still developing their strength and coordination.

Speed Reserve: The Key to Longer Distances

Speed reserve refers to the difference between a swimmer's maximum sprinting speed and their speed during longer, sustained efforts. Developing a substantial speed reserve is essential for improving performance in longer distances. When a swimmer has a higher maximum speed, they can sustain a faster pace more comfortably over longer distances.

Neuromuscular Efficiency

Training at high speeds enhances neuromuscular coordination, allowing swimmers to maintain technique and efficiency even as they fatigue during longer races. Improved neuromuscular efficiency translates to smoother and more powerful strokes, essential for sustaining speed over longer distances (Ross et al., 2001).

Economy of Movement

A swimmer with a higher speed reserve can swim at a given pace with less relative effort, conserving energy for the latter stages of a race. This concept, known as running economy in track and field, applies similarly in swimming, where efficiency is key to performance (Saunders et al., 2004).

Psychological Confidence

Knowing they possess a higher speed reserve boosts a swimmer's confidence, allowing them to push harder and maintain higher intensities during competition. This psychological edge can be the difference between winning and losing in closely contested races (Jones & Carter, 2000).

Speed Progression: An Example of Speed Reserve in Action

To achieve significant performance improvements, swimmers need to develop a speed base instead of an aerobic base. This concept is crucial for understanding how speed reserve influences performance in longer distances. Swimmers must achieve certain times in shorter distances before they can excel in longer events. This progression ensures that they have the necessary speed reserve to sustain faster paces over longer distances. Lets look at 2 examples:

10U Swimmer 1 Progression to 200 Free

25 Free: 16.5 to 13.50 (3sec)

50 Free: 33.37 to 29.10 (4.27sec)

100 Free: 1:14.71 to 1:04.97 (9.74sec)

200 Free: 2:44.83 to 2:23.34 (21.49sec)

10U Swimmer 2 Progression to 200 IM

50 Fly: 36.55 to 32.09 (4.46sec)

50 Back: 39.88 to 35.61 (4.27sec)

50 Breast: 44.84 to 41.30 (3.54sec)

50 Free: 32.86 to 29.95 (2.91sec)

200 IM: 2:57.02 to 2:38.68 (18.34sec)

While working with both of these swimmers we work almost exclusively on improving top end speed to improve across all event distances. Both of these swimmers did not do a single repeat over 100 yards in practice and their longest practice of the season was 2400 yards. Previously both swimmers regularly were completing practices that were over 3000 yards with repeats over 200 yards in practice. Neither swimmer significantly fell off the pace of the other swimmers and closed the final 50 close to or faster than the swimmers that finished with similar final times. These are just 2 examples from this past season, as the average improvement of swimmers from this group was 15.2% across all events significantly above the average of 7.2% for this age group.

By developing a speed base, swimmers build a substantial speed reserve, allowing them to perform better in longer distances. This approach ensures that swimmers do not merely rely on aerobic capacity but leverage their maximum speed to enhance performance across all events.

The Role of Longer Swims

While the emphasis is on short, fast repetitions, longer swims do have their place in training. However, these should be done at easy paces with plenty of rest to ensure proper technique is maintained. These sets should be used sparingly and should be age-appropriate, ensuring they contribute to overall development without compromising speed and technique.

Avoiding Threshold Swimming

Overuse of threshold swimming—moderate-intensity, prolonged efforts—can be detrimental. This type of training diminishes the body's ability to produce force and contributes to high attrition rates in the sport. Young swimmers subjected to excessive threshold training often experience burnout, both physically and mentally, leading to an alarming rate of dropout.

A study by Seiler and Kjerland (2006) found that high-volume, moderate-intensity training can lead to reduced performance in elite athletes, as it fails to develop the necessary high-intensity adaptations. This supports the argument that excessive threshold training is counterproductive, especially for young swimmers.


By focusing on short, fast repetitions, prioritizing technique, and understanding the importance of speed reserve, coaches can foster a more effective and sustainable approach to aerobic development in 14U swimmers. This method not only enhances performance across all distances but also promotes long-term engagement and enjoyment in the sport.


- Burgomaster, K. A., Hughes, S. C., Heigenhauser, G. J., Bradwell, S. N., & Gibala, M. J. (2008). Six sessions of sprint interval training increases muscle oxidative potential and cycle endurance capacity in humans. Journal of Applied Physiology, 98(6), 1985-1990.

- Gibala, M. J., Little, J. P., van Essen, M., Wilkin, G. P., Burgomaster, K. A., Safdar, A., ... & Tarnopolsky, M. A. (2006). Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance. Journal of Physiology, 575(3), 901-911.

- Weston, A. R., Myburgh, K. H., Lindsay, F. H., Dennis, S. C., & Noakes, T. D. (1997). Skeletal muscle buffering capacity and endurance performance after high-intensity interval training by well-trained cyclists. European Journal of Applied Physiology and Occupational Physiology, 75(1), 7-13.

- Ross, A., Leveritt, M., & Riek, S. (2001). Neural influences on sprint running: training adaptations and acute responses. Sports Medicine, 31(6), 409-425.

- Saunders, P. U., Pyne, D. B., Telford, R. D., & Hawley, J. A. (2004). Factors affecting running economy in trained distance runners. Sports Medicine, 34(7), 465-485.

- Jones, A. M., & Carter, H. (2000). The effect of endurance training on parameters of aerobic fitness. Sports Medicine, 29(6), 373-386.

- Seiler, S., & Kjerland, G. O. (2006). Quantifying training intensity distribution in elite endurance athletes: is there evidence for an “optimal” distribution? Scandinavian Journal of Medicine & Science in Sports, 16(1), 49-56.

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