Is strength training anaerobic exercise?

There is actually no absolute yes or no to this question. Most of the strength training we have daily contact with belongs to the category of anaerobic exercise, but there are also some low-intensity and continuous strength training that are aerobic-dominated.

When I first got into fitness, I defaulted to strength training = anaerobic. Later, after practicing for five or six years, and after going through many pitfalls, I realized that it really depends on the specific situation. For example, when you are training for a PR with a heavy weight, like when I was doing a 140kg deadlift last month, I held my breath during the whole process, which lasted less than 3 seconds. After the pull, I took half a minute to slow down and let go of my breath. My muscles were sore for several days. At this time, the energy supply completely relies on the phosphagen system, which does not require the participation of oxygen. It is a typical anaerobic exercise. Even if you usually do muscle hypertrophy training, a set of 12 squats with a 1-minute rest in between, the oxygen supply during each set simply cannot keep up with the consumption, and it relies mainly on glycolysis for energy, which is still in the anaerobic category. Many people can't walk the next day after training their legs. This is the soreness caused by the delayed accumulation of lactic acid produced by anaerobic metabolism.

But don’t be fooled. When I was losing weight last summer, I tried 40 minutes of continuous light-weight circuit strength training. I used small dumbbells of 1kg and 2.5kg. I did kettlebell swings, dumbbell shoulder presses, and bent-over rowing movements. I did 20 times in each group, with only 20 rests in between. Seconds, I could maintain even breathing throughout the whole process, and I never felt suffocated or out of breath. The oxygen uptake measured by the sports watch I was wearing at that time has been stable at about 62% of my maximum oxygen uptake. At this time, aerobic energy supply is actually dominant. Would you say that the strength training at this time is considered anaerobic? It's obviously not right.

In fact, no one in the fitness circle or sports science circles directly equates strength training with anaerobic exercise. The core of judgment is never whether you use dumbbells or barbells for resistance, but the intensity and dominant energy supply system during exercise - just like you cannot say that running is all aerobic, and the 100-meter sprint is also a standard anaerobic exercise. The same logic applies to strength training, and there is no need to be framed by rigid classifications.