Document Detail


Dangerous curves. A perspective on exercise, lactate, and the anaerobic threshold.
MedLine Citation:
PMID:  9118720     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
A number of general observations can be made from these recent studies. Lactate is a ubiquitous substance that is produced and removed from the body at all times, even at rest, both with and without the availability of oxygen. It is now recognized that lactate accumulates in the blood for several reasons, not just the fact that oxygen supply to the muscle is inadequate. Lactate production and removal is a continuous process; it is a change in the rate of one or the other that determines the blood lactate level. Rather than a specific threshold, there is most likely a period of time during which lactate production begins to exceed the body's capacity to remove it (through buffering or oxidation in other fibers). It may be appropriate to replace the term "anaerobic threshold" to a more functional description, since the muscles are never entirely anaerobic nor is there always a distinct threshold ("oxygen independent glycolysis" among others has been suggested) Lactate plays a major role as a metabolic substrate during exercise, is the preferred fuel for slow-twitch muscle fibers, and is a precursor for liver gluconeogenesis. The point at which lactate begins to accumulate in the blood, causing an increase in ventilation, is important to document clinically. Irrespective of the underlying mechanism or specific model that describes the process, the physiologic changes associated with lactate accumulation have significant import for cardiopulmonary performance. These include metabolic acidosis, impaired muscle contraction, hyperventilation, and altered oxygen kinetics, all of which contribute to an impaired capacity to perform work. Thus, any delay in the accumulation of blood lactate which can be attributed to an intervention (drug, exercise training, surgical, etc) may add important information concerning the efficacy of the intervention. A substantial body of evidence is available demonstrating that lactate accumulation occurs later (shifting to a higher percentage of Vo2max) after a period of endurance training. In athletes, the level of work that can be sustained prior to lactate accumulation, visually determined, is an accurate predictor of endurance performance. Presumably, these concepts have implications related to vocation/disability among patients with cardiovascular and pulmonary disease, but few such applied studies have been performed outside the laboratory. Blood lactate during exercise and its associated ventilatory changes maintain useful and interesting applications in both the clinical exercise laboratory and the sport sciences. However, the mechanism, interpretation, and application of these changes continue to rely more on tradition and convenience than science.
Authors:
J Myers; E Ashley
Publication Detail:
Type:  Journal Article; Review    
Journal Detail:
Title:  Chest     Volume:  111     ISSN:  0012-3692     ISO Abbreviation:  Chest     Publication Date:  1997 Mar 
Date Detail:
Created Date:  1997-04-24     Completed Date:  1997-04-24     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0231335     Medline TA:  Chest     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  787-95     Citation Subset:  AIM; IM    
Affiliation:
Cardiology Division, Palo Alto Department of Veterans Affairs Medical Center, Stanford University, Calif, USA.
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MeSH Terms
Descriptor/Qualifier:
Anaerobic Threshold*
Exercise*
Humans
Lactates / blood*
Muscle Fatigue
Respiration
Chemical
Reg. No./Substance:
0/Lactates

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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