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Toolbox: The Interval Arc
I’ve participated in this sport for more than two decades and with every passing year, I became more and more precise with my training. Although there are elements of discipline in precision, it is not the same thing.

Discipline just means never missing a workout. That’s a given. If you have a workout schedule stick to it. Precision means doing the schedule in exactly the perfect manner so as to extract every possible bit of improvement out of each and every cycle. Precision means making sure every aspect of every workout is tightly controlled and done within extremely narrow and rigid parameters.

This article will teach you how to establish those parameters.

The King of precision this year was without a doubt Chris Froome.

This series will teach you that over the course of a three week interval cycle, there will be a perfect way to do every interval and even though each interval is the same length and same basic intensity, no two intervals should be done exactly alike.

I call this the Interval Arc.

Philosophy or Method?
My personal approach to the Interval Arc is something that I have developed over the years based on first hand information gleaned from carefully monitoring my own training and my clients’ training.

It’s worked exceptionally well for me but, until now, I’ve always thought of it as more of a general philosophy than a defined method. Something that I understood intuitively but that couldn’t really be put down on paper or recorded and tracked objectively. But just last week, in answering a routine question from a client, it all came spilling out and I realized for the first time that it is something that can be put clearly and cleanly into words.

The question was, “How hard should I go on my first workout after a rest week?” Normally I would answer the question with a heart rate recommendation, a power guideline, a perceived exertion suggestion. Most likely it would be a combination of all three, depending on my knowledge of how the rider trains and what methods work best for them in defining their workout parameters.

As I wrote out my answer to his question, it occurred to me that while I knew exactly what the best way for him to do the workout was, I didn’t have a clear, conscious awareness of how I had actually arrived at those numbers. It had become something so intuitive to me that I had never bothered to think about the nuts and bolts of how it actually works.

I pondered this for a while and was happy to discover that I did in fact know exactly where the numbers came from and how I arrived at them.

Let’s lay out the basic concepts in this first article, and then we will follow up with a specific plan for progressing through a training cycle.

At the core of the workout recommendations I am going to make is the concept of periodized training. What this means is that training is done in blocks or training cycles. For our purposes, we will assume that a training cycle consists of three weeks of work and one week of rest. Each of the three weeks will include three interval sessions, which will consist of one to six intervals each, depending on the type of interval. Generally speaking, the longer the interval, the less repetitions.

In order to avoid plateaus, each cycle has a different emphasis in terms of the energy system to be stressed. The length of the interval determines the intensity of the effort and therefore which energy system will be stressed. The shorter the interval, the higher the heart rate, power and perceived exertion will be. Which energy system to focus on is determined by the time of the year and the nature and timing of the rider’s goals.

Block Training
Many of us keep the same general pattern throughout every week, with sprints or a club race on Tuesdays, climbing intervals on Wednesdays, time trials on Thursdays, club rides or races on Sunday. While there is variety, the tendency with this type of program is that your efforts are scattered all through different ranges, yet you’re not getting enough stimulus at any one intensity for maximal benefit.

Instead, the general philosophy with block training is that you focus on one system very intensively and “perfect” it, then move on to the next intensity or system. Typically, this means progressing from longer, more aerobic efforts early in the training year to shorter and more anaerobic efforts as your racing season arrives.

Each three-week interval cycle is followed by a week of rest. After a complete reboot and recovery, the next cycle begins with a new emphasis. The order and timing of the cycles is designed to get the rider closer and closer to a peak performance at a priority event.

Heart Rate vs Perceived Exertion
The way 175 beats per minute feels to your body can be very different from one day to the next. On one day it can feel like a 7 (out of 10) and a week later it can feel like a 9.5.

Generally it’s your level of fatigue that determines how a given heart rate feels on a certain day. There is a definite relationship between perceived exertion and heart rate and the standing of that relationship can be used to pinpoint the amount of fatigue you should have on each day of a cycle.

When you are well rested it will feel easy to ride at the top of your heart rate zones. As you get more fatigued over the course of several weeks of hard training, it will become harder to keep your heart rate in the zone.

If you are not finding noticeable heart rate depreciation over the course of a hard block of training or a dramatic increase after a recovery week then chances are you are not recovering to a wholly rested state and you’ll need to rest again until you are absolutely sure that all fatigue is gone from your system. This could take weeks or even months depending on how badly over-trained you are. Rest, rest and rest some more. Then when you are absolutely sure you are completely rested, rest for one more week. Consider it an investment in the future.

Critical Power
The simplest and most effective use of a power meter is to use it to measure critical power. I define this as the highest average power you can achieve over a given period of time. You will have a different critical power for each length interval you do and unlike heart rate, your critical power will increase over time.

Each training cycle should focus on a single energy system, which means intervals of a similar length. It is the quest for a new, higher critical power for that month’s interval length that drives each and every workout of the cycle. Ideally it will be on the very last interval workout of the cycle that the highest critical power is reached. How high that number is compared to your previous best critical power for that interval length at the same time of the year will tell you how successful the training cycle was.

Tracking Training
The more you train and the more you learn to recognize these indications, the more efficiently you can train. This is where tracking power, heart rate, AND your perceived exertion in a training diary can really help in your analysis. Power by itself is fairly meaningless without tying it in to your physiological (heart rate) and psychological (perceived exertion) responses to that effort.

So in your training diary, don’t just download the heart rate and power data and leave it at that. Write down subjective notes of how the workout felt, how hard you had to push mentally to complete that workout, and also what else might be going on in your life that may be affecting your riding.

Next time, we will outline exactly how to ride intervals and progress through a block of training.

About Josh
Josh Horowitz is the host of Broken Bones Garage, a daily webcast featuring segments on training, sports psychology, nutrition and gritty stories from his days racing in the pro peloton.

You can follow the or check out for the latest episodes.

As a coach, Josh has trained national champions, world champions and Tour de France stage winners along with hundreds of amateur racers and recreational riders. His innovative articles on training, strategy, nutrition and sports psychology have appeared in USA Today, The Wall Street Journal, Bicycling Magazine and The Huffington Post.


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