In the 1999 study, "High speed running performance is largely unaffected by hypoxic reductions in aerobic power." (Weyand, et al), researchers predicted that moderate hypoxia (reduced levels of oxygen) would reduce maximal human running speed during all-out runs lasting 25 seconds or more.
However, what they found was that despite markedly decreasing the rate of oxygen uptake while sprinting, runners could run just as fast in sprints up to 60 seconds and nearly as fast for sprints of up to two minutes. The loss of aerobic energy was fully compensated for by the anaerobic metabolism for sprints up to one minute and partially compensated for hypoxic sprints lasting up to 150 seconds.
Keep in mind that 150 seconds, or 2 minutes and 30 seconds is a pedestrian 800 meter time for a male athlete.
In 2000, Weyand, et al. tested the hypothesis that differences in top speed among runners was based on the amount of force applied to the ground and not more rapid limb repositioning in the air ("Faster top running speeds are achieved with greater ground forces not more rapid leg movements").
The researchers concluded that the predominant factor in high speed running is the amount of mass-specific force applied to the running surface to support the body at ground contact.
In 2003 “High-speed running performance: a new approach to assessment and prediction,” Bundle, et al, hypothesized that it was possible to accurately predict all-out running speed for runs of 3 seconds up to 4 minutes duration using an algorithm based upon the maximum speeds supported by the anaerobic and aerobic powers of a runner.
The algorithm derived from this study has greater than 97% accuracy in predicting running times.
In 2004 Weyand and Bundle published "Energetics of High-speed running: integrating classical theory and contemporary observations."
One conclusion from the study: "...our empirical framework could be used to analyze the relationship between metabolism and muscular performance in other modes of exercise or conceivably within individual muscle cells and tissues. Such investigations could determine whether skeletal muscle fatigue during whole-body exercise has the intrinsic, general, and quantifiable metabolic basis suggested by our findings.
In 2005, Weyand, et al. published "Sprint performance-duration relationships are set by the fractional duration of external force application"
They concluded that decrements in performance are set by the fractional duration of the relevant muscular contractions. Additionally, they found that "...the large absolute differences in sprint performance-duration relationships of sprint and endurance athletes are essentially invariant when expressed in the terms of our anaerobic reserve model. Specifically, when we expressed the performance curves of these athletes in relation to the difference between their mechanical maximums for speed and the metabolic maximums that they could support aerobically (i.e. the anaerobic speed reserve), we found that they all conformed to the same relationship."
The study results suggest that speed loss during high speed running might be dictated by reliance on the anaerobic metabolism.
In 2006, Bundle, et al, in the study, "A metabolic basis for impaired muscle force production and neuromuscular compensation during sprint cycling" stated: "We conclude that impaired muscular force production and compensatory neuromuscular activity during sprint locomotion are triggered by a reliance on anaerobic metabolism for force production."
The term “speed endurance” was not mentioned in any of the aforementioned research papers.
While each study might take some time to read and digest, they should be of great interest to every coach, trainer and athlete. The case for a re-examination of many of the coaching methods used today has never been stronger because of the works listed above.
It’s clear from the research that lack of oxygen is not the cause of speed decrements (1999) during high speed running since the anaerobic metabolism the runner relies on (2005) does not use oxygen as part of its fuel supply. That’s why it’s called anaerobic (living or active in the absence of free oxygen). It is just as clear that the dependence upon the anaerobic metabolism causes impaired muscular force production (2006).
A runner begins to slow down (decrement in performance-2005) when the muscular force production necessary to maintain mass-specific support force to the ground at toe-down (2000) is impaired. Impairment in this case is the inability of fast twitch fiber (anaerobic metabolism) to create tension because there is a sufficient supply of “fuel” to maintain work until there are no fibers remaining for recruitment. Muscles relying on oxygen (slow twitch fibers) continue to create tension until the fuel supply (aerobic metabolism) is exhausted despite any remaining non-recruited fibers.
In their 1998 version of their book "Sports Speed," by George Dintiman, Bob Ward and Tom Tellez, the authors wrote that "Speed endurance training will not help you take a faster or longer step. It will, however, prevent you from slowing down late in the game, at the end of the long sprint, or after sprinting several times with little rest in between. You've seen many examples of poor speed endurance in different sports."
They suggest that speed endurance is easy to improve, requiring no more than running short sprint distances two or three times per week, keeping a record of the number of sprint repetitions, the distance sprinted and the length of recovery time between each repetition.
They suggest that the runner should increase the sprint distance and decrease the recovery time between each repetition in subsequent workouts.
The authors state that speed endurance will improve in a period of six to eight weeks.
This is not new information for most coaches and athletes. However, there are fundamental flaws in the assumption of the means by which speed endurance improved.
Their book suggests that strength and plyometric training are necessary parts of speed development on an ongoing basis. Was either one (or both) of these a factor in the improvement of speed endurance? Is it possible they were the actual causes of improved speed endurance?
From a physiological standpoint, the authors propose a training method that is opposite of what research has discovered: Fast sprinting is based upon mass-specific force application which, because of it’s reliance on the anaerobic metabolism, triggers speed decrements as fibers lose ability to create tension so reducing recovery time would reduce the amount of fibers available to create tension for each repeat run. Longer recovery times would increase the number of fibers available.
Running as fast as possible, unaided by any other training method, can improve final time and speed endurance. The reason for this is that running creates increased muscle loading from the effects of gravity. However, adding other methods of training, such as weight lifting, will show significantly more improvements in speed. Again, increased muscle loading is the primary factor.
Lifting heavy weights recruits the fibers necessary for the runner to apply more support force in relation to their mass at ground contact.
“Sport Speed” missed the mark in several areas; primarily because much of the research available today did not exist when the book was written.
The more likely candidate for improving speed endurance is strength training not reduction of recovery time.
The authors stated that “Speed endurance training will not help you take a faster or longer step.” Based upon their prescribed method of training, this is a true statement. However, the strength training that increases stride length while reducing ground contact time also improves speed endurance.
What could be more efficient than that?
Barry Ross