Saturday, November 11, 2017

Bicycling Performance Metrics

How hard am I working? Am I pushing myself and getting the maximum from my training efforts? These are common questions for any cyclist focused on a high quality workout.

There are a number of metrics (or measures) of how hard you are working as you cycle.

The simplest of these is a rating of perceived exertion (RPE), a numerical self-assessment of your perception of personal effort on a ride (or other activity) that requires no additional equipment. With a little practice, anyone can use this measure.

More complex, but also more precise, are several laboratory-derived measurements such as lactate threshold (LT) or oxygen uptake (VO2). But as they require specialized equipment, they are not really available to the average cyclist.

Between these extremes we have the cycle computer, heart rate monitor, and power (watt) meters.

What follows is a summary of the most commonly used metrics in the physiology and cycling literature.

Perceived Exertion (perceived effort)

The RPE is a simple self-scoring of how hard you feel you are pushing yourself. The original RPE scale ranged from 6 to 20 and assumed that adding a 0 to your level of perceived effort would correspond with your heart rate (i.e. if you were resting, a 6 on the scale your heart rate would be in the neighborhood of 60). There is also a condensed 10-level version. 

Although RPE isn't accurate enough for detailed physiologic studies, research has demonstrated an amazingly high correlation for an individual from day to day. In other words if you felt you were exercising at 6 out of 10 (somewhat hard) on two different days, your heart rates would be quite similar.

Additional links:

Energy versus Power

ENERGY is a quantity (or amount) of FORCE and is measured in joules, ergs, or calories. 

When energy is applied (to move an object, a bicycle and rider for example) WORK is being done.  

POWER is the RATE at which that work is done (energy is applied to the task) and is measured in watts. It takes more power to do the same work over a shorter period of time. Power in the bicycle world is expressed in Watts. 1 Watt = 0.86 Calories per hour. A biologic Calorie (capital C) is equal to 1000 physical chemistry calories (small c).

An example: You use 100 Calories of energy on a 1 hour ride and then later in the day do another 100-Calories ride in only 30 minutes. You did the same amount of work on both rides, but the 30 minute ride was more difficult. You needed to be a more "powerful" rider to complete it in 30 instead of 60 minutes. 

In terms of power:

100 Calories over .5 hours = 200 Calories/hour. 200 Cal/hour divided by 0.86 = average power output of 232 Watts.

100 Calories over 1 hour = 100 Cal/hour. 100 Cal/hour divided by 0.86 = average power output of 116 Watts, a much easier ride (less power applied) even though the same work was done.

Your road speed reflects the amount of power being delivered to the pedals. But air resistance increases exponentially with speed so you can't just substitute road speed for watts being generated.

Another example may help in the explanation. To win a race, or finish first on a ride (assuming an equal weight of bikes and riders, aerodynamics, etc) you need to power your pedals at a HIGHER AVERAGE WATTAGE than your competitors. If all riders and their bikes are the same weight, you will all have expended the same total energy in the event. But as the winner spent less time on the course, his/her average energy expenditure per minute (or wattage) will have been the highest of all the riders.

Peak power output is a measurement of the maximum power you can generate over a short, several second interval (e.g a power lift in the gym or a sprint on the bike). Peak power reflects quadricep muscle strength, while average power output (over 30 minutes for example) reflects BOTH muscle strength and your level of conditioning, to allow you to use those muscles for a longer period of time before they fatigue.

So we really have 2 power measurements – peak power and average power:

  • Peak power: the maximum power, usually in watts, you can produce in a short (several second) burst.
  • Average power: a power level you can maintain over a much longer period of time. 

When you read about cycling performance, the number most commonly referenced is the average power. It is measured with a power meter which records watts of power being delivered to the pedals (and then via the chain to the rear wheel).

Metabolic Measures

Let's review some basic cardiovascular physiology. Oxygen is required to maximize the efficient metabolism of carbohydrates and fats in order to  produce Adenosine Triphosphate (ATP), the compound that powers muscle cell contraction.

The delivery of oxygen to muscle cells is a multi-step process.

  • First, we need to move oxygen from the air we breathe into the blood stream. In a normal individual, this step, which depends on lung capacity and the diffusion of oxygen across the alveolar wall into the blood, is NOT rate limiting.
  • The oxygen binds to hemoglobin in the red blood cells and is then transported to the muscle cells. The amount of oxygen delivered to the muscle cells depends partly on the oxygen concentration in the blood  (Training, EPO, and blood doping all increase the blood hemoglobin levels and in turn the amount of oxygen that will bind to a cc or milliliter of blood).
  • The volume of blood passing by individual cells also determines how much oxygen is delivered. The volume increases with an increasing heart rate and stroke volume (the volume of blood pumped per beat). The stroke volume, and thus oxygen delivery, increases with training.
  • Finally, oxygen is extracted from the blood by the muscle cells. A training program will increase the efficiency of oxygen extraction by increasing the density of small blood vessels or capillaries around individual muscle fibers.

Additional links:

Heart rate

The body adjusts the heart rate to meet our oxygen needs. As the intensity of exercise increases, the body responds by increasing the heart rate. Thus it is an easy way to quantify exercise intensity.

Maximum Heart Rate (MHR)

Everyone has an individualized maximum heart rate or MHR. As muscle oxygen delivery = heart rate x stroke volume, our heart rate indicates the relative amount of oxygen being delivered per minute, and the MHR the upper limits of oxygen utilization. As it is much more easily measured than maximum oxygen consumption (VO2max) (read below), which requires a physiology lab and expensive equipment, the MHR is often used as a surrogate.

% Maximum Heart Rate (%MHR)

This number is a reflection of the intensity of aerobic effort. A higher %MHR indicates a greater aerobic effort.

VO2 (oxygen consumption)

VO2 is a direct measure (heart rate was an indirect measure) of the amount of oxygen being extracted from the air you breathe to produce ATP to power muscle (and other cellular) activity. It is expressed as a volume (V) per specified time interval (usually 1 minute).


VO2max is the maximum volume of oxygen that an individual can extract from the air by breathing and represents the upper limit of aerobic (or oxygen dependent) metabolism.

As levels of exertion outstrip the cardiovascular system's ability to deliver the necessary oxygen (exceeding the individual's VO2max), anaerobic (or oxygen independent) energy production takes over. Anaerobic metabolism is not only less efficient (less ATP is formed per gram of muscle glycogen metabolized) with a more rapid depletion of muscle glycogen stores, but leads to a progressive build up of lactic acid and other metabolites that ultimately impair muscle cell performance.


This is a measure of how close an individual is to their personal aerobic maximum expressed as a % of their personal VO2max.

Lactate Threshold (LT; also known as functional threshold power or FTP, anaerobic threshold or AT, maximal lactate steady state or MLSS), and onset of blood lactate or OBLA)

In an exercising muscle, the blood flow to individual muscle cells is quite variable. The cells that receive less oxygen will produce more lactic acid (from anaerobic metabolism) than those that are well perfused with oxygen-rich blood. In addition, muscle cells with an adequate oxygen supply also actively remove lactate from the blood. The blood lactate level reflects the final balance between production and clearance.

If exercise intensity is plotted against blood lactate levels (see graph), there is a point at which the blood lactate concentration begins a rapid rise. We call this  exercise intensity the lactate threshold.  Although generally expressed as a %VO2max or %MHR, it can also be stated as an absolute power output (in watts).

Lactic acid has a direct negative effect on both muscle cell contraction and cellular energy production.

When there is excess oxygen being delivered to a muscle cell, both fat and carbohydrates are used to supply energy for muscle contraction. As the oxygen supply becomes more limited, fat metabolism falls off. And when oxygen demand finally outstrips supply, the cell becomes anaerobic and can only metabolize glycogen. Because anaerobic carbohydrate metabolism is less efficient (than aerobic metabolism), producing less ATP per molecule of glycogen metabolized, there is less total energy available before you bonk – run out of gas.

An individual's lactate threshold varies with their level of conditioning. A training program increases the number of capillaries per muscle cell as well as increasing the rate at which lactate is removed from the blood. The net effect is an increase in the LT as a %V02max.

The lactate threshold is in the range of 50 to 60% MHR in untrained individuals and with training will increase to 80 to 85% MHR. This means that for a similar level of exercise intensity (same %V02max or %MHR), the trained individual produces fewer inhibitory products of anaerobic metabolism, and internal energy supplies can support this power output (watts) for a longer time. Some competitors in an event might be able to generate a higher peak power output in a sprint, but the ultimate winner will be the rider who is able to maintain a higher average wattage for the entire event.

Metrics to monitor your performance improvement.

I break performance metrics into 3 groups..

The first group monitors our real-time level of exertion just as a tachometer or speedometer in a car reflects how hard the engine is working. Percent maximum heart rate (%MHR), percent maximum oxygen uptake (%VO2max), and power output objectively identify how hard we are working. They help us track the intensity of our intervals or keep us from going out too fast on a long ride .

The second group tracks hard-wired physiologic upper limits which even with training don't improve significantly. Maximum heart rate is an excellent example. No matter how hard you train, this upper limit is unchanging. Likewise VO2max tends to be a static number. With training we can learn to push through the discomfort - tolerating higher levels of lactic acid for example - performing better at these “maximums” (and in competition), but the absolute numbers don't really change.

The third group of metrics is used to measure your progress over a season or as part of a regular reassessment in a training program.

Before we look at my favorites in this third group, I want to emphasize the importance of eliminating, as much as possible, any variables which might impact results. If you are going to be assessing your improvement (or lack thereof) you want the most reproducible and accurate results possible.
Using an indoor trainer (with the same bike and tires) is a simple way to minimize external (weather) and equipment variables from day to day. Reproducibility is especially important for the power and lactate threshold measurements described below.

Additional testing considerations:

  • Test at the same time of day and with the same timing in relation to your last meal.
  • Maintain the same resistance (or gearing) on your trainer from session to session.
  • Keep the room temperature constant. (A fan is often a helpful addition.)
  • Keep notes, including the timing of the test in your training cycle and a self assessment of your fatigue level before and after the test interval.
  • Finally, you might want to go the extra step and do the testing after a day off the bike.

1. Personal bests

Most of us have favorite routes and track our PRs or personal best times.  It is an easy measure of improvement as the season progresses, but because it is influenced by various uncontrollable variables, especially weather and traffic, it is imprecise.

2. Peak Power (maximal anaerobic or sprint effort)

This is the measure of your maximum power output. Its advantage is that it avoids the negative impacts of both fatigue and the build up of acidic byproducts in the muscles from an all out maximal anaerobic effort.

To perform this test go all out for six seconds  with gearing set at a level allowing you maximize your RPMs without the need to change gears. From a dead stop, standing, give it your all. Measure peak watts achieved (or top speed on a cycling computer).

3. Average Power (maximal aerobic power)

In this test, you identify the maximum average power you can sustain for three minutes. The intent is to approach, but not exceed, an anaerobic effort with its build up of anaerobic metabolites. If you start too fast (sprint speed), and go at an anaerobic pace, the build up of these acidic metabolites will negatively impact your three minute performance.

Using a resistance that lets your maintain your cadence for the full 3 minutes (no need to downshift to an easier gear near the end) and calculate an average power (or speed) over the full 3 minutes (monitoring splits can help in the calculation).

4. Lactate Threshold (maintainable power; 20 – 60 minutes)

This test identifies the wattage (or speed) that can be sustained for time-trial and similar intensity events of up to 1 hour duration. It is, I feel, the best measure of overall cycling fitness. With a duration longer than the average power metric, it naturally keeps you at an intensity where there is an equilibrium between lactate production and lactate removal. Go too fast, and the higher levels of lactate will slow you down until things come back into balance.

The first step is to identify a resistance that allows you to maintain a relatively steady pace for a 20 minutes ride. Your watts or speed may vary a bit, generally slower at the start, but at the end of the 20 minute interval you should feel you have given your all.

Your LT is approximately 0.95 x your average power (or speed) for the full 20 minutes. Why subtract 5%? Because you are using a 20 minute test to reflect an intensity you could maintain for a full hour's ride. The shorter interval tends to be about 5% faster than a full 60 minute effort. 

Wednesday, July 5, 2017

Keys to Improvement

Have you decided you want to become a faster rider? You are tired of finishing at the back of the pack on your weekend rides? Or perhaps you feel you have reached a performance plateau?

Just increasing your weekly mileage will not get you the results you are looking for.  The key to improvement in your performance will be in changing the intensity, not volume, of your training miles. What is your next step?

First, you need to have put in your 400 or 500 early season base training miles. You need these miles to help strengthen the ligaments and tendons around your joints or in the muscles to lessen the odds of an injury by stressing them.

Then you need to review your weekly riding schedule and add both

intervals and
resistance work 

to your training program.


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Monday, July 3, 2017

Keys to Improvement - Resistance Training

Resistance training (gym work, weight training) will improve your cycling performance.

It is not as powerful a factor in training as improving your cardiovascular efficiency, but it may provide the edge that helps you beat your buddies to the finish on a weekend ride.

Why does it help? There are several possibilities that come to mind. The common factor is an improvement in the potential power power output that the muscle can delivere to the pedals of your bike.

 Power = energy produced per unit of time = watts

If you produce more power with your cycling muscles, you will move your bicycle at a faster speed.

The first possibility, suggested in the article, is that resistance exercises (which require that all the muscle fibers in a single muscle work together to achieve maximal force of contraction) improve the efficiency (co-ordination) of a muscle's nerve/muscle units. If the muscle fibers in the muscle (your quadriceps for example) are working in a highly coordinated fashion, all contracting in concert, it will increase power output.

The second is that resistance exercise may improve the velocity (speed) at which the muscle fibers contract when the nerve stimulation arrives. A faster contraction translate into more force generated per unit time which translates into more power (watts).

Finally, resistance exercise will increase the strength of a muscle, as the individual fibers increase in size in response to the stress of increasing loads (as weights are added). That is why you can lift greater weights as training progresses. And once again, being able to produce a more forceful muscle contraction means more muscle power is available.

Thus a well rounded training program should be built around both intervals to improve the cardiovascular aspects of high end performance as well as include components of resistance training to maximize the muscles power potential.

And it may not need to be an all out session at the gym. This article (the original reference) suggests that you don't have to push heavy weights to improve muscle strength. It suggests that instead of pushing weights of 80 - 90% of your maximum for 10 reps, you can use lighter weights (30 - 50% of your one time maximum) for up to 25 reps (to the point of fatigue) and gain the same benefit.

Thus it is not tissue injury and repair that leads to strength improvement but the stress of achieving the total muscle fatigue. This approach not only should decrease the risk of tissue injury that might sideline your biking, but eliminate the barrier of needing to undergo an uncomfortable workout to achieve improvement.

My recommendations would be to add 2 days a week of resistance work a week to your training program and do some standing climbs on a regular basis which might increase leg strength as effectively as work in the weight room.


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Tuesday, June 20, 2017

Keys to Improvement - Interval Training

Interval training is the single most effective addition to a training program designed to improve your performance on the bicycle. The training is based on the biologic principle that stress in biologic systems produces changes (physical and metabolic) to adapt the organism to the stress. This principle is common across all biologic systems – from trees adapting to prevailing winds to increases in strength with weight training in humans.

If you want to ride faster, high intensity work intervals (segments of exercise ridden at a pace that you can't talk easily) alternating with rest intervals (to catch your breath) need to be part of your training program. They will improve your performance more than increasing your total miles (training volume) ridden at a moderate pace. High-aerobic intensity endurance interval training is significantly more effective in improving VO2max than performing the same total work at or below your lactate threshold (~ 70% HRmax).

An interval training program includes a series of bouts of intense physical activity (the work interval or WI) alternating with periods of recovery (the rest interval or RI). The rest interval allows the body to recover and prepare for the another period of maximum stress. Using several sets of intermittent stress/recovery, interval training increases the total time spent at one's peak level of performance for the day's training. A study in runners found that continuous, maximal performance (to exhaustion) could be sustained for only 0.8 miles while a similar level of peak exertion could be maintained for a total of over 4 miles when the training session included periods of relaxation.

And as this study shows us, the intensity of peak effort is a major factor in improvement.

But not the only factor as illustrated in this study. Time spent at maximum effort and intensity interact. It suggests that once a minimal threshold has been passed (probably around the lactate threshold of ~70%VO2mx) the total time spent at maximum exertion can have a disproportionate effect compared to intensity in stimulating improvement. To quote: “Accumulating 32 min of work at 90% HR max induces greater adaptive gains than accumulating 16 min of work at ∼95% HR max despite lower RPE.”

The down side of intervals as a training tool is the observation that training program drop out rates double when intervals are part of the program.

If you have limited time to train, intervals are the preferred approach to maximize improvement for time spent. A study in a group of sedentary participants demonstrated the efficiency of intervals for training. It included two exercise routines - one with intervals and second steady moderate workout. There was also a 3rd control group with no exercise program.
  • The interval group..."warmed up for two minutes on stationary bicycles, then pedaled as hard as possible for 20 seconds, rode at a very slow pace for two minutes, sprinted all-out again for 20 seconds, recovered with slow riding for another two minutes and then finally pedaled all-out for a final 20 seconds before they cooled down for three minutes. The entire workout lasted 10 minutes."
  • The endurance group " a moderate pace on a stationary bicycle at the lab for 45 minutes, with a two-minute warm-up and three-minute cool down."
The results? "Twelve weeks of brief intense interval exercise improved indices of cardio-metabolic health to the same extent as traditional endurance training in sedentary men, despite a five-fold lower...time commitment."
As you deciding how intervals might fit into your training schedule, keep these 2 points in mind.

a) Your current level of fitness will determine the benefit you might gain. The less trained you are, the greater the benefit from interval training. At the extreme, highly trained elite athletes improve only marginally with intervals but still use them to maintain their high level of fitness.

b) The purpose of the intervals you chose to use depends on the goal of your training. If it is for a sprint event, then the intervals you will use will be structured differently than for a long distance endurance event.


I divide intervals into 2 groupings – aerobic (intensity below VO2max) and anaerobic (intensity >VO2max).

Both types stimulate similar adaptive changes in the heart, lungs, and smaller blood vessels within the muscle that then work together to increase the delivery of oxygen to the exercising muscle.

Aerobic intervals (done at less than VO2max) also stimulate changes in cell enzymes and energy pathways that improve the efficiency of use of fat and glycogen by the exercising muscle.

Anaerobic intervals (done at > 100% VO2max and thus less dependent on fat as an energy source) stimulate adaptive changes to buffer and remove the acidic byproducts of anaerobic metabolism. This increases the ability to work at anaerobic levels for longer and longer times. Although many authors suggest that lactic acid is the primary metabolic culprit, there is a significant body of literature that suggests other acidic byproducts are the real limiting factor in anaerobic sprint activity. Studies in subjects who, because of a genetic defect, do not produce lactic acid demonstrate the same discomfort with anaerobic exercise as normal riders.

In 2015 Place et al demonstrated that 1) antioxidants seem to blunt the biologic response to interval training and 2) highly trained athletes seem to derive less relative benefit from their interval training.

Another study suggested that resistance exercise (weight training) induces mitochondrial changes similar to those seen using cycling intervals. Thus resistance training fits nicely as a supplement to (and should be part of) more traditional aerobic interval training programs.
In summary, the changes from interval training include:
  • adaptation in the heart (pump for the blood) to pump more blood per minute through the lungs to extract oxygen and deliver it to the muscle cells.
  • development of more capillaries per muscle fiber which translates into more blood delivered to individual exercising muscle cells every minute. This means more oxygen for use by the now more efficient mitochondria as well as the ability to carry away greater amounts of the waste products of both aerobic and anaerobic activity. 
  • changes in muscle cell metabolic machinery to increase the amount of oxygen that can be used by the cell per minute in the breakdown of muscle glycogen to produce ATP. These changes are thought to occur in the cell powerhouse, the mitochondria and extend the length of time until one becomes anaerobic in activity at or above VO2max
  • improvement in our ability to deal with the muscle discomfort of anaerobic level activity and exercise longer at any level of exertion.


Remember that I have arbitrarily divided intervals into 2 groups based on the intensity of the WI (work interval).
  • Aerobic - intensity < VO2max (or 105% VO2max) and
  • Anaerobic - intensity > 105% VO2max
To improve your VO2max, you will need to exercise at an intensity that is above your Lactate Threshold (about 70%VO2max or 70% Maximum Heart Rate). .

Once you have crossed that threshold, improvement increases with increasing exercise intensity until you reach an upper limit at about 105-110% VO2max (or anaerobic metabolism). At that point, further intensity does not appear to provide additional stimulus to improve your VO2max. . There are two possible explanations for an upper limit.
  • First, once you reach this limit it is difficult to maintain intensity and the total “work” (effort x time at effort) you are doing with the interval. And the total work at maximum effort which may be the stimulus to improvement, begins to decrease. 
  • Second, the actual molecular stimuli may be maximal at your VO2max and thus greater exertion adds no additional stimulus to adapt.
This does not mean there is not a benefit from anaerobic intervals, just that they do not appear to increase VO2max. They still appear to improve the ability to remove anaerobic metabolism waste products.

Thus you should use anaerobic intervals (intensity >VO2max ) to improve sprinting ability. And aerobic intervals to improve your VO2max and thus the speeds you can maintain without slipping into anaerobic metabolism.


We know that the longer an interval (of equal intensity) the better the improvement in VO2max. . But the duration (length of time you can hold any interval pace) depends on the intensity of the interval. The more intense your interval pace, the shorter the time you can maintain it. Even competitive athletes can maintain these maximum exertion intervals for only 30 seconds before they gradually slow.

The duration of an aerobic work intervals (below VO2max) depends on the interval intensity. You can hold an interval at 70% VO2max (Lactate threshold) longer than one at your VO2max.

For a VO2max interval, 4 minutes is a common duration noted in the literature. This fits nicely with the simple approach to measuring your VO2max which is often defined as the fastest speed you can maintain over a ¾ mile course, which is usually 3 or 4 minutes.

Anaerobic intervals are generally 15 to 30 seconds at a perceived exertion (PE) of 10.

Your goal should be a total time of 10 to 20 minutes of hard pedaling (the total time of the work intervals themselves - don't count warm up, recovery, or cool down). If you are just beginning an interval program, start with 5 minutes of peak effort per riding session (total interval time for any training day) and work up from there.

It is not clear to me if there is a liner relationship between the total time ridden at any work interval intensity and VO2max improvement i.e. a total riding of 8 minutes at WI intensity leads to twice as much improvement in VO2max as a total time of 4 minutes. Just as you get greater improvement with your first resistance training sets, the first 2 or 3 minutes may get you 50% of the total potential improvement, the next 2 or 3 minutes another 30 or 40% (rather than another 50%), and the final 2 or 3 minutes only 10%. This could explain why the new programs using fewer short intervals are so successful – they take advantage of this early disproportionate response. There is no indication of an upper limit beyond which further interval time becomes unproductive although the more work intervals you ride, the more difficult it is to keep up your intensity.


To maximize the benefit from interval training, it makes sense that you'd like to maximize your training minutes (total work interval minutes for the day) at the planned level of exertion (Lactate Threshold, VO2max, Anaerobic).

The rest interval is important in preparing you for the next intense work interval. If you don't rest long enough, the intervals will gradually decrease in intensity over the session, and the total minutes spent at maximum exertion will decrease.

It is not necessary that your heart rate return entirely to normal before the next interval. If you are using a heart rate monitor, for example, wait for your heart rate to drop to 60 or 65% of your maximum heart rate. If you are using perceived exertion (i.e. how you feel) to decide, wait until your breathing has returned to it's normal depth and rate.

The rest interval should be active rest (easy spinning) and the duration of the rest interval, as you might expect, dependent to a degree on the duration of the exercise interval. Generally the duration of the active rest should be equal to the work interval with the caveat that if you are finding you can not hold your interval intensities, you should lengthen the recovery time.

Don't forget your 20 to 30 minute warm up and 15 minute cool down at the beginning and end of your daily session. I like this common sense approach used by Dr. Mirkin:
  • I take a very slow 10-minute warm up.
  • If my legs still feel tired or stiff or I have localized pain after the warm up, I take the day off.
  • If my legs recover during the warm up, I then do a series of standing 50-pedal-stroke intervals fast enough to make me short of breath each time, followed by a slow recovery of however long it takes to get my breath back and for my muscles to feel fresh again. I do not time recoveries, since starting an interval before full recovery would slow down my next interval.
  • As soon as my legs start to feel heavy, I stop the interval workout and start my slow and short cool down.

My definition of an interval set: one work interval and one rest interval = 1 interval set.

I have never seen data or a recommendation for total interval sets per day and think it will end up being a highly individualized number based on how many sets you can do before your work interval intensity begins to fall off. For 4 minute aerobic intervals, 4 sets seems a number. For anaerobic intervals I suspect 8 or 10 sets will be the upper limit for most riders.

What if you don't have the time for the number of interval sets you had planned for the day? We know from weight-training studies that the first set or two of resistance exercise provides the majority of the stimulus for improvement with multi-set workouts. If you do five sets of bench presses, for instance, much of the benefit occurs during the first set. The second set stimulates most of the remaining improvement possible from the session. The final three sets do relatively little.

It is likely that the same applies to interval training. Thus the first one or two sets (exercise and recovery = 1 set) of intervals are the most likely to provide the bulk of the training benefit with the remaining intervals subject to the law of diminishing returns. So just two sets may provide the majority of the possible benefits.

It may be that if you spread your interval sets throughout a 2 or 3 hour ride it will get you just as much benefit as putting them together in a 30 or 40 minute session as you have the same total time spent at your maximum intensity in both scenarios. If so, you might get similar benefit if you did your 8 – 30 second intervals dispersed throughout a 2 or 3 hour ride as doing them all in the first hour.


The intensity and duration of your intervals will impact the third factor in an interval training program, the frequency of your interval training days. The longer your intervals, the more minor muscle damage and the more need for an easier riding day in your training plan before another interval session.
Most trainers recommend 2 focused interval days per week – probably based on the results in the study to be presented shortly.

Dr. Mirkin is a proponent of incorporating some training stress (intervals) into every riding day (even on a slow easy day). But at the same time he advocates listening to your bodies and getting off the bike for a rest day if your legs are telling you that it is not a day to ride. So when he talks about intervals, you have to pay close attention to be sure you understand which type of interval he is addressing.

Per Dr. Mirkin, "A sound endurance program should include .... one or two workouts with many short intervals, and probably at least one workout that includes a few long intervals each week." The dedicated short interval days would include 6 or 8 - 30 second intervals. The long interval day would be 2 or 3 - 2 minute intervals. And the remainder of the riding days that week would have "mini-intervals" embedded on a random basis.


The most significant study (I coould find) comparing different approaches to interval training was published in 2015 by Stoggl and Sperlich.
Study participants were high level competitive athletes. Four training regimens, all of which included 6 riding days a week, were compared.
  • High Volume Training (HVT) – 5 days of riding 1 – 3 hours at 65 – 70% VO2max (below the lactate threshold or LT) and a single day a week riding for an hour at LT.
  • Threshold Training (THR) – 4 days of riding at Lactate Threshold ~ 70 – 80% VO2max, a fifth day with intervals just slightly above LT, and a sixth recovery below the LT.
  • High Intensity Interval training (HIIT) – which included one stretch of 12 out of 16 days of intervals at 90 – 95% MHR
  • Polarized Training (POL) - 2 interval days a week (at 90 – 95% MHR) with the remaining 4 days recovery riding below the LT.

The HIIT and POL intervals days were structured with a 20 minute warm up, then four sets of 4 minute intervals with a 3 minute recovery between them, and finally a cool down. The interval intensity was 90 – 95% MHR (or close to VO2max).

The authors documented a significantly greater increase in VO2max with Polarized Training over the HIIT program, presumably due to the benefit of the additional recovery time in POL. A clear indication that where intervals are concerned, more (interval time) is indeed less (improvement in VO2max).


If you have a heart rate monitor, you can key intervals to your maximum heart rate. Ride your intervals at 80 to 90% of your maximum heart rate, then spin easily until your heart rate drops to 60 to 65% of maximum.

Find a road where small hills come one after another. Fly up one side, blast down the other and use your momentum to conquer the next rise.
Rhythm is everything. Here's how to keep yours on successive climbs: As you ride into a hill that takes just seconds to climb, shift one gear lower (next larger cog) than you might normally use. Stay seated and spin for about two thirds of the climb. If you're riding with others, they'll probably be standing, pedaling slower than you and maybe pulling a little ahead. Don't worry about getting dropped. Keep spinning. You're saving your legs.

In the final third of the hill, click to a bigger gear (next smaller cog), stand and apply the pressure. Your legs will still have snap, thanks to spinning to this point. When you hit it right, you'll know where the phrase "dancing up the hill" comes from.

This was a suggestion from the webzine. When you're training alone, sprinting against imaginary opponents can be deadly dull. Next time you feel like some speed work, use telephone poles as sprint markers. After warming up, start by sprinting from one pole to the next and then spinning easily for 4 poles. Repeat 3-5 times.

To vary the drill and increase the effective length of your sprint, go all out for 2 poles, spin easily for the next 4, and repeat 3 times. Of course, all telephone poles aren't the same distance apart. Use the varying spacing to simulate race conditions. After all, you never know how long you'll need to sprint. Go hard to the next pole, no matter how far it is, then spin for a minute or two to recover.
Follow this with another sprint between poles. It's perfect for developing the ability to rev up in an instant and then hold your speed for the required distance.

These training techniques simulate what happens in road racing. They're great workouts and guaranteed monotony-busters as well. Warm up and settle into a single pace line moving at a moderate speed. Then try one of the following:
  • Rear Attacks. The last person in line charges past the group, creating a breakaway. When she gets about 200 yards ahead, the pace line works to pull her back. Everyone rides easily for a few minutes, then another rider springs from the rear. Repeat 3 or 4 times.
  • Bridges. When she's about 50 yards clear, another rider chases her down while the pack keeps a steady tempo. Once together, the breakaway pair eases up and drifts back to the bunch. Then two more riders repeat the drill. Continue until everyone has participated.
  • Chases. One rider stops by the side of the road as if getting a wheel change or taking what Phil and Paul call "a natural break." Another rider drops back like a dutiful teammate, and then the two work together to chase down the group. Repeat with pairs of riders.
You can decrease your time on long endurance rides with a little interval training. You might try these two tricks on your next long ride.
  • Vary your speed. Vary the effort level within each ride. Don't lock into a pace that's neither too hard nor too easy. A little variety will lead to improvement in your times.
  • Do 4 sprints every hour. Fast accelerations of even 10-30 seconds can raise your average cruising speed. It doesn't have to be an all-out sprint. Simply stand and accelerate until you spin out the gear, then sit down and spin up to 10 rpm faster. Hold this rpm for several more seconds, then back down gradually. Separated these intervals by 15-20 minutes of riding at your normal pace.
When you are on a long ride a slow, meandering pace can make you feel sluggish or even bored. Before that happens, give your legs a little lift. Throw in a short "pick me up interval" every few minutes. Pickups are like sprints but not as hard.

Watch for opportunities. Get out of the saddle and accelerate away from stop signs, over short hills, out of turns or past the lair of a troublesome mutt. Don't script these pickups. Instead, do them when the terrain or situation asks for it. To do a pickup, choose a cog 2-3 teeth smaller (higher gear) than you'd normally use for the situation. So, if you'd usually roll over a rise in a 53x21-tooth, use the 53x19. Don't sprint all-out. That's not the purpose. Instead, simply stand and wind up the gear for 10-12 seconds.

Effort should be about 80% of a flat-out sprint. You shouldn't be panting after you sit down. A few deep breaths should get you back to the ride's baseline effort. You'll be amazed at how much better you feel on longer rides when you relieve saddle pressure and treat your legs to these brisk efforts.


Assuming you do not have a family or personal history of heart disease, is there a level of exercise that is dangerous or too much for a normal, healthy person? This article ( in the NYT implies that there is not. But the caveat is that the heart is healthy, and silent myocardial ischemia (which could be unmasked with the stress of interval training) is all too common.

There is sound evidence that there is indeed an upper limit for cardiac healthy exercise. The curve of benefits versus exercise volume doesn't just plateau, it probably starts to drop off as the extremes are reached. These three studies suggest there is a reason to remain skeptical.
How would I suggest you approach this sticky issue? First, the benefits. Assuming you have no family or personal history of cardiac disease, there is no solid data on an upper limit of beneficial exercise (where more is really less health wise).

Then the risks. The two health risks from high intensity cycling are musculoskeletal (or overuse) injuries and cardiovascular.

The musculoskeletal injuries are known to all of us who exercise and participate in aerobic sports. Overuse leads to injury. And the cure is to listen to your body, and if it hurts when you are using it, decrease your activity level.

There is no evidence that short term, high level work interval exertion (30 second anaerobic intervals or 4 minute aerobic intervals) is harmful to the heart. Although acute stress might cause some modest cardiac muscle injury (and leakage of muscle enzymes into the blood where they can be measured) this heals within a few days, and only with repeated injury/healing/injury does scarring appear to be a risk. Thus the cardiovascular risks appear to be from repeated stress at the ultraendurance event level. (Pushing through the pain, as it were.)

My suggestion?
  • Intervals to improve your aerobic fitness should not be a worry. If there is any question of vague discomfort or you are just starting an aerobic exercise program, see your physician and get a cardiac stress test.
  • There should be absolutely no worries about long rides once or twice a week to get your musculoskeletal systems in shape for longer rides.
  • As you train, listen to your body.
    • If it hurts (bones, joints, butt) when you use it, reassess and modify your program.
    • If your legs are tired as you do start intervals, take a day off, do some easy spinning (with light interval stress if you feel compelled) and come back ready for another try the next day.


I am going to digress a bit on Dr. Mirkin's philosophy of daily metabolic stress to enhance performance - what he calls "no junk miles”. Junk miles are a focus on total miles, ridden at any speed, as compared to a focus on how hard you are riding that day. The ideal solution is a balance of 1) adequate miles to be comfortable on the bike for long rides as well as 2) intervals of some sort every day you ride.

How did we arrive at what had been gospel - twice a week intervals? Why not do intervals more frequently? The medical literature is interesting in how standards develop. A study is done, in this case looking at interval training twice a week. Subsequent investigators use the same frequency for their studies. And without further investigation twice a week becomes the defacto "optimum". The demands of a balanced training program reinforce this frequency.

You need a long day at some point during the week to get use to longer times on the saddle, an occasional day of restful spinning to minimize the risk of overtraining and burnout, maybe a ride during the week with friends, a day or two off the bike with bad weather or to take care of family or work responsibilities, and soon an ideal training week has room for just 2 (or perhaps 3) focused interval days.

But this personal observation courtesy of Dr. Mirkin suggests that you should incorporate periods of increased exertion (work intervals) into every ride. He came to this conclusion based on personal observations that the more traditional approach was not working for him and his tandem partner. In his words: "....every time that you exercise intensely, you damage your muscles. You know this has happened when your muscles feel tight, heavy or sore on the next day. To deal with this soreness, we followed a program of racing as fast as we could three times a week (Tuesdays, Thursdays and Saturdays). On the other four days we would recover by riding 20 to 30 miles slowly, at about 10 to 11 miles per hour. But something was wrong with this program because we were gradually losing our ability to ride as fast as we had in a previous year. We were doing too many junk miles on our four recovery days each week."
He decided that fewer rest days were actually better for them, and that when he eliminated the rest days (at least a regimented number per week) he actually had less overall muscle pain. He also speculated that every ride should include some stress to provide the stimulus to maintain or improve his speed. And finally, he felt that the only reason to do extra easy miles was to acclimate the riders' butts and shoulders to prolonged time in the saddle. Basically that "....Slow riding or running does not increase your ability to take in and use oxygen and it does not make your muscles stronger."

So they changed their training - not more rest, but more intervals "...riding a short distance fast enough to make you very short of breath. Then you slow down until you recover your breath, and keep on alternating short fast bursts with slow recoveries until your legs start to feel stiff and heavy. Then you stop the workout for that day." Intervals were worked into every riding day. Maybe 50 - 100 pedal strokes (which at a normal cadence is about a minute). And this number was based on how the legs felt. Not an arbitrary number to be mindlessly achieved. "On some interval days, we would do 50 pedal-stroke repeats, resting between each long enough to get our breath back. Other days we would do 100 or 150 pedal stroke repeats. We never plan to do a fixed number of intervals. Instead we would stop the intervals as soon as our legs started to feel heavy or stiff, or when our legs did not recover and continued to feel tired a minute after finishing a fast interval."

So instead of a mandatory one or two rest days every week, they rested based on how they felt. "...then as you continue to ride, your leg muscles usually start to feel better and you can ride fast after you have warmed up. However, if your legs do not feel fresh after you have warmed up for more than 15 minutes, you should just take the day off. So some weeks this might lead to more days off the bike, and other weeks riding everyday might happen."

With this approach it was the duration and intensity of intervals that would change from day to day. Not the traditional 2 days of focused interval riding with intervals that might be longer in duration. And the total riding time might end up being less than the average "preplanned" ride. Even on what would traditionally be a long slow distance ride, intervals (hills could be substituted) were done. Not as a focused period of time within the ride, but randomly throughout the ride (a fartlick or mini-interval). And finally, even on a rest day of easy spinning there would be mild changes in tempo throughout the ride.
But this required one to listen to their legs. Along with adding the physiologic stress of interval training to every ride was the concept of backing off, or stopping completely, if the legs were tired after the warm up. Not an 'I must ride' approach to training. My guess is that a lot of us take this approach already, varying our tempo.

How would I summarize Dr. Mirkin's approach??
  • First, if you have the time, you can benefit from daily riding (or 6 days a week). You may feel better than if you were focused on taking 2 days off the bike each week.
  • Rest is part of training. But it is not incorporated into your training program as a preplanned rest day, but by listening to your body - and being disciplined about it. If you are tired after your warm up, stop. Get off the bike. You have had your daily ride and will benefit more from the rest than the additional miles.
  • The traditional 2 focused interval days (at or near VO2max) is still part of the overall program of stressing physiologic stressing of the cardiovascular and muscle systems. But you are adding, within the limits of how you feel, lesser levels of stress to every ride - counted pedal revolutions, a sprint up a hill, a race to the next light post or telephone poll.
We need to change our focus from a preplanned weekly schedule of riding days of different types and instead look at each day as it comes - rest if tired, push a bit every time we are on the bike, and still keep a day or two of focused interval training.

  • There is a minimal level of aerobic stress (an intensity threshold) needed to stimulate the changes that will increase your VO2max which will in turn increase your average speeds when you are riding aerobically (non sprint).

  • The total amount of time riding at work interval intensity is the most important factor in determining VO2max improvement. The rest interval allows you to increase the total riding time at that intensity.

  • You should develop a good mileage base (300 to 500 miles) before adding intervals to your training program. Adding the stress of intervals with a lower mileage base increases the risks of musculoskeletal injury.
  • Your training schedule needs to include adequate recovery time. Overuse of intervals can be counterproductive. Intervals are most effective when they are part of a POL program and limited to two high intensity sessions a week. If your legs feel tired after you have warmed up, cut short or eliminate intervals that day.
  • There does not appear to be additional benefit from riding intervals as hard as possible (that is doing an interval at sprint or anaerobic levels above 105% of your VO2max).

  • Likewise there is no significant improvement in VO2max derived from doing riding longer rides at more leisurely intensities (less than 70 – 80% VO2max).

  • Consider incorporating intervals into all of your training rides. Even on a “recovery” day, if you feel good on the bike, change it up, but keep them short and of lower intensity. This modification of interval training does require flexibility and the commitment to avoid intervals when you are feeling tired. Your training schedule would then include dedicated interval days plus random intervals on other rides (even long slow days) to stimulate the muscles.
    Here is an example of how you might fit daily intervals into a weekly riding schedule:
    • Short Intervals (anaerobic) – Once focused day a week of 6 to 8 30 scond intervals. Done at your all out maximum (a sprint and thus most certainly anaerobic). Short enough to allow you to apply and maintain maximal force on the muscle for the entire interval. 
    • Mini Intervals (fartleks) – Good for any day on the bike. A purposeful increase in your speed during a slow easy or other non interval day. They build some metabolic stress into the ride. A short, perhaps 50 pedal revolutions in duration, increase in cadence and then back to base line. Speed up to the next telephone pole. Count pedal revolutions. Push up a short hill. All qualify as a mini interval.
    • Rest is important. There should be time allowed during the week for a rest day, but Incorporate it into your riding program by listening to your body – and being disciplined about it. Not because it is on the calendar. If you are tired after your warm up, stop. Get off the bike. You have had your daily ride and will benefit more from the rest than the additional miles. Look at each day as it comes – rest if tired, push a bit every time we are on the bike, and still keep a day or two of focused interval training.
  • You also need your non interval training miles. The successful use of intervals in a training program requires the balance of some dedicated interval time but also adequate total riding miles (the total number of hours on the bike per week). 
    It is the combination of intensity of exercise (best achieved with intervals) and total time on the bike (or volume) of exercise (from the long slow distance rides) that determines a cyclist's overall performance in an event or on a longer ride


I use the approach advocated by Dr. Mirkin – some cardiovascular stress every day but with the day's intensity modified as I see how I feel after warming up on the bike.

My training week is generally composed of
  • 2 days including 3 or 4 longer, aerobic intervals
  • 1 day with 6 or 7 30 second anaerobic intervals
  • 3 days at about 70% VO2max that include other “mini-intervals” or an occasional anaerobic interval depending on how I feel.
  • 1 rest day.

Aerobic Intervals

I have a ¾ mile relatively flat course that I use to determine my VO2max. Basially the speed you can hold for ¾ mile is your VO2max speed. I use the same ¾ mile distance for my aerobic interval, doing 3 or 4 work intervals for a day's session.

Anaerobic Intervals

Again I have a flat, straight course that I can ride without being distracted. When you are pushing it, you don't want to worry about cars coming from the side. I do 6 or 7 intervals in a session. But I also throw in an anaerobic intervals randomly on other days as well.


I try to mix it up on other days. Sprinting up a short hill is a favorite.


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