How to structure cardio training?

[Aethelwulf]

I'm asking anyone who has some decent experience in doing cardio training.

I've recently started back at a gym after a good three years absent. Prior to my break my priority was pretty much hypertrophy. I know how to structure my workouts when it comes to muscle building. But now, my priorities have changed. I'm more interested in getting very lean and developing decent cardiovascular fitness.. But I'm a complete noob when it comes to this.

Do the same principles apply to this kind of training as with weight training? By that I mean, in weight training you stick to a specific weight/rep range for either strength or hypertrophy, and you stick to this for a set period for maximum effectiveness, instead of alternating week by week. In my cardio training, which is mainly running, is it better to stick to calorie burning for 8 weeks for example.. And then after this, switch to intensity workouts like sprinting and shuttle runs for 8 weeks. Or is a mixture of the two week by week effective?

Asking for a friend!

[Venti]

I'd recommend to check programs that train for marathons and how they are built. It's common that the exercise done in them is mostly done on the easy end of heart rate (less than 70% of maximum heart rate). Going to 70-90% is often done once a week or even less and over 90% is very rare. I'm not into aerobic exercise myself but this is how it's done from what I've seen. I think it's because capillary formation and oxygen transfer have most capacity to improve in aerobic conditioning and they are best trained without lactic acid. Don't quote me on this though that's only my reasoning for why marathon programs are the way they are.

Faster results can be achieved by training on the lactic acid zone (sprints), especially for shorter distances like the mile. This method is something I have tried and while it gets results it hits a wall fast. I think the results mostly come from building resilience to lactic acid. Training with higher intensity also transfers the results very poorly to longer distances like 10km, marathon, triathlon etc.