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Old 04-17-2009, 05:19 PM   #73
Barry Ross
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Join Date: Jan 2009
Posts: 16

Originally Posted by Donald Lee View Post
I'll think over more later on what you posted, but in reference to speed endurance, I just mean distances beyond which top speeds are reached.

A few quick thoughts:

1. I do agree with maximizing mass specific force in order to increase top speed and RFD.

2. Once top speeds are reached, however, fatigue comes in to play. As higher threshold fibres become fatigued, due to intramuscular coordination, other higher threshold fibres are recruited. If all or nearly all fibres are indeed recruited at top speeds, why not spend some time on speed endurance?

3. Does the ability to not train speed endurance for sprinting have anything to do with the fact that the force in sprinting is expressed in milliseconds (which does not allow for maximal contraction)? Does it also not have anything to do with elastic energy contributions?

I could be way off base with #3, but it's a random thought that popped into my head.
Hi Donald,

Since we agree on point No. 1 above, lets examine 2 and 3:

It is not intramuscular coordination that causes muscles to fatigue, it is the overabundance of ATP.

In "A metabolic basis for impaired muscle force production and neuromuscular compensation during sprint cycling", Bundle AJP 2006, the authors state:

"We conclude that impaired muscle force production and compensatory neuromuscular activity during sprinting are triggered by a reliance on anaerobic metabolism for force production."

The response I've seen from numerous books and online training sites regarding the improvement of "speed endurance" never describe the mechanism by which speed endurance is actually enhanced. In other words, what's in the "black box" of speed endurance work that creates change?

Bundle's study concluded that muscle impairment (manifested as rate of speed decrement) is caused by an abundance of ATP: "The results we present here indicate that a dependence on nonoxidative pathways of ATP resynthesis impairs muscle force production during locomotion."

In other words (and per Dr. Weyand), the abundance of ATP allows the runner to work fibers until they are no longer able to create the tension necessary to continue at high speed.

In addition (same study), "During fatiguing submaximal contractions, measures of EMG are known to increase throughout the effort. This response has been attributed to motor unit recruitment because motor neuron firing rates during these contractions have generally decreased or exhibited little net change"

From a personal conversation with Dr. Weyand, muscle fiber EMG increases as newly recruited motor units (MU's) come on line to aid in speed maintenance.

If this is the case, then increasing the number of larger, faster firing motor units should result in reducing rate of speed decrement.

So how do we make them available?

The only way we can is by lifting heavy weights, since this is where the greatest muscle tension is needed. Submaximal lifts of 75% 1 RM or lower will not recruit the fastest firing units (which means that power lifts are not helpful since they are below 80% of max)

The concept of speed decrement over time is the basis of the algorithm we use. Once again, with 97% accuracy in predicting running times it's difficult to argue against it.
Over the last five years we've been using this tool to measure improvements in speed endurance to the point where we are confident that the short runs dictate the long runs. Short fast runs combined with maximal lifts (>85%) improve running performance over the short and the long.

When coaches suggest that speed endurance work reduces rate of speed decrement, they are not necessarily incorrect...but they are not maximizing the ability of their athletes, regardless of the level of the athlete.

You might be wondering about the elite runners regarding this issue. The elite sprinter may offset some of these issues by the fact of what makes them elite--they are able to apply significantly greater amounts of mass-specific force during shorter ground contact times; perhaps to the point that they are not recruiting and using all of their available MU's at each ground contact.
The fact that most elite male sprinters in the last 20-25 years has shown multiple equal ground contact times over 10m segments also tends to strengthen the possibility.

No and no
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