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Related Concept Videos

Fatigue01:21

Fatigue

744
Fatigue occurs when materials rupture under repeated or fluctuating loads, even at stress levels far below their static breaking strength. It typically results in brittle failure, even for ductile materials. It is a critical consideration in designing machines and structural components subjected to repetitive or varying loads. The nature of these loadings can range from fluctuating loads like unbalanced pump impellers causing vibrations to repeatedly bending a thin steel rod wire back and forth...
744
Muscle Recovery and Fatigue01:24

Muscle Recovery and Fatigue

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Muscle fatigue refers to the decline in a muscle's ability to maintain the force of contraction after prolonged activity. It primarily stems from changes within muscle fibers. Even before experiencing muscle fatigue, one may feel tired and have the urge to stop the activity. This response, known as central fatigue, occurs due to changes in the central nervous system, namely the brain and spinal cord. While there is no single mechanism that induces fatigue, it may serve as a protective...
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Imbalances in Cardiac Output01:26

Imbalances in Cardiac Output

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The heart's primary function is to pump blood throughout the body, maintaining a balance between blood sent out (cardiac output) and blood returning (venous return). If this balance is disrupted, it can result in congestive heart failure (CHF), a severe condition where the heart becomes an inefficient pump, leading to inadequate blood circulation.
CHF can occur due to the failure of either side of the heart. Left-side failure leads to pulmonary congestion—the right side continues to send...
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Acute Respiratory Failure-IV01:23

Acute Respiratory Failure-IV

436
Respiratory failure can manifest suddenly or gradually, characterized by a rapid decline in PaO2 and a rapid rise in PaCO2. This situation indicates a severe respiratory problem that may quickly become a life-threatening emergency. One of the early signs of hypoxemic Acute Respiratory Failure (ARF) is a change in mental status due to the brain's sensitivity to oxygen levels and changes in acid-base balance. Symptoms such as restlessness, confusion, and agitation suggest inadequate oxygen...
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Updated: Dec 19, 2025

A Rapidly Incremented Tethered-Swimming Maximal Protocol for Cardiorespiratory Assessment of Swimmers
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Acute:Chronic Workload Ratio: Conceptual Issues and Fundamental Pitfalls.

Franco M Impellizzeri, Matthew S Tenan, Tom Kempton

    International Journal of Sports Physiology and Performance
    |June 6, 2020
    PubMed
    Summary

    The acute:chronic workload ratio (ACWR) is not supported for injury prevention. Current evidence does not establish a causal link, and the metric has statistical flaws, making it unreliable for training recommendations.

    Keywords:
    critical analysisinjuriestraining loadtraining principles

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    Area of Science:

    • Sports Science
    • Exercise Physiology
    • Injury Epidemiology

    Background:

    • The exponential increase in research on training load and injury has led to numerous prognostic factors.
    • The acute:chronic workload ratio (ACWR) has emerged as a popular metric for assessing injury risk.
    • The assumption of causality when manipulating prognostic factors introduces significant conceptual and methodological challenges.

    Purpose of the Study:

    • To critically evaluate the causal assumptions and statistical properties of the acute:chronic workload ratio (ACWR) as a prognostic factor for injury.
    • To determine if current evidence supports the use of ACWR in training-load management for injury reduction.
    • To identify the limitations and potential misinterpretations associated with ACWR in practical applications.

    Main Methods:

    • Review of existing literature on training load, ACWR, and injury.
    • Analysis of the conceptual and statistical underpinnings of ACWR as a causal prognostic factor.
    • Examination of the evidence for a causal relationship between ACWR manipulation and injury risk reduction.

    Main Results:

    • No studies have adequately estimated the causal effects of ACWR on injury.
    • The ACWR metric suffers from known issues with ratio data and unrecognized assumptions, leading to inaccuracies.
    • ACWR is an ambiguous metric lacking a clear background rationale for its causal role in injury risk.

    Conclusions:

    • There is no current evidence to support the use of ACWR in training-load management systems or for injury prevention recommendations.
    • The statistical properties of ACWR render it an inaccurate and problematic metric for practical application in sports.
    • The use of ACWR may lead to inappropriate recommendations and introduce statistical artifacts, complicating injury risk interpretation.