High-intensity cardio

Hard cardio makes you breathe heavily enough that speaking more than a few words takes effort. It includes fast running intervals, hard cycling and HIIT sessions that alternate demanding efforts with recovery. You might choose it to practice working at higher intensities or because you prefer bursts of effort to a longer steady session.

A short workout can still demand a lot. Warming up, resting between efforts and recovering afterward all take time. Feeling close to vomiting isn't a measure of workout quality, and every session doesn't need to be an all-out effort.

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You need an intensity that matches your current ability, recovery between efforts and room to recover between sessions. Movement control still matters when tired, especially in workouts with jumping or fast changes of direction.

Keeping up with a class can tempt you beyond what you can manage. Copying an advanced session after a long break can leave you sore, injured or unwilling to return.

People stop because the next session feels like an appointment to suffer. Fatigue, soreness and recovery also compete with work and other activities.

It's easy to alternate between going too hard, taking an extended break and punishing yourself on the return. A less demanding version may be one you actually repeat, even if it looks less impressive than the workout you pictured.