HIIT vs LISS: The Basics
HIIT (High-Intensity Intervals)
30-60 seconds all-out effort, then 60-120 seconds recovery. Total time: 15-25 minutes.
Heart rate: 85-95% max during work
Calories: 200-300 in 20 min
Afterburn: 50-200 extra calories over 24-48hrs
LISS (Steady State Cardio)
Comfortable pace you can maintain. Walking, easy cycling, swimming. Total time: 30-60 minutes.
Heart rate: 50-65% max
Calories: 250-400 in 45 min
Afterburn: Minimal
Reality check: HIIT's "afterburn" effect is hyped. It adds maybe 6-15% extra calories. Helpful but not the game-changer social media claims.
What The Science Actually Shows
For Fat Loss: It's a Tie
2017 meta-analysis of 28 studies: identical fat loss when total calories burned are matched.
Translation: 300 calories from HIIT = 300 calories from LISS for fat loss purposes.
For Strength Athletes: LISS Wins
2012 study: high-intensity cardio reduced strength gains compared to low-intensity cardio.
HIIT activates AMPK which can shut down mTOR (muscle growth pathway). Too much HIIT = compromised gains.
The "Fat Burning Zone" Myth
LISS burns more fat percentage during exercise (50-65%). HIIT burns mostly carbs.
But it doesn't matter. You lose fat when in caloric deficit over time, regardless of fuel source during exercise.
The Honest Pros and Cons
HIIT
Pros:
Time-efficient (15-25 min)
Improves VO2 max faster
Small metabolic boost after
Cons:
Higher injury risk
Harder to recover from
Can interfere with lifting
LISS
Pros:
Lower injury risk
Can be done daily
Promotes recovery
Cons:
Time-consuming (45-60 min)
Can be boring
No performance benefits
Practical Workout Protocols
Copy-paste these into your training
HIIT Protocols
Beginner (Bike)
5 min warm-up
20s all-out, 100s easy
Repeat 8x
5 min cool-down
Intermediate (Treadmill)
5 min warm-up
45s sprint, 75s walk
Repeat 10x
5 min cool-down
Advanced (Rower)
5 min warm-up
30s all-out, 30s rest
Repeat 12-15x
5 min cool-down
Critical: If you can do HIIT daily, you're not going hard enough during work intervals.
LISS Options
Incline Walking
3-5% grade, 3-4 mph, 30-45 min
Cycling
Comfortable pace, 40-60 min
Swimming
Continuous laps, 30-45 min
Rowing
Steady state, 30-40 min
My Personal Protocol
What actually works for fat loss + muscle maintenance
Recommended Weekly Split
Monday: Upper Body + 20 min HIIT
Tuesday: Lower Body
Wednesday: 45 min incline walk
Thursday: Upper Body + 30 min LISS
Friday: Lower Body
Saturday: 20 min HIIT
Sunday: Rest or easy walk
Critical Rules:
Never do HIIT before leg day
Limit HIIT to 2x weekly if lifting heavy
Separate cardio and weights by 6+ hours if possible
Take at least one full rest day
Common Mistakes to Avoid
Daily HIIT
If you can do true HIIT daily, you're not going hard enough
Ignoring Heart Rate
Get a monitor. HIIT needs 85-95% max HR, LISS needs 50-65%
HIIT Before Legs
Your squat and deadlift will suffer. Do it after or another day
False Intensity
If you can talk during work intervals, that's not HIIT
The Bottom Line
For fat loss: total calorie deficit matters more than cardio type. Both HIIT and LISS work when calories burned are matched.
For busy people: 2x HIIT weekly
For strength athletes: Prioritize LISS, use HIIT sparingly
The best cardio is the one you'll actually do consistently. I've seen people get shredded doing only walking.
Calculate Your Cardio Needs
Scientific References
- Keating SE, Johnson NA, Mielke GI, Coombes JS. A systematic review and meta-analysis of interval training versus moderate-intensity continuous training on body adiposity. Obes Rev. 2017;18(8):943-964.
- Wilson JM, Marin PJ, Rhea MR, et al. Concurrent training: a meta-analysis examining the interference of aerobic and resistance exercise. J Strength Cond Res. 2012;26(8):2293-307.
- LaForgia J, Withers RT, Gore CJ. Effects of exercise intensity and duration on the excess post-exercise oxygen consumption. J Sports Sci. 2006;24(12):1247-64.
- Fyfe JJ, Bishop DJ, Stepto NK. Interference between concurrent resistance and endurance exercise: molecular bases and the role of individual training variables. Sports Med. 2014;44(6):743-62.
- Gibala MJ, Little JP. Physiological basis of brief vigorous exercise to improve health. J Physiol. 2020;598(1):61-69.