Trickle Down Physiology
So what’s trickle down physiology?
Basically it means using very short intense workouts (the higher training zones) to build endurance (the lower training zones) — hence the trickle down.
A decade or two ago, it was thought the only way to build endurance was to perform long slow workouts – called LSD, for long slow distance. Many cyclists, runners, and triathletes still rely on these workouts to this day. And in truth, they still have benefit for endurance athletes. Building a strong aerobic engine is key to continued progress in endurance sport.
So why not just stick to LSD?
Going long and slow all the time has its limits. Many athletes get stuck in a plateau and only develop one gear or one speed. But the main hardship to LSD workouts is the shear amount of time.
Frankly, many people just don’t have time to do these types of workouts. At least not every day. The time-strapped athlete likely won’t have 16 hours a week to spend drilling away in LSD workouts every day.
Maybe they have time to do an LSD workout once or twice a week, mainly on the weekends. But what would be the best way to get the most out of the rest of the workouts? How do we structure the weekdays to work for us?
This is where trickle-down physiology comes in.
By working at a very high intensity — often much higher than our Threshold effort — we end up doing a couple of things.
- We get more efficient at this very high intensity level, so we will be able to work at this high effort for longer, and
- we will also be making ourselves more efficient at every level of effort below that.
So our Threshold gets bumped up and even our long slow distance pace gets bumped up as well.
Often I’ll have a client come to me for help that just wants to be able to finish easier and perhaps quicker on the 80-mile bike tour they do every summer. They might average about 8 miles per hour on the uphills and about 14-15 mph on the flat roads. After implementing these high intensity intervals for a few weeks they can hold 16-18 mph on the flats and are climbing more consistently at 9-10 mph, with no change in their perceived effort.
The intervals scaled up their long slow distance pace.
Another way to think of it is in terms of heart rate. Previously, their heart rate that was 160 beats per minute (bpm) while climbing at 8 mph on their local hill, is now 152 bpm. So they can bump their speed up to 9-10 mph where their heart rate settles at that 160 bpm level.
HIIT is very easy to integrate into cycling, because on the bike we produce relatively low forces and impacts through our joints.
Running is another story. Very high ground reaction forces pass through our body when we run and this is magnified when we run fast. This is why it’s important to make sure to have a very solid history of running before you start very intense intervals. A reasonable rule of thumb? Being able to manage 15-20 miles a week without any injuries before starting to think about inserting faster intervals in a training plan.
A nice supple surface to run on is also key. Stay away from concrete or asphalt. Trails are great as are grassy fields (although beware of holes and divots – scope out your area before you start running hard). Golf courses are optimal if you can get permission to use them. But a nice local high school track is just fine too .
Most of the regimens for HIIT are named after the scientists that have studied different protocols. Tabata (1996), Gibala (2006), Timmons are the most notable.
All are slightly different takes on the same theme: short intervals, followed by short rest, and a short overall workout duration. For example, Tabata’s “IE1 protocol” consists of 20 seconds of ultra-intense exercise followed by 10 seconds of rest, repeated continuously for 4 minutes (8 cycles).
A 2008 study by Gibala found that 2.5 hours of HIIT training produced equivalent aerobic fitness as 10.5 hours of aerobic work! Who wouldn’t want an over 4X return on their training investment?!?
Other research has shown that HIIT increases insulin sensitivity and also beats out aerobic training for fat burning potential as well.
So how to go about it?
What would be the best way for an endurance athlete to go about using these intervals? That’s going to depend on:
- current level of fitness
- what the goal race distance is
- the amount of experience at that race distance
Adopting one of the standard protocols, like Tabata, is a possibility, but something to keep in mind is that you can benefit from this trickle down training even working at any effort level at or above your Threshold. If your goal race length is longer than 1 hour then the effort involved is below Threshold….so working at or above Threshold gets you faster at your race length.
This type of trickle down work can help you get more done in less time. So experiment with these and reap the benefits in time and fitness.
Tabata, Izumi; Nishimura, Kouji; Kouzaki, Motoki; Hirai, Yuusuke; Ogita, Futoshi; Miyachi, Motohiko; Yamamoto, Kaoru (1996). “Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max”. Medicine & Science in Sports & Exercise 28 (10): 1327.
Gibala, M. J.; Little, J. P.; Van Essen, M.; Wilkin, G. P.; Burgomaster, K. A.; Safdar, A.; Raha, S.; Tarnopolsky, M. A. (2006). “Short-term sprint interval versus traditional endurance training: Similar initial adaptations in human skeletal muscle and exercise performance”. The Journal of Physiology 575 (3): 901.
He lives with his wife and two kids and runs multiple businesses in Grand Junction, Colorado.