Explained – when to train low, when to train high

Wondering when to vary your workload intensity, and by how much? We reveal how you should split your time between building base endurance and top-end speed


It’s been proven that going hard too often overloads the capacity to absorb, whereas steady training improves fitness and encourages good technique. The theory behind keeping training effort in most sessions at low intensity is not just a theory, but has been shown in practice, looking at the training intensity of many successful endurance athletes.


From 4-minute track cyclists to 6-minute rowers, through to 14-minute 5km runners and stage-racing junior cyclists, marathoners and Ironman athletes, from Norway to New Zealand, Kenya to France – athletes performing at a high level (and not just full-time professionals) tend to train at low intensity for 75%-90% of their training volume.

On average, for top-end athletes, high-intensity training above threshold occurs in approximately two to three sessions per week, accumulating lactate and therefore split into intervals (see below). In contrast, many amateur triathletes (and other endurance enthusiasts) often include many sessions that have random threshold, above- threshold or ineffective duration intervals. The sessions aren’t planned, but are simply based on reactions to who else turns up, who’s encountered on the road or how they feel once warmed up. My observation is that too many endurance amateurs fail to acknowledge how steady training can build fitness and that interval work really does need to be hard.

What is high-intensity interval training (HIIT)?

Interval training: why and how

So yes, in part you’re right that going hard does yield improvements, yet so too does steady work (60-80% of HRmax). This is most likely the most effective split, let’s call it 80:20, because low-stress work can still be achieved over many consecutive sessions and days. Yet, just as importantly, the athlete can do their quality work in 2–3 sessions a week. Voilà: a big fitness and technique base with top-end results.

Best heart rate zones for running

The triathlete’s complete guide to heart rate zone training

Best heart rate training zones for cycling

The main problem with this method is actually convincing driven people to ease off in the majority of their sessions and to do fitness/ability/talent-defining efforts in just 2–3 set pieces per week. So to get the most from this training methodology, follow these pointers:

– Know where 80% of your HR maximum is so you can stay in zone 1 when required. Session goals include technique work, endurance and cross-training.

– Know your threshold (around 85% HRmax) to ensure that intervals cause lactate build-up. Session examples: 8–12 x 30sec maximal with 4.5mins recovery; 6–10 x (5 x 40secs hard, 20sec recovery) with 3min breaks; 4 x 8mins with 2–4 mins recovery.

– Plan your sessions and stick to them, even if you move sessions around within the week.


How to gauge if you’re running aerobically or anaerobically

What is lactate and lactate threshold?

Explained: why lactic acid is your friend, not foe

(Image: Jonny Gawler)