Do both — with most of your cardio easy and a small, protected slice genuinely hard. That's the unglamorous answer, and it's also how the best-conditioned endurance athletes on earth structure their training: the bulk of their volume at conversational LISS intensity, a couple of true interval sessions a week, and very little in between.
The reason it works is that HIIT and LISS aren't rivals competing for one job. They develop different qualities at different costs, and a cardio diet made of only one of them leaves fitness on the table.
LISS, defined properly
LISS — low-intensity steady state — is continuous movement at a pace you could hold while chatting: brisk walking, relaxed cycling, an unhurried jog along the waterfront. The test isn't the activity, it's the effort. If you're bargaining with yourself to keep going, it has stopped being LISS. Done correctly, it strengthens the aerobic machinery that powers everything else you do, and it's gentle enough to repeat most days without stacking up fatigue.
Two stimuli, two price tags
Intervals push your ceiling: repeated near-maximal efforts teach your heart and muscles to produce and tolerate high output, and they do it in very few minutes — at the price of a recovery bill that limits how often you can pay it. LISS deepens the foundation under that ceiling, improving how efficiently you process oxygen and how quickly you bounce back between hard efforts — at the price of time, since the dose has to be generous to matter. Neither can buy what the other sells.
The split that works: mostly easy, a little hard
In endurance sport this shape is called polarized training, and the logic transfers cleanly to regular life: keep the easy days truly easy so the hard days can be truly hard. In practice, a week might hold one to three interval sessions — how many belongs to the HIIT frequency question — surrounded by walks, easy spins, or relaxed cardio that leaves you fresher than it found you. The proportion is the point: hard work is the seasoning, easy work is the meal.
The grey zone: where cardio goes to stall
The common failure isn't picking the wrong method — it's blending them into one. When every session is moderately hard, nothing is easy enough to recover on and nothing is hard enough to push your ceiling, so progress flatlines while tiredness quietly compounds. The middle intensity feels productive precisely because it's uncomfortable, which is what makes the trap so sticky.
Escaping it takes discipline in both directions, and objective feedback helps enormously — a live number is much harder to argue with than a feeling, which is a big part of why training with heart rate works.
If your week forces a choice
- Time-poor but recovering well: bias HIIT — two short, coached sessions such as HIIT classes in North Vancouver hold a lot of fitness on very little clock, with walking as your easy volume.
- New to training, heavily stressed, or coming back from a layoff: bias LISS for a couple of months and let intensity be something you graduate into.
- Neither constraint applies: run the mostly-easy split above and stop choosing.
More side-by-side breakdowns of formats and methods live in the compare section if you're weighing options beyond cardio intensity.
Common questions
How easy is easy enough for LISS?
You should be able to speak in full sentences the whole way through and finish feeling like you could continue. If an 'easy' session leaves you flattened, it was a grey-zone session wearing a disguise.
Is LISS pointless if I only have two hours a week?
Not pointless, but it's the first thing to shrink. On a tight budget, spend the structured hours on intervals and strength, then harvest easy volume from life — commutes, hills, dog walks, errands on foot.
Can I decide mid-workout to turn an easy session into intervals?
Finishing an easy session with a few short pickups is fine, but 'making it count' halfway through usually just manufactures grey-zone mush. Give each session one job before you start and let it do that job.
Does LISS require cardio machines?
No — walking, easy hiking, swimming, or a relaxed spin all qualify, and around the North Shore the flat harbourside routes make pleasant easy-day terrain. Continuous and genuinely comfortable are the only requirements.
