How do I improve my cardio?

Build a base of easy, conversational-pace aerobic work two to four times a week, then add one or two harder interval sessions. Most of your volume should feel comfortable and the hard sessions should be genuinely hard. Progress duration before intensity.

Start with the base

Easy aerobic work is the foundation because it can be repeated often without heavy fatigue. Walking briskly, cycling, rowing, or easy jogging at a pace where you can hold a conversation builds the capillary density, mitochondrial content, and stroke volume that everything else sits on. If you can only manage one type of session, make it this one.

A sensible progression

• Weeks 1 to 4: Three easy sessions of 20 to 30 minutes. No intervals yet.
• Weeks 4 to 8: Extend the longest session to 40 to 50 minutes, keeping the pace easy.
• Weeks 8 onward: Add one interval session, for example six rounds of two minutes hard with two minutes easy.
• Later: A second harder session, only if recovery from the first is comfortable.

Increase total weekly duration by around 10 percent at a time. Doubling volume in a week is the most reliable way to acquire a niggling injury.

Why most of it should be easy

Hard sessions produce sharp improvements but cost a great deal of recovery, so you can only do a few each week. Easy work produces slower improvement per session but can be repeated almost daily. The combination gives you more total adaptation than filling the week with intervals, which is why endurance athletes spend most of their time going slowly.

Judging your effort

The talk test is reliable and free. Easy means full sentences. Moderate means short sentences. Hard means single words. A heart rate monitor adds precision but changes nothing fundamental.

What to expect

Noticeable change usually appears within four to six weeks: The same pace feels easier, and your heart rate recovers faster after effort. Progress is measured by what a given effort feels like, not just by pace. The physiology behind it is covered in Exercise Physiology and Energy Systems.