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. https://www.ncbi.nlm.nih.gov/pubmed/17414804

But not the only factor as illustrated in this study. https://www.ncbi.nlm.nih.gov/pubmed/21812820 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 "rode...at 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). https://www.ncbi.nlm.nih.gov/pubmed/17414804 .

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. https://www.ncbi.nlm.nih.gov/pubmed/19910820 . 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. https://www.ncbi.nlm.nih.gov/pubmed/19910820 
  • 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. https://www.ncbi.nlm.nih.gov/pubmed/24066036 . 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. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3912323
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 Roadbikerider.com 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 (https://well.blogs.nytimes.com/2015/12/30/can-too-much-exercise-harm-the-heart/) 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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Introduction -- Cycling Performance Tips Ebook

In the late 1980's I wrote Bicycling Fuel as a nutrition guide for cyclists. I wanted something based on sound physiology and medical studies/published articles, and to avoid the personal testimonials which were all too frequent among my friends.  Then in the early 1990's when the book went out of print, I transitioned the content to a website cptips.com with the intent to maintain the same philosophy of solid recommendations based on data.

Over the years, as I ran across performance tips on equipment and training programs, I added these to the website. Thus the focus is now on all aspects of performance improvement for cyclists.

I've regularly toyed with the idea of an ebook summarizing the website content into a short read that would be more useful for the average recreational cyclist. And for those interested in the background studies, the website remains available.

If you find this ebook helpful, a few dollars for your "purchase" is always appreciated to help defray my monthly ISP expenses. (I included a PayPal link on the blog. )

The downside of using the blog format is it wants to keep my posts in chronological order while I want the flexibility to address chapters as I have time. For example, Interval Training has been of interest to many readers of my FaceBook Page so I am doing it as the first.

My first entry in the blog archives will be a Table of Contents which will then remain at the top. I will then update it as I add chapters. It will become more useful as time passes.

I hope you enjoy the content. Feel free to send me questions and feedback via cptipshome@gmail.com

Dick Rafoth MD


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Table of Contents -- Cycling Performance Tips Ebook


Performance Metrics

Keys to Improvement