Is Circuit Training an Aerobic Activity?

First let’s show the difference in aerobic and anaerobic activity.

Aerobic Activity:

– Aerobic activity is defined as using fuel in the presence of oxygen for energy.

– Aerobic exercise such as running or bicycling, use all three pathways to produce ATP:  Phosphagen (about 10 seconds), Anaerobic Glycolysis (about 2 minutes, before steady state is achieved), and Aerobic Glycolysis or Oxidative (after phosphagen and anaerobic systems have fatigued.)

-Aerobic glycolysis uses aerobic respiration to produce ATP via fatty acids and glucose breakdown.  This pathway occurs in the mitochondria of the cell and is used to generate energy in sustained activities.

Anaerobic activity:

Anaerobic energy is produced from stored ATP. The process requires no oxygen, and it does not have to be carried out in the presence of oxygen as its only by-product is lactic acid. Lactic acid accumulates and causes fatigue during high-intensity exercises such as weightlifting or sprinting; hence why these types of sports require short bursts of intense effort rather than aerobic exercise which requires a lower intensity over longer periods of time. This type of training results in the development of strength and power, but not endurance. The energy processes during anaerobic bouts are Phosphagen and Anaerobic glycolysis or lactic acid system (LAS), which produces ATP through metabolism without oxygen present.

Circuit training is often mistakenly thought of as an aerobic activity. Although circuit training provides cardiovascular benefits, it is not aerobic in nature. Running, walking, and bicycling are aerobic activities because they require oxygen to produce energy. Circuit training is not aerobic because it does not use oxygen to generate the energy required for the activity. It relies on short bursts of anaerobic activity followed by brief rest periods that allow for recovery before the next burst of activity can occur. Oxygen is used in the recovery, not to produce energy. Also, a requirement for aerobic activity is that the same muscle must undergo a contract and release cycle, repetitively over a specified period of time, usually at least 20 minutes.  In circuit training, as in a series of 10 weight training exercises, different muscle groups are exercised. In the activity itself within each exercise, the exercise is performed with a concentric and eccentric contraction. The muscle remains contracted in a constant state without full release, even though it is undergoing a shortening and lengthening.  The release happens upon discontinuation of the set; therefore, allowing blood flow to flood to the muscle being exercised in the recovery cycle.

Despite the confusion, circuit training like any other type of weightlifting is great for cardiovascular benefit; not only strengthening your heart but providing a myriad of other benefits that make it the most important activity you can do.