HIIT vs Moderate Cardio: Which Should Your Clients Choose?

The wrong question

"HIIT or cardio?" is often a false question. Most clients need both — in different proportions depending on their goal, level and recovery capacity.

What HIIT really is

HIIT (High-Intensity Interval Training) alternates phases of maximal or near-maximal effort (85–95% HRmax) with active or passive recovery phases.

Protocol examples:

Tabata: 20 sec effort / 10 sec rest × 8 = 4 minutes
30-30: 30 sec sprint / 30 sec walk × 10–15 min
Pyramid: 10 sec, 20 sec, 30 sec, 40 sec, 30 sec, 20 sec, 10 sec with equal rest

Where HIIT excels:

High EPOC (post-exercise oxygen consumption) → calories burned after the session
Improves aerobic and anaerobic capacity simultaneously
Time-efficient (20 min vs 45 min)
Variety — psychologically stimulating

HIIT limitations:

High joint impact if poorly programmed
Hard to sustain 3+ times/week without overtraining
Unsuitable for complete beginners (injury risk, negative experience)
Contraindicated during intense strength training (competing recovery)

What moderate cardio (LISS) really is

LISS (Low-Intensity Steady State) refers to any continuous effort at moderate intensity, between 55 and 70% HRmax, maintained for 30 to 60 minutes.

Examples: brisk walking, easy cycling, moderate-pace swimming, elliptical.

Where LISS excels:

Low joint impact — accessible to everyone
Promotes active recovery
Fat oxidation as primary energy substrate (lipolysis zone)
Doesn't interfere with muscle recovery if intensity is controlled
Sustainable: can be practised daily

LISS limitations:

Less time-efficient
Quick plateau if not progressive
Risk of adaptation (the body becomes efficient, burns less)

How to decide for each client

Client profile	Recommendation
Complete beginner	LISS only for the first 4 weeks
Weight loss, good fitness level	2× HIIT + 2× LISS per week
Muscle gain	LISS only, low volume (2×/week, 30 min)
Sports performance	HIIT priority based on the sport
Stressed client, disrupted sleep	LISS — HIIT amplifies cortisol
Joint injury	LISS only (swimming or cycling for knee issues)

The 80/20 rule in endurance

The highest-performing endurance athletes train at 80% low intensity, 20% high intensity. This rule, known as "Polarised Training", applies as well to elite runners as to intermediate fitness clients.

Many coaches do the opposite: too much HIIT, not enough aerobic base. Result: quick adaptation, early plateau, overtraining risk.

Practical integration in itwu

Create "HIIT Cardio" and "LISS Cardio" modules in your library, with defined exercises and durations. Assign them alongside strength modules based on each client's profile.