Dose-Response and Running

Dose-response

Are you familiar with the concept of dose-response?  It is used in the medical world to describe the relationship between the dose and response to a drug.

Definition — a graph of the relationship between dose and response (effect) wherein all possible degrees of response between minimum detectable response and a maximum response are producible by varying the dose or drug concentration, i.e., the curve is continuous.

While most laymen may not use the term dose-response, most of us have experience with it.  How so?  Generally our experience with dose-response is in the use of medicine.  For example, if you have a headache and decide to take some aspirin, how do you know how much aspirin to take?  Simple, you read the directions on the bottle and take the directed 2 tablets for adults.  What if your 10-year old child has a headache?  Does the child also get 2 tablets?  Most parents know that the answer is NO.  Children get a smaller dose.  Why?  Because of their smaller body mass they require a smaller dose to experience the same response.  What if you gave the child the same dosage as you give an adult?  Does the child’s headache go away faster?  No, it does not.  The response to the medicine does not continually increase forever – there is a maximum response so that additional medicine does not result in additional desired response.  In fact, if you give the child too much aspirin you can actually overdose the child and cause irreparable harm.

Here’s another example.  During my tour of duty in Somalia each Sunday was malaria pill day.  Each Sunday my unit would take our anti-malaria pills, supervised so that no-one forgot and came down with malaria.  However, after we had been in Somalia about 2 months one of my sergeants came down with malaria.  He was accused of not taking his malaria pills and there was talk of administrative punishment for this sergeant – a bad thing for a career soldier.  Once his blood work was returned all talk of irresponsibility and punishment vanished though.  The doctors explained that the anti-malaria medicine dosage he was receiving was inadequate in this man to prevent the strain of malaria prevalent in Somalia.  This sergeant was a big man, about 230 lbs or so, and the dose we were all receiving was appropriate for a 180 lb man.  Due to his much larger size the sergeant was not given an adequate dose to prevent malaria.  After this incident dosage was then modified so that the larger soldiers took a larger dose, appropriate to their body mass.

Though I used it in my two examples above, bodymass is not the only thing that affects dose-response; other factors also influence or determine the dose-response relationship.  However, whether it is bodymass or other factors that determine dose-response for any drug, the point is that dose-response exists.

Different people, different results

Not only is dose-response a fact, but it is also a fact that not all people will respond exactly the same to the same dosage.  Some people are more sensitive to medicines than other people and reach maximum response at a lower dosage than others.  Some respond poorly and require a higher than normal dosage to experience a normal response.  Some peoples’ maximum response is greater than others’ maximum response.  Sometimes people don’t respond at all to a particular drug or, even worse, respond negatively.  These are the reasons why you hear things such as “there is a 60% response rate with the use of this drug” rather than a 100% cure rate with every drug.  People don’t all respond exactly the same.  And since not all people respond exactly the same, some will require more or less of a particular drug and some will respond more or less than others.

There are obviously nuances I haven’t covered here, but the fact is there is a dose-response relationship in medicine and dosage is prescribed based on differences in pertinent physical characteristics.

Dose-Response in Running

My guess is that we all generally accept the reality of dose-response in medicine and the need for individualizing dose based on individual characteristics, but what does this have to do with running?  While we may all agree that when it comes to medicine there is a dose-response relationship, let’s consider the idea as it applies to exercise.

I submit that there is a dose-response to exercise just as there is a dose-response to medicine.  Dose-response to exercise is not determined by the same factors as in medicine; it is determined by other physical characteristics.  In any case though, the relationship exists all the same.  Dose-response applies equally to medicine and exercise.  And just like taking drugs, some people reach their maximum exercise response at a smaller dose while other people have a higher dose requirement to reach their maximum exercise response.  The maximum exercise response of some individuals is going to be higher than the maximum exercise response of other people.  And some people aren’t going to respond at all.

Not only does dose-response to exercise exist, conventional training theory implies and accounts for the existence of dose-response in running, though it does not address it directly.  For example, beginners are advised to NOT train at the same volume as experienced runners.  Experience has taught that beginners cannot train at the same volume as more experienced runners.  Beginners are advised to build their weekly mileage slowly to allow time to adapt to training.  This is an example of prescribing a dose to a particular group of people based on certain characteristics and is an application of the dose-response concept.  Another example would be the advice to young, physically immature runners to NOT run the same weekly mileage as adult runners who have reached physical maturity.  Other examples exist that I won’t cover right now; the above are sufficient to make the point that dose-response is part of conventional training wisdom, though it is not directly articulated.

The error of establishing dose-response with small groups

To correctly establish dose-response for any group a sufficiently large and appropriate population needs to be systematically tested to ensure applicable and accurate results.  Importantly, the dose-response for that group may not be applicable to other groups and especially is likely not applicable to humans as a whole.

One of the challenges to conventional training is its general prescription to all runners that increasing mileage is a prerequisite for reaching maximum performance. If running 3 days a week is good, then running 5 days is better. If running 30 miles per week is good, then you will run even better when you increase to 50 miles per week. Lydiard has long proposed that runners build up to as much as 100 miles per week while Hadd promotes increasing weekly mileage to more than 100 miles. The general focus of conventional training is on increasing mileage and that as long as the runner can handle it, then running higher mileage is better than running lower mileage, up to a peak of about 100 miles per week. The support for this belief comes from the empirical observation that elites run high mileage, which is interpreted to mean that high mileage is the best training method for all. 

I believe it is an error to suggest that all people require the same high dose to achieve maximum response.  To use one small group of individuals to establish the proper dose for the entire human population is an error.  However, isn’t that what anyone who says “this is what the elites do and therefore that is how the rest of us generally need to train” is doing?

Wouldn’t I be making the same error if I used a group of first time runners to establish dose-response?  “We have discovered that beginner runners can safely run up to 15 miles per week and that running higher mileages do not result in improved performance, instead it results in injury.  Therefore, we prescribe 15 miles as the maximum dose required for all runners at all times.”  Sounds kind of ridiculous doesn’t it?  I suspect that anyone with any running experience would challenge the above statement.  On many occasions advocates of high mileage training have pointed out to me that many research studies are conducted on beginner and non-elite runners and therefore the results aren’t applicable to experienced or elite runners.  This argument utilizes the dose-response concept as its foundation.

As ridiculous as the statement that everyone should run 15 miles per week or less may sound, isn’t it the same thing as saying “we have discovered that elite runners achieve their best performance when they run 100 miles per week and, therefore, all humans at all times should strive to build up to 100 miles per week.”?

If you recognize that the first statement about proper dose-response as determined solely with data from beginner runners as invalid, you should also admit that the second statement about proper dose-response as determined solely by data from elite runners is equally invalid.  In both cases, the groups are too small and insufficient to prescribe the correct dosage for all humans.

Generally though, while the first statement will be dismissed by many, the second statement will be accepted for one reason – elites are the fastest runners.  Since speed is the desired response, the speed of the elites alone is enough to cause many runners accept the second statement as true, even though the second statement uses exactly the same flawed methodology to establish dose-response as the first statement.

Summary

Traditionally the term dose-response has been used to describe the relationship between the dose and response to a drug.  However, there is also a dose-response relationship to exercise too.  Conventional training wisdom applies the concept of dose-response of exercise to some degree, but does not articulate the existence of this dose-response.  To determine the correct dose-response for a group of people, a sufficiently large and appropriate subject pool must be tested.  While the results will be applicable to that particular group they may not be applicable to other groups or to the human population as a whole.  The challenge with high mileage proponents is that the same dosage – i.e. high weekly mileage and an emphasis on increasing weekly mileage to as high as 100 miles per week for all runners – is prescribed for all runners, with little to no acknowledgement of the very different dosage requirements of different people.

Dose-response teaches us that any one training prescription is not “best” for everyone.  Your goal should be to determine the exercise dose-response that works best for you.


Comments

Dose-Response and Running — 2 Comments

  1. Pingback: Dose-Response and Running | Training Science

  2. Dose-Response may seem too complicated for the typical running article – but I think that the runner who wants a long and fulfilling running life should pay attention

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