Not sure which cardio style fits your training? Here's what HIIT, SIT, and LISS actually mean, how to do each one, and how to pick the right one for you.
Quick Definitions
HIIT (High Intensity Interval Training): Intervals done at high effort (not all-out) with rest in between.
SIT (Sprint Interval Training): A specific type of interval training done at supramaximal "all-out" effort for very short bursts, with longer rest so you can repeat that same intensity.
LISS (Low Intensity Steady State): Also called Zone 2 cardio. Steady movement at a moderate, conversational pace for a longer duration.
The Main Difference: HIIT vs SIT
The primary difference between HIIT and SIT is:
Timing: how long you work and how long you rest
Intensity: how hard you push during the work effort
SIT is harder and shorter, with longer recovery. HIIT is hard and sustained, with more equal recovery.
How to Perform SIT (Sprint Interval Training)
SIT parameters:
Intensity: ~110% supramaximal effort (as close to "all-out" as you can safely manage)
Work interval: 30 seconds or less
Recovery: 30 seconds to 4 minutes
Goal of recovery: recover enough to hit that same supramaximal effort again
How do you know you're working hard enough? If you can't talk and feel like you're giving everything you've got, you're at the right intensity. Trust your effort over your heart rate. During rest, you can stop completely or move lightly; whatever helps you recover enough to go all-out again.
How many intervals? When you're new to SIT: often 2–3 efforts is all you can hit at true intensity. As you get more trained: 8–10 efforts is ideal.
Example SIT session (simple version):
10 min warm-up
3–6 rounds of:
10–30 sec sprint effort
1–4 min recovery (move lightly or rest)
Cool down
No gym equipment? Try outdoor sprints, stair sprints, high knees at max speed, burpee sprints, or squat jumps.
How to Perform HIIT (High Intensity Interval Training)
HIIT parameters:
Intensity: 80–95% effort (the shorter the interval, the higher the effort)
Work interval: 45 seconds to 4 minutes
Recovery: variable, often 1:1 work-to-rest (example: 2 minutes hard, 2 minutes easier/rest)
The goal of HIIT: Tap into VO₂ / sustainable anaerobic efforts for metabolic conditioning (building fitness and work capacity)
Example HIIT session (simple version):
10 min warm-up
4–8 rounds of:
1–4 min hard effort (80–95%)
1–4 min recovery (often equal time)
Cool down
No gym equipment? Try mountain climbers at max speed, burpee intervals, squat jump repeats, or running intervals outdoors.
Benefits of SIT vs HIIT
Benefits of SIT
SIT can be especially useful in postmenopausal years, and is associated with:
Increased lean muscle mass
Reduced fat mass (including belly fat)
Improved insulin sensitivity
Lower blood sugar levels
Potential cognitive benefits (supports working memory and cognition)
Benefits of HIIT
HIIT provides a strong metabolic stimulus that can support:
Fitness improvements
Body composition changes that support performance
Helpful outcomes for women who are perimenopausal and postmenopausal
Important note: SIT is technically a form of HIIT, but because SIT is more intense, it may create a stronger stimulus and therefore a higher degree of certain benefits.
Reference: Next Level - Dr. Stacy T. Sims (2022)
LISS Defined (Low Intensity Steady State / Zone 2)
LISS (Zone 2) is steady cardio at a moderate effort where:
You can comfortably maintain a conversation
Your heart rate is about 65–70% of your maximum heart rate (MHR)
How to estimate your Zone 2 heart rate
Estimate max heart rate: 220 − age
Multiply by 0.65 and 0.70 to get your Zone 2 range
Example (age 50):
Max HR: 220 − 50 = 170
Zone 2 range: 110–119 bpm (65–70% of 170)
Why should I do LISS (Zone 2)?
LISS can help with:
Improved endurance (better oxygen use and fat burning)
Recovery between harder workouts
Reducing risk of overtraining
Supporting training during a fat loss phase, especially when calories are lower and energy isn't at its peak
Ideas for LISS Workouts
You can use almost any cardio mode, as long as you keep the intensity in Zone 2.
Examples: jogging, cycling (outdoors or stationary bike), swimming laps or treading water (with a belt), stair climber, rowing machine, ski erg, hiking, elliptical, climbing stairs, speed walking on undulating terrain
Mix-and-match option: You can also rotate through different modes in one session (example: 20 minutes stair climber + 20 minutes treadmill + 20 minutes bike).
How do I know which cardio is right for me?
Choose SIT if you want very short, all-out efforts with longer rest, and you can recover enough to repeat true intensity.
Choose HIIT if you want hard intervals you can sustain for 45 seconds to 4 minutes, often with equal rest.
Choose LISS (Zone 2) if you want a steady, conversational pace cardio session that supports endurance and recovery.
On days your program offers a choice: Pick LISS if you're feeling sore, tired, or newer to cardio. Pick HIIT or SIT when you're feeling strong and recovered.
If you're unsure which style fits your current goal, choose the one you can do consistently and safely, then build from there.