Intense-Exercise Recovery Timeline (~1 week)

Immune-SC-muscle-v12

We’ve made several timelines on the adaptive-response that follows intense exercise ranging from: 2-3 months it takes to “get in shape” to the the 12 hours it takes to cement muscle-memory in the brain. One topic we have not discussed is the 1-week it takes to recover-and-rebuild from an intense bout of exercise.

Interesting, it is the immune-system (not stem cells) that manage the whole repair and rebuilding process. To use a building analogy, the immune system: (1) demolishes the old building (damaged muscle) and (2) erects the steel-sub-structure (extracellular matrix). Only then do the stem-cells install plumbing, electricity and internet (new muscle). On other words, the immune-cellsbuild the building” while the stem-cellsmake it functional.”

OVERVIEW HEALING PROCESS:

  • DAYS 1-2: “soreness” = “cleaning”
    During this period, damage-signals from the the muscle activate stems cells to start growing and attract immune cells to “cleanup the mess” Neutrophils and M1-macrophages are the dominant immune cells during this period and their main jobs are to (1) remove debris and damaged cells (2) help stem-cells proliferate and (3) prevent stem-cells from turning into muscle cells just yet.
  • DAYS 3-5: “achy-ness” = “rebuilding” During this period M1-macrophages change into M2-macrophages which specialize in laying the foundation for new muscle. In collaboration with regulatory T-cells (Tregs) and fibroblasts, these immune-cells lay down the extracellular matrix (which new muscle will rely on for structural support) and helps all the new stem cells turn into new muscle cells.

    timeline-v19

     

    REFERENCES:

    1. Tidball, J.G. Regulation of muscle growth and regeneration by the immune system Nat. Rev. Immunol. 2017,17, 165
    2. Murphy, K. Janeway’s Immunobiology 8th Ed. Garland Science 2012
    3. Boron, W.F.; Boulpaep, E.L. Medical Physiology, 2nd ed. 2011 Saunders
    4. Black, C.D.; Gonlach, A.R.; Hight, R.E.; Renfroe, J.B. Time-course of recovery of peak oxygen uptake after exercise-induced muscle damage Respir. Physiol. & Neurobiol. 2015,216, 70.
    5. Arpaia, N; et al. A Distinct Function of Regulatory T Cells in Tissue Protection Cell 2015,162, 1078.
    6. Dalia, D; et al. A Special Population of Regulatory T Cells Potentiates Muscle Repair Cell 2013,155, 1282.
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      This work by Eugene Douglass and Chad Miller is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

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