LISS (Low-Intensity Steady State)

LISS: what is it?

LISS got a reputation as the boring, outdated option in the years when everything had to be high-intensity. That reputation was wrong, and the endurance world never believed it: elite endurance athletes spend the large majority of their training hours at exactly this intensity. What LISS does that intervals cannot is accumulate a large volume of aerobic stimulus without demanding much recovery, which means it can be added to a week that is already full of hard work.

How to find the right intensity

Three ways, in increasing order of precision. The talk test: the client should be able to hold a full conversation in complete sentences. Heart rate: roughly 60 to 70% of maximum, or zone 2 in a five-zone model. Nasal breathing: many clients can hold LISS pace while breathing through their nose, and lose it as soon as they drift too hard.

Almost everyone goes too hard. The intensity that feels right is usually zone 3, which is where LISS stops delivering its benefit and starts costing recovery. Expect a client to complain that the correct pace feels pointlessly slow for the first few weeks - that complaint is the sign you got it right, not wrong.

What it actually builds

Sustained easy work drives peripheral adaptation: more mitochondria, denser capillary networks, better fat oxidation, higher stroke volume through sustained cardiac filling. Those adaptations raise the ceiling that hard sessions push against, and they improve the client's ability to recover between hard efforts, both within a session and across a week.

It also does something no interval session does: it lets a client accumulate a lot of training with almost no orthopaedic or systemic cost. That is why it works so well for beginners, older clients, people in a calorie deficit, and anyone whose recovery capacity is already stretched by hard lifting.

Programming it

Start at whatever duration the client can genuinely hold - twenty minutes is a real starting point - and extend by five to ten minutes every week or two before touching the intensity. Duration is the variable that matters here; if you find yourself raising the pace, you are drifting toward a tempo session.

Choose the modality by joint tolerance and by whether the client will actually do it. Brisk walking, incline treadmill walking, easy cycling, rowing at a low rate, swimming and hiking all work. For a client carrying a lot of bodyweight or coming back from a lower-limb injury, cycling and incline walking spare the joints in a way that running does not.

• Extend duration before you raise intensity.
• Fasted or fed makes little difference to fat loss over a week. Do whichever the client tolerates.
• Slot it on non-lifting days or several hours after a strength session.
• It stacks well with daily step targets - the goal is total easy volume, not one heroic session.

LISS in a fat-loss phase

LISS is the most controllable way to add energy expenditure to a deficit, because it costs almost no recovery and therefore does not compete with the strength work that preserves muscle. That is its real advantage, not the fat-oxidation story. It is true that a higher proportion of the fuel burned at low intensity comes from fat, but total energy balance across the day and week is what drives fat loss, not the fuel mix within one session.

The practical trap is escalating it. When progress stalls, adding another two hours of cardio a week works for a while and then stops, leaving the client with no room to manoeuvre. Adjust food and daily steps first; keep added structured cardio as a lever you have not yet pulled.