Paradoxical sprinting

Yesterday I had done a mid-aerobic 16Km run to assess how feasible it might be for me to aim for the long run pace recommended in the Furman half marathon training program.  I achieved my self-selected target of 85 minutes (5:19 min/Km), with a mean heart rate of 126, which for me is in the lower part of the mid-aerobic zone.  However, despite being quite pleased with my run, I was a little dismayed by how far my pace was below the pace recommended for the majority of long runs in the Furman program (HMP+12 sec/Km or 4:53 min/Km for a target HM time of 99 min).  There is no doubt that increasing the pace from 5:19 min/km  to 4:53 min/Km would put me well into the upper aerobic zone.  So if I were to adhere strictly to the recommended paces, all three of the key weekly sessions in the program would involve a substantial amount of running near or above lactate threshold.  Such a program would appear to create a significant risk of injury or illness. 


According to the article by Amby Burfoot in Runners World in Feb 2006 the injury rate among the group of 25 runners in a study of the Furman marathon program in 2004 was not high.  One withdrew from the program on account of injury, and three dropped down from the marathon program to the half marathon program on account of minor injury.  However  it is not clear what the baseline fitness of the group was, nor how strictly they adhered to the recommended paces.  Thus, my interim conclusion is that  I would need to modify the long run (for example by starting at a slower pace and increasing to near race-pace in the later stages as suggested by Rick)  or to abandon the Furman approach altogether and opt for a higher volume, lower intensity program.


Reviewing yesterdays run makes me wonder whether there is in fact any need for me to take risk of embarking on a potentially stressful program with a lot of running near the lactate theshold.  


Evaluating aerobic capacity

The energy cost of running a given distance is almost independent of the speed (see  Cameron et al., “Energy Expenditure of Walking and Running,” Medicine & Science in Sport & Exercise,  Dec. 2004).  When running in the aerobic zone, the majority of energy is provided by oxidation of glucose.  The amount of glucose and oxygen delivered to muscle is determined by heart rate, cardiac stroke volume and the efficiency of extraction of oxygen and glucose by the muscles. The efficiency of extraction is largely determined by the density of mitochondria and capillaries.  The main goals of aerobic training are to increase stroke volume and the density of mitochondria and capillaries.  At a given level of fitness, stroke volume and the density of mitochondria and capillaries can be regarded as constant, and the number of metres that can be covered per heart beat is a useful indicator of aerobic capacity. 


In the past I have found the number of metres per heart beat recorded over distances in the range 15-20Km, is fairly constant regardless of the pace provided I remain within the aerobic zone.  Furthermore, this measurement provides a moderately good estimate of potential half marathon pace, provided that the race is run near to lactate threshold.  For example in the latter months of 2007, my average distance per heart beat recorded in 8 training runs at various paces in the low and mid-aerobic zone was 1.44 (range 1.38 to 1.48 metres/beat).  I ran a half marathon race in September in 101 min 24 sec with mean heart rate 142. Thus in the race I achieved 1.46 metres per beat, which was within the range I had achieved during training runs.


In yesterday’s 16K run, I achieved 1.49 metres per beat.  This is exactly the aerobic capacity required to achieve my half-marathon  target time of 99 minutes, provided I can sustain an average heart rate of 142 beats per min for the duration of the race.  Thus my current aerobic capacity is slightly larger than my capacity in 2007, and is already adequate to allow me to achieve my target time provided my endurance is adequate.  At present I do not have the endurance to maintain an average heart rate of 142 for 21 Km, but nonetheless, yesterdays run suggests that I already have the capacity to deliver oxygen and glucose to the muscles at the required rate.  Of course many things can go wrong in a race, but at least I feel confident that my target is achievable.  My major goal for the summer is therefore to increase my endurance while avoiding illness or injury. 


Building endurance

The grueling long runs recommended by the Furman program would almost certainly produce the required increase in endurance, provided I did not suffer illness or injury.  However, I am inclined to think that the safest way to achieve my target is to embark upon a lower intensity, higher volume program that will further increase my basic aerobic capacity.  If I could produce an additional 2% increase in aerobic capacity I would only need to maintain an average heart rate of 139 in the race, which I am quite confident that I could do.  On the other hand, if I could manage to maintain a mean heart rate of 142, with an additional 2% capacity I could expect a time of around 97 minutes.


Thus, at this stage, the best strategy would appear to be to devote most of my efforts in the next six months to improving my basic aerobic capacity.  The safest way to do this is likely to be a Lydiard style program.  However, I also have a secondary objective and that is to increase my stride length and speed.  Forty years ago, my typical stride length when running in the upper aerobic zone was almost 2 metres, now it is only about 1.1 metres.  I think that the biggest factor in this loss of stride length is loss of leg strength. 


Increasing speed

One of my reasons for exploring the feasibility of the Furman approach was the hope that doing a higher proportion of my running in the upper aerobic and anaerobic zones would increase my leg strength and therefore increase my stride length and speed.  However, my exploration of the principles underlying the Lydiard approach has led me to question this. 


Lydiard maintained that anaerobic work is not the best way to increase speed.  Rather, speed is best increased by short sprints that utilize the alactic energy system.  Short sprints of around 10 seconds duration are fuelled mainly by ATP reserves and creatine.  Provide there is adequate recovery between sprints, the stressful acidosis produced during anaerobic workouts can be avoided.  Speed work can be compatible with basic aerobic conditioning provided acidosis is avoided.  Lydiard advocated speed work throughout all phases of the training cycle.


To test the feasibility of incorporating speed work within an aerobic conditioning phase, this morning I did an easy 20Km run, but incorporated 10 short sprints within the final few Km.  Each sprint was at 9/10 effort but lasted less than 10 seconds (typically covering only 50-60 metres).  Between the sprints I jogged at a very easy pace to allow full recovery of the ATP and creatine levels.  I was surprised at how invigorating these sprints were.  Despite the fact that I had run 36 Km within about 24 hours, my legs actually felt quite fresh.  I had not been entirely sure about the wisdom of incorporating these sprints during a weekend in which I had also increased distance substantially, but I decided that this was the best way to get a convincing answer to the question.  I did of course monitor carefully for any signs of local tightness in my muscles during the sprints, but in fact with each successive sprint, my legs actually felt more relaxed.  On today’s evidence, it appears to be feasible to include sprinting within a recovery run.


Maybe I should wait to see how my legs feel tomorrow before jumping to conclusions, but at this stage I am hopeful that it might be possible to achieve the goal of increasing aerobic capacity without sacrificing speed simply by incorporating short sprints within the recovery runs.


This of course raises the question of hills, but that is a topic for another day.

5 Responses to “Paradoxical sprinting”

  1. Ewen Says:

    My metres per beat is greater in a half marathon race. Not sure why, or if that’s an aberration. In the 2007 Melbourne Half (1:40:48) it was 1.40m (ave HR of 150). On Sat 7th March I ran 16.5k in 95:38 @ AHR 131, so 1.32m per beat.

    Anyway, the Lydiard style approach does seem a better (and safer) way to build the aerobic capacity. The short sprints do seem very useful for leg strength/stride length (and fast-twitch activation). I’ll be interested to see if you’re sore the next day. I remember running maybe 20 x 50m with full recovery once and my quads were very sore for a couple of days.

    Having them within an easy/long run seems sensible, as the alactic system is totally different to the aerobic. I find I can do some short sprints at the end of an aerobic run even if I’ve felt tired on the run (as I was this afternoon)… managed 2 short hill sprints and felt OK doing them. I might follow your idea though and do some of these on flatter ground.

    I have started doing some general aerobic runs on “rolling hills” near home, and I can see that these will be useful for “leg strength”. My usual course, although hilly, has just one long gentle hill, not constant ups and downs.

  2. canute1 Says:

    Maybe the accuracy of the prediction of my HM time in 2007 from metres /beat recorded in preceding training runs was a fluke. I certainly accept that many factors such as hills, nature of the surface and air temperature are likely to produce inaccuracy in any prediction based on heart rate, so I shouldn’t take the prediction based on my run last Saturday too seriously.
    I was pleased to find that I had only very mild stiffness in my muscles this morning after the sprints yesterday. I was quite comfortable running up and down stairs during the course of my day at work.
    I will be interested to hear how your short hill sprints work out.

  3. rick Says:

    I’ve used Lydiards leg speed session for quite a while, since the summer of 2007 I think, when used during the base training I think he recommends running them at your 1 mile pace on a smooth grass surface, slightly downhill or with the wind, the idea being to work on increasing leg speed, not really strength or stride length!

  4. rick Says:

    Many people get hooked up on the idea of 100 miles a week when thinking of LYDIARS training system, BUT they should bare in mind that PETER SNELL use to average 6 min mile pace for the weeks training! his 10 mile tempo run [ marathon pace] was at around 5.30 pace, so you can see that his 100 miles per week was a mire 10 hours of running, yet for the like of us maybe we could only cover 70- 80 miles per week
    So really we should be looking at time rather than distance!
    I found 10 hours was about as much as I could handle taking into account having a very physical job!

  5. sarkrunse Says:

    Solid information. will definitely come back again soon.

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