{
  "id": 381946,
  "title": "August Krogh’s Nobel winning discovery of oxygen supply to muscles",
  "url": "https://urgent.news/2026/08/09/august-kroghs-nobel-winning-discovery-of-oxygen-supply-to-muscles",
  "topic": "science",
  "section": "Science",
  "published": "2026-08-09T13:38:15.000Z",
  "source": {
    "name": "The Hindu - Sci-Tech",
    "slug": "the-hindu-sci-tech",
    "url": "https://www.thehindu.com/sci-tech/health/august-kroghs-nobel-winning-discovery-of-oxygen-supply-to-muscles/article71324296.ece"
  },
  "original_language": "en",
  "account": "In 1920, Danish physiologist August Krogh was honored with the Nobel Prize in Physiology or Medicine for his discovery regarding the regulation of capillary motor mechanism. His focus lay in understanding how muscles receive ample oxygen when their demand spikes during exercise. Krogh demonstrated that adjustments in capillary circulation could facilitate this increased demand by positioning blood closer to muscle fibers and amplifying the surface area for oxygen exchange. The implications of this research were substantial for medicine, as a comprehension of oxygen reaching tissues is crucial in scenarios where blood supply is compromised, such as cardiovascular diseases, peripheral vascular diseases, diabetes, and non-healing wounds. Krogh's contributions have since paved the way in understanding tissue injury, wound healing, exercise physiology, and the effects of restricted blood flow. Born on November 15, 1874, in Grenaa, Denmark, Schack August Steenberg Krogh pursued his initial studies in medicine at the University of Copenhagen, starting in 1893. He later switched his focus to zoology and joined the laboratory of physiologist Christian Bohr, becoming captivated by respiration and gas exchange in living organisms. After obtaining his zoology degree in 1899, Krogh continued his work in Bohr's laboratory. He integrated experimental biology with precise measurements, devising instruments for the study of physiological processes. In 1916, Krogh became the professor of zoophysiology at the University of Copenhagen. His research centered on the movement of oxygen from blood to tissue. Regardless of the activity level of muscles, these muscles require a significant boost in oxygen consumption. Oxygen present in the blood must undergo diffusion from capillaries through the surrounding tissue to reach individual cells. Hence, the distance between a cell and a capillary that is well-supplied with blood greatly impacts oxygen delivery. Krogh delved into capillary distribution within muscle and compared the oxygenation rates of restive and active tissues. His observations led him to notice that more capillaries seemed to be engorged with blood when muscles were active. In articles published in The Journal of Physiology in 1919, Krogh merged these observations with mathematical calculations involving oxygen diffusion. He posited that the introduction of additional capillaries into functional use during activity would augment the available exchange surface area and diminish the distance oxygen had to traverse through tissue. This work served as the bedrock for what is now recognized as the Krogh cylinder model, a theoretical model elucidating oxygen diffusion from a capillary into the adjacent tissue. Beyond merely describing disparities in capillary perfusion, Krogh hypothesized a capillary motor regulating mechanism, which he believed manipulated capillary diameter and blood content in response to the functional requirements of tissue. This concept was acknowledged by the Nobel Committee in 1920, which recognized Krogh's work in his Nobel lecture. Krogh described how the number of blood-filled capillaries fluctuates with tissue activity, arguing that additional capillaries are brought into play during muscular activity, hence increasing the area available for oxygen exchange. While certain elements of Krogh's original explanation have been revised over time, his capillary motor-regulating mechanism remains a significant insight. Today, capillaries are understood not merely as vessels that can be completely closed or opened but rather as playing a more nuanced role in capillary recruitment, involving changes in the pattern and extent of capillary perfusion. Krogh's central idea, however, continues to hold true: the organization of the capillary network and the distance oxygen must traverse through tissue are key factors determining oxygen delivery. Krogh's professional trajectory also entwined with another pivotal medical breakthrough - insulin. In 1922, he embarked on a trip to North America with his wife, Marie Krogh, who suffered from diabetes. Encouraged by her condition, he decided to investigate the emerging insulin treatment. During this journey, Krogh visited Toronto, where Frederick Banting, Charles Best, and their colleagues had pioneered methods for producing insulin. Krogh subsequently gained authorization to utilize the Toronto method for insulin production in Scandinavia. Upon returning to Denmark, he collaborated with physician Hans Christian Hagedorn and pharmacist August Kongsted. The inaugural Danish patient received insulin treatment in March 1923, and Nordisk Insulinlaboratorium was established in the same year. Krogh continued his physiological studies post-Nobel recognition, showcasing how physical principles and quantitative measurements could elucidate biological processes. The Krogh cylinder remains a valuable conceptual model for studying oxygen diffusion, although contemporary research has fine-tuned the model using a deeper understanding of blood flow, oxygen gradients, and the three-dimensional structure of capillary networks. Krogh retired from the University of Copenhagen in 1945 but remained active in research until his passing in Copenhagen on September 13, 1949, at the age of 74. Over a century later, the delivery of oxygen to tissues is comprehended as involving cardiac output, blood flow, arteriolar regulation, capillary perfusion, blood oxygen content, diffusion, and tissue metabolism. Krogh's original hypothesis has evolved, yet his decision to concentrate on microscopic circulation transformed the comprehension of how blood supplies individual tissues.",
  "summary": "August Krogh’s research showed how capillaries regulate blood flow to meet tissue oxygen needs",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 2,
    "also_reported_by": [
      {
        "outlet": "The Hindu Health",
        "title": "August Krogh’s Nobel winning discovery of oxygen supply to muscles",
        "url": "https://urgent.news/2026/08/09/august-kroghs-nobel-winning-discovery-of-oxygen-supply-to-muscles-382441",
        "published": "2026-08-09T13:38:15.000Z"
      }
    ]
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}