A forumite took issue with my original post on this subject. The following are my comments to him.
> All of that and in the end you state:
>
> My recommendation is to ignore any advice that says
> that it is necessary to always use a 1-2% incline
> adjustment to compensate for the lack of wind
> resistance. Instead, use the combination of speed
> control and incline adjustment that best makes a
> treadmill run "feel like" it is giving you the
> training benefit that you desire.
>
> So then the 1 to 2% guideline is quite appropriate is
> it not?
Since it is often difficult to interpret emotion within the written word, I’m unsure if your comment is dripping with sarcasm or intended to be tongue-in-cheek. :-) With your permission, I will assume that you have a sense of humor and intend the latter. :-)
Seriously. No, I do not think the 1-2% guideline is "quite appropriate". It is appropriate at times for some runners. But, a blanket 1-2% guideline for everyone to specifically compensate for the lack of air resistance misleads many runners in many situations and can actually make treadmill running more difficult than over-ground running. It is a "sound bite" response to questions that people post on these forums in a serious attempt to understand treadmill running vs. outdoor running. And it is a response that addresses only one of several factors that should be considered....and it’s one that is relatively minor, to the point of being insignificant for most runners. I think those who are seeking thoughtful guidance to serious questions deserve more than that.
> If you and arepper take issue with the study I used
> for having a small sample size then I assume you take
> that same tact with McMiken and Daniels sinc this
> study had one FEWER subjects than the Jones and Doust
> study I used.
I don't "take issue" with the study. As far as I know, it was conducted carefully and in compliance with good scientific practices. I simply observed that, as arepper noted, it did have a small sample size comprised of highly trained runners, which may or may not be representative of a broad spectrum of runners of all levels of ability. And, although I did not know it, I am not at all surprised that the McMiken and Daniels study utilized about the same sample size. I suspect that all such studies are directed to the high performance end of the running spectrum and use similarly small sample bases. I doubt if any researcher has the resources, especially time and money, to spend on large samples of a broader spectrum of runners.
All of the studies we, collectively, have mentioned arrived at a similar basic conclusion....all other parameters being equal, running at speeds below a certain threshold and at 0% incline is equivalent to running outdoors and the lack of air resistance is insignificant, whereas above that threshold an incline adjustment is needed to make the two running conditions equivalent at the same pace. What differed between the studies was the level of that threshold....5:22, 6:00 or 8:03 min/mile. That is what interested me and I speculated about it. You clarified one of the potential reasons that I had suggested (sample size) so as to indicate that it probably isn't a factor. At least not for those two studies, which arrived at significantly different thresholds....6:00 vs. 8:03....although there still could be other differences between their specific sample bases.
Actually, the extract that you cited from the McMiken and Daniels' report of their study indicates that the submaximal portion of their study only extended to a 6:00 pace and they found that "neither VO2 max nor aerobic requirements of running were significantly different in track and treadmill determinations". So, they didn't really arrive at a "threshold" point. If they had continued submaximal tests to faster paces, they might have confirmed Davies' conclusion that the threshold is at a pace of 5:22.
In any event, the thresholds demonstrated by all of the studies occur at speeds which are faster than the typical training paces of most runners, thus indicating that there is no significant difference between running on a treadmill at 0% incline and outdoors in calm air for most runners. In my opinion, this indicates that it makes no sense to tell the majority of runners that they should compensate for something that doesn't really affect them.
> I would also note that these studies were done almost
> 20 years apart. It is possible the technology
> advanced to make more valid measurements with less
> error.
I seriously doubt that the availability of more modern equipment and technology makes the recent study more accurate or valid than the earlier ones. The conclusions of all of these studies reflect relative data, not absolute measurements. Any inaccuracies resulting from equipment and/or techniques should affect both treadmill and track measurements equally in each study. Such measurement inaccuracies should cancel and not affect the final conclusions, regardless of the technological era in which the studies were conducted. I suspect the benefit of newer technology is to make the control and analysis processes easier, not to increase their accuracy. ”....but then again, what do I know?", since I am not an expert in this area. ;-)
> Treadmill calibration is certainly an issue, but it
> is a red herring in this case and only clouds the
> issue in a theoretical discussion.
I agree that treadmill calibration would cloud the issue in a theoretical discussion concerning the effect of air resistance, per se. That’s why I didn’t mention it in that part of my post. I only raised the point at the end of the post when pointing out that air resistance pales in comparison to other factors, such as treadmill calibration, in the broader subject of comparing treadmill and over-ground running....which is what people come to the forum to seek information. In that context, the air resistance issue is the red herring because it is irrelevant for most runners.
> If the treadmill
> calibration is off (and the likelihood is pretty good
> if using a health club treadmill from my experience)
> then it is all moot as you are not going to be sure
> that is going on.
Precisely the point! I could not agree more! A miscalibrated treadmill, which is common, as you said, can make all other factors, such as lack of air resistance, moot....even for the minority of runners who are fast enough to be noticeably affected by the lack of air resistance.
> Lastly, I would not use the testing protocol to
> support your notion in that the incline on the
> treadmill is done at the end of the test for a few
> possible reasons one of which is safety. In Dave's
> LEAP lab, when the treadmill is going at sub 5 min
> pace at it would be at the end of a VO2max test the
> potential for someone losing balance is pretty high
> (actually had a to catch a kid on a treadmill one
> time when he stumbled running at 4:30 ish pace). In
> these cases, increasing the grade is a means to
> safely increase the intensity to "max out".
I think I understand your point. It’s a good one. Perhaps safety is one reason Martin and Coe reduced the pace from 5:00 to 6:00 min/mile for the last few minutes of their test protocol when they cranked up the incline to max out a runner’s VO2.
The bottom line to all of this is that I think that, regardless of what the studies indicate, focusing on compensating for lack of air resistance is taking a component (micro) view of a subject that really begs for a system (macro) view. And it isn’t even one of the more significant components. Even worse, depending on the other components, introducing an automatic adjustment for it can often actually produce inequality between treadmill and over-ground running.
Jim2
Sunday, January 22, 2006
Saturday, January 21, 2006
The 1% Incline Treadmill Myth
As is usual in winter, the interest on these forums concerning running on a treadmill is at a peak. There have been several threads recently on this subject on the Training and Marathon forums....perhaps on other forums, as well. In most of those threads, someone usually mentions the “guideline” of using a 1-2% incline when running on a treadmill to compensate for the lack of air resistance that one experiences when running outdoors. In fact, it happened again as recently as yesterday in a thread titled “OK to do LR on treadmill?” on the Training Forum.
When I see mention of the “equalizing” incline factor, I often post a caution against blindly following the concept, as I did a few days ago in another thread on the Training Forum titled “Treadmill vs. Jogging On Ground”. (See http://forums.runnersworld.com/message.jspa?messageID=7649859&tstart=50) In that same thread, there was a lengthy “debate” concerning the value of the incline adjustment, which I didn’t read until yesterday. On one side of the debate was arepper, who postulated that: there is no merit to using the incline; running at zero incline on a treadmill is equal to running on a flat surface outdoors; and a study that ExPhysRunner referenced to demonstrate that need for a 1-2% incline is flawed. On the other side of the debate were ExPhysRunner, jwd1113 and dcx693 who argued that arepper’s position had no scientific basis and theirs did. ExPhysRunner challenged arepper and anyone else to offer other studies that might shed more light on the subject. No one did. The debate finally ended when, I think, nothing was being resolved and all participants tired of it.
So, which side of the debate was correct? In my opinion, both were....at least in what each side was trying to say. ExPhysRunner, jwd1113 and dcx693 were absolutely correct in that there is an air resistance, and that “some” effort is needed to overcome it, when running outdoors that is absent when running on a treadmill. That has long been a scientifically proven fact. OTOH, arepper was correct in that the use of an incline to compensate for the lack of air resistance and, thus, make treadmill running equivalent to outdoors is a greatly overblown theory, in most cases is not necessary at all, and in many instances can make the treadmill more difficult than outdoor running at the same pace. Let me attempt to explain that apparent dichotomy.
I am going to reference two of the most technically comprehensive books on running physiology that have ever been published:
1) “Better Training for Long Distance Runners” by Dr. David Martin, physiologist, and Peter Coe, engineer and father and coach of Sebastion Coe, who was perhaps the greatest middle-distance runner of all time.
2) “Lore of Running” by Dr. Tim Noakes, physician, physiologist, and marathoner.
Martin and Coe In their book, they discuss at length a treadmill stress test that they have used to measure the cardiopulmonary fitness of runners. They described four general constraints they considered in designing their treadmill test protocols. They described the fourth constraint as follows (the bold emphasis is mine to highlight relevance to our subject):
“The fourth testing constraint is that the environmental data collection conditions should be kept as constant as possible to optimize detection of changes in athletes’ fitness from one test session to the next. We kept relative humidity at 35% to ensure effective evaporative cooling. We also maintain our laboratory room at a relatively cool 17 degrees C (63 degrees F) during testing. It is also appropriate to keep the treadmill running conditions as similar to over-ground running as possible. At least through velocities as fast as 6 min/mile (268 m/min), submaximal O2 as measured with treadmill running is insignificantly different than that measured with track running (McMiken and Daniels 1976). Biomechanical differences in running stride between the moving treadmill belt and over-ground running are minimal.
“Although over-ground running creates air resistance, such resistance brings an added aerobic demand only at velocities considerably faster than those routinely used in our evaluations. According to the studies of Pugh (1970), the effect of air resistance starts to increase O2 consumption measurably only at faster paces. As an example, at a pace of 4:35 min/mile (13 mi/hr; 350 m/min), the additional aerobic demand is 5.7 ml/kg/min. Indeed, this added energy demand to a front-runner in a fast-paced race is used to advantage as a tactical maneuver by runners who remain in that runner’s wind shadow.”
The treadmill stress tests conducted by Martin and Coe lasted for 26 minutes with no rest breaks until the final 3 minutes of recovery. The first 14 minutes were run at paces of 7:30 min/mile for the first 2 minutes, 6:40 for 3 minutes, 6:00 for 3 minutes, 5:30 for 3 minutes and 5:00 for 3 minutes....all at zero percent incline. The next 9 minutes were run at 6:00 min/mile and progressive inclines of 4%, 6%, 8% and 10% (2 minutes each), with a final one minute at 11%. The test ended with 3 minutes of recovery.
A couple of things are interesting to note:
1) They viewed running at zero percent incline as being “insignificantly different than that measured with track running” and did not see a need to compensate for lack of air resistance by introducing a treadmill incline until the late stages of the test when inclines were used to max out VO2, which was one of the objectives of the test.
2) They also addressed the other major consideration that most often comes up when discussing treadmill running here on these forums....biomechanical differences with over-ground running. And they didn’t consider such differences to be significant.
Noakes He doesn’t discuss treadmill running, per se, in his book. However, he does discuss a similar subject relative to the effect of air resistance and that Martin and Coe made reference to....drafting in a race. The principle is the same, but reversed. In the case of drafting, the object is to avoid air resistance to conserve energy, as opposed to running on a treadmill where the “myth” is to use incline to simulate air resistance to increase energy used to be the same as running outdoors. Both concepts are predicated on the effect that air resistance has on the runner. The following is what Noakes has to say about air resistance and drafting (again, the bold emphasis is mine):
“One of the first scientists to study the influence of wind speed on running performance was the great British physiologist Dr. Griffiths Pugh, whose work on effects of altitude on athletic performance is among the classic contributions on that topic. Pugh performed four different studies designed to measure how wind speed and the gradient of the running surface influence the oxygen cost of running (1970). His studies showed that the extra cost of running into a facing wind increased as the square of the wind speed. Thus the oxygen cost of running into a 66-km/hr head wind increases by 30 ml/kg/min. Similarly, running up an 8% incline increases the oxygen cost of running by about 20 ml/kg/min.
“Pugh also showed that at the speeds at which middle-distance track events are run (6 m/s or about 67 seconds per 400m), about 8% of the runner’s energy is used in overcoming air resistance. But by running directly behind a leading runner (or drafting) at a distance of about 1 m, the athlete can save 80% of that energy. In a middle-distance race this would be equivalent to a savings of about 4 seconds per lap. However, Pugh considers it unlikely that in practice the following athletes would ever be able to run as close to the lead runner to benefit to this extent. By running slightly to the side of the lead runner, the following runner would probably benefit by about 1 second per lap.
“Another researcher to study the benefits of drafting was Californian Chester R. Kyle (1979). His calculations suggest that at world-record mile pace, a runner running 2 m behind the lead runner would save about 1.66 seconds per lap, which generally confirms Pugh’s estimations.
“These findings explain why track athletes find pacers to be such essential ingredients in aiming for world records. In addition, these findings explain why world records in the sprints are set at altitude. During sprinting, the energy cost of overcoming air resistance rises to between 13 and 16% of the total cost of running. Thus, the sprinter benefits greatly by running at an altitude where air resistance is considerably reduced. It is interesting that when a runner is racing on a circular track, an optimum strategy is to accelerate into the wind and to decelerate when the wind is from behind, the opposite of what one would expect.
“The Briton Dr. Mervyn Davies (1980/81) extended Pugh’s findings. Davies used essentially the same techniques as Pugh but included observations on the effects of running downhill and of following winds of different speeds.
“Davies found that when a runner was measured on a treadmill, facing winds of up to 18 km/hr had no effect on the oxygen cost of running. But the same conditions on the road will have a very marked effect. On the treadmill, the athlete does not move forward and thus does not expend energy overcoming wind resistance. However, an athlete who runs on the road into a wind of 18 km/hr faces an actual wind speed equal to that of his or her running speed plus that of the prevailing wind.
“The practical relevance of this is that on a calm day, anyone running slower than 18 km/hr (about a 2:21 marathon pace) will not benefit by drafting in the wake of other runners. However, runners stand to gain significantly by drafting at faster speeds or when running into winds that, when added to their running speeds, would make the actual wind speed greater than 18 km/hr.”
Everything that Noakes says about Pugh’s and Kyle’s studies with air resistance involves either strong head winds or very fast running paces. It was Davies who extended Pugh’s studies to calm wind and following wind conditions.
I infer from Davies and Noakes’ conclusions that, if 18 km/hr (11.16 mi/hr or 5:22 min/mile) is the threshold for drafting to become beneficial in calm air, then, similarly, 5:22 pace is the threshold at which the lack of air resistance becomes a factor when running on a treadmill.
Actually, the study that ExPhysRunner referenced also found that there was no difference between oxygen consumption on a treadmill at 0% incline and outdoor running at slower paces, although the paces at which there was no difference (9:11 and 8:03 min/mile) were considerably slower than those determined by Davies (5:22 min/mile) and referenced by Martin and Coe (“at least to 6:00 min/mile”). Perhaps these variations resulted from differences in test protocols. Or, perhaps it relates to one of the reasons arepper felt that the study that ExPhysRunner referenced was flawed....a very small sample base of nine runners. And, apparently, all of them were highly trained runners since the test conditions extended to a pace of 5:22 min/mile. In any event, the sample certainly wasn’t representative of a broad cross section of runners. Of course, that might also be the case in Pugh’s and Davies’ studies.
In my opinion, the bottom line to all of this is that ExPhysRunner and his supporters are right in that there is air resistance imposed on all runners at all paces when running over-ground. However, arepper is also right in that for most runners it’s a “So what?” issue. The impact of energy consumption expended to overcome calm air resistance for most runners is insignificant, immeasurable, and not worth attempting to specifically compensate for with a predetermined incline adjustment when on a treadmill. In fact, all of the above data, including that in the study referenced by ExPhysRunner, indicates that cranking in an incline “adjustment” just because someone says you should can make treadmill more difficult than running over-ground for everyone running slower than 8:00, 6:00 or 5:22 min/mile....take your pick of whose data you think is most credible.
And there is a final consideration, which was the basis of my previous post on this subject, that this is really a very minor variable among several that determine the differences between treadmill and over-ground running. Other more significant variables include outdoor climate, treadmill calibration, and outdoor terrain. Heck, in Noakes book, he even mentions the drag caused by short hair, loose fitting clothing, or long hair as having as much or more energy cost....4%, 4.2% and 6.3%, respectively....as air resistance for the pace that most runners run. A long haired runner can just get a haircut and gain more than 2%. In comparison, calm air resistance costs the 4:30 min/mile runner, the middle-distance track runner referenced in Pugh’s study above, 8%. And it is a very small fraction of that for us mere mortals.
My recommendation is to ignore any advice that says that it is necessary to always use a 1-2% incline adjustment to compensate for the lack of wind resistance. Instead, use the combination of speed control and incline adjustment that best makes a treadmill run “feel like” it is giving you the training benefit that you desire.
Jim2
When I see mention of the “equalizing” incline factor, I often post a caution against blindly following the concept, as I did a few days ago in another thread on the Training Forum titled “Treadmill vs. Jogging On Ground”. (See http://forums.runnersworld.com/message.jspa?messageID=7649859&tstart=50) In that same thread, there was a lengthy “debate” concerning the value of the incline adjustment, which I didn’t read until yesterday. On one side of the debate was arepper, who postulated that: there is no merit to using the incline; running at zero incline on a treadmill is equal to running on a flat surface outdoors; and a study that ExPhysRunner referenced to demonstrate that need for a 1-2% incline is flawed. On the other side of the debate were ExPhysRunner, jwd1113 and dcx693 who argued that arepper’s position had no scientific basis and theirs did. ExPhysRunner challenged arepper and anyone else to offer other studies that might shed more light on the subject. No one did. The debate finally ended when, I think, nothing was being resolved and all participants tired of it.
So, which side of the debate was correct? In my opinion, both were....at least in what each side was trying to say. ExPhysRunner, jwd1113 and dcx693 were absolutely correct in that there is an air resistance, and that “some” effort is needed to overcome it, when running outdoors that is absent when running on a treadmill. That has long been a scientifically proven fact. OTOH, arepper was correct in that the use of an incline to compensate for the lack of air resistance and, thus, make treadmill running equivalent to outdoors is a greatly overblown theory, in most cases is not necessary at all, and in many instances can make the treadmill more difficult than outdoor running at the same pace. Let me attempt to explain that apparent dichotomy.
I am going to reference two of the most technically comprehensive books on running physiology that have ever been published:
1) “Better Training for Long Distance Runners” by Dr. David Martin, physiologist, and Peter Coe, engineer and father and coach of Sebastion Coe, who was perhaps the greatest middle-distance runner of all time.
2) “Lore of Running” by Dr. Tim Noakes, physician, physiologist, and marathoner.
Martin and Coe In their book, they discuss at length a treadmill stress test that they have used to measure the cardiopulmonary fitness of runners. They described four general constraints they considered in designing their treadmill test protocols. They described the fourth constraint as follows (the bold emphasis is mine to highlight relevance to our subject):
“The fourth testing constraint is that the environmental data collection conditions should be kept as constant as possible to optimize detection of changes in athletes’ fitness from one test session to the next. We kept relative humidity at 35% to ensure effective evaporative cooling. We also maintain our laboratory room at a relatively cool 17 degrees C (63 degrees F) during testing. It is also appropriate to keep the treadmill running conditions as similar to over-ground running as possible. At least through velocities as fast as 6 min/mile (268 m/min), submaximal O2 as measured with treadmill running is insignificantly different than that measured with track running (McMiken and Daniels 1976). Biomechanical differences in running stride between the moving treadmill belt and over-ground running are minimal.
“Although over-ground running creates air resistance, such resistance brings an added aerobic demand only at velocities considerably faster than those routinely used in our evaluations. According to the studies of Pugh (1970), the effect of air resistance starts to increase O2 consumption measurably only at faster paces. As an example, at a pace of 4:35 min/mile (13 mi/hr; 350 m/min), the additional aerobic demand is 5.7 ml/kg/min. Indeed, this added energy demand to a front-runner in a fast-paced race is used to advantage as a tactical maneuver by runners who remain in that runner’s wind shadow.”
The treadmill stress tests conducted by Martin and Coe lasted for 26 minutes with no rest breaks until the final 3 minutes of recovery. The first 14 minutes were run at paces of 7:30 min/mile for the first 2 minutes, 6:40 for 3 minutes, 6:00 for 3 minutes, 5:30 for 3 minutes and 5:00 for 3 minutes....all at zero percent incline. The next 9 minutes were run at 6:00 min/mile and progressive inclines of 4%, 6%, 8% and 10% (2 minutes each), with a final one minute at 11%. The test ended with 3 minutes of recovery.
A couple of things are interesting to note:
1) They viewed running at zero percent incline as being “insignificantly different than that measured with track running” and did not see a need to compensate for lack of air resistance by introducing a treadmill incline until the late stages of the test when inclines were used to max out VO2, which was one of the objectives of the test.
2) They also addressed the other major consideration that most often comes up when discussing treadmill running here on these forums....biomechanical differences with over-ground running. And they didn’t consider such differences to be significant.
Noakes He doesn’t discuss treadmill running, per se, in his book. However, he does discuss a similar subject relative to the effect of air resistance and that Martin and Coe made reference to....drafting in a race. The principle is the same, but reversed. In the case of drafting, the object is to avoid air resistance to conserve energy, as opposed to running on a treadmill where the “myth” is to use incline to simulate air resistance to increase energy used to be the same as running outdoors. Both concepts are predicated on the effect that air resistance has on the runner. The following is what Noakes has to say about air resistance and drafting (again, the bold emphasis is mine):
“One of the first scientists to study the influence of wind speed on running performance was the great British physiologist Dr. Griffiths Pugh, whose work on effects of altitude on athletic performance is among the classic contributions on that topic. Pugh performed four different studies designed to measure how wind speed and the gradient of the running surface influence the oxygen cost of running (1970). His studies showed that the extra cost of running into a facing wind increased as the square of the wind speed. Thus the oxygen cost of running into a 66-km/hr head wind increases by 30 ml/kg/min. Similarly, running up an 8% incline increases the oxygen cost of running by about 20 ml/kg/min.
“Pugh also showed that at the speeds at which middle-distance track events are run (6 m/s or about 67 seconds per 400m), about 8% of the runner’s energy is used in overcoming air resistance. But by running directly behind a leading runner (or drafting) at a distance of about 1 m, the athlete can save 80% of that energy. In a middle-distance race this would be equivalent to a savings of about 4 seconds per lap. However, Pugh considers it unlikely that in practice the following athletes would ever be able to run as close to the lead runner to benefit to this extent. By running slightly to the side of the lead runner, the following runner would probably benefit by about 1 second per lap.
“Another researcher to study the benefits of drafting was Californian Chester R. Kyle (1979). His calculations suggest that at world-record mile pace, a runner running 2 m behind the lead runner would save about 1.66 seconds per lap, which generally confirms Pugh’s estimations.
“These findings explain why track athletes find pacers to be such essential ingredients in aiming for world records. In addition, these findings explain why world records in the sprints are set at altitude. During sprinting, the energy cost of overcoming air resistance rises to between 13 and 16% of the total cost of running. Thus, the sprinter benefits greatly by running at an altitude where air resistance is considerably reduced. It is interesting that when a runner is racing on a circular track, an optimum strategy is to accelerate into the wind and to decelerate when the wind is from behind, the opposite of what one would expect.
“The Briton Dr. Mervyn Davies (1980/81) extended Pugh’s findings. Davies used essentially the same techniques as Pugh but included observations on the effects of running downhill and of following winds of different speeds.
“Davies found that when a runner was measured on a treadmill, facing winds of up to 18 km/hr had no effect on the oxygen cost of running. But the same conditions on the road will have a very marked effect. On the treadmill, the athlete does not move forward and thus does not expend energy overcoming wind resistance. However, an athlete who runs on the road into a wind of 18 km/hr faces an actual wind speed equal to that of his or her running speed plus that of the prevailing wind.
“The practical relevance of this is that on a calm day, anyone running slower than 18 km/hr (about a 2:21 marathon pace) will not benefit by drafting in the wake of other runners. However, runners stand to gain significantly by drafting at faster speeds or when running into winds that, when added to their running speeds, would make the actual wind speed greater than 18 km/hr.”
Everything that Noakes says about Pugh’s and Kyle’s studies with air resistance involves either strong head winds or very fast running paces. It was Davies who extended Pugh’s studies to calm wind and following wind conditions.
I infer from Davies and Noakes’ conclusions that, if 18 km/hr (11.16 mi/hr or 5:22 min/mile) is the threshold for drafting to become beneficial in calm air, then, similarly, 5:22 pace is the threshold at which the lack of air resistance becomes a factor when running on a treadmill.
Actually, the study that ExPhysRunner referenced also found that there was no difference between oxygen consumption on a treadmill at 0% incline and outdoor running at slower paces, although the paces at which there was no difference (9:11 and 8:03 min/mile) were considerably slower than those determined by Davies (5:22 min/mile) and referenced by Martin and Coe (“at least to 6:00 min/mile”). Perhaps these variations resulted from differences in test protocols. Or, perhaps it relates to one of the reasons arepper felt that the study that ExPhysRunner referenced was flawed....a very small sample base of nine runners. And, apparently, all of them were highly trained runners since the test conditions extended to a pace of 5:22 min/mile. In any event, the sample certainly wasn’t representative of a broad cross section of runners. Of course, that might also be the case in Pugh’s and Davies’ studies.
In my opinion, the bottom line to all of this is that ExPhysRunner and his supporters are right in that there is air resistance imposed on all runners at all paces when running over-ground. However, arepper is also right in that for most runners it’s a “So what?” issue. The impact of energy consumption expended to overcome calm air resistance for most runners is insignificant, immeasurable, and not worth attempting to specifically compensate for with a predetermined incline adjustment when on a treadmill. In fact, all of the above data, including that in the study referenced by ExPhysRunner, indicates that cranking in an incline “adjustment” just because someone says you should can make treadmill more difficult than running over-ground for everyone running slower than 8:00, 6:00 or 5:22 min/mile....take your pick of whose data you think is most credible.
And there is a final consideration, which was the basis of my previous post on this subject, that this is really a very minor variable among several that determine the differences between treadmill and over-ground running. Other more significant variables include outdoor climate, treadmill calibration, and outdoor terrain. Heck, in Noakes book, he even mentions the drag caused by short hair, loose fitting clothing, or long hair as having as much or more energy cost....4%, 4.2% and 6.3%, respectively....as air resistance for the pace that most runners run. A long haired runner can just get a haircut and gain more than 2%. In comparison, calm air resistance costs the 4:30 min/mile runner, the middle-distance track runner referenced in Pugh’s study above, 8%. And it is a very small fraction of that for us mere mortals.
My recommendation is to ignore any advice that says that it is necessary to always use a 1-2% incline adjustment to compensate for the lack of wind resistance. Instead, use the combination of speed control and incline adjustment that best makes a treadmill run “feel like” it is giving you the training benefit that you desire.
Jim2
Monday, January 16, 2006
Treadmill Running
In my opinion, using a 1-2 percent incline to simulate the "wind resistance" created by your body moving forward through the air when running outside is one of the most overblown "theories" in running. There are several other variables between road and treadmill running that are much more significant than wind resistance. I think the three biggest ones are treadmill calibration, climate and terrain.
(1) Treadmill calibration. It can range all over the place and make a particular 'mill easier or harder than running outside. The first 'mill I owned was a bargain basement model that was very noticeably harder to run on when set at zero percent incline than running outdoors under comparable climatic conditions. I had to adjust training paces to about 30 sec/mile slower than outside for an equivalent workout. Adding a 1-2% incline would have just made it even more difficult than road running. OTOH, my current 'mill, that has a minimum incline setting of 1%, and the 'mills I mostly use at the gym, when set to their minimum incline of zero percent, feel about the same as running outdoors.
(2) Terrain. Unless you run on a track, terrain outdoors is seldom dead flat, or zero percent. It's usually undulating. The undulations can range from subtle to mountainous. Thus, either intensity varies throughout a run or pace has to be varied to maintain a constant intensity. Except for when running hill repeats on a 'mill, how often do most people vary incline and pace to simulate variable outdoor terrains?
(3) Climate. It can be almost anything outside. In most indoor settings, climatic control systems almost always maintain conditions at 70-72 degrees, 50-60% humidity and no wind....and they are the same day after day. But, what if climatic conditions outside are ideal for running.....50 dry, windless degrees? Running in 50 degree temperature outside would be much "easier" than running the same pace in 70-72 degrees inside on a mill. So, should one jack up the back of the mill to simulate running downhill in that case to compensate for not having the great outdoor conditions? OTOH, if it is 96 degrees with 90% humidity on a hot summer day, should one crank the incline up to 5-6 percent to make running as difficult as outside? Actually, the 70-72 degree indoor environment really doesn't make for good running conditions, especially for long distances or speedwork.
The "compensating for the lack of wind resistance" theory implies that the lack of relative movement between your body and the surrounding air makes running easier. However, I think that the lack of relative air movement over the body indoors can be a disadvantage, rather than a benefit, which can make running harder. Air flow aids dissipation of body heat generated by running. If there is no air flow over the body, cooling is reduced. And we all know that cooling is a significant factor in determining the ease or difficulty of running.
So, just what combination of outdoor conditions is the incline adjustment intended to compensate for? And why? Very few days have ideal outdoor running conditions. If most days outdoors are different, what's wrong with an indoor run on a 'mill being different than some set of "standard, but undefined" outdoor conditions? Why cherrypick one relatively minor indoor/outdoor variable and recommend an incline adjustment for it?
What do we do when outdoor conditions vary? We adjust pace. What's wrong with doing the same on a 'mill to "compensate" for whatever the differences are between indoors and outdoors? Making an incline adjustment to compensate for the lack wind resistance is simply adding one more factor in selecting pace.
Bottom line....I think that using a 1-2 percent incline on a 'mill to specifically "simulate the wind resistance of running outdoors" is a meaningless thing to do. I think that adjusting pace to get the training intensity that you want under the environmental conditions that you face, whether on the road or the treadmill is more practical. And running indoors on a 'mill is simply another environmental factor in choosing paces.
The problem with blindly following studies that "prove" that running on a mill is easier than outdoors because of the lack of wind resistance and that adding 1-2% incline to the mill will make them equal is that such studies are conducted under precisely controlled, lab-type conditions. However, we run in the real world where conditions vary widely. I prefer to keep my mind open and adjust both incline and pace to achieve the training effect that I desire for each specific treadmill run.
Physiology is another matter. Many people experience foot or lower leg discomfort while or after running on a 'mill at zero percent incline. In such cases, using a slight incline is smart. That just becomes an additional factor to consider in selecting treadmill pace.
Jim2
(1) Treadmill calibration. It can range all over the place and make a particular 'mill easier or harder than running outside. The first 'mill I owned was a bargain basement model that was very noticeably harder to run on when set at zero percent incline than running outdoors under comparable climatic conditions. I had to adjust training paces to about 30 sec/mile slower than outside for an equivalent workout. Adding a 1-2% incline would have just made it even more difficult than road running. OTOH, my current 'mill, that has a minimum incline setting of 1%, and the 'mills I mostly use at the gym, when set to their minimum incline of zero percent, feel about the same as running outdoors.
(2) Terrain. Unless you run on a track, terrain outdoors is seldom dead flat, or zero percent. It's usually undulating. The undulations can range from subtle to mountainous. Thus, either intensity varies throughout a run or pace has to be varied to maintain a constant intensity. Except for when running hill repeats on a 'mill, how often do most people vary incline and pace to simulate variable outdoor terrains?
(3) Climate. It can be almost anything outside. In most indoor settings, climatic control systems almost always maintain conditions at 70-72 degrees, 50-60% humidity and no wind....and they are the same day after day. But, what if climatic conditions outside are ideal for running.....50 dry, windless degrees? Running in 50 degree temperature outside would be much "easier" than running the same pace in 70-72 degrees inside on a mill. So, should one jack up the back of the mill to simulate running downhill in that case to compensate for not having the great outdoor conditions? OTOH, if it is 96 degrees with 90% humidity on a hot summer day, should one crank the incline up to 5-6 percent to make running as difficult as outside? Actually, the 70-72 degree indoor environment really doesn't make for good running conditions, especially for long distances or speedwork.
The "compensating for the lack of wind resistance" theory implies that the lack of relative movement between your body and the surrounding air makes running easier. However, I think that the lack of relative air movement over the body indoors can be a disadvantage, rather than a benefit, which can make running harder. Air flow aids dissipation of body heat generated by running. If there is no air flow over the body, cooling is reduced. And we all know that cooling is a significant factor in determining the ease or difficulty of running.
So, just what combination of outdoor conditions is the incline adjustment intended to compensate for? And why? Very few days have ideal outdoor running conditions. If most days outdoors are different, what's wrong with an indoor run on a 'mill being different than some set of "standard, but undefined" outdoor conditions? Why cherrypick one relatively minor indoor/outdoor variable and recommend an incline adjustment for it?
What do we do when outdoor conditions vary? We adjust pace. What's wrong with doing the same on a 'mill to "compensate" for whatever the differences are between indoors and outdoors? Making an incline adjustment to compensate for the lack wind resistance is simply adding one more factor in selecting pace.
Bottom line....I think that using a 1-2 percent incline on a 'mill to specifically "simulate the wind resistance of running outdoors" is a meaningless thing to do. I think that adjusting pace to get the training intensity that you want under the environmental conditions that you face, whether on the road or the treadmill is more practical. And running indoors on a 'mill is simply another environmental factor in choosing paces.
The problem with blindly following studies that "prove" that running on a mill is easier than outdoors because of the lack of wind resistance and that adding 1-2% incline to the mill will make them equal is that such studies are conducted under precisely controlled, lab-type conditions. However, we run in the real world where conditions vary widely. I prefer to keep my mind open and adjust both incline and pace to achieve the training effect that I desire for each specific treadmill run.
Physiology is another matter. Many people experience foot or lower leg discomfort while or after running on a 'mill at zero percent incline. In such cases, using a slight incline is smart. That just becomes an additional factor to consider in selecting treadmill pace.
Jim2
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