something wrote:
Where can i find this study Richard_?
Here is the study: Trappe S, Harber M, Creer A, Gallagher P, Slivka D, Minchev K, Whitsett D., Single muscle fiber adaptations with marathon training, J Appl Physiol, 2006, 101: 721-727.
Here is the article I wrote on the topic:
Adaptations to Marathon Training
Running a marathon requires a significant amount of specific marathon training in order to prepare the body to handle the stress of running 26.2 miles. If an average runner attempts to run a marathon without adequate training they are unlikely to be able to run the entire distance. Instead, at some point during the race they will most likely become exhausted and will slow to a “death march” to the finish assuming they don’t drop-out from fatigue or sustain an injury that forces them to abandon the race. Non-runners who attempt a marathon without training are almost assured of becoming exhausted and unable to complete the race or to sustain a race-ending injury. On the other hand, as few as 16 weeks of proper training will enable most people, even non-runners, to successfully complete a marathon.
Clearly, the body adapts with training so that what was once hard or beyond the capabilities of the body becomes easier or possible with proper training. The 10 mile run that might be impossible for a non-runner to complete prior to starting run training is transformed into an easy run once adequate training is conducted.
What adaptations occur within the body that transforms a non-runner unable to run even modest distances into a person capable of running 26.2 miles without stopping and without injury? The traditional answer given by exercise physiology to this question is centered on the body’s ability to absorb, transport, and utilize oxygen, using terms such as VO2max, lactate threshold, and running economy to explain the adaptations that occur within the body. Is this answer accurate? Does the traditional answer fully or mostly explain the changes in the body that enable someone to transform from a non-runner or recreational runner into a marathon runner? A new research study suggests that the traditional answers do not tell the full story and, instead, that other physiological changes within the body may more accurately explain the increased running capabilities from marathon training. Let’s take a look at this recent research and see what it has to teach us.
Research
Previous research on marathon training success has focused heavily on the physiological parameters having to do with aerobic capacity. Researchers have extensively measured the VO2max, lactate threshold, and running economy of a wide variety of marathon runners, from the fastest of the elites to those runners finishing many hours later. This research has shown that runners of similar physiological profiles often perform very differently in the marathon. For examples, two runners with very similar VO2max levels may finish the marathon with very different times. Despite very similar physiological profiles one is a significantly faster runner than the other. It is obvious, then, that other, as yet unidentified, factors play a significant role in marathon performance.
One physiological component that may contribute significantly to performance but has received sparse attention from researchers is muscle. Relatively little research has been done on the role muscle function plays in distance running performance. Knowing this, in 2006 a group of researchers from Ball State University decided to examine the changes occurring in muscles during marathon training. They hypothesized that significant changes would take place in the muscles.
Ball State University offers a university class designed to prepare students physically and mentally to complete a marathon following a proven, 16 weeks, 4-days-per-week marathon training program. Several years ago this program was compared in a research study to a 6 days-per-week program and found to be equally effective. Since then, hundreds of students have followed this program and completed a marathon.
The program is a fairly standard marathon training program that takes non-runners and recreationally active subjects and gradually increases their training volume over a period of 16 weeks. The key run in this program is the weekly long run, which progresses from an initial distance of 5 miles up to two 18 mile long runs. Weekly training volume begins at 15 miles and increases to a peak of 36 miles. With the emphasis being on marathon completion rather than maximum performance, all training runs are conducted at an easy pace.
The researchers recruited subjects participating in the marathon training class and tested them on 3 separate occasions: before the 16 week training plan, after 13 weeks of training, and after a 3 week taper and marathon. The subjects were tested the standard physiological measures, including VO2max, running economy, heart rate, and body weight. Additionally, muscle biopsies were conducted to determine such measures as single muscle fiber diameter, peak power, shortening velocity, power characteristics, and oxidative enzyme activity.
Results
All the subjects successfully completed the marathon. The average time was 4:54 hr:min, with a range of 3:56 hr:min to 5:35 hr:min.
Aerobic adaptations
There were few changes in the runners’ aerobic capacity. Oxidative enzyme activity (citrate synthase activity), which is a measure of the muscles ability to produce energy aerobically, increased by 37%. Interestingly, despite the increase ability of the muscles to produce energy aerobically there was no statistically significant change in VO2max (49.5 vs. 52 ml/kg/min). There was a trend for an increase in absolute VO2 from 3.37 l/min to 3.5 l/min, but the change was not large enough to be significant. Running economy improved at the submaximal running speed of 9.65 km/hr (similar to training & marathon pace), with an absolute decrease in oxygen consumption of 2.43 vs 2.28 l/min and relative oxygen consumption decreasing from 36.0 to 33.6 ml/kg/min. The aerobic adaptations are summed in table 1.
Muscle adaptations
In contrast to the modest adaptations in the cardiovascular system, there were significant changes in the muscles of the runners. First, slow twitch & fast twitch oxidative muscle fibers decreased 21% & 23% respectively in size (diameter). This is significant because all things being equal, smaller fibers are weaker than larger fibers. However, despite the decrease in size of the muscle fibers, the contractile ability of the muscles actually increased. Peak force (strength) stayed the same in the slow twitch fibers and increased 18% in fast twitch oxidative fibers. Strength in relation to the decreased fiber size increased approx. 60% in both fiber types. Muscle power also increased. Absolute power output increased in slow twitch fibers by 56% and in fast twitch oxidative fibers by 53%. Relative power output increased 100% in slow twitch fibers and 84% in fast twitch oxidative fibers. Additionally, slow twitch fibers increased their shortening velocity 28%. Table 2 sums the changes in muscle contractility.
Discussion
What should we make of all the above? What do all those changes mean? First, we note that the training program was successful in preparing these subjects to complete the marathon. As was pointed out at the beginning of this article, few non-runners can run the entire marathon distance without proper training. So, this training program produced sufficient improvements in fitness to allow these subjects to complete the marathon.
What the results of this study shows, then, is that the physiological changes that occurred in these subjects that enabled them to run a marathon took place in the muscles, not in the cardiovascular system. All of the changes occurred in the muscles – strength, power, contraction speed, and oxidative enzyme activity were improved in one or both fiber types. Even running economy, which improved 6%, now appears to be a muscle factor as research indicates running economy is determined more by muscle fiber type than cardiovascular factors.(3,4) Indeed, VO2max did not improve as a result of training and the increased power output of the muscle likely explains the 6% decreased submaximal oxygen consumption at the 9.65 km/hr pace. In short, major changes in muscle contractility accompanied by changes in the muscles ability to produce energy aerobically are what allowed these subjects to successfully run a marathon.
Are these results unique or surprising? No, they are not as other studies have produced similar findings. A study of collegiate cross-country runners found their slow twitch fibers contraction speed to be at the upper end of the range typically observed for human slow twitch fibers.(5) One study examining the effects on muscle fiber function of a 21 day taper in swimmers found increased muscle contraction speed, strength, & power accompanied a 4% increase in performance.(6) A study of master runners showed that their slow twitch fibers contracted 20% faster than matched sedentary adults.(7) In fact, the researchers calculated that during running the master runners slow twitch fibers “…would produce more than twice as much power…” as the slow twitch fibers of the sedentary runners. Finally, 7 years of research data on Lance Armstrong indicated that the primary physiological adaptation that occurred between ages 21 and 28 was an 18% improvement in power-to-weight ratio. His performance during this same time period improved from young pro-cyclist to multiple winner of the Tour de France though no changes occurred in his aerobic capacity during this same time period. This indicates that the increased power output is what enabled the performance improvements.(8)
Summary
Exercise physiologists have traditionally focused on changes in aerobic capacity to explain improvements in endurance fitness and performance. However, runners with very different performance abilities can have very similar aerobic capacities and changes in running performance are not always accompanied by changes in aerobic capacity. In an attempt to explain these discrepancies some researchers have begun examining other factors that may play a role in endurance performance.
In particular, a few researchers have attempted to determine if changes in muscle fiber contractility accompany changes in endurance performance. A recent study on adaptations with marathon training found minor cardiovascular changes but very large changes in muscle strength, power, & contraction speed. The changes in muscle fiber capability most likely explain the physiological improvements that enabled the subjects to successful run a marathon. The changes revealed by this research are supported by multiple other studies that have found similar changes in muscle strength, power, and rate of contraction with endurance training.
Reference:
1. Trappe S, Harber M, Creer A, Gallagher P, Slivka D, Minchev K, Whitsett D., Single muscle fiber adaptations with marathon training, J Appl Physiol, 2006, 101: 721-727.
2. Dolgener FA, Kolkhorst FW, Whitsett DA., Long slow distance training in novice marathoners, Res Q Exerc Sport, 1995, 65:339-346.
3. Coyle E, Sidossis L, Horowitz J, Beltz J., Cycling efficiency is related to the percentage of Type 1 muscle fibers, Med Sci Sports Exer, 1992, 24(7), 782-788.
4. Horowitz J, Sidossis L, Coyle E., High efficiency of Type 1 muscle fibers improves performance, Int J Sports Med, 1994, 15(3), 152-157.
5. Harber MP, Gallagher PM, Creer AR, Minchev KM, Trappe SW., Single muscle fiber contractile properties during a competitive season in male runners, Am J Physiol Regul Intergr Comp Physiol, 2004, 287: R1124-R1131.
6. Trappe S, Costill D, Thomas R., Effect of swim taper on whole muscle and single muscle fiber contractile properties, Med Sci Sports Exerc, 2000, 32(12), 48-56.
7. Widrick J, Trappe S, Costill D, Fitts R., Force-velocity and force-power properties of single muscle fibers from elite master runners and sedentary men, Am J Physiol, 1996, 271(Cell Physiol 40), C676-C683.
8. Coyle E., Improved muscular efficiency displayed as Tour de France champion matures, J Appl Physiol, 2005, 98: 2191-2196.