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Saturday, April 28, 2012

High Intensity Interval Training

Some time ago,  I wrote an article called "Do This and You Will Win".  In that post, I suggested  performing interval training as follows:  "ride absolutely as hard as you can for one minute, then soft pedal as easy as you can for three minutes, repeat 5-8 times or until you think you see Jesus." Assuming that the rider also raced on the weekends, these intervals would be done once a week. 
Since writing that article, I have read numerous critiques of interval training, and heard talk from fellow racers about what they think is the best interval training method.  This made me wonder what is the best interval training protocol or if there even is a best method.  As I think back, I can not even remember exactly the source of my High-Intensity Interval Training (HIT) method.  It certainly didn't come from Lemond's "Complete Book of Cycling."  Nor did it come from Edward 'Eddie B' Borysewicz's "Bicycle Road Racing:  The Complete Program for Training and Competition."  And it definitely did not come from Joe Friel's "Cyclist's Training Bible" (though all are recommended books).  My best guess is that I adopted my interval protocol from an article that I read in Bicycling Magazine, probably a couple decades ago, and it probably was written by Edmund Burke (who was well known for writing science-based training articles).

So my current question is two-fold.  First, is my previously recommended method  for improving cycling performance good advice?  And second, are there other HIT protocols that are equal or better? Or to put it another way, is there an ultimate interval?

The importance of intervals

Before I go straight to the answer, I should first explain the importance of HIT, and why it has value.  It is well established among exercise physiologists and others, that any amount of exercise followed by recovery will increase fitness for sedentary (unfit) individuals.  For beginner and moderately-trained cyclists, increased duration and increased frequency of riding combined with recovery is all that is required to further increase fitness.  Unfortunately, this method of increasing fitness has a ceiling and once this threshold is reached, no amount of increased typical or ordinary riding (aka sub-maximal exercise or below threshold markers) will continue to improve a rider's fitness.  As Laursen & Jenkins state, "in the highly trained athlete, an additional increase in sub-maximal exercise training (i.e. volume) does not appear to further enhance either endurance performance or associated variables such as maximal oxygen uptake (VO2max), anaerobic threshold, economy of motion and oxidative muscle enzymes".   In citing Ben Londeree's research, the authors note that "it appears that once an individual has reached a VO2max >60ml/kg/min, endurance performance is not improved by a further increase in submaximal training volume."  This is not meant to downplay the importance of high-volume training, but to highlight that there is a fixed limit for improving fitness by this method alone.   

 Interestingly, not only is adding a HIT program to your training necessary to reach your full cycling potential, but it can also dramatically speed up the rate at which fitness is achieved.  It is generally believed that it can take several years to go from being an unfit to a highly fit bike racer; however research suggests otherwise.  For example:  Hickson showed that after just 10 weeks of HIT, VO2max could be rapidly increased (+44%; p<0.05) and four of his subjects approached or exceeded 60ml/kg/min in this short time frame.  This does not mean that any cyclist can become an elite rider (>70ml/kg/min for men and >60 for women) in a very short period, though many can become "highly fit" (>60 ml/kg/min for men, >52 ml/kg/min for women) in a relatively short period of time.    Fitness gains initially occur rapidly and  depend on the volume, intensity and frequency of training; as greater fitness is achieved, it appears that the development of the physiological capacities witnessed in elite athletes does not continue to come about quickly.  It may take years of high training loads before an individual reaches his or her full athletic potential through vascular and muscular adaptations.  Outside of developing one's physiology, it can also take years to fully master the sport by developing racing and psychological skills (tactics, equipment, diet, technique, psychology, etc).   

Another interesting and valuable fact about HIT is that, to a significant degree, when compared to aerobic (submaximal) training alone,  it can reduce the exercise time required to achieve or maintain a particular level of fitness, as illustrated by Johnathan P. Little, and especially by Iaia FM, Hellsten Y, Nielsen JJ et al. In short, if you have limited time to exercise/train, then interval training is even more important and efficient for the gaining and maintaining fitness.

I have mentioned  VO2max quite a few times in this article, so it is important to understand a few basics points about it.  VO2max (also maximal oxygen consumption, maximal oxygen uptake, peak oxygen uptake or maximal aerobic capacity) reflects the physical fitness of the individual; it is the maximum capacity of an individual's body to transport and use oxygen during incremental exercise.  While there certainly are other measures of fitness, maximal oxygen uptake (VO2max) is widely accepted as the single best measure of cardiovascular fitness and maximal aerobic power.  In this article, 60 ml/kg/min is used as the critical minimal threshold number for defining a "highly trained cyclist".  For perspective and to see the full spectrum of comparative VO2 max measurements, classified from unfit (32 ml/kg/min) to world class cyclists (90 ml/kg/min) see my article "Comparative Measurements of Maximal Outputs for Cyclist".

There is a reason why I emphasize the distinction between "highly fit cyclists" (VO2max >60ml/kg/min) and lesser-fit cyclists (including sedentary individuals): research shows that "highly fit cyclists" do not respond to exercise stimuli in the same manner as unfit and moderately fit cyclists.  Highly fit cyclists typically will not improve from further increased training volume (with enough volume they will actually get worse), whereas lower fit cyclists will almost always improve with increased training volume.  Also, unfit and poorly fit cyclists can dramatically improve their fitness using nearly any HIT protocol, whereas highly fit cyclists not only exhibit considerably smaller gains, but in many cases they will not make any improvements at all with a HIT protocol that is not correctly designed for them (intensity level,  repetitions, rest duration, and frequency).

Research findings from HIT studies

Below (Table One) are some findings from high intensity interval training studies in sedentary and recreationally-active individuals.  (Source: Laursen & Jenkin's, "The Scientific Basis for High-Intensity Interval Training:  Optimizing Training Programmes and Maximizing Performance in Highly Trained Endurance Athletes."  )  The findings are organized by year of publication, and each study is referenced with links at the bottom of this article.  Collectively, they show that lower fit riders respond well to a wide range of interval protocols - and importantly, many of these studies are the foundation for later research that looks for the best HIT protocols for highly fit cyclists.   The general trend seen in these HIT protocols is to lower the work duration as the intensity is increased.  The studies also increase the number of repetitions as the intensity level is lowered to a specific work duration.  Rest between intervals tends to increase in proportion to the amount of work that is done as the intensity increases, and the total number of repetitions is typically determined by fatigue. Tabata's design is a bit of an exception to this trend with a 20 second work duration and a 10 second rest, but his protocol could be described as one 4 minute intermittent high intensity interval.   


key to the abbreviations used in the charts
Surprises

One of the biggest surprise findings for early researchers (and for myself while researching this topic) was that short 20-30 second HIT could improve both VO2max and 40k time trial results.  By training with short, intense intervals which use primary anaerobic energy (see figure 1 below) a person can achieve significant improvements in long sustained efforts, which largely rely on aerobic energy such as 40 kilometer time trialing.  This isn't exactly intuitive.

 The Ultimate Interval

So, what is the ultimate interval?  First we must ask what is it we are trying to enhance?  As we can see from Figure 1 above, short intense events such as track racing require very high anaerobic capacities and endurance events such as 40k time trialing require very high aerobic capacities.  However, for the purposes of this article, I avoid the topic of "sprinting" (5-15 maximal bursts) and focus on HIT for longer time frames that are commonly used in time trialing and criterium racing.  (Sprint training could be discussed in a future article).   With this in mind, I present a collection of findings from high-intensity interval training in highly trained cyclists, below in Table 2.  These are currently the best and most cited studies that I could find on the topic.  It is also important to reiterate that these studies are on highly trained cyclists; as mentioned previously, they respond to exercise stimuli differently than unfit and recreational cyclists.

So, which is the best?  Let me quote one of the lead researchers, Paul Laursen,:  "It is not possible to unequivocally state that one HIT group improved to a greater extent than the other HIT groups."  ("Interval training program optimization in highly trained endurance cyclists").  However, he does go on to pick out the HIT protocol performed at the intensity of Pmax and a duration of Tmax with a 1:2 work-recovery ratio, as being superior by a small margin to the others.    Ian Dille published an excellent article in Bicycling Magazine titled "The Ultimate Interval", in which he describes this particular HIT protocol in understandable terms.   But to call this particular interval the ultimate interval is a little bit premature.  It is extremely effective, but when we look at the last HIT study in table 2, in only 2 weeks, a group of higher fit cyclists (higher starting VO2max) improved nearly as much as the supposed ultimate interval group did in 4 weeks, while using dramatically different protocols.

So, what we see is that there are likely MANY different HIT protocol designs that are equally effective.  The general rule for an ideal HIT protocol appears to be to lower the work duration as the intensity is increased, and to increase the number of repetitions as the intensity level is lowered to a specific work duration.  Rest duration between intervals tends to increase in proportion to the amount of work that is done as intensity increases, and the total number of repetitions is typically determined by fatigue.

HIT applied in the real world

I would generally advise executing a HIT regimen based on research and not on intuition or hearsay.  Any of those shown in table 2 are satisfactory.  However, it can be difficult if not impossible to follow these protocols if a person does not have power meters and access to lab equipment for calculating precise PPO, Pmax and Tmax.  Even if you have a power meter, it can be very hard.  For example to determine PPO, you need to find your highest 30-second power output completed during an incremental test where resistance is increased by 15 watts every 30 seconds, starting at a workload of 100watts.  Your Pmax is calculated by finding the corresponding power output that is measured at VO2max during a progressive exercise test, and Tmax is time to exhaustion at Pmax.  Laursen deemed test subjects fully exhausted when they could not keep their cadence above 60 rpm.  Sounds simple?  No, it's not.


You may be able to estimate a PPO by testing yourself on a stationary trainer and using a powermeter device.  After lightly warming up begin riding at 100 watts. Increase power by 30 watts every minute (you will have to control your wattage by cadence primarily) until you reach exhaustion (failure to maintain a 60 rpm cadence).  Wattage at PPO is going to be higher than at Pmax by a small unknown amount.  Pmax can only be determined accurately in a lab environment that can measure VO2max with it's corresponding watt output.   However, you can estimate you Pmax by taking the average wattage produced over a 5 minute maximal effort and multiply that by .934 (based on writings from Andrew Coggan and only applies to highly fit cyclists).

Without a power meter you could just simply follow my simple "no tool" method (other than a watch).  I can not unequivocally state that this protocol is as good as the proven studies below, but based on the principles of HIT it should produce comparably similar results.  All you have to do is ride as hard as you can for one minute and rest three minutes or until you subjectively feel recovered and do it again and again until exhaustion or you see Jesus.  When you see Jesus, that's when you know it's time to stop.

Training volume considerations with HIT

All of the highly trained cyclists in the studies cited maintained a high-volume low intensity (submaximal) training ranging from 285 kilometer plus minus 95 kilometers (177 miles plus minus 59 miles) per week, both before and during the study.  In a review of HIT research Laursen (see 23 below) states that, "a polarized approach to training, whereby about 75% of total training volume is performed at low intensities, and 10-15% is performed at very high intensities, has been suggested as an optimal training intensity distribution for elite athletes who perform intense exercise events."  

For cyclists who race every weekend, I would suggest doing only one interval session per week in order to avoid over-training and consider the weekend races collectively as a second interval.  There are a number of bike racers who use racing to get themselves into shape.  This is tried and true, but I speculate that controlled intervals, bi-weekly as described in Table 2 (below) may be superior.   This may be because while racing will certainly produce stress that can trigger fitness, the efforts produced during a race may not be as completely exhausting as an ideal interval session or with the optimal amounts of intensity and work duration.  And because racing has little to no rest opportunities, most cyclists are likely to race more strategically-minded than HIT-minded. 


1.  Hickson RC, Bomze HA, Holloszy JO. Linear increase in aerobic power induced by a strenuous program of endurance exercise
2. Henritze J, Weltman A, Schurrer RL, et al. Effects of training at and above the lactate threshold on the lactate threshold and maximal oxygen uptake
3.  Simoneau JA, Lortie G, Boulay MR, et al. Human skeletal muscle fiber type alteration with high-intensity intermittent training
4.  Simoneau JA, Lortie G, Boulay MR, et al. Effects of two high-intensity intermittent training programs interspaced by detraining on human skeletal muscle and performance
5.  Green HJ, Fraser IG. Differential effects of exercise intensity on serum uric acid concentration
6.  Nevill ME, Boobis LH, Brooks S, et al.  Effect of training on muscle metabolism during treadmill sprinting
7.  Keith SP, Jacobs I, McLellan TM. Adaptations to training at the individual anaerobic threshold
8.  Linossier MT, Dennis C, Dormois D, et al.  Ergometric and metabolic adaptation to a 5-s sprint interval training
9.  Burke J, Thayer R, Belcamino M. Comparison of effects of two interval-training programmes on lactate and ventilatory thresholds
10.  Lindsay FH, Hawley JA, Myburgh KH, et al. Improved athletic performance in highly trained cyclists after interval training
11.  Tabata I, Mishimura K, Kouzaki M, et al.  Effects of moderate intensity endurance and high-intensity intermittent training on anaerobic capacity
12.  Westgarth-Taylor C, Hawley JA, Rickard S, et al.  Metabolic and performance adaptations to interval training in endurance trained cyclists
13.  MacDougall JD, Hicks AL, MacDonald JR, et al.  Muscle performance and enzymatic adaptations to sprint interval training
14.  Ray CA.  Sympathetic adaptations to one-legged training
15.  Green H, Tupling R, Roy B, et al.  Adaptations in skeletal muscle exercise metabolism to a sustained session of heavy intermittent exercise
16.  Rodas G, Ventura Jl, Dadefau JA, et al.  A short training programme for the rapid improvement of both aerobic and anaerobic metabolism
17.  Parra J, Cadefau JA, Rodas G, et al.  The distribution of rest periods affects performance and adaptations of energy metabolism induced by high-intensity training in human muscle
18.  Harmer AR, McKenna MJ, Sutton JR, et al.  Skeletal muscle metabolic and ionic adaptations during intense exercise following sprint training in humans
19.  Laursen PB, Shing CM, Peake JM, et al.  Interval training program optimization in highly trained endurance cyclists
20.  Laursen PB, Blanchard MA, Jenkins DG  Acute high-intensity interval training improves Tvent and peak power output in highly trained males
21.  Laursen PB, Shing CM, Peake JM, et al.  Influence of high-intensity interval training on adaptations in well-trained cyclists
22. Spencer MR, Gastin PB Energy system contribution during 200- to 1500- m running in highly trained athletes
23.  Laursen PB Training for intense exercise performance:  high-intensity or high-volume training? 




19 comments:

  1. Excellent Working Dear Friend Nice Information Share all over the world.cheap bicycle shops london.God Bless You..olympic park cycles

    ReplyDelete
  2. One study that I purposefully left out was, "Effects of different interval-training programs on cycling time-trial performance" conducted by Nigel Stepto, et al. My reasoning for this is that his study muddied an already long and complicated article. I think it's more helpful to discuss this study in the comment section as opposed to the main article for the reasons listed below.

    In the studies by both Stepto and Laursen they have research on a work duration of 1 minute and at first glance the intensities look the same: 100% PP and 100% PPO. This can easily lead one to believe that both studies are testing the same interval protocols (work duration and intensity) but in actuality they are totally different intensities. Stepto's PP was determined by an incremental exercise test starting at a load of 3.3 W/kg, maintained for 150 seconds then increased first by 50 watts, then 25 watts every 150 seconds until fatigue (he calls this peak aerobic power). Laursen's PPO intensity calculation is quite different. He starts at 100 watts, and increases the workload 5 watts every 10 seconds until fatigue (failure to maintain at least 60 rpm).

    This would certainly result in a higher work intensity level for Laursen's subjects compared to the methods that Stepto used. Also Laursen uses 20 repetitions vs Stepto's 12 reps and the rest duration is also entirely different: 2 minutes for Laursen and 4 minutes for Stepto.

    The cool thing about Stepto's study (from my point of view) is that he did use highly fit cyclists, and he found no significant enhancements in performance with his design (12 x 60 s @100%PP.) Had he used unfit or recreationally fit cyclists, I'm sure he would have had a positive improvement with that exact design, and more importantly, his study shows (when compared with Laurens) that intensity and number of repetitions matter. Highly fit cyclists require greater amounts/levels of both intensity and number of repetitions for improving physical fitness, particularly with highly fit cyclists.

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  3. David, I would fall under the highly fit group, and gereraly train around 10 hours per week. In the past I have followed Chris Carmichaels training plans. As you probably know, and have read, he came out with "time crunched cyclist". Well, I decided to give it a shot for my summer peak race season. I am 3 weeks in, and doing well in races I have competed so far. My question is, (assuming you have read) do the power intervals in these work outs fall into HIT training? Or based on your research, should I change up the work loads, to gain the most benifits from this style of training?

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    Replies
    1. Dave, I haven't yet purchased or read Carmichael's book,
      "The Time-Crunched Cyclist: Fit, Fast, and Powerful in 6 Hours a Week". From reading reviews on his work, it appears to be good stuff. I'm sorry that I can't comment on his interval designs, but Carmichael does have a good repetition in the field of training.

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    2. Dave, thanks for the quick reply! I will continue as planned. Plan is to start my peak for the Boise Twilight July 14th, then hold the fitness for Nationals in the beginning of September. (Little longer then I want or possibly can, but that is the hand I am delt) One more question for you. What is your thoughts on standard gearing 53 X 39. Vs. Compact 50 X 34?

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    3. Dave, running a compact crank is the equivalent to doing a half a gear shift down (smaller gear/larger cog) than the 53 x 39 (with the rear derailleur). I think that either would be fine in most circumstances. I would be slightly more concerned with the cassette/freewheel gearing though (depending on the terrain). Check out ,Sheldon Brown's gear calculator. I think you might find it helpful.

      Also the topic of gear choice might lead you to think about cadences and wonder what the ideal cadence is for biking. I have that topic covered in my article, "Ideal Cadence for Competitive Cycling".

      I hope this is helpful for you.

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    4. I have been reading all your blogs through out the day. Lots of great tips and info for me. Outstanding job! I will be doing some testing with the cadence and my watts now for sure. I fall into the catagory of spin faster and you save your legs and energy theory.

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  4. Dave, where would you say these types of intervals fall within an annual schedule? Would you do base/SST/LT through the winter, and then add these on during a build period (early Spring)? Would you continue doing SST/LT work in addition to these HIT intervals, or would you remove the longer intervals entirely at that point?

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    Replies
    1. Bryan, high intensity interval training can be done throughout a training system and are absolutely necessary for peak fitness. Unfortunately removal of HIIT will result in reduced fitness within a matter of several days. Typically the mainstream technique for training is some variety of periodization training. Periodization accounts for most sports being seasonal and allows for reduced fitness immediately following a season (good for psyche) and rebuilding in stages as a new season starts and hopefully timing fitness for a specific race or set of races. Typically the early stages are "base miles" and interval training isn't added until early or late spring. I think this makes sense in some cases, however, using this technique strictly (especially with delayed interval training) has a few draw-backs. One, if you postpone interval training too late, you risk not achieving your maximum fitness at a specific time, and even if you time your fitness perfectly right it's easily possible to miss your event due to illness, injury, unforseen personal issues, etc. And then there's simply unknownable/unaccountable factors (stress variances?, sleep?, gut microbes?, etc) that seem to result in unpredicted strength.

      My general point is to consider not letting fitness drop too much in the off season if you are very serious about the sport and begin interval training earlier than later. As Laursen wrote "a polarized approach to training, whereby about 75% of total training volume is performed at low intensities, and 10-15% is performed at very high intensities, has been suggested as an optimal training intensity distribution for elite athletes who perform intense exercise events." I think this is a fairly safe way to go.

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  5. Very valuable post David. I'm preparing for a 300K event in about half a year and I like to pimp my (actually very traditional) training plan with HIIT workouts. So your post is a source of inspiration for me! Thank you for sharing your ideas!

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  6. David, How much of a factor do terrain and climate effect training and fitnessin respect to interval training? I lived in a very hilly region of the country. In one route you'd ride from one 7-9% grade to the next. In a sense you'd be riding intervals on every ride and the greater your fitness the more miles (intervals) you'd get in. That idea has changed a little for me because I now live in a hilly/flatish region where wind is a big factor. Does riding in challenging terrain and under difficult circumstances such as strong winds, cold weather serve the same or equal to interval training per se?

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    Replies
    1. John, "riding in challenging terrain and under difficult circumstances" will most certainly enhance fitness. This is especially true for unfit riders and less true for fit riders (VO2 max > than 60 ml/kg/min).

      There is a training methodology that is based on the previously mentioned style of riding called "Fartlek", in which the terrain and pace are varied to enhance conditioning.

      The key to greater fitness is intensity over time. Fartlek training is fine for variation, but I personally prefer and recommend structured training protocols in order to correctly (or ideally) dose the amounts of work and recovery periods.

      A hilly and windy route will indeed force intensity, which is ideal for Fartlek training, but potentially undesirable for a recovery day.

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  7. I have always believed that a good coach should be part scientist, part psychologist and a bit of a sportsman. @David Henderson: I think you will make an awesome coach because you know how to make sense of science in a useful way.
    I really loved reading your article. You could have easily got it published in a sports journal as a review.

    ReplyDelete
    Replies
    1. Saurabh Sharma: Thank you very much for your comment! :-)

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  8. great research about the importance of interval between any kind of exercise or practicing any other thing.
    interval training for women

    ReplyDelete
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