REGRETFULLY, THIS PAGE IS BEING BUILT.
PLEASE CHECK IN FREQUENTLY!

Critical Elements Resulting in Limiting Factors

Introduction: While recalling running a marathon, the athlete stated his race pace did not decrease from the start of race until the last four miles. He progressively intensified his running effort to increase his use of leg power, and therefore, he maintained his pace. Also his remembered a parallel escalation of leg pain, overall tiredness, and other symptoms. Have you noticed any of the following groups and their factors influencing your running or cycling?

Falter- to hesitate or waver in action, purpose, intent; stagger, stumble

• Increased muscular drive (i.e., effort)
• Weak, wobbly legs

Hinder – to cause delay, interruption, or difficulty in; hamper

• Increased overall tiredness
• Increased leg and overall pain

Impede – to slow down, deter

• Loss of concentration
• loss of motivation
• Wanting to do something else

Aggravate – to worsen

• Heat: hot head
• Cold: frozen fingers
• Rain: soaked all through
• Wind: had go buck a head wind
• High altitude: short of breath

What hints do these factors offer? What might be the ‘weak links’ in the processes supporting us? Just how well do they lessen our performing in an endurance event? And how can we work with them to maximize our abilities?

These articles for the Critical Elements section are organized in a “top-down” manner. They emphasize changes in the integrated regulation of these whole body functions before discussing systemic or even cellular changes. The first article will briefly discuss the actual neurobiological functions that are activated soon after beginning of the distance event. Then the next articles will address the groups of factors listed above to pursue the critical elements that limit each group as the distance event progresses. If you are very curious about these critical elements, sneak a look in Article 6.

How are the Motor and Support Systems Organized and Activated?

ARTICLE 1: Getting Started

What are the specific mechanisms involving in starting to walk, run, or cycle? And what are their critical elements? This article begins our hunt by describing the overall architecture and operation of gait producing mechanisms used for running and cycling. Then are the weak links of these mechanisms and their interacting that result in limiting endurance?

Before this article dives into recent advances in exercise neurobiology, some of you may want to review the basics of organization and control of motor performance. Feel free to download a chapter I wrote in 1974, “Interrelationships of the Motor and Metabolic Support Systems during Work and Fatigue”. That chapter was published in Simonson’s second book in his Work Capacity and Fatigue Series (Simonson & Weiser, 1976). From here on, this article will be reorganizing and updating that chapter.

(Download PDF file of Chapter)

Let’s condense and update that chapter. First, current knowledge will briefly summarized for the locomotor processes regulating initiation, maintenance, and modifying gait. Then, of course, an update will be made for the nutritional, perceptual, motivational, emotional, and other systems. Importantly, they support the locomotor command center, motor units, and motor sensory neurons that help us move along. Along the way, we will ask and reask the following questions: How do our motor and support systems work together, and where are the weak links?

Let’s begin with Figure 1 that is my 2008 locomotor schema modified from we presented in 1976 at the Borg Symposium. It describes how we are organized and operating as we begin to walk, run, or cycle.

“Go” is the conscious or unconscious feedforward signal from our locomotor command center to start, speed up, slow down, or maintain moving along. Various parts of the “motor” cortices sends an output signal down neural pathways, part shared with other cortical structures, like the midbrain autonomic and  locomotor centers with the rest going down to the spinal cord. Motor neurons in the spinal cord signal their group of muscle fibers to contract at crucial points of the gait cycle.

In and around the muscles and in joints, nerve endings track the resulting movement and signal their neurons in the spinal cord. They feed their information back to motoneurons and up through attentional channels to a comparator, i.e., the circle with an “X” inside, and to nutritional, motivational, emotional, and other systems. At the comparator, this information is matched to memorized prior experiences; the resulting degree of matching is sent to the command center.

Now, it’s time to reintroduce the supporting processes. The model below will be the guide for the finding many of the weak links. Note there is no separation between mind and body. (Go to more of this Article)

What are the Crucial Elements that Limit Performance? 

Article 2:  FALTER 

Falter- to hesitate or waver in action, purpose, intent, etc.

• Increased muscular drive (i.e., effort)
• Weak, wobbly legs

This article will continue with a top-down description specifically of locomotor pattern like running and cycling. It will focus on recent advances in neuroscience of the control and support of gait. First current knowledge of cortical structures regulating initiation and maintenance of gait will briefly summarized, then information about the supraspinal mechanisms regulating changes in gait and medullary/spinal motor pattern generating gait will be described.

(Go to Article 2)

 Article 3: HINDER

 Hinder – to cause delay, interruption, or difficulty in; hamper

• Increased overall tiredness
• Increased leg and overall pain

(Go to Article 3)

Article 4: IMPEDE

Impede – to slow down, deter

• Loss of concentration
• loss of motivation
• Wanting to do something else

(Go to Article 4)

Article 5: AGGRAVATE

Aggravate – to worsen

• Heat: hot head
• Cold: frozen fingers
• Rain: soaked all through
• Wind: had go buck a head wind
• High altitude: short of breath

In other races, like the 1967 Holyoke US Trials for the Pan-American Games,

• a very hot head and body, and

at high altitude, like running a half marathon up Pikes Peak,

• very short of breath (i.e., dyspnea)

(Go to Article 5)

(Return to Limiting Mechanisms)