The Impact of Interval Training on the Anaerobic and Aerobic Systems

Depending on the interval training (IT) workload and intensity, the human body requires both aerobic and anaerobic energy to perform physical work (Clark, Sutton, & Lucett, 2015; Beyranvand, 2017). Besides the food and nutrient intake which provide working energy in the form of adenosine triphosphate (ATP), both the anaerobic (without oxygen) and aerobic (with oxygen) systems utilize ATP as the main energy source for work production. The pathway for each energy system, however, is different. For example, when the workload is at a low intensity, the predominant aerobic energy system will oxidize carbohydrates and fats to make ATP to supply working demand of the muscles (Clark et al., 2015; Beyranvand, 2017). 

​In contrast, the anaerobic system pathway provides ATP energy to perform a high-intensity physical work, but without the need of oxygen (Clark et al., 2015). Although very short in duration, at about 10-15 seconds, the anaerobic system is activated when the aerobic system could no longer provide enough oxygen to the mitochondria of the working muscle (Clark et al., 2015). For instance, as the physical workload and intensity increase in repeated short sprints, and the supply of oxygen could not meet the working demand of the working leg muscles, the body has to rely on the anaerobic system to continue the performance of the physical work of the sprinting (Clark et al., 2015). Surprisingly, the aerobic and anaerobic energy systems are constantly working together for either low-intensity or high-intensity physical work of the muscles (Ziemann et al., 2011). 

Knowing how the human body energy systems interrelated, interval training seems to provide the most impact to improve the aerobic and anaerobic systems, because every sport uses a combination, straddling between the two energy systems (Clark et al., 2015). In one randomized study by Beyranvand (2017), sprint interval training (SIT) for two sessions per week, for four weeks, has shown to increase VO2max in 16 trained female futsal players. Even with such a low volume of IT, these trained female athletes improved 5.8% VO2max (Beyranvand, 2017). The intervention of SIT in this study recorded similar improvement in enzyme activities of aerobic and anaerobic metabolism, specifically with the improvement of anaerobic metabolism from 3% to 10%.
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In a latest similar study, Jordan et al (2018) also performed SIT, but with a vertical treadmill to assess the aerobic and anaerobic running ability of 30 males (22 ± 4 years), active students, who play intermittent sprint-type sports. Unlike the previous study, this study lasted six weeks, 3 sessions per week, each session had the participants to run 4-6, 30 seconds sprints. Similar to the other study, the VO2max increased by 6.2% in the vertical treadmill run, while the control group VO2max increased by 5.5% (Jordan et al., 2018). 

There is a consensus that interval training, especially high-intensity interval training (HIIT), is the best possible way to improve aerobic capacity (Ziemann et al., 2011; Clark et al., 2015). The impact of IT on the human energy systems—aerobic and anaerobic—is beneficial not only to elite athletes, but also the general population. Maintaining weight or gaining a higher an anaerobic threshold, interval training works within the heart rate and training zones to utilize the body energy systems to perform optimal physical performance (Clark et al., 2015). Thus, because the human body energy systems work together, interval training will provide the best total aerobic and anaerobic solution, not an isolate one (Cavar et al., 2019). But, like everything else improvement takes time and steady commitment, so start out interval training from a base aerobic base first (Clark et al., 2015).
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References
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Beyranvand, F. (2017). Sprint interval training improves aerobic and anaerobic power in trained female futsal players. International Journal of Kinesiology and Sports Science, 5(2), 43. doi:10.7575/aiac.ijkss.v.5n.2p.43

Cavar, M., Marsic, T., Corluka, M., Culjak, Z., Zovko, I. C., Müller, A., . . . Hofmann, P. (2019). Effects of 6 weeks of different high-intensity interval and moderate continuous training on aerobic and anaerobic performance. Journal of Strength and Conditioning Research, 33(1), 44-56. doi:10.1519/jsc.0000000000002798

Clark, M., Sutton, B. G., & Lucett, S. (2015). NASM essentials of sports performance training. Burlington, MA: Jones & Bartlett Learning.

Jordan, A. R., Claxton, D., Purvis, A., Barnes, A., & Fysh, M. (2018). Sprint interval training on the vertical treadmill improves aerobic and anaerobic running performance. Journal of Exercise Rehabilitation, 14(1), 106-112. doi:10.12965/jer.1835122.561

Ziemann, E., Grzywacz, T., Łuszczyk, M., Laskowski, R., Olek, R. A., & Gibson, A. L. (2011). Aerobic and anaerobic changes with high-intensity interval training in active college-aged men. Journal of Strength and Conditioning Research, 25(4), 1104-1112. doi:10.1519/jsc.0b013e3181d09ec9