HIIT vs Moderate Cardio: Which Should Your Clients Choose?
HIIT saves time; moderate cardio is accessible and easy to recover from. The right answer depends on your client: goal, level and recovery.
By L'équipe I Train With You
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The wrong question
"HIIT or cardio?" is often a false choice. Most clients need both, in proportions that depend on their goal, level and recovery. For adults, the World Health Organization recommends a weekly volume of aerobic activity (at least 150 to 300 minutes of moderate intensity, or 75 to 150 minutes of vigorous intensity) on top of muscle strengthening (WHO guidelines, 2020).
To combine these sessions with strength work and nutrition in one follow-up, see our personal trainer software page.
What HIIT really is
High-intensity interval training alternates very hard efforts (often around 85 to 95% of maximum heart rate) with active or passive recovery.
Example protocols:
- 20 seconds on, 10 seconds off, 8 times (4 minutes)
- 30 seconds fast, 30 seconds walking, for 10 to 15 minutes
- Pyramid: 10, 20, 30, 40, 30, 20, 10 seconds of effort with equal rest
What HIIT does well: improves cardiorespiratory fitness in little time, suits busy clients, and adds variety.
Its limits: high joint impact depending on the exercises (jumps, sprints), significant fatigue that makes more than 2 or 3 sessions a week hard on top of strength training, poor fit for complete beginners, and intensity to be cleared by a doctor in case of cardiovascular disease or risk factors.
What moderate cardio really is
Continuous effort at an intensity where you can still speak in short sentences (often around 60 to 70% of maximum heart rate), held for 30 to 60 minutes: brisk walking, cycling, swimming, rowing or the elliptical at a steady pace.
What it does well: low joint impact, easy to recover from and compatible with strength training, can be done often, and builds the aerobic base that intense work relies on.
Its limits: takes longer for the same fitness gain, can feel monotonous, and progress slows if duration or pace never change.
How to decide for each client
| Profile | Starting point |
|---|---|
| Complete beginner | Moderate cardio only for the first weeks, then short intervals introduced gradually |
| Fat loss, good fitness | Moderate cardio plus 1 or 2 interval sessions a week, with suitable nutrition |
| Muscle gain | Moderate cardio in a reasonable volume to protect recovery |
| Sports performance | Depends on the sport and competition calendar |
| Tired client, poor sleep | Favour moderate cardio until recovery is back |
| Joint pain | Supported activities (cycling, swimming, rowing) and medical advice if needed |
The 80/20 split in endurance
Endurance athletes typically do most of their training volume (often around 80%) at low intensity and the rest at high intensity (Seiler, 2010). For recreational clients, keep the principle: an easy base with a small share of intensity, rather than hard sessions every time. To organise this over weeks, see our training periodisation guide, and for building a full plan, how to create a personalised training program.
Practical integration in I Train With You
Create "Intervals" and "Endurance" modules in your library with exercises, durations and rest times, and assign them alongside strength modules based on each client's profile. Clients find their session in their app, with the timer and end-of-rest beeps.