Training Guides / Training science
Cardio: HIIT vs LISS
High-intensity intervals or steady low-intensity cardio? Compare the two, see how much cardio public health guidelines recommend and how to fit it around lifting.
Lifting builds strength and muscle; cardio builds the heart, lungs and endurance. Both matter for health, and they work well together when planned sensibly. The two main styles of cardio are HIIT (high-intensity interval training) and LISS (low-intensity steady state).
General education only. If you have a heart condition, high blood pressure or other health concerns, talk to a doctor before starting vigorous exercise.
How much cardio do you need?
The World Health Organization recommends adults do at least 150 to 300 minutes of moderate-intensity aerobic activity, or 75 to 150 minutes of vigorous-intensity activity, each week, or an equivalent mix, plus muscle-strengthening activities on two or more days. US physical activity guidelines give the same core numbers. Moderate means you can talk but not sing; vigorous means you can only say a few words without pausing for breath.
HIIT vs LISS compared
| HIIT | LISS | |
|---|---|---|
| What it is | Short hard efforts with rest between | Continuous easy to moderate effort |
| Example | 8 x 30 s hard on a bike, 90 s easy between | 40-minute brisk walk, easy cycle or jog |
| Session length | 10 to 25 minutes | 30 to 60+ minutes |
| Feels | Very hard, breathless | Comfortable, conversational |
| Fitness benefits | Raises maximum aerobic capacity efficiently | Builds aerobic base, easy to recover from |
| Recovery cost | Higher; can interfere with leg training | Low |
| Injury risk | Higher with running sprints | Low |
| Best for | Short on time, sport conditioning | Beginners, recovery days, high weekly volume |
Both improve cardiovascular fitness. Studies comparing them for fat loss generally find similar results when the total calories burned are similar; overall diet matters far more. See TDEE and calories.
Sample sessions
HIIT (bike or rower): 5-minute easy warm-up; 6 to 10 rounds of 30 seconds hard and 90 seconds easy; 5-minute cool-down.
LISS: 30 to 45 minutes of brisk walking on an incline, easy cycling or swimming at a pace where you can hold a conversation. Many coaches call this "zone 2" training.
Fitting cardio around lifting
- Separate them when you can: cardio on non-lifting days, or several hours apart.
- If on the same day, lift first when strength is the priority.
- Choose low-impact options such as cycling, rowing or incline walking, which interfere less with leg training than lots of running.
- Keep HIIT to 1 or 2 sessions a week. It is demanding; most of your cardio can be easy.
- Daily steps count. Walking adds activity with almost no recovery cost.
A simple weekly template
| Day | Training |
|---|---|
| Mon | Lift |
| Tue | LISS 30 to 40 min |
| Wed | Lift |
| Thu | HIIT 15 to 20 min |
| Fri | Lift |
| Sat | Long walk, hike or sport |
| Sun | Rest |
Cardio does not "kill gains" when the amount is reasonable and you eat enough. The concern applies mostly to very high volumes of running. See sleep and recovery for keeping total fatigue in check.