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From Fellrnr.com, Running tips
Created page with "While the Long Run is a core part of training for endurance races, there is relatively little scientific evidence available. This entry summarizes the evidence I have been abl..."
While the Long Run is a core part of training for endurance races, there is relatively little scientific evidence available. This entry summarizes the evidence I have been able to locate.
=Correlations between The Long Run and Performance=
This section summarizes the studies that correlate the long run against various factors including marathon finish time and hitting the wall, or injury rate.
==The Long Run and Marathon Performance==
An evaluation of marathon finish times against training from the 1970s<ref name="Slovic-1977"/> is shown below. There is an obvious correlation between the finishing time and both the longest run and overall mileage.
{| class="wikitable"
!Time!!Max Week!!Longest run!!Number of 20+ mile runs!!Mileage over two months
|-
|2:25:00
|106
|22.3
|2.7
|627
|-
|2:38:00
|86
|20.9
|2.7
|477
|-
|2:54:00
|80
|21.5
|2.9
|445
|-
|3:08:00
|64
|20.5
|1.9
|331
|-
|3:23:00
|57
|18.2
|1.1
|291
|-
|3:38:00
|58
|18.8
|1.2
|312
|-
|3:53:00
|46
|17
|0.7
|224
|-
|4:15:00
|42
|15.3
|0.4
|208
|-
|4:52:00
|37
|13.1
|0.3
|174
|}
{| class="wikitable"
|- valign="top"
|[[File:Longest Run.jpg|none|thumb|500px|The length of the longest run against finish time.]]
|[[File:Number of 20plus mile runs.jpg|none|thumb|500px|The number of 20+ mile long runs against finish time.]]
|}
Another similar study showed that the number of runs over 16, over 20 miles, the length of the longest run and overall mileage are correlated with finish time<ref name="McKelvie-1985"/>. One study separated out overall mileage from the long run<ref name="Dolgener-1994"/>. In that study, two groups of runners did the same long run schedule but their overall weekly mileage either increased from 18 miles to 39 miles, or from 23 miles to 49 miles. The marathon performance was identical between the groups, suggesting that long run distance may be more important than overall mileage.
==The Long Run and Hitting the Wall==
A study of 315 marathon runners evaluated the factors that are correlated with reported 'Hitting the Wall'. The length of the longest run but not weekly mileage was correlated hitting the wall<ref name="BumanBrewer2008"/>. Further analysis showed that a longest long run of 20 miles or less increased the chance of hitting the wall by 50%<ref name="BumanBrewer2009"/>.
==Injuries==
I found no studies that showed a correlation between the length of the long run and injuries. There is some evidence that the increase in mileage<ref name="Walter-1989"/>, overall monthly mileage<ref name="Lysholm-"/> or both<ref name="Fredericson-2007"/> is correlated with injuries.
==Correlation is not Causation==
What little scientific evidence we have correlates better marathon outcomes with longer distance long runs. However, the evidence does not indicate if the longer distance long runs cause the improved marathon outcome or if better runners tend to do longer runs.
[[File:Correlation.png|none|thumb|500px|XKCD's explanation of correlation and causation, from [http://xkcd.com/552/], also available as a [http://store.xkcd.com/products/correlation Tee Shirt] (I want one).]]
=Glycogen Depletion =
The evidence from the [[Glycogen]] depletion patterns may give some insight into the long run. We see that glycogen is depleted from some fibers before others<ref name="selective"/>. This pattern suggests that some slow twitch fibers are used first, and as these become exhausted, other fibers are recruited in their place. Slow twitch fibers are used first, but over time more and more fast twitch fibers are recruited. This may be one mechanism behind the benefits of the long run; it exhausts the most accessible fibers and therefore trains the other fibers. It is possible that without the long run, only the same, easily recruited fibers are trained. It is also conceivable that by using fast twitch fibers for endurance exercise, the long run will change the nature of these fibers.
=Muscle Damage=
Running, and especially [[Downhill Running]] tends to produce muscle damage and [[Delayed_Onset_Muscle_Soreness| Delayed Onset Muscle Soreness]]. This damage immediately weakens the muscles, with recovery and remodeling of the muscle fibers taking around 14 days<ref name="images"/>. After a single bout of DOMS, the muscle fibers undergo 'profound adaptations' to be more resilient<ref name="images"/>. It seems reasonable that this mechanism is a key benefit of the Long Run. Therefore a long run should be long enough to create some muscle damage, while balancing the risk of injury.
<gallery widths=300px heights=200px caption="Muscle damage from eccentric exercise (downhill running)">
File:EccentricA.JPG|Muscle before downhill running<ref name="images"/>
File:EccentricC.JPG|Immediately after downhill running<ref name="images"/>. Notice the disruption to the dark bands (z-bands) that are part of the muscle structure showing there is immediate damage.
File:EccentricD.JPG|One day later<ref name="images"/>, the damage and disruption is worse, indicated some continued breakdown.
File:EccentricB.JPG|Muscle 14 days later<ref name="images"/>, structurally recovered (other metrics do not return to pre-exercise levels at 14 days).
</gallery>
=Anecdotal Advice=
Given the limited scientific information, it seems reasonable to examine the anecdotal advice that is available.
* There are instances of remarkable performances without running long in training. For instance, [http://en.wikipedia.org/wiki/Grete_Waitz Grete Waitz] never ran more than 12 miles in training before winning the 1979 New York Marathon. However, at the time she was a world class track and cross country athlete who trained at 80-90 miles per week<ref name="GreteWaitz"/>. Her book on marathon training emphasizes the importance of the long run<ref name="WaltzBook"/>.
* Most training plans peak at 20 miles, though JD has 22 mile runs and Jeff Galloway has a 26 mile (2 min/mile slower with walking breaks)
* A consensus of caches suggests a single 20 mile run for novice marathoners and 3-6 long runs peaking at 23 miles for the more experience. <ref name="Higdon"/>.
* Some coaches recommend limiting the length of the long run to a percentage of the weekly mileage, often in the range 25-35%. The rationale for this unclear, and this recommendation could encourage high levels of [[Training Monotony]].
* Using time rather than distance for long runs is sometimes suggested, as a 16 mile run at 11 min/mile would take a similar time to 22 miles at 8 min/mile. For instance, Jack Daniels does not recommend novice marathoners to do a long run longer than 2.5 hours<ref name="JDArticle"/>. This approach may be based around the belief that runs longer than 2 or 3 hours provide little or no additional benefit<ref name="OverLongRun"/>. While there are some animal studies that show the benefits of endurance training plateaus, these studies looked at a limited aspect of endurance (cytochrome c)<ref name="Terjung-1976"/><ref name="Dudley-1982"/> and other animal studies do not show this plateau<ref name="Powers-1994"/>.
* It is often noted that ultramarathon runners do not train with proportionately long training runs. So a runner training for a 100 mile race will not run 76 mile long runs, which would be the equivalent to a 20 mile run for a marathon. In fact, the great ultrarunner Ray Krolewicz does not do training runs longer than 22 miles<ref name="RayK"/>. However, ultrarunners often run many long runs close together. For instance, Ray has done more than one 22 miler on each day of the weekend<ref name="RayK"/>, and 'back to back' long runs of 20-30 miles are commonly prescribed<ref name="UltraPlans"/>. Also, ultrarunners typically race frequently enough for the races to contribute to their overall training.
* It seems that many runners who run over 24 miles often do so in organized events, even if they are using the event for training rather racing.
=Recommendations=
Here is my personal interpretation of the scientific and anecdotal evidence.
* For marathon running, the longest long runs should be over 20 miles.
* There may be some injury risk to longer long runs, but it seems more likely that the injury risk comes from ramping up the length of the long run too quickly.
* Looking at the time for [[Endurance Adaptations]] to occur, it seems likely that most marathon training plans tend to be too short for many novice runners. Some are as short as four months, but even six months may be too short for many runners.
* The ideal pace for long runs is unclear, but almost all marathon runners train at slower than race pace for their long runs.
=References=
<references>
<ref name="BumanBrewer2008">{{cite journal|last1=Buman|first1=Matthew P.|last2=Brewer|first2=Britton W.|last3=Cornelius|first3=Allen E.|last4=Van Raalte|first4=Judy L.|last5=Petitpas|first5=Albert J.|title=Hitting the wall in the marathon: Phenomenological characteristics and associations with expectancy, gender, and running history|journal=Psychology of Sport and Exercise|volume=9|issue=2|year=2008|pages=177–190|issn=14690292|doi=10.1016/j.psychsport.2007.03.003}}</ref>
<ref name="Higdon">{{Cite book | last1 = Higdon | first1 = Hal. | title = Marathon : the ultimate training guid | date = 2005 | publisher = Rodale | location = Emmaus, Penn. | isbn = 1-59486-199-4 | pages = }}</ref>
<ref name="Slovic-1977"> {{Cite journal | last1 = Slovic | first1 = P. | title = Empirical study of training and performance in the marathon. | journal = Res Q | volume = 48 | issue = 4 | pages = 769-77 | month = Dec | year = 1977 | doi = | PMID = 271323 }}</ref>
<ref name="BumanBrewer2009">{{cite journal|last1=Buman|first1=Matthew P.|last2=Brewer|first2=Britton W.|last3=Cornelius|first3=Allen E.|title=A discrete-time hazard model of hitting the wall in recreational marathon runners|journal=Psychology of Sport and Exercise|volume=10|issue=6|year=2009|pages=662–666|issn=14690292|doi=10.1016/j.psychsport.2009.04.004}}</ref>
<ref name="McKelvie-1985">{{Cite journal | last1 = McKelvie | first1 = SJ. | last2 = Valliant | first2 = PM. | last3 = Asu | first3 = ME. | title = Physical training and personality factors as predictors of marathon time and training injury. | journal = Percept Mot Skills | volume = 60 | issue = 2 | pages = 551-66 | month = Apr | year = 1985 | doi = | PMID = 4000875 }}</ref>
<ref name="Fredericson-2007">{{Cite journal | last1 = Fredericson | first1 = M. | last2 = Misra | first2 = AK. | title = Epidemiology and aetiology of marathon running injuries. | journal = Sports Med | volume = 37 | issue = 4-5 | pages = 437-9 | month = | year = 2007 | doi = | PMID = 17465629 }}</ref>
<ref name="Dolgener-1994">{{Cite journal | last1 = Dolgener | first1 = FA. | last2 = Kolkhorst | first2 = FW. | last3 = Whitsett | first3 = DA. | title = Long slow distance training in novice marathoners. | journal = Res Q Exerc Sport | volume = 65 | issue = 4 | pages = 339-46 | month = Dec | year = 1994 | doi = | PMID = 7886283 }}</ref>
<ref name="Walter-1989">{{Cite journal | last1 = Walter | first1 = SD. | last2 = Hart | first2 = LE. | last3 = McIntosh | first3 = JM. | last4 = Sutton | first4 = JR. | title = The Ontario cohort study of running-related injuries. | journal = Arch Intern Med | volume = 149 | issue = 11 | pages = 2561-4 | month = Nov | year = 1989 | doi = | PMID = 2818114 }}</ref>
<ref name="Lysholm-">{{Cite journal | last1 = Lysholm | first1 = J. | last2 = Wiklander | first2 = J. | title = Injuries in runners. | journal = Am J Sports Med | volume = 15 | issue = 2 | pages = 168-71 | month = | year = | doi = | PMID = 3578639 }}</ref>
<ref name="GreteWaitz">Grete Waitz's Tips For First-Time Marathoners http://running.competitor.com/2010/06/features/grete-waitz%E2%80%99s-tips-for-first-time-marathoners_10606 </ref>
<ref name="WaltzBook">{{Cite book | last1 = Waitz | first1 = Grete | last2 = Averbuch | first2 = Gloria | title = Run your first marathon : everything you need to know to reach the finish lin | date = 2010 | publisher = Skyhorse Pub. | location = New York | isbn = 1-61608-036-1 | pages = }}</ref>
<ref name="JDArticle">Marathon Training: Shorten the Long Run | Active.com http://www.active.com/running/Articles/Marathon-Training--Shorten-the-Long-Run </ref>
<ref name="RayK">TRAINING WISDOM FROM AN ULTRAMARATHONING LEGEND http://www.ncctrackclub.com/articles/RayKrolewiczLEGEND.html </ref>
<ref name="UltraPlans">UltraLadies Running Club Trail 100-Mile Event Training Schedule - Trail Run Events http://www.trailrunevents.com/ul/schedule-100m.asp </ref>
<ref name="OverLongRun">Are You Overemphasizing The Marathon Long Run? http://running.competitor.com/2012/07/training/are-you-overemphasizing-the-marathon-long-run_55719/2 </ref>
<ref name="Dudley-1982">{{Cite journal | last1 = Dudley | first1 = GA. | last2 = Abraham | first2 = WM. | last3 = Terjung | first3 = RL. | title = Influence of exercise intensity and duration on biochemical adaptations in skeletal muscle. | journal = J Appl Physiol | volume = 53 | issue = 4 | pages = 844-50 | month = Oct | year = 1982 | doi = | PMID = 6295989 }}</ref>
<ref name="Terjung-1976">{{Cite journal | last1 = Terjung | first1 = RL. | title = Muscle fiber involvement during training of different intensities and durations. | journal = Am J Physiol | volume = 230 | issue = 4 | pages = 946-50 | month = Apr | year = 1976 | doi = | PMID = 178189 }}</ref>
<ref name="Powers-1994">{{Cite journal | last1 = Powers | first1 = SK. | last2 = Criswell | first2 = D. | last3 = Lawler | first3 = J. | last4 = Ji | first4 = LL. | last5 = Martin | first5 = D. | last6 = Herb | first6 = RA. | last7 = Dudley | first7 = G. | title = Influence of exercise and fiber type on antioxidant enzyme activity in rat skeletal muscle. | journal = Am J Physiol | volume = 266 | issue = 2 Pt 2 | pages = R375-80 | month = Feb | year = 1994 | doi = | PMID = 8141392 }}</ref>
<ref name="selective">Selective glycogen depletion in skeletal muscle fibers of man following sustained contractions [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1331072/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1331072/] </ref>
<ref name="images">Neuromuscular disease-associated proteins and eccentric exercise [http://jp.physoc.org/content/543/1/297.full.pdf http://jp.physoc.org/content/543/1/297.full.pdf] </ref>
</references>
=Correlations between The Long Run and Performance=
This section summarizes the studies that correlate the long run against various factors including marathon finish time and hitting the wall, or injury rate.
==The Long Run and Marathon Performance==
An evaluation of marathon finish times against training from the 1970s<ref name="Slovic-1977"/> is shown below. There is an obvious correlation between the finishing time and both the longest run and overall mileage.
{| class="wikitable"
!Time!!Max Week!!Longest run!!Number of 20+ mile runs!!Mileage over two months
|-
|2:25:00
|106
|22.3
|2.7
|627
|-
|2:38:00
|86
|20.9
|2.7
|477
|-
|2:54:00
|80
|21.5
|2.9
|445
|-
|3:08:00
|64
|20.5
|1.9
|331
|-
|3:23:00
|57
|18.2
|1.1
|291
|-
|3:38:00
|58
|18.8
|1.2
|312
|-
|3:53:00
|46
|17
|0.7
|224
|-
|4:15:00
|42
|15.3
|0.4
|208
|-
|4:52:00
|37
|13.1
|0.3
|174
|}
{| class="wikitable"
|- valign="top"
|[[File:Longest Run.jpg|none|thumb|500px|The length of the longest run against finish time.]]
|[[File:Number of 20plus mile runs.jpg|none|thumb|500px|The number of 20+ mile long runs against finish time.]]
|}
Another similar study showed that the number of runs over 16, over 20 miles, the length of the longest run and overall mileage are correlated with finish time<ref name="McKelvie-1985"/>. One study separated out overall mileage from the long run<ref name="Dolgener-1994"/>. In that study, two groups of runners did the same long run schedule but their overall weekly mileage either increased from 18 miles to 39 miles, or from 23 miles to 49 miles. The marathon performance was identical between the groups, suggesting that long run distance may be more important than overall mileage.
==The Long Run and Hitting the Wall==
A study of 315 marathon runners evaluated the factors that are correlated with reported 'Hitting the Wall'. The length of the longest run but not weekly mileage was correlated hitting the wall<ref name="BumanBrewer2008"/>. Further analysis showed that a longest long run of 20 miles or less increased the chance of hitting the wall by 50%<ref name="BumanBrewer2009"/>.
==Injuries==
I found no studies that showed a correlation between the length of the long run and injuries. There is some evidence that the increase in mileage<ref name="Walter-1989"/>, overall monthly mileage<ref name="Lysholm-"/> or both<ref name="Fredericson-2007"/> is correlated with injuries.
==Correlation is not Causation==
What little scientific evidence we have correlates better marathon outcomes with longer distance long runs. However, the evidence does not indicate if the longer distance long runs cause the improved marathon outcome or if better runners tend to do longer runs.
[[File:Correlation.png|none|thumb|500px|XKCD's explanation of correlation and causation, from [http://xkcd.com/552/], also available as a [http://store.xkcd.com/products/correlation Tee Shirt] (I want one).]]
=Glycogen Depletion =
The evidence from the [[Glycogen]] depletion patterns may give some insight into the long run. We see that glycogen is depleted from some fibers before others<ref name="selective"/>. This pattern suggests that some slow twitch fibers are used first, and as these become exhausted, other fibers are recruited in their place. Slow twitch fibers are used first, but over time more and more fast twitch fibers are recruited. This may be one mechanism behind the benefits of the long run; it exhausts the most accessible fibers and therefore trains the other fibers. It is possible that without the long run, only the same, easily recruited fibers are trained. It is also conceivable that by using fast twitch fibers for endurance exercise, the long run will change the nature of these fibers.
=Muscle Damage=
Running, and especially [[Downhill Running]] tends to produce muscle damage and [[Delayed_Onset_Muscle_Soreness| Delayed Onset Muscle Soreness]]. This damage immediately weakens the muscles, with recovery and remodeling of the muscle fibers taking around 14 days<ref name="images"/>. After a single bout of DOMS, the muscle fibers undergo 'profound adaptations' to be more resilient<ref name="images"/>. It seems reasonable that this mechanism is a key benefit of the Long Run. Therefore a long run should be long enough to create some muscle damage, while balancing the risk of injury.
<gallery widths=300px heights=200px caption="Muscle damage from eccentric exercise (downhill running)">
File:EccentricA.JPG|Muscle before downhill running<ref name="images"/>
File:EccentricC.JPG|Immediately after downhill running<ref name="images"/>. Notice the disruption to the dark bands (z-bands) that are part of the muscle structure showing there is immediate damage.
File:EccentricD.JPG|One day later<ref name="images"/>, the damage and disruption is worse, indicated some continued breakdown.
File:EccentricB.JPG|Muscle 14 days later<ref name="images"/>, structurally recovered (other metrics do not return to pre-exercise levels at 14 days).
</gallery>
=Anecdotal Advice=
Given the limited scientific information, it seems reasonable to examine the anecdotal advice that is available.
* There are instances of remarkable performances without running long in training. For instance, [http://en.wikipedia.org/wiki/Grete_Waitz Grete Waitz] never ran more than 12 miles in training before winning the 1979 New York Marathon. However, at the time she was a world class track and cross country athlete who trained at 80-90 miles per week<ref name="GreteWaitz"/>. Her book on marathon training emphasizes the importance of the long run<ref name="WaltzBook"/>.
* Most training plans peak at 20 miles, though JD has 22 mile runs and Jeff Galloway has a 26 mile (2 min/mile slower with walking breaks)
* A consensus of caches suggests a single 20 mile run for novice marathoners and 3-6 long runs peaking at 23 miles for the more experience. <ref name="Higdon"/>.
* Some coaches recommend limiting the length of the long run to a percentage of the weekly mileage, often in the range 25-35%. The rationale for this unclear, and this recommendation could encourage high levels of [[Training Monotony]].
* Using time rather than distance for long runs is sometimes suggested, as a 16 mile run at 11 min/mile would take a similar time to 22 miles at 8 min/mile. For instance, Jack Daniels does not recommend novice marathoners to do a long run longer than 2.5 hours<ref name="JDArticle"/>. This approach may be based around the belief that runs longer than 2 or 3 hours provide little or no additional benefit<ref name="OverLongRun"/>. While there are some animal studies that show the benefits of endurance training plateaus, these studies looked at a limited aspect of endurance (cytochrome c)<ref name="Terjung-1976"/><ref name="Dudley-1982"/> and other animal studies do not show this plateau<ref name="Powers-1994"/>.
* It is often noted that ultramarathon runners do not train with proportionately long training runs. So a runner training for a 100 mile race will not run 76 mile long runs, which would be the equivalent to a 20 mile run for a marathon. In fact, the great ultrarunner Ray Krolewicz does not do training runs longer than 22 miles<ref name="RayK"/>. However, ultrarunners often run many long runs close together. For instance, Ray has done more than one 22 miler on each day of the weekend<ref name="RayK"/>, and 'back to back' long runs of 20-30 miles are commonly prescribed<ref name="UltraPlans"/>. Also, ultrarunners typically race frequently enough for the races to contribute to their overall training.
* It seems that many runners who run over 24 miles often do so in organized events, even if they are using the event for training rather racing.
=Recommendations=
Here is my personal interpretation of the scientific and anecdotal evidence.
* For marathon running, the longest long runs should be over 20 miles.
* There may be some injury risk to longer long runs, but it seems more likely that the injury risk comes from ramping up the length of the long run too quickly.
* Looking at the time for [[Endurance Adaptations]] to occur, it seems likely that most marathon training plans tend to be too short for many novice runners. Some are as short as four months, but even six months may be too short for many runners.
* The ideal pace for long runs is unclear, but almost all marathon runners train at slower than race pace for their long runs.
=References=
<references>
<ref name="BumanBrewer2008">{{cite journal|last1=Buman|first1=Matthew P.|last2=Brewer|first2=Britton W.|last3=Cornelius|first3=Allen E.|last4=Van Raalte|first4=Judy L.|last5=Petitpas|first5=Albert J.|title=Hitting the wall in the marathon: Phenomenological characteristics and associations with expectancy, gender, and running history|journal=Psychology of Sport and Exercise|volume=9|issue=2|year=2008|pages=177–190|issn=14690292|doi=10.1016/j.psychsport.2007.03.003}}</ref>
<ref name="Higdon">{{Cite book | last1 = Higdon | first1 = Hal. | title = Marathon : the ultimate training guid | date = 2005 | publisher = Rodale | location = Emmaus, Penn. | isbn = 1-59486-199-4 | pages = }}</ref>
<ref name="Slovic-1977"> {{Cite journal | last1 = Slovic | first1 = P. | title = Empirical study of training and performance in the marathon. | journal = Res Q | volume = 48 | issue = 4 | pages = 769-77 | month = Dec | year = 1977 | doi = | PMID = 271323 }}</ref>
<ref name="BumanBrewer2009">{{cite journal|last1=Buman|first1=Matthew P.|last2=Brewer|first2=Britton W.|last3=Cornelius|first3=Allen E.|title=A discrete-time hazard model of hitting the wall in recreational marathon runners|journal=Psychology of Sport and Exercise|volume=10|issue=6|year=2009|pages=662–666|issn=14690292|doi=10.1016/j.psychsport.2009.04.004}}</ref>
<ref name="McKelvie-1985">{{Cite journal | last1 = McKelvie | first1 = SJ. | last2 = Valliant | first2 = PM. | last3 = Asu | first3 = ME. | title = Physical training and personality factors as predictors of marathon time and training injury. | journal = Percept Mot Skills | volume = 60 | issue = 2 | pages = 551-66 | month = Apr | year = 1985 | doi = | PMID = 4000875 }}</ref>
<ref name="Fredericson-2007">{{Cite journal | last1 = Fredericson | first1 = M. | last2 = Misra | first2 = AK. | title = Epidemiology and aetiology of marathon running injuries. | journal = Sports Med | volume = 37 | issue = 4-5 | pages = 437-9 | month = | year = 2007 | doi = | PMID = 17465629 }}</ref>
<ref name="Dolgener-1994">{{Cite journal | last1 = Dolgener | first1 = FA. | last2 = Kolkhorst | first2 = FW. | last3 = Whitsett | first3 = DA. | title = Long slow distance training in novice marathoners. | journal = Res Q Exerc Sport | volume = 65 | issue = 4 | pages = 339-46 | month = Dec | year = 1994 | doi = | PMID = 7886283 }}</ref>
<ref name="Walter-1989">{{Cite journal | last1 = Walter | first1 = SD. | last2 = Hart | first2 = LE. | last3 = McIntosh | first3 = JM. | last4 = Sutton | first4 = JR. | title = The Ontario cohort study of running-related injuries. | journal = Arch Intern Med | volume = 149 | issue = 11 | pages = 2561-4 | month = Nov | year = 1989 | doi = | PMID = 2818114 }}</ref>
<ref name="Lysholm-">{{Cite journal | last1 = Lysholm | first1 = J. | last2 = Wiklander | first2 = J. | title = Injuries in runners. | journal = Am J Sports Med | volume = 15 | issue = 2 | pages = 168-71 | month = | year = | doi = | PMID = 3578639 }}</ref>
<ref name="GreteWaitz">Grete Waitz's Tips For First-Time Marathoners http://running.competitor.com/2010/06/features/grete-waitz%E2%80%99s-tips-for-first-time-marathoners_10606 </ref>
<ref name="WaltzBook">{{Cite book | last1 = Waitz | first1 = Grete | last2 = Averbuch | first2 = Gloria | title = Run your first marathon : everything you need to know to reach the finish lin | date = 2010 | publisher = Skyhorse Pub. | location = New York | isbn = 1-61608-036-1 | pages = }}</ref>
<ref name="JDArticle">Marathon Training: Shorten the Long Run | Active.com http://www.active.com/running/Articles/Marathon-Training--Shorten-the-Long-Run </ref>
<ref name="RayK">TRAINING WISDOM FROM AN ULTRAMARATHONING LEGEND http://www.ncctrackclub.com/articles/RayKrolewiczLEGEND.html </ref>
<ref name="UltraPlans">UltraLadies Running Club Trail 100-Mile Event Training Schedule - Trail Run Events http://www.trailrunevents.com/ul/schedule-100m.asp </ref>
<ref name="OverLongRun">Are You Overemphasizing The Marathon Long Run? http://running.competitor.com/2012/07/training/are-you-overemphasizing-the-marathon-long-run_55719/2 </ref>
<ref name="Dudley-1982">{{Cite journal | last1 = Dudley | first1 = GA. | last2 = Abraham | first2 = WM. | last3 = Terjung | first3 = RL. | title = Influence of exercise intensity and duration on biochemical adaptations in skeletal muscle. | journal = J Appl Physiol | volume = 53 | issue = 4 | pages = 844-50 | month = Oct | year = 1982 | doi = | PMID = 6295989 }}</ref>
<ref name="Terjung-1976">{{Cite journal | last1 = Terjung | first1 = RL. | title = Muscle fiber involvement during training of different intensities and durations. | journal = Am J Physiol | volume = 230 | issue = 4 | pages = 946-50 | month = Apr | year = 1976 | doi = | PMID = 178189 }}</ref>
<ref name="Powers-1994">{{Cite journal | last1 = Powers | first1 = SK. | last2 = Criswell | first2 = D. | last3 = Lawler | first3 = J. | last4 = Ji | first4 = LL. | last5 = Martin | first5 = D. | last6 = Herb | first6 = RA. | last7 = Dudley | first7 = G. | title = Influence of exercise and fiber type on antioxidant enzyme activity in rat skeletal muscle. | journal = Am J Physiol | volume = 266 | issue = 2 Pt 2 | pages = R375-80 | month = Feb | year = 1994 | doi = | PMID = 8141392 }}</ref>
<ref name="selective">Selective glycogen depletion in skeletal muscle fibers of man following sustained contractions [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1331072/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1331072/] </ref>
<ref name="images">Neuromuscular disease-associated proteins and eccentric exercise [http://jp.physoc.org/content/543/1/297.full.pdf http://jp.physoc.org/content/543/1/297.full.pdf] </ref>
</references>
