High volume v high intensity, and long term plans

As the daylight hours shorten and we enter the final few weeks of autumn, I am thinking about goals for the coming months.  Looking back, it has been a frustrating summer.  A debilitating illness in June and July torpedoed my preparation for the Robin Hood half marathon in September. My eagerness to determine whether or not I could recover sufficient fitness by September led to a series of problems, the most serious of which was intense over-activity of my parasympathetic nervous system that clamped my maximum heart rate at around 142 bpm in mid-August.  On September 13th, I lined up for the race in a seriously under-prepared state.  My aerobic fitness was not too bad, but I had not prepared my muscles for the rigors of a half marathon race.  Perhaps it was unsurprising that I tore a hip adductor while making a sharp turn across an uneven patch of roadway at about 6 miles.  I did manage to complete the 13.1 miles with a markedly shortened stride and virtually no airborne phase, in a time a little over 103 minutes.  I was pleased that I had managed to get to the finish, and I learned a few things along the way, but overall it was a very frustrating summer. 

Among the things the summer has emphasized is that acquiring aerobic fitness is only a small part of what is required.  If I am going to recover the ability to race at paces in any way comparable to the paces I used to run in my youth, after allowing for the effects of 4 decades of aging since that time, I need a long term plan.  I would like to run a good marathon again, but because I currently work about 50-60 hours per week, there is no possibility that I could do enough training to do justice to a marathon in the near future. 

I plan to reduce my working hours substantially in 2011.  So my goal is a ‘good’ marathon in 2012, but what could be described as a ‘good’ marathon?  Using the WAVA adjustment for age, my races of 40 years ago indicate that, all being well, I might be capable of a marathon time around 3 hours in my late 60’s.  However, several minor ailments which I have had since childhood and which caused minimal problems in young adulthood, have been much more troublesome since my fifties, so a 3 hour marathon is clearly out the question for 2012. For the time being I will set a provisional target in the range 3:15 to 3:30, and refine this target more precisely in light of what appears plausible as 2012 approaches. 

How should I prepare myself?  The major debate in endurance training is the debate between focus on high intensity and high volume training.

 

High intensity

The father of high intensity training was the German coach and cardiologist, Woldemar Gerschler, who developed the concept of interval training: bursts of anaerobic activity separated by brief recovery epochs.   This approach led in a fairly direct path via coaches such as  Franz Stamfl, to Roger Bannister’s demolition of the 4 minute barrier for the mile in 1954.   The parallel development of a similar approach led Emil Zatopek to gold medals in the 5000m. 10,000m and marathon in Helsinki in 1952, though it might be argued that Zatopek combined high intensity with high volume. 

More recently, the Furman Institute have developed a program based on only three running sessions per week entailing high intensity with modest volume.  The Furman program is supported by scientific evidence about the most efficient way to enhance aerobic metabolism, and the studies performed by the Furman Institute provide clear evidence that the program works in practice.  In an article in Runners World in Feb 2006, Amby Burfoot, reported that 15 of a group of 25 amateur runners who undertook the Furman program in preparation for the Kiawah Island Marathon while maintaining their usual commitments to jobs and family, set personal best times.

The paces specified for the three weekly runs in the Furman program: an interval session; a tempo session; and a long run, are all very demanding.  My own judgment is that the program places a little too much emphasis on aerobic development and not quite enough on development of endurance, but I have no doubt that for a runner with the determination to adhere to the program, it offers a good prospect of achieving the target time.  At first sight, the demanding paces might appear to carry a substantial risk of injury.  However, the fact that there are only three running sessions per week provides a fairly generous amount of time for recovery between sessions, thereby minimizing the cumulative fatigue that predisposes to injury.  In the Runners World article, Amby Burfoot reported that there was only a modest injury rate among the group of 25 runners in the Furman marathon study in 2004.   Injury forced one to withdraw from the program, and minor injury led three to drop from the marathon program to the half marathon program.

Because I think the Furman program does not place enough emphasis on endurance, I consider that it is only a useful program in the final four months of preparing for a target race once a sound base has been established.  I do not consider it is suitable  as the mainstay of a three year campaign, though I will reconsider it as I prepare for a few targeted half-marathons along the way.  I might consider a modified version of the program in the final phase of the campaign in 2012  but perhaps I should not make too many assumptions this far in advance 

 

High volume

The father of the high volume approach was Arthur Lydiard.  He promoted periodization of training with the major emphasis on the base building period, in which most the important feature was running about 100 miles per week at ‘a good aerobic pace’.  The spectacular tally of Olympic gold medals by Lydiard’s protégés, Peter Snell (800m, Rome 1960; 800m and 1500m, Tokyo 1964); Murray Halberg (5000m, Tokyo 1964), Lasse Viren (5000m. and 10000m, Munich 1972); and Pekka Vasala (1500m, Munich 1972) leaves little doubt that Lydiard’s approach can be extremely effective.  

More recently, coaches such as Hadd have reformulated Lydiard’s approach for an era in which heart rate monitors have facilitated a scientific approach to high volume training.  While Hadd’s approach is based on the sound practical foundation developed by Lydiard, and incorporates some sensible suggestions about using the HRM to monitor progress, ironically, his science appears to be based on a mis-reading of the scientific literature.  He appears to have mis-interpreted Dudley’s studies of rats (’Influence of Exercise Intensity and Duration on Biochemical Adaptations in Skeletal Muscle,’ Journal of Applied Physiology, vol. 53, pp. 844-850, 1982).  Dudley subjected laboratory rats to 8 weeks of training involving running on a treadmill 5 times per week at various intensities and for various durations.  He measured the increase in cytochrome oxidase, a group of enzymes located in mitochondria, that catalyze the final steps of oxidative metabolism.  The amount of cytochrome oxidase provides a good measure of aerobic metabolic capacity. Examination of Dudley’s data clearly demonstrates that the gains in aerobic capacity increased with increasing intensity of training up to VO2max, not only in muscles dominated by fast twitch fibres, such as white vastus, but also in muscles with predominant slow twitch fibres, such as soleus.  It is only at supra-maximal intensity levels above VO2max that there is any evidence of a lesser rate of improvement in aerobic capacity with increasing intensity.  Furthermore, at these supramaximal levels the total duration of training was less, and the lesser improvement in aerobic capacity might reasonably be attributed to decreased duration of running rather than inhibition of aerobic development.

It is not only evidence from studies of rats, but also the majority of evidence from studies of humans demonstrates that training intensities in the range between the anaerobic threshold (at which lactate accumulation accelerates) and VO2max (beyond which heart rate does not increase despite increasing power output) are effective for improving aerobic capacity.  In the study by Gibala and colleagues comparing 6 sessions of high intensity sprint cycling consisting of 4 to 6 30second sprints with 6 session of endurance training consisting of 90-120 minutes of cycling at 65% of VO2max, over a two week period, similar improvements in performance; muscle oxidative capacity; muscle buffering capacity; and muscle glycogen content were produced even though the total training time commitment was only 2.5 hours for the sprint training compared with 10.5 hours for the endurance training (J Physiol Vol 575, pp 901-911, 2006). Unfortunately, Hadd’s interpretation of Dudley’s data appears to have contributed to a fear among his disciples that exceeding lactate threshold during training will damage the development of aerobic capacity.   I believe this fear is unfounded.

It is also important to note that both Lydiard and Hadd advocate that a substantial proportion of training should be near the upper end of the aerobic zone.  Lydiard refers to running at a ‘good aerobic level’ and recommends the use of three different intensities that span the aerobic range, with several runs a week at the highest of these levels – a pace he designates as  ¾ pace.  As discussed in my post on 9th April 2009, Lydiard’s ¾ pace corresponds approximately to lactate threshold pace.  Similarly, except in weeks in which the weekly mileage is increasing substantially, Hadd typically recommends two runs per week at heart rate that is about 10 bpm below the lactate threshold value.  While I think that Hadd’s science is questionable, I think that in practice, many of his recommendations for training have great merit.

 

How do African runners train?

The current dominance of African runners, including Kenesa Bekele, world record holder for the 5000m and 10,000m, and Haile Gerbselassie, world record holder for the marathon, suggests that they must be training effectively.  It is probably simplistic to assume that all African distance runners train similarly, but nonetheless, the bulk of the evidence suggest that many do a large amount of their training at a pace near to lactate threshold.  In a study comparing black South African runners with whites, Tim Noakes and colleagues found that the black and white runners had similar average weekly running volume (60 miles per week) but the black runners did 36% of their running at  above 80% of VO2max, while the white runners did only 14% of their running above this level (Journal of Applied Physiology, vol. 75, pp.1822-1827, 1993).  However it was not simply a matter of the black runners trying harder.  The black runners produced lower levels of lactate when running at a specified intensity.  Most notably they exhibited 32% lower blood lactate concentration when exercising at VO2max.  Furthermore, they were able to sustain an isotonic contraction at 70% of maximal force for about twice as long as the white runners, despite having a similar proportion of high endurance type 1 (slow twitch) muscle fibres.  This suggests that they had a much greater degree of development of the aerobic capacity of their type 2A fibres.   In my mind, the most plausible explanation is that many years of running at paces in the upper aerobic zone had produced great development of aerobic capacity, especially of type 2A fibres, allowing them to maintain training paces at or above 80% of VO2max without undue stress.

Thus, it appears that African runners dominance is due at least in part to doing a higher proportion of their training  at fairly high intensity (eg 80% of VO2max), but there is an important caveat: the African runners produce a lower level of lactate when training at high intensity.  This is consistent with anecdotal reports that elite African runners train hard but avoid remorselessly punishing their bodies.  Furthermore, anecdotal evidence suggests many have been running since childhood and it is likely that this has provided a crucial foundation.  It might be dangerous to assume that a runner with only a few years of regular training could safely do large volumes of training near to lactate threshold.

 

So which is better: high intensity or high volume?

It is clear that both high intensity and high volume approaches can produce improved aerobic capacity. In a runner with moderate baseline fitness but under-developed aerobic capacity, either approach will lead to improved performance.  Perhaps the most important issue is avoiding injury.  The high power output required for high intensity running places great acute stresses on muscles, but cumulative fatigue associated with high volume training can result in failure to mount a well integrated reaction to an unexpected jolt, and lead to tearing of an already exhausted muscle.  Looking back over the years, I can attribute approximately the same number of muscle injuries to inadequate preparation for increase in volume as to inadequate preparation for increase in intensity.    

At elite level, the distinction between the programs lessens, as the choice is between high volume with fairly high intensity (eg a substantial proportion at tempo runs at 80% of VO2max) on the one hand, and fairly high volume including a substantial number of high intensity interval sessions, on the other.  Either of these options is probably only feasible for individuals with a very well established base level of fitness.  The evidence from laboratory studies suggest that aerobic fitness can be increased most efficiently by training at high intensity, and therefore a program with a substantial number of anaerobic interval a sessions is probably the most efficient way to increase aerobic fitness.   However, while aerobic fitness is crucial for distance running, it is not the only thing that matters.  The current dominance of African distance runners suggests that high volume at fairly high intensity (eg mainly near lactate threshold) might be preferable, though my own opinion is that years of running, starting in childhood, is the major factor accounting for the success of African runners.

 

My own younger days

I was never an elite athlete, although I suppose I could have reasonably described myself as a sub-elite marathon runner, with my best times in the range 2 hours 20 min to 2 ½ hours.  Perhaps surprisingly I have no precise record of my best races, maybe because I did not consider myself a serious athlete.  During my running ‘heyday’ I was actually more interested in mountaineering.  Insofar as I trained systematically at all, I aimed to run moderately large volumes (occasionally up to 100 miles per week) at a ‘good aerobic pace’.  I used to consider that there was little point in running any slower than 6 minute mile pace.  I preferred to spend my time walking in the hills or climbing mountain rather than running slowly.   So perhaps my training could be classified as Lydiard style though I rarely did the high volumes recommended by Lydiard.  On the other hand, I did some tigerish hill walking and mountaineering.  The other point to note is that like some of the Africans, I ran to and from school as a youngster, and during my teens, I simply regarded running as a normal form of locomotion.  I also played a lot of football and basketball.  But that was a long time ago.

 

The risks of too much training

Not only does training present a risk of acute injury but also a risk of overtraining.  There are two forms of overtraining : the sympathetic and the parasympathetic.  These are characterized by impaired performance accompanied by psychological a features such as fatigue and low motivation; together with a complex array of abnormalities of the autonomic nervous system and hormonal function.  As discussed in my post of 29th June, one of the most thought provoking aspects of over-training is the possibility that it is associated free radical damage arising from the failure to re-cycle ADP.  

The high energy molecule, ATP (adenosine triphosphate), is the immediate source of the energy that drives muscle contraction.  It is a molecule consisting of a purine (adenine) and a ribose sugar molecule  linked via high energy chemical bonds to three phosphate groups.  When ATP is harnessed to drive muscle contraction, it is split to produce ADP (adenosine diphosphate) and a phosphate ion.  Most of the ADP is re-cycled in the process of regenerating ATP in the final stage of either aerobic or anaerobic metabolism.  However, a proportion of the ADP is not recycled, but instead is degraded to uric acid.  The process of degradation of ADP generates free radicals – very reactive molecules that can damage muscle tissue by oxidation.  Such damage would be expected to have long-lasting effects, and perhaps even be irreversible, especially in the older runner.

The facts regarding free radical damage remain uncertain.  There is ambiguous evidence regarding the benefits of anti-oxidant supplements.  However, after weighing-up the various strands of evidence, I am inclined to believe that for the runner who wants to continue to enjoy running into old age, one of his or her maxims should be to train as little as is necessary to achieve his or her goals.

 

The challenge

Thus, I am on the horns of a dilemma.  I believe that the successes of contemporary African distance runners, and perhaps even my own modest successes as a marathon runner four decades ago, were based on the cumulative benefits of many years of vigorous exercise.  Yet, there is also a body of evidence suggesting that excessive training might ultimately result in long term damage.   I am therefore going to have to make some shrewd judgments in the design of my campaign to yet again run a creditable marathon and to continue to enjoy running for many years after.

In the past few weeks I have been doing a lot of thinking about this challenge, and I have almost completed crafting my plan – a plan that will no doubt require adjustment as the years go by.  It is a plan that entails periodization.  Every period will include ‘foundation’ activities designed to promote continuous development of blood vessels supplying heart and leg muscles, and the development of the aerobic capacity of type 2A muscle fibres, as I believe that both of these adaptations are an essential foundation for engaging in moderately high intensity training without subjecting the body to remorseless stress.  Each period will also have a specific focus.  The specific focus of the first period will be improving the strength of my leg muscles. 

In my next posting I will provide an outline of the overall plan for the campaign to run a good marathon in 2012, together with a more detailed account of the plan for phase 1.

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15 Responses to “High volume v high intensity, and long term plans”

  1. Ewen Says:

    Thanks Canute. Plenty of food for thought there. I’ll be interested in your plan for the next few years. 2012 is a fair way off to be thinking about marathon specific training, although good aerobic development in the next 2 years would be good value.

    Even amongst the African runners there would be variation in terms of intensity vrs volume. For example, Rick showed me the following link:
    http://www.runblogrun.com/2009/10/training_log_of_one_robert.html which shows Cheruiyot running 280 km per week with just two ‘intense’ sessions. Then there’s Wanjiru who’s of the ‘Italian School’, and after many years of big miles is now on around 140 km per week with much more intensity. So, two different ways to get to the same time – 2:05.

    I’ve had success with Hadd – even running a good (for me) 1500m time, with little speedwork. The main drawback for older runners is the time it takes to ‘restrengthen’ fast-twitch fibres and regain an efficient longer stride.

    I’m interested in trying a Furman-style program, but using 3 distinct weeks: A week of higher volume (Lydiard base – about 120k), followed by a week with a couple of sessions of tempo/interval (lower volume), then a week of ‘speed’ – a couple of sessions of sprinting/hills/drills (lower still volume). Maybe this program would be less prone to overtraining?

    Whatever program we do, it has to be ‘fun’ and doable over the long term. I’d like to be running into my 80s.

  2. canute1 Says:

    Ewen, Thanks for the link to Robert Cheruiyot’s training program. As you point out, African runners do not all train in the same way, and the evidence suggests it is possible to run a marathon in 2:05 with either a high volume or a high intensity program. Cheruiyot’s 280 Km per week should certainly be classed as high volume. It is of interest that Larry Eder’s comment on Cheruiyot’s program is : ‘I sure hope this puts that easy running detritus finally to bed. To race fast, one must train consistently and at a high quality….’.
    However, despite the fact that all of the sessions look quite daunting at first sight, I am not sure that this is really the case. Apart from 2 interval sessions, his weekly program is dominated by 12 runs of 15 Km in 50-60 min (average pace 16.5 Km/hour). This is a little less than 1min/Km (or 1.5 min/mile) slower than his marathon pace. According to Daniels’ formula, 16.5Km/hr would require oxygen consumption of 53 l/min/Kg. Similarly Daniels’ formula indicates that a marathon in 2:05 requires an oxygen consumption of 68.4 l/min/Kg and corresponds to a VO2max of around 82 l/min/Kg. These calculations suggest that Cheruiyot does the 15Km runs at around 65% of VO2max. Even allowing for the fact that we should be cautious in applying Daniels’ formula to an exceptional athlete, it does appear that the bulk of his training is an easy pace – at least easy for him. The daunting thing is the sheer volume.

  3. Ewen Says:

    Canute, I had similar thoughts about Elder’s comments on the training. 15km in an hour (even if it’s sometimes 16k), is very easy running for an athlete of Cheruiyot’s ability. His 2:06:23 is right on 3:00 per km, so 4:00 per km for aerobic runs is 33% slower than marathon pace. That would be like a 3 hour marathoner running 5:40 per km (which is often my pace and I’m nowhere near a 3 hour marathon).

    Also, the 1000m intervals are only at marathon race-pace. I’m sure he’d be capable of 2:40 for 1000s if he wished. So the interval sessions are not that intense. I totally agree that the sheer volume of his training is daunting – twice what Wanjiru is reportedly running. I reckon the intensity of Wanjiru’s training would be equally daunting!

  4. rick Says:

    http://www.runningwarehouse.com/LearningCenter/TrainKenyan.html

  5. rick Says:

    and here is a video of rod dixon showing he was using gravity a long time before pose and chirunners

  6. RICK Says:


    HERE IS A MOTIVATION VIDEO FOR YOU AS YOU TRAIN FOR YOUR 2011 MARATHON

  7. canute1 Says:

    Rick, Thanks for the trade secrets of the Kenyans; the thing that emerges strongly is a sense of flexibilty of approach rather than a robot-like adherence to a rigid pace and distance schedule. Thanks also for the links to the Rod Dixon videos; they provide food for thought about both running style and aslo mental strategies.

  8. RICK Says:

    Well the thing is, I bet you never had a heart rate monitor or Garmin when you ran a super fast 2.20!
    We can get so wound up about H-rate, speed etc that we forget about our natural computer, our BRAIN!!!
    MAYBE NIKES SLOGAN ‘JUST DO IT’ has more meaning than we realize!

  9. RICK Says:

    Canute, do you think a forward lean of the body [FROM THE ANKLES]can really help a runner run faster?
    Is it gravity or the fact that leaning forward from the ankles allows one to land more under your COG that might increase speed and do kenyan runners really lean forward when they run;

    http://www.asbweb.org/conferences/2005/pdf/0852.pdf
    http://www.dryessis.com/wp/?p=349

    which is best to lean or not to lean, that is the question that I ask???

  10. canute1 Says:

    Rick,
    It is possible that lean from the ankles is helpful, but not because gravity provides net propulsion. When running on a level surface, any lowering of the COG under the influence of gravity must be reversed for by an equal rise in the COG at some other stage of the gait cycle. However, I believe that the gravitational torque acting in the second half of stance can help encourage a reflexive muscular contraction that helps get the swing leg forward quickly so that it lands at least a little in front of the COG to enable it to support the body in the next stance phase.

    This reflex contraction of leg muscles is readily perceptible when the sprinter accelerates for the blocks. The reason why sprinters propel themselves from a crouched position is partly that this position allows a good push against the blocks, but also that being out of balance for the first five strides forces a very brisk reflex contraction of the leg muscles to get the swing leg forwards on each stride far enough to prevent a fall on the face. In the first four or five strides the COG actually rises by about 50cm, and the work that provides this elevation is done by the muscles.

    When running at a steady pace, a distance runner should remain nearly in balance at all times to avoid waste of energy. However, because it is necessary to have the foot on the ground for a short but appreciable length of time in each stance phase, there must inevitably be a small amount of unbalancing in opposite directions in the first and second half of stance. Granted that there will be some unbalancing it makes sense to maintain an alignment of the body that maximises the efficiency with which the leg can be brought forwards during the airborne phase. Keeping the pelvis forwards with the hip extended slightly at the end of stance (ie leaning from ankles rather than hips) helps promote an efficient forward swing of the legs because the hip flexors are ‘spring loaded’ at the point of lift off.

    So in conclusion I think lean from the ankles is helpful because it promotes efficient muscle contraction that drives the forward swing of the leg. Gravity does not provide net propulsion but it does promote a propulsive contraction of the leg muscles.

  11. RICK Says:

    THANKS GREAT ANSWER
    cheers

  12. Simon Wegerif Says:

    Dear Canute,

    I have recently found your blog and read with particular interest the articles on your measurement & diagnosis of autonomic dysfunction that kept you out of action earlier in the year.
    Although an electronics engineer by trade, I am a keen cyclist and have read a number of journal articles whilst creating ithlete – an app for the iPhone that measures parasympathetic HRV to provide a daily training intensity recommendation with the aim of avoiding overtraining. The apparent contradiction between the 2 observed states of overtraining I now believe is possibly linked to the Polyvagal Theory of Prof Stephen Porges, who argues (though not without detractors) that mammals respond to stress (mental or physical) using branches of the autonomic nervous system in the order that they evolved, with the most recent (withdrawal of parasympathetic RSA) first, then sympathetic, then a more basic form of parasympathetic ‘vegetative vagus brake’ originating from the dorsal motor nucleus. This latter is associated with ‘freeze & feign death’ behaviour and may also protect us from ourselves in extreme circumstances. I have not seen Porges theory linked to athletic overtraining in any literature, but it seems plausible and attractive as an explanation. It could also be an explanation for the sustained parasympathetic activity that you observed.

  13. canute1 Says:

    Simon, Thanks for your comment. Yes, I have been intrigued by Porges polyvagal theory, and have followed the controversy that it has generated. I think that the ‘freeze and feigh death’ reaction might well be related to the parasymapthetic form of over-training.
    I would be interested to hear more about ithlete.

  14. Simon Wegerif Says:

    Dear Canute

    ithlete (www.myithlete.com) is an easy to use application for iPod / iPhone touch that helps any endurance athlete regulate their training scientifically & optimise the balance between load & recovery. The basic idea is to take a 1 min measurement every morning and use the app’s guidance to determine whether you train as normal according to your plan, refrain from high intensity for that day, or take the day off completely. This has been shown in research to be a more effective way of improving running speed at threshold than a standardised plan, and should really help avoid overtraining.

    I would like to weigh in a little on the volume vs intensity debate. I have recently read a stimulating paper from Journal of Strength and Conditioning Research, 2007, 21(3), 943-949 that reported a controlled experiment on elite cross country runners and concluded that time spent in Zone 1 (below ventilatory threshold ~70% max HR) had a much higher impact on performance improvement than time spent in Zone 2 (up to anaerobic threshold). Time spent in Zone 3 (above anaerobic threshold) was only 8% of total. Conclusion – endurance athletes should spend 90+% of training time at an easy pace! This view has been expanded across other sports by respected coach Joe Beer in this month’s Peak Performance newsletter. My own experience of riding lots of slow, pleasurable miles in the French Alps this summer tends to reinforce the effectiveness, since I have been riding close to best ever after adding a little ‘top end’ work on my return. Hope this helps!

  15. canute1 Says:

    Simon, Thanks for that comment, and thanks in particular for drawing my attention to the study by Esteve-Lanoa from Madrid, and colleagues. They report that a program comprising low, mid and high intensity training in the ratio 80:12:8 produces greater improvement in a 10.4 K cross county race that a program with a ratio of 67:25:8 of low, middle and high intensity. In other words, a program with 25% of mid-zone training is less effective than a program in which about half of that mid-zone training is replaced by low zone training. It should be noted that the individuals with 80% of low zone training spent more hours training (average 100 hours over 18 weeks compared with average 75 hours in the group with 67% low zone training), but the total load (volume x intensity) was similar in the two groups. The authors conclude: ‘These results provide experimental evidence supporting the value of a relatively large percentage of low-intensity training over a long period (5 months), provided that the contribution of high-intensity training remains sufficient.’
    They do not conclude that an athlete should spend 90+% of training time at an easy pace. Even the group with 80% low intensity training performed a substantial amount of demanding work. They did 2 intense sessions per week in many weeks, in addition to regular weight training, and also running 5 cross country races (2x 5Km and 3 x10Km) not including the final assessment. Nonetheless, I think the practical conclusion is that training in the mid-zone produces less benefit that an similar work load (volume x intensity) in the low zone provided the program includes sufficient high intensity work. In other words, this study does support the proposal that mid-aerobic ‘grey zone training’ is a limited value.

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