Running Tips

THE RUNNING RESEARCH NEWS WEEKLY TRAINING UPDATE

 

ISSUE # 37    FEBRUARY 7, 2005

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Hi Everyone,

 

    I hope that your week is off to a great start.  Two weeks ago, in Training Update # 35, I asked all of you how it was possible for top Tour-de-France athletes to cycle at an intensity above 90 percent of VO2max for 75 minutes continuously, when the world's-best runners can manage to sustain such intensity for less than half that amount of time.  I promised that the top response would earn a free copy of my e-book, Great Workouts for Popular Races.

 

    The answers poured in - 87 in all.  Each answer was insightful, making my job very difficult (so tough that we won't have another contest for at least four weeks).  One response, though, stood out above the rest, and so I can announce to you that the winner of the e-book is ..........

 

    An orthodontist from East Lyme, Connecticut.

 

    That's right - Jeff Kozlowski, DDS, is the winner.  In addition to carrying out great work on teeth, Jeff also happens to be a very good cyclist and triathlete, and he wrote: "I believe that, among other reasons, the mechanical advantage provided by a bike's gears in cycling gives cyclists the opportunity to modify muscle recruitment during sustained, high-intensity effort.  A cyclist performing a time trial can use gears to change the cadence (while maintaining high power), and this change in cadence enables the cyclist to use different muscle groups and types to his/her advantage.  The recruitment of additional muscle groups and different muscle-fiber types would theoretically delay the onset of fatigue in the working muscles as a whole.  For example, in the time trials I have completed I averaged a cadence of about 105, but over the course of the whole ride I utilized cadences as low as 85 and as high as 120.  Of course, cadence can be terrain- and wind-dependent, but these cadence numbers hold true for me even when I am riding on a trainer inside.  When a cyclist feels fatigue at one cadence, he/she can simply shift gears to initiate a higher or lower cadence and thus recruit new collections of motor units which are less fatigued."

 

    Jeff is really onto something there.  His analysis reminds me of a conversation the great Sammy Lelei and I had on a hot day many years ago as I tried to keep up with him on the 15-K run from the city of Eldoret to his farm.  After about 10K of hard running, he said to me:

 

    "Are you tired, Bwana Owen?"

 

    "Yes - very."

 

    "Then, simply run faster," he said.

 

    The suggestion seemed ludicrous at the time, but Sammy was starting to leave me in the dust, and so I made an attempt to pick up my pace to a 5-K-like intensity.  To my astonishment, I suddenly felt great, with no hint of fatigue, a scenario which I later attributed to the possibility that I had recruited an entirely new set of (non-fatigued) motor units as a result of the shift to the faster velocity.  I have used this strategy many times since and still find that I can knock down fatigue dramatically - even after 90 minutes or more of fatiguing running - just by "changing gears" and stepping up the pace.

 

    Jeff's excellent argument and Sammy's acute advice remind me also of Veronique Billat's research, in which she demonstrated that runners who change velocity fairly frequently are more economical than runners who run at a dead-on, rock-steady pace.  In theory, the pace-changing runners are constantly recruiting new batches of relatively fresh muscle fibers, and thus their efficiency of running is better because the number of muscle cells active at any one time is reduced (when muscle cells lose their ability to exert a certain level of force and a runner insists on maintaining a constant pace, the nervous system likes to dial up other cells to work along with the original ones to maintain the required propulsive force).

 

    Of course, as Jeff pointed out later in his response, runners don't have as many options as cyclists do when it comes to cadence.  Few runners could run the gamut from 85 all the way up to 120 strides per minute over the course of 75 minutes of hard (above-90-percent-of-max) running and have a highly successful run; their running economy would suffer greatly.  In contrast, cyclists practice cadence-changing all the time and become highly efficient at the process.

 

    Jeff raised several other strong points in his detailed response, including the notions that the higher heart rates associated with running, compared with cycling (for a given percentage of VO2max), might spike fatigue during running, and that the cumulative trauma associated with dealing with an impact force which is ~ three to four times body weight with each step may magnify perceptions of fatigue during running, forcing earlier quitting (or the adoption of slower speed and a lighter percentage of max aerobic capacity).

 

    Many other Update readers also wrote particularly strong responses.  For example, several individuals pointed out that the eccentric nature of muscle activity during running may greatly magnify fatigue.  Some suggested that the characteristic muscle damage which is associated with eccentric contractions might force a shut-down of highly intense running after 30 minutes or so.  This argument is fairly logical and appealing, but note that eccentric-contraction-related damage does not usually "show up" in the muscles until 24 to 48 hours after a hard effort, so it is unclear whether it can produce fatigue so quickly - after just a half-hour.  Note, too, that it is unclear why such muscle-damage-induced fatigue would be so intensity-specific.  For example, marathon runners also experience leg-muscle mashing as they run, but they can continue running for over two hours.  Is the slightly lower intensity associated with the marathon (85 to 88 percent of VO2max vs. a bit above 90 percent of VO2max) really enough to limit the proposed connection between muscle damage and fatigue?

 

    On the eccentric theme, Hugh Trenchard (another Update subscriber) pointed out that eccentric contractions cause muscle fatigue more rapidly, compared with concentric contractions, and even provided a reference (Journal of Applied Physiology, Vol. 75, pp. 1545-1551).  This is a particularly appealing approach to understanding the differences between cyclists and runners in their abilities to sustain high intensities.  It is not that cyclists' muscles do not undergo eccentric contractions; such muscle activities are present whenever there is controlled movement at a joint.  As a cyclist's knee comes up during a revolution on the pedal, for example, the hamstrings work eccentrically to control this movement.  The difference is that in running the muscles seem to work hardest when they are working eccentrically; in cycling, they seem to work hardest when they are operating concentrically.  During running, for example, the quads work most intensely when the foot is on the ground and the quads are attempting (eccentrically) to control knee flexion.  During cycling, the quads work most powerfully during the pedal downstroke, a concentric action which involves straightening the leg.  Mr. Trenchard came close to getting the e-book.

 

    Other possible explanations for the cycling-running disparity include:

 

    (1) Body-temperature increases associated with working above 90 percent of VO2max are less dramatic in cyclists, compared with runners, because heat loss by conduction is greater in cycling as a result of the higher speed (Dr. Alejandro Mondolfi).

 

    (2) Cyclists enjoy "mini-rests" while going downhill and around corners which tend to limit fatigue (many responders said this).  In a similar vein: When runners relax their muscles completely, they collapse, and so they can't relax their muscles thoroughly.  In contrast, when cyclists relax their muscles completely (to rest), they simply coast and lose speed at a fairly slow rate.  An interesting aspect of this is that on relatively flat terrain aerodynamic drag is the main force which slows cyclists down, and aerodynamic drag is proportional to the cube of cycling velocity.  Thus, backing off just slightly on cycling pace would produce a significant energy saving (a 1-percent velocity reduction might produce a 3-percent energy saving) (all this from Eric Bean, who also almost captured the e-book).

 

    (3) Because of the non-impact nature of cycling, cyclists can complete relatively larger amounts of high-intensity training, compared with runners, and thus can better tolerate high intensities during time trials and races (several responders).

 

    (4) EPO utilization may be greater among Tour-de-France cyclists, compared with elite runners (many).

 

    Many readers said that the cycling advantage was due to the fact that the bike itself supported body weight, whereas in running the leg and core muscles were forced to carry most of the load.  While this is true, it does not actually explain why cyclists can continue at > 90 percent for a longer period, compared with runners.  It simply means that a higher fraction of the oxygen actually utilized during running will go toward body support, compared with cycling, but it does not explain why this means that above-90 activities need to be curtailed more quickly when running is the sport of choice.

 

    The take-home message for all of us?  One of the reasons that cycling is a great form of cross training for running is that once runners become fairly fit on the bike they can sustain high fractions of VO2max for an extended period of time - often longer than would be the case for running.  Exercise scientists believe that enhancements of muscle-cells' abilities to utilize oxygen are most likely to occur as a result of high-intensity training, especially high-intensity exercise which is sustained for an extended period of time.  Thus, red-hot cycling training may uniquely bolster the oxidative capacities of runners' leg muscles.  When these bolstered leg muscles are utilized for "pure" running training, running-workout quality improves, and competitive performances subsequently rise.  Cycling is thus a "good way to go," when it comes to cross training, and it's nice that most runners find that they can recover from high-quality cycling workouts fairly quickly.

 

   

With very kindest regards,

 

Owen Anderson