If you think of the athletes’ body in terms of its systems, Respiratory, Circulatory, Muscular and Nervous systems. Then you can start to see how HIIT training and Endurance training provide different stresses to each of those systems. Am I an expert in each system heck no, but to understand athletic performance I believe it is important to understand each system and its role
There are other systems in the body as well, Urinary, Digestive, lymphatic, reproductive, Endocrine (hormones). But for now, I’m focusing on the first four.
In HIIT you are usually pushing one system to the max then forcing the other systems to compensate, recover then repeat x times until you can’t anymore or your jerk of a coach tells you to stop. For example, get on the bike, or rower, or track and crush some 30 seconds all out intervals, with 30 seconds of rest. Repeat 10-15 times. You will be maxing out your muscular system and pushing your nervous system as well. Then your heart and lungs kick in to compensate as your muscles are maxing out their utilization of oxygen and need more of it. So with HIIT you are maxing out your systems which is beneficial as your pushing your utilization of that o2 and pushing your delivery systems to get the 02 there. But its very time limited you can only do so much before your exhausted and puddle of goo. NB- the Muscle Oxygen sensor has been great for guiding this HIIT, instead of counting fingers.
Now for endurance training, zone 2, LS(teady)D, the aim is to keep all the systems working but not one system hitting its limit which would result in kicking in another to compensate. Where 95% of cyclists stray from this is they feel its too “easy” and there is nothing to be gained. And begin to start going harder.(AKA more watts more watts more watts then crack) Well if you’re a well-trained athlete riding at 65% of FTP or 50% of MAP its pretty manageable for an hour or two, but what about 6? Just because it feels easy doesn’t mean your body isn’t working. There are plenty of benefits of doing just that kind of training, your laying down the foundation to then build up with that fun HIIT, capillarization, inter-muscular coordination, mitochondria, and getting into how your body uses and stores energy as well. And there are metrics for measuring your growth and improvement with endurance training. (hint: its not just more power) So if you really want to build your aerobic capacity and endurance try your best to do MORE time in that level or zone. Unfortunately, life does come into play and is a limiting factor for many.
I Stole this screenshot from a recent webinar by Tim Cusick of WKO4 (so full credit to him, can be found on WKO4 youtube called “Building and tracking the aerobic engine") This slide is a very detailed look at 4 options to work on that foundational aerobic capacity.
I’ll put the caveat that this is a good time to do some x-training as well, so it could be endurance run/ski/snowshoe/row as your heart and lungs don’t know what your limbs are doing. (but you need to be in each sports specific zone)
So where am I going with all this? Basically, that there is a time and place for everything, as an athlete or just a human being you should look at incorporating both HIIT and Endurance training as they both have benefits that the other doesn’t have.
My advice to any athlete looking to gain some performance this season is to put some time into that “Chronic Aerobic Foundation” When you hit a hill and your HR spikes and your powermeter is reading 400 or your hr monitor is flashing 190 you may be pushing on some limiters. Regardless of what your AVG power is when you get home. Instead gear down, ride the hill, enjoy the scenery and go LONGER. I promise you if you commit to that then the hard training or HIIT will go even better down the road.