INDOOR TRAINING: Training Terminology and Intervals


Let’s look at the exercise terminology used in most cycling applications and training systems. “Zones” are used to define different levels of workout effort. Different training systems use a different number of zones, and those systems with a similar number of zones may define them slightly differently.

Most cycling app websites will show how their zones are figured or you can read reference books on cycling by Joe Friel, Arnie Baker, and Chris Carmichael. Andy Pruitt’s Complete Medical Guide for Cyclists is another good reference. Joe Friel’s Fast After 50 and The Cyclist’s Training Bible, 5th edition, are my overall favorites. But if you look at all those authors’ offerings, there are good books on cycling and triathlon training and diet, with many found in our local libraries.

I won’t try to explain the various training systems zones (makes my head hurt), but I will give you a general overview and an explanation of the more commonly terms used.

  • Functional Threshold Power (FTP) is also called “hour power” and “Anaerobic Threshold” Power. Currently this is the most commonly used and discussed metric.  Lactate Threshold Power (LTP) is slightly different (to sports scientists only pretty much) but so similar it is often used in the same context.
  • Functional Threshold Heart Rate (FTHR) is generally your average heart rate for the hour test. Several training systems such as Carmichael Training Systems and Joe Friel’s use shorter FTHR tests with your average heart rate (HR) multiplied by a factor specific to the test length and methodology. Some methods have you do a longer effort (for example, thirty minutes) and discard the first part of the test to account for heart rate taking longer to catch up with your effort level than either power or speed. Power and heart rate from the same test use different sets of factors to set the zones. A system’s Power Zone 3 and Heart Rate Zone 3 will be at different percentages of that system’s testing results.  
  • Aerobic Capacity and VO2 Max are used interchangeably. They refer to the maximum volume of oxygen an athlete can use per minute relative to body weight to produce energy during an all-out sustained effort. There are lab tests for this, but the most common test used is a maximal five-minute effort on the bike. Your average power or heart rate is used.
  • Aerobic Threshold (AeT) is a relatively low level of intensity indicated by light breathing and a feeling that you could maintain the effort for a few hours. It occurs at about 60% of your aerobic capacity/VO2max or around 80% of lactate threshold.
  • Perceived Exertion (PE) uses various scales 1–3, 1–10, 1–20, etc. These are discussed in training books and online references. Using a 1–10 scale, 1 would be the least effort while 10 would be a maximum effort sustainable for a short burst such as thirty seconds.


Long endurance sessions on an indoor trainer are something that can be pretty awful. Most people find it much easier to do interval sessions of an hour or so. While the one-hour sessions won’t give you the same benefits that a two- to four-hour session will, you can get many benefits in an hour or so by doing some type of structured intervals. “Intervals” involve riding at a certain rate (speed, power, heart rate, cadence) for set periods of time. You alternate between some higher level of effort and a period of rest or lesser effort. This is repeated multiple times for one or more sets (groups of intervals). This is frequently referred to as HIIT (high intensity interval training). There are many, many varieties of intervals, and many more variations and combinations.

Two general rules for intervals are:

(1) If you don’t know what you can handle, it is best to err on the easy side, then increase in subsequent sets or workout days as needed. I have found this particularly true for me as an old guy, although it is also valid for any age.

(2) If you can’t meet the workout target, stop or adjust the workout. Either it was too difficult to be beneficial or you are having a bad day.

You can gauge your effort level required for trainer intervals based on one or more of the following:

  • Speed from a rear-wheel speedometer. If you only have a speedometer on your indoor bike, you can use speed rather than power as your metric; recognize that this will be specific to your trainer and bike wheel (different tire circumference yields different speed). Speed measurements lag behind when effort changes. Speed is greatly affected by winds and terrain. Fifteen mph against a headwind or on a hill is a very different level of effort than fifteen mph on a flat road with no headwind.
  • Perceived exertion. There are at least three scales used by training systems: 1–3, 1–10, and 1–20; 1 being the least effort and the higher number being the hardest effort.
  • Heart rate. This is great information and not too costly for the equipment. Heart rate measurements lag behind changes in effort level, so it is not useful for very short intervals.
  • Power. This has become the training standard for several reasons. It is the same outdoors and indoors. It is not affected, as is speed, by hills or wind speeds encountered outdoors. Measurement is immediately in sync with changes in effort. 150 watts of power is always the same level of effort; you just go slower against a headwind or up a hill.

The level of effort you use can be based on previous experience and familiarity with your effort levels or by doing one or more fitness tests on your own or with guidance from a coach or app. More info on fitness tests comes later in this doc.

While power meters are great, if you do not have one you can still gauge your effort level required for indoor intervals based on perceived exertion alone. Adding a heart rate monitor and a rear-wheel speedometer gives you lots of feedback to monitor your efforts and progress. Add a cadence sensor to make cadence drills easier to monitor.

Power meters are great, but a rear-wheel speedometer and a heart rate monitor cost less and provide sufficient feedback when used thoughtfully. But a power meter makes it easy to move your indoor specific training outside whenever you want.


Following are just a few examples of intervals. Testing can give you more exact targets, but you can also start out by guesstimating your targets and adjusting to what you find you can do. If guesstimating, I’d suggest to err on the low side. If it turns out to be too easy, increase the resistance in the subsequent set or workout. Aim to make the effort level difficult but not impossible to hit for the last rep.

30 30s. These are 30 seconds at a pretty high level of effort and 30 seconds off, repeated in this example six to twelve times. You might start off with two sets of 6 and progress to sets of 7, 8, 9, or more as you get stronger. Or instead of adding more reps, add more resistance depending on your goals. The level of effort would be tailored to what you can do at the targeted effort level. If you’re starting with sets of 6, the 30 30s difficult part might be done at somewhere around your Aerobic Capacity/VO2max/5-minute test rate. The lower effort would be less than half that. If you are looking to start with sets of 10, you would need to use a lower-effort level than if you were doing sets of 6. Testing with a coach, an app, or on your own can give you a clearer target. And remember the two general rules for intervals from the section above.

Five- or eight-minute efforts. These would be done at a less intense effort (that is, an effort level you could maintain for twenty minutes), with longer rest periods of three to five minutes. You would start at one or two sets with a number of reps and time length you can handle. The “rest” effort can be varied depending on your goals for the workout.

Low Cadence Power Intervals. One example would be repeats of three minutes at FTP at 60 rpms, followed by two minutes at 75% FTP at 100 rpms. The effort level and number of repeats would depend on what you can handle.

Over/Unders. These are efforts alternating between going “over” then “under” a certain level such as FTP or Aerobic Capacity (VO2max/5-minute test rate). An example is two minutes at 105% of FTP then two minutes at 90% FTP, repeated five times for two sets. The effort level and number of reps and sets tailored to what you can handle.

Steps. Once fully warmed up, do two-minute steps (for example, 5 up and 4 down with no rest periods).

  • If using PE (perceived exertion), using the 1 to 10 scale, do steps of two minutes each at a PE of 4-5-6-7-8-7-6-5-4. This is an eighteen-minute set. Base the number of sets and the length of each interval on your fitness. You might start with one-minute steps and over time progress to one-and-a-half-minute then two-minute intervals.
  • If using MPH, recognizing that different trainers have different resistance, pick a range that you can do with your trainer. Example in mph using two-minute steps: 16-17-18-19-20-19-18-17-16. This gives you an eighteen-minute set. Speed will be determined by a combination of fitness and trainer resistance.
  • If you use Heart Rate beats per minute (BPM) instead, one way would be to do steps changing by five beats per minute. Heart rate is a bit trickier since it lags behind your change in effort level. You won’t get to your target until at least halfway through the interval. This example uses two-minute steps of 110, 115, 120, 125, 130, 125, 120, 115, 110.
  • If using Power you might start at  a certain power value we will call “X”.  Your Step workout might be two-minute intervals, for a total of eighteen minutes, at the following power values:  X, X+10, X+20, X+30, X+40, X+30, X+20, X+10, X.   The “X” power value would be set for you based on fitness testing or past experience with what you can do.

These are examples only. Your physiology, fitness level, and workout goals will determine the target speeds or heart rates or power you use. Power from a meter is consistent. Speed will be determined by a combination of fitness and trainer resistance (20 mph on your trainer might be 15 on mine). Heart rate is highly variable among individuals and not comparable between individuals. I rode for many years with two other riders of the same approximate age and ability. Danny had a very low heart rate (15–20 below “averages”), Dave had a very high heart rate (30–35 above “averages”), and mine was in the average range; but we were almost identical in overall riding performance for typical club ride distances. Danny could back the pace off by one or two mph and go all day so maybe his low heart rate indicated something. Dave and I, with quite different heart rates, were very close in sprinting ability and endurance (or lack of).

You don’t have to follow a structured plan when training, but it can help you schedule and structure your training to better meet your cycling goals. Setting a specific goal or two can help motivate you as you see progress toward your goals. A goal could be to ride a frequent route at an average pace two mph faster than what you did last year. Such a general goal is good, but even better is setting intermediate goals to help check your progress and motivate you toward meeting the long-term goal. Intermediate goals might include:

(1) Increase my power or speed used in my two-minute intervals by 2/10 mph each week. If using cadence, increase my cadence for a thirty-second interval from 100 to 105, etc.

(2) Get more aerodynamic by riding in the drops. Start by riding in the drops for five minutes at a time. Each week increase by one minute.

Detailed training plans help many stay motivated and remain on schedule to meet their riding goals. A personal coach can help make a plan tailored to your goals that is adjusted based on your feedback. Online cycling apps offer a wide variety of interval choices, and most have fitness testing. They all have good components and offer free trials so you can see if you like their offerings. But one critique is that their plans can be too hard for some. For a brief review of Zwift, Rouvy, Sufferfest, TrainerRoad, and RGT Cycling, see my article “The Basics of Indoor Training” on the MVBC blog.

Cross Training and Indoor Training: If you primarily cross train in the off season, adding a little time on the trainer will avoid loss of cycling-specific skills and fitness so your spring transition back to last summer’s bike fitness will be quicker. Just doing one or two short (that is, twenty to thirty minutes) trainer sessions a week focused on maintaining a smooth pedal stroke reduces any cycling specific losses. An example: warm up for ten minutes, ride one minute at a cadence ten rpms higher than normal, then one minute at normal cadence, and repeat seven times. Then cool down for six minutes. When doing these drills, especially if you are vigorously cross training, don’t make these too hard on your legs. Use a pretty easy resistance/gear level. Let your cross training take care of your leg strength training; these workouts are primarily to maintain and increase your pedaling smoothness.