Hard intervals may improve fitness more than steady exercise; one cycling study reported gains of up to 46% in six months. Bicycling’s article reviews ways to raise [VO2 Max]( /biomarkers/cardiovascular/vo2-max), a measure of how much oxygen your body can use during hard exercise. For the VO2 Max Training community, its clearest takeaway is that hard intervals can help beyond steady exercise alone. The article cites a study of 40 moderately trained people. It found that High-Intensity Interval Training (HIIT) improved VO2 Max more than long, steady runs. This means alternating hard efforts with easier recovery periods. The excerpt does not give the size of that difference. A separate study of cyclists reported improvements of up to 46% over six months. People in that study did interval sessions three times per week. Up to 46% is not an average or a promise. The excerpt does not show the full range of results. It also leaves out details such as interval length and starting fitness. That does not mean easy sessions have no value. The article also describes how long, easy exercise helps the body use oxygen better. It notes that VO2 Max can become more stable as endurance athletes improve. For members tracking their own numbers, the useful comparison is change over time. A shared log could include starting VO2 Max, weekly interval sessions, and steady exercise time. Recording how the number was measured also adds context. Comparing those details with community peers is more useful than chasing the largest reported gain. What changes have you seen in your VO2 Max after adding hard intervals, and over what time period?