{"id":8221,"date":"2026-10-01T21:22:16","date_gmt":"2026-10-01T19:22:16","guid":{"rendered":"https:\/\/blueportance.com\/knowledge-base\/expert-guides\/living-flows\/continuous-flow-organization\/biological-rhythms-alternation-renewal\/"},"modified":"2026-10-25T22:44:06","modified_gmt":"2026-10-25T21:44:06","slug":"biological-rhythms-alternation-renewal","status":"publish","type":"page","link":"https:\/\/blueportance.com\/en\/knowledge-base\/expert-guides\/living-flows\/continuous-flow-organization\/biological-rhythms-alternation-renewal\/","title":{"rendered":"KB 3_Expert Guide_02_Living Flows_01_Continuous-Flow Organization_09_Biological Rhythms: Alternation, Pulsation and Renewal"},"content":{"rendered":"\n\n<!-- BDC\u2014 Continuous-Flow Organization - A9_Biological Rhythms: Alternation, Pulsation and Renewal \u2014 Blue Portance -->\n\n<style>\n    .bp-bdc-breadcrumb{\n      max-width: 900px;\n      margin: 0 auto;\n      padding: 20px 16px 0;\n      font-size: .85rem;\n      color: #6b7280;\n    }\n    .bp-bdc-breadcrumb a{\n      color: #2a7fba;\n      text-decoration: none;\n    }\n    .bp-bdc-breadcrumb a:hover{\n      text-decoration: underline;\n    }\n\n  .bp-figure {\n      margin: 40px auto;\n      text-align: center;\n      max-width: 760px;\n  }\n\n  .bp-figure img {\n      display: block;\n      margin: 0 auto;\n      max-width: 100%;\n      height: auto;\n      border-radius: 8px;\n  }\n\n  .bp-figure figcaption {\n      margin: 10px auto 0;\n      max-width: 650px;\n      text-align: center;\n      color: #666;\n      font-size: 0.85em;\n      line-height: 1.45;\n  }\n\n  .bp-fig-title {\n      display: block;\n      margin: 0 0 4px;\n      padding: 0;\n      font-style: normal;\n      font-weight: 700;\n      font-size: 1em;\n      color: #333;\n      line-height: 1.3;\n  }\n\n  .bp-fig-text {\n      display: block;\n      margin: 0;\n      padding: 0;\n      font-style: italic;\n  }\n  \n    .bp-bdc-navigation a::before{content:\"\u2190 \";}\n  <\/style>\n\n<nav class=\"bp-bdc-breadcrumb\" aria-label=\"Breadcrumb\">\n  <a href=\"\/en\/\">Blue Portance<\/a> \u2192 <a href=\"https:\/\/blueportance.com\/en\/knowledge-base\/\">Knowledge Base<\/a> \u2192 <a href=\"https:\/\/blueportance.com\/en\/knowledge-base\/expert-guides\/\">Expert Guides<\/a> \u2192 <a href=\"https:\/\/blueportance.com\/en\/knowledge-base\/expert-guides\/living-flows\/\">Living Flows<\/a> \u2192 <a href=\"https:\/\/blueportance.com\/en\/knowledge-base\/expert-guides\/living-flows\/continuous-flow-organization\/\">Continuous-Flow Organization<\/a> \u2192 Biological Rhythms\n<\/nav>\n\n\n\n\n<section class=\"bp-bdc-wrap\">\n\n  <header class=\"bp-bdc-hero\">\n    <h1>9. Biological Rhythms: Alternation, Pulsation and Renewal<\/h1>\n    <p>Knowledge Base \u2013 Expert Guide: Continuous-Flow Organization<\/p>\n    <div class=\"bp-bdc-meta\">Blue Portance Knowledge Base \u00b7 Non-commercial reproduction permitted with source attribution<\/div>\n  <\/header>\n\n  <p>\n    Living systems do not operate in a perfectly uniform regime. Many biological functions instead show pulsations,\n    alternations or fluctuations organized over time: cardiac activity, breathing, muscle activity, body\n    temperature, blood pressure, the secretion of many hormones, metabolism and sleep. These phenomena, however, do not all\n    belong to the same type of rhythm. Some are generated by internal physiological oscillators, while others are\n    synchronized by the environment. Still others result from activity, movement or repeated exposure to a load.\n    Overall, across different timescales, living organisms display rhythms, pulsations and fluctuations that organize\n    certain physiological functions and vary the mechanical, fluid and metabolic conditions to which tissues are\n    subjected. Variability is therefore not necessarily disorder. It can instead be a functional property of living\n    systems, provided it remains compatible with the system&#8217;s capacity for regulation and recovery.\n  <\/p>\n\n  <nav class=\"bp-bdc-toc\" aria-label=\"Contents\">\n    <h2>Contents<\/h2>\n    <ul>\n      <li><a href=\"#definition-rythme\">1. What Is a Biological Rhythm?<\/a><\/li>\n      <li><a href=\"#echelles-temps\">2. Rhythms at Different Timescales<\/a><\/li>\n      <li><a href=\"#horloges-synchroniseurs\">3. Biological Clocks and Synchronizers<\/a><\/li>\n      <li><a href=\"#pulsations-cardio-respiratoires\">4. Cardiac and Respiratory Pulsations<\/a><\/li>\n      <li><a href=\"#alternances-activite-repos\">5. Activity\u2013Rest Alternations<\/a><\/li>\n      <li><a href=\"#variabilite-regulation\">6. Variability Is Not the Absence of Regulation<\/a><\/li>\n      <li><a href=\"#rythmes-cycles-mecaniques\">7. From Biological Rhythms to Mechanical Cycles<\/a><\/li>\n      <li><a href=\"#charge-decharge-rythmes\">8. Loading, Unloading and Mechanical Rhythms<\/a><\/li>\n      <li><a href=\"#rythme-frequence\">9. A Rhythm Is More Than Its Frequency<\/a><\/li>\n      <li><a href=\"#donnees-assise\">10. Data on Sitting<\/a><\/li>\n      <li><a href=\"#niveaux-interpretation\">11. The Four Levels of Interpretation<\/a><\/li>\n      <li><a href=\"#retenir\">12. Key Takeaways<\/a><\/li>\n      <li><a href=\"#references\">Scientific References<\/a><\/li>\n    <\/ul>\n  <\/nav>\n\n  <article class=\"bp-bdc-content\">\n\n  <section id=\"definition-rythme\">\n  <h2>1. What Is a Biological Rhythm?<\/h2>\n\n  <p>\n    A biological rhythm is a variation that repeats according to an identifiable temporal organization. It can\n    be described by several parameters:\n  <\/p>\n  <ul>\n    <li>a period;<\/li>\n    <li>a frequency;<\/li>\n    <li>an amplitude;<\/li>\n    <li>a phase;<\/li>\n    <li>a degree of regularity;<\/li>\n    <li>possible synchronization by the environment.<\/li>\n  <\/ul>\n\n  <p>\n    The <strong>period<\/strong> is the duration of one complete cycle. The <strong>frequency<\/strong> is the\n    number of cycles per unit of time; it is therefore inversely related to the period. The\n    <strong>amplitude<\/strong> describes the magnitude of the variation, while the <strong>phase<\/strong>\n    indicates the moment at which the phenomenon reaches a given level.\n  <\/p>\n\n  <p>\n    Moreover, a rhythm may be highly regular or may show variability in period and amplitude. However, this variability does not\n    necessarily cancel out the temporal organization of the phenomenon.\n  <\/p>\n\n  <p>\n    It is also important to distinguish between:\n  <\/p>\n  <ul>\n    <li>rhythm, which has an identifiable temporal organization;<\/li>\n    <li>oscillation, which refers to a repeated variation;<\/li>\n    <li>fluctuation, which may be less regular;<\/li>\n    <li>variability, which describes the diversity of the values and intervals observed.<\/li>\n  <\/ul>\n\n  <p>\n    These notions may overlap, but they are not synonymous.\n  <\/p>\n\n  <\/section>\n\n  <section id=\"echelles-temps\">\n  <h2>2. Rhythms at Different Timescales<\/h2>\n\n  <p>\n    Biological rhythms are often classified according to their period.\n  <\/p>\n\n  <h3>Ultradian Rhythms<\/h3>\n  <p>\n    Ultradian rhythms have a period shorter than twenty-four hours. They include, in particular:\n  <\/p>\n  <ul>\n    <li>heart rhythm;<\/li>\n    <li>respiratory rhythm;<\/li>\n    <li>certain hormonal secretions;<\/li>\n    <li>oscillations in neuronal activity;<\/li>\n    <li>variations in muscle activity.<\/li>\n  <\/ul>\n\n  <h3>Circadian Rhythms<\/h3>\n  <p>\n    In contrast, circadian rhythms have a period of approximately twenty-four hours. They involve, in particular:\n  <\/p>\n  <ul>\n    <li>the sleep\u2013wake cycle;<\/li>\n    <li>body temperature;<\/li>\n    <li>blood pressure;<\/li>\n    <li>the secretion of certain hormones;<\/li>\n    <li>metabolic activity;<\/li>\n    <li>cycles of activity and rest.<\/li>\n  <\/ul>\n\n  <p>\n    Indeed, almost every function in the body can be influenced by circadian organization, in ways specific to each\n    tissue <span class=\"bp-inline-ref\">(Inserm, 2017)<\/span>.\n  <\/p>\n\n  <h3>Infradian Rhythms<\/h3>\n  <p>\n    Infradian rhythms have a period longer than twenty-four hours. For example, they may involve certain seasonal, hormonal\n    or reproductive functions.\n  <\/p>\n\n  <p>\n    This classification therefore shows that the body is subject to several timescales at once. In other words, a single cell or tissue\n    can receive fast, daily and slower signals that combine without necessarily being perfectly synchronized.\n  <\/p>\n\n  <\/section>\n\n  <section id=\"horloges-synchroniseurs\">\n  <h2>3. Biological Clocks and Synchronizers<\/h2>\n\n  <p>\n    Circadian rhythms, in particular, are generated by internal mechanisms called biological clocks. In mammals, for example, a central clock\n    located in the suprachiasmatic nuclei of the hypothalamus helps coordinate the body&#8217;s rhythms.\n  <\/p>\n\n  <p>\n    Peripheral clocks also exist in many organs and tissues. Specifically, they contribute to the temporal coordination of\n    metabolism, hormone production, cellular activity and behavior\n    <span class=\"bp-inline-ref\">(Moore-Ede et al., 1982; Duez et al., 2013)<\/span>.\n  <\/p>\n\n  <p>\n    These rhythms are endogenous, but they are synchronized by external factors called synchronizers. Light is the main synchronizer, but food intake, physical activity, social schedules and the\n    sleep\u2013wake cycle also play a role\n    <span class=\"bp-inline-ref\">(Inserm, 2017)<\/span>.\n  <\/p>\n\n  <p>\n    This organization shows that living systems are both autonomous and responsive to their environment. They\n    have internal rhythms, but they adjust them according to the temporal information they receive.\n  <\/p>\n\n  <p>\n    The temporal dimension thus complements the notions of flow, renewal and adaptation presented in the\n    previous articles.\n  <\/p>\n\n  <\/section>\n\n  <section id=\"pulsations-cardio-respiratoires\">\n  <h2>4. Cardiac and Respiratory Pulsations<\/h2>\n\n  <p>\n    To begin with, cardiac activity produces rhythmic variations in pressure and flow within the vascular system. Consequently, these\n    variations influence the mechanical conditions to which the vessels and surrounding tissues are subjected.\n  <\/p>\n\n  <p>\n    Breathing also produces cyclic variations in volume and pressure in the thorax and abdomen. During\n    inspiration, contraction of the diaphragm increases thoracic volume and changes intrathoracic pressure.\n    Conversely, expiration shifts these gradients in the opposite direction.\n  <\/p>\n\n  <p>\n    Overall, these rhythms may contribute to:\n  <\/p>\n  <ul>\n    <li>the renewal of respiratory gases;<\/li>\n    <li>the adjustment of blood flow;<\/li>\n    <li>pressure variations within the vessels;<\/li>\n    <li>venous return;<\/li>\n    <li>certain conditions of lymphatic filling or propulsion.<\/li>\n  <\/ul>\n\n  <p>\n    Heartbeats and respiratory movements do not, however, have equivalent effects in every region of the body.\n    Instead, their influence depends on posture, activity, tissue compliance, local gradients and the properties of the\n    vascular and lymphatic networks\n    <span class=\"bp-inline-ref\">(Negrini &amp; Moriondo, 2011; Scallan et al., 2016; Wiig &amp; Swartz, 2012)<\/span>.\n  <\/p>\n\n  <p>\n    They therefore do not constitute a single mechanism that would uniformly renew all of the body&#8217;s fluids.\n  <\/p>\n\n  <\/section>\n\n  <section id=\"alternances-activite-repos\">\n  <h2>5. Activity\u2013Rest Alternations<\/h2>\n\n  <p>\n    In general, biological activity involves many alternations:\n  <\/p>\n  <ul>\n    <li>muscle contraction and relaxation;<\/li>\n    <li>wakefulness and sleep;<\/li>\n    <li>activity and rest;<\/li>\n    <li>feeding and fasting;<\/li>\n    <li>loading and unloading;<\/li>\n    <li>temporal variations in molecular synthesis and degradation.<\/li>\n  <\/ul>\n\n  <p>\n    However, these processes do not necessarily function as two mutually exclusive phases. Molecular synthesis and\n    degradation can occur simultaneously while varying according to different rhythms.\n  <\/p>\n\n  <p>\n    Depending on the function involved, alternating between demand and recovery can also alter resource use, the\n    accumulation of certain metabolic products and the conditions for recovery. Its effects nonetheless depend on\n    the duration, the intensity and the state of the system concerned.\n  <\/p>\n\n  <p>\n    Moreover, a period of rest does not mean a complete halt in biological activity. Indeed, metabolism, thermoregulation, tissue\n    repair and many cellular processes continue.\n  <\/p>\n\n  <p>\n    Conversely, a period of activity does not mean that all functions are constantly elevated. Instead, biological\n    systems modulate their activity and retain phases of recovery or reorganization.\n  <\/p>\n\n  <\/section>\n\n  <section id=\"variabilite-regulation\">\n  <h2>6. Variability Is Not the Absence of Regulation<\/h2>\n\n  <p>\n    A biological rhythm may show variations in period, amplitude and phase. This variability may stem, for example, from:\n  <\/p>\n  <ul>\n    <li>changes in the environment;<\/li>\n    <li>physical activity;<\/li>\n    <li>temperature;<\/li>\n    <li>diet;<\/li>\n    <li>stress;<\/li>\n    <li>sleep;<\/li>\n    <li>age;<\/li>\n    <li>disease states;<\/li>\n    <li>interactions between several rhythms.<\/li>\n  <\/ul>\n\n  <p>\n    A perfectly regular function is not necessarily healthier than one that shows small variations. After all, living\n    systems must be able to adapt their activity to changing conditions. Research on physiological complexity\n    has in fact linked a loss of variability in several physiological systems \u2014 cardiovascular regulation,\n    pulsatile hormone secretion, electroencephalographic activity \u2014 with aging and a reduced capacity to adapt to\n    physiological stress <span class=\"bp-inline-ref\">(Lipsitz &amp; Goldberger, 1992)<\/span>.\n  <\/p>\n\n  <p>\n    The opposite conclusion should, however, be avoided: variability is not automatically beneficial. For instance, a large,\n    disorganized fluctuation, or one incompatible with the system&#8217;s regulatory capacity, may reflect a\n    disturbance.\n  <\/p>\n\n  <p>\n    The key notion is therefore not variability in itself, but <strong>functional, regulated\n    variability<\/strong>.\n  <\/p>\n\n  <\/section>\n\n  <section id=\"rythmes-cycles-mecaniques\">\n  <h2>7. From Biological Rhythms to Mechanical Cycles<\/h2>\n\n  <p>\n    To begin with, not all of the repetitive phenomena described in this article are biological rhythms in the same sense.\n  <\/p>\n\n  <p>\n    Some are generated by internal physiological oscillators, such as circadian, cardiac or respiratory rhythms.\n    Others, in contrast, result from activity, movement or repeated exposure to a load.\n  <\/p>\n\n  <p>\n    What they have in common, however, is that they introduce temporal organization and alternation into the\n    conditions to which tissues are subjected.\n  <\/p>\n\n  <p>\n    In particular, this distinction matters for the rest of the guide. Mechanical cycles are not necessarily endogenous; instead, they\n    can be produced by:\n  <\/p>\n  <ul>\n    <li>walking;<\/li>\n    <li>muscle contraction;<\/li>\n    <li>respiratory movements;<\/li>\n    <li>changes in support;<\/li>\n    <li>postural movements;<\/li>\n    <li>the mechanical environment;<\/li>\n    <li>a support surface that allows or imposes variation.<\/li>\n  <\/ul>\n\n  <p>\n    Earlier, A6 showed how movement can modulate pressures and deformations. A7 then clarified that tissue response depends on\n    the duration, the rate and the mechanical history of the load. A9 thus revisits these notions from the standpoint\n    of their <strong>temporal organization<\/strong>.\n  <\/p>\n\n  <\/section>\n\n  <figure class=\"bp-figure\">\n    <img decoding=\"async\"\n      src=\"https:\/\/blueportance.com\/wp-content\/uploads\/flux-a9-1-biological-rhythms-physiological-pulsations-and-mechanical-cycles.png\"\n      alt=\"Comparison of biological rhythms, physiological pulsations and mechanical cycles.\"\n      class=\"bp-figure-image\"\n      loading=\"lazy\"\n    >\n\n    <figcaption class=\"bp-figure-caption\">\n      <span class=\"bp-fig-title\">\n        Figure 1 \u2014 Biological rhythms, physiological pulsations and mechanical cycles\n      <\/span>\n\n      <span class=\"bp-fig-text\">\n        Different phenomena share the same temporal dimension without involving the same mechanisms. \u00a9 Blue Portance 2026.\n      <\/span>\n    <\/figcaption>\n  <\/figure>\n\n  <section id=\"charge-decharge-rythmes\">\n  <h2>8. Loading, Unloading and Mechanical Rhythms<\/h2>\n\n  <p>\n    Tissues can be subjected to mechanical cycles of loading and unloading. These cycles directly alter local\n    deformations, stresses, pressures and volumes. As a result, these variations can displace interstitial fluid and,\n    depending on the intensity, the duration and the region involved, alter certain local conditions of\n    perfusion or lymphatic transport.\n  <\/p>\n\n  <p>\n    The response nonetheless depends on several parameters:\n  <\/p>\n  <ul>\n    <li>the amplitude of loading and unloading;<\/li>\n    <li>the duration of each phase;<\/li>\n    <li>the frequency of the cycles;<\/li>\n    <li>the ratio between loaded and unloaded time;<\/li>\n    <li>the regularity or variability of the cycles;<\/li>\n    <li>the time available for recovery;<\/li>\n    <li>the initial state and mechanical history of the tissue.<\/li>\n  <\/ul>\n\n  <p>\n    These parameters are essential because a rapid, small or imposed alternation does not necessarily produce the same\n    effect as a slower, larger or self-controlled alternation.\n  <\/p>\n\n  <\/section>\n\n  <figure class=\"bp-figure\">\n    <img decoding=\"async\"\n      src=\"https:\/\/blueportance.com\/wp-content\/uploads\/flux-a9-3-mechanical-alternation-alone-does-not-guarantee-recovery.png\"\n      alt=\"Comparison of continuous loading, insufficient alternation and alternation with recovery.\"\n      class=\"bp-figure-image\"\n      loading=\"lazy\"\n    >\n\n    <figcaption class=\"bp-figure-caption\">\n      <span class=\"bp-fig-title\">\n        Figure 2 \u2014 Mechanical alternation alone does not guarantee recovery\n      <\/span>\n\n      <span class=\"bp-fig-text\">\n        The presence of alternation is not enough: its effects depend on amplitude, duration, region and tissue condition. \u00a9 Blue Portance 2026.\n      <\/span>\n    <\/figcaption>\n  <\/figure>\n\n  <section id=\"rythme-frequence\">\n  <h2>9. A Rhythm Is More Than Its Frequency<\/h2>\n\n  <p>\n    The frequency of a cycle is not enough to determine its effects.\n  <\/p>\n\n  <p>\n    For example, two alternations with the same frequency may differ in:\n  <\/p>\n  <ul>\n    <li>their amplitude;<\/li>\n    <li>the duration of the loading phase;<\/li>\n    <li>the duration of the unloading phase;<\/li>\n    <li>the speed of transition;<\/li>\n    <li>their regularity;<\/li>\n    <li>their direction;<\/li>\n    <li>whether they can be modulated;<\/li>\n    <li>the recovery time available.<\/li>\n  <\/ul>\n\n  <p>\n    A rapid, low-amplitude mechanical oscillation should therefore not be equated with an alternation that\n    includes sufficient unloading and a recovery time suited to the tissue in question.\n  <\/p>\n\n  <p>\n    An ex vivo study comparing static and cyclic pressures applied to human skin (neonatal tissue) showed that\n    exposure to cyclic pressure altered the tissue&#8217;s tensile mechanical properties less than a static pressure of\n    the same magnitude maintained continuously\n    <span class=\"bp-inline-ref\">(Edsberg et al., 1999)<\/span>. However, this finding, obtained on a specific tissue model\n    outside a living organism, cannot be generalized to all tissues or transposed directly to perfusion or\n    lymphatic transport. It nonetheless illustrates that whether a load is continuous or intermittent can\n    influence the tissue&#8217;s mechanical response, independently of frequency alone.\n  <\/p>\n\n  <p>\n    Likewise, an imposed variation does not necessarily have the same effect as a spontaneous adjustment that the\n    person can initiate, direct or stop.\n  <\/p>\n\n  <p>\n    This distinction is particularly important for sitting. In fact, the mere presence of movement is not enough to\n    establish its mechanical relevance.\n  <\/p>\n\n  <\/section>\n\n  <figure class=\"bp-figure\">\n    <img decoding=\"async\"\n      src=\"https:\/\/blueportance.com\/wp-content\/uploads\/flux-a9-2-the-effect-of-a-cycle-depends-on-its-entire-time-organization.png\"\n      alt=\"Two cycles with the same frequency but different amplitude, loading duration, transition speed and recovery.\"\n      class=\"bp-figure-image\"\n      loading=\"lazy\"\n    >\n\n    <figcaption class=\"bp-figure-caption\">\n      <span class=\"bp-fig-title\">\n        Figure 3 \u2014 The effect of a cycle depends on its entire time organization\n      <\/span>\n\n      <span class=\"bp-fig-text\">\n        The same frequency can correspond to very different mechanical exposures. \u00a9 Blue Portance 2026.\n      <\/span>\n    <\/figcaption>\n  <\/figure>\n\n  <section id=\"donnees-assise\">\n  <h2>10. Data on Sitting<\/h2>\n\n  <p>\n    Studies by Makhsous et al. show that pressure-relief maneuvers and seat configurations can alter interface\n    pressures and certain perfusion indicators, in specific populations and protocols\n    <span class=\"bp-inline-ref\">(Makhsous et al., 2007, 2012)<\/span>.\n  <\/p>\n\n  <div class=\"bp-box bp-box--info\">\n    <strong>Caution<\/strong>\n    <p>\n      For instance, in the 2007 study, a single episode of pressure relief did not necessarily guarantee complete and immediate\n      recovery of perfusion. This finding therefore underscores the importance of load duration and of the recovery time\n      available. In addition, in the fifteen young, healthy women studied by Makhsous et al. (2012), the five seat designs\n      tested altered pressure distribution and certain perfusion indicators in the buttock and thigh tissues. The\n      limited duration of the trials and the characteristics of this population do not allow these results to be\n      generalized to all people or all sitting situations, nor do they support direct conclusions about an effect\n      on interstitial transport or lymphatic flow.\n    <\/p>\n  <\/div>\n\n  <p>\n    They do show, however, that interpreting support conditions cannot be limited to an instantaneous\n    measurement: seat configuration, load duration, unloading patterns and recovery time must also be taken into\n    account.\n  <\/p>\n\n  <\/section>\n\n  <section id=\"niveaux-interpretation\">\n  <h2>11. The Four Levels of Interpretation<\/h2>\n\n  <div class=\"bp-box bp-box--info\">\n    <ul>\n      <li><strong>Chronobiological<\/strong> \u2014 Living systems operate according to rhythms and alternations of\n      different periods.<\/li>\n      <li><strong>Mechanical<\/strong> \u2014 Loading and unloading cycles alter stresses, deformations and\n      weight-bearing areas.<\/li>\n      <li><strong>Physiological<\/strong> \u2014 These variations may influence certain local conditions of perfusion,\n      interstitial or lymphatic transport, and tissue recovery.<\/li>\n      <li><strong>Clinical<\/strong> \u2014 A benefit for pain, comfort or tissue health cannot be automatically\n      inferred from the mere presence of a rhythm or an alternation.<\/li>\n    <\/ul>\n  <\/div>\n\n  <p>\n    In short, this hierarchy avoids confusing an observed temporal phenomenon with a demonstrated physiological effect, or a\n    physiological effect with a clinical benefit.\n  <\/p>\n\n  <\/section>\n\n  <section id=\"retenir\">\n  <h2>12. Key Takeaways<\/h2>\n\n  <p>\n    In summary, living systems display several forms of temporal organization. Biological rhythms organize, in particular:\n  <\/p>\n  <ul>\n    <li>cardiac activity;<\/li>\n    <li>breathing;<\/li>\n    <li>metabolism;<\/li>\n    <li>the secretion of many hormones;<\/li>\n    <li>certain variations in muscle activity;<\/li>\n    <li>the sleep\u2013wake cycle;<\/li>\n    <li>certain cellular activities.<\/li>\n  <\/ul>\n\n  <p>\n    In contrast, mechanical cycles of loading and unloading are not necessarily endogenous biological rhythms. They do,\n    however, introduce an additional temporal organization into the conditions to which tissues are subjected.\n  <\/p>\n\n  <div class=\"bp-box bp-box--info\">\n    <p>\n      <strong>The response of living systems depends not only on the nature of a demand, but also on how it is\n      organized over time: period, frequency, amplitude, duration of exposure, alternation and opportunity for\n      recovery.<\/strong>\n    <\/p>\n  <\/div>\n\n  <p>\n    When sitting, changes in support can alter the distribution and duration of local mechanical stresses. The\n    goal is not to provoke constant fidgeting, but to preserve a capacity for variation that is compatible with\n    stability, the task at hand and the person&#8217;s needs.\n  <\/p>\n\n  <p>\n    This temporal organization becomes especially important when the opportunities for variation decrease. A10\n    will therefore examine what happens when the same mechanical configuration and the same weight-bearing areas\n    are maintained for a prolonged period.\n  <\/p>\n\n  <\/section>\n\n  <hr>\n\n  <section id=\"references\">\n    <div class=\"bp-box bp-box--info\">\n      <h2>Scientific References<\/h2>\n\n      <h3>Chronobiology and Biological Rhythms<\/h3>\n      <ol>\n        <li>Duez, H., Sebti, Y., &amp; Staels, B. (2013). Horloges circadiennes et m\u00e9tabolisme : int\u00e9gration des signaux m\u00e9taboliques et environnementaux. <em>M\u00e9decine\/Sciences<\/em>, 29(8\u20139), 772\u2013777. https:\/\/doi.org\/10.1051\/medsci\/2013298017<\/li>\n        <li>Inserm. (2017). <em>Chronobiologie<\/em>. La science pour la sant\u00e9. https:\/\/www.inserm.fr\/dossier\/chronobiologie\/<\/li>\n        <li>Moore-Ede, M. C., Sulzman, F. M., &amp; Fuller, C. A. (1982). <em>The Clocks That Time Us: Physiology of the Circadian Timing System<\/em>. Cambridge, MA: Harvard University Press.<\/li>\n      <\/ol>\n\n      <h3>Physiological Variability and Regulation<\/h3>\n      <ol>\n        <li>Lipsitz, L. A., &amp; Goldberger, A. L. (1992). Loss of &#8220;complexity&#8221; and aging. Potential applications of fractals and chaos theory to senescence. <em>JAMA<\/em>, 267(13), 1806\u20131809.<\/li>\n      <\/ol>\n\n      <h3>Cardiorespiratory Pulsations and Lymphatic Function<\/h3>\n      <ol>\n        <li>Negrini, D., &amp; Moriondo, A. (2011). Lymphatic anatomy and biomechanics. <em>The Journal of Physiology<\/em>, 589(Pt 12), 2927\u20132934. https:\/\/doi.org\/10.1113\/jphysiol.2011.206672<\/li>\n        <li>Scallan, J. P., Zawieja, S. D., Castorena-Gonzalez, J. A., &amp; Davis, M. J. (2016). Lymphatic pumping: mechanics, mechanisms and malfunction. <em>The Journal of Physiology<\/em>, 594(20), 5749\u20135768. https:\/\/doi.org\/10.1113\/JP272088<\/li>\n        <li>Wiig, H., &amp; Swartz, M. A. (2012). Interstitial fluid and lymph formation and transport: physiological regulation and roles in inflammation and cancer. <em>Physiological Reviews<\/em>, 92(3), 1005\u20131060. https:\/\/doi.org\/10.1152\/physrev.00037.2011<\/li>\n      <\/ol>\n\n      <h3>Cyclic Loading and Tissue Response<\/h3>\n      <ol>\n        <li>Edsberg, L. E., Mates, R. E., Baier, R. E., &amp; Lauren, M. (1999). Mechanical characteristics of human skin subjected to static versus cyclic normal pressures. <em>Journal of Rehabilitation Research and Development<\/em>, 36(2), 133\u2013141.<\/li>\n      <\/ol>\n\n      <h3>Sitting, Interface Pressure and Perfusion<\/h3>\n      <ol>\n        <li>Makhsous, M., Priebe, M., Bankard, J., et al. (2007). Measuring tissue perfusion during pressure relief maneuvers: insights into preventing pressure ulcers. <em>The Journal of Spinal Cord Medicine<\/em>, 30(5), 497\u2013507. https:\/\/doi.org\/10.1080\/10790268.2007.11754584<\/li>\n        <li>Makhsous, M., Lin, F., Hanawalt, D., Kruger, S. L., &amp; LaMantia, A. (2012). The effect of chair designs on sitting pressure distribution and tissue perfusion. <em>Human Factors<\/em>, 54(6), 1066\u20131074. https:\/\/doi.org\/10.1177\/0018720812457681<\/li>\n      <\/ol>\n    <\/div>\n  <\/section>\n\n  <\/article>\n\n  <!-- NAVIGATION -->\n  <nav class=\"bp-bdc-box bp-bdc-navigation\" aria-label=\"Topic navigation\">\n    <strong>Navigation<\/strong>\n    <p>\n      <a href=\"https:\/\/blueportance.com\/en\/knowledge-base\/expert-guides\/living-flows\/continuous-flow-organization\/\">\n        Back to the Continuous-Flow Organization guide\n      <\/a>\n    <\/p>\n    <p>\n      <a href=\"https:\/\/blueportance.com\/en\/knowledge-base\/expert-guides\/living-flows\/\">\n        See the topic: Living Flows\n      <\/a>\n    <\/p>\n    <p>\n      <a href=\"https:\/\/blueportance.com\/en\/knowledge-base\/expert-guides\/\">\n        Explore the Expert Guides section of the Knowledge Base\n      <\/a>\n    <\/p>\n  <\/nav>\n\n  <!-- NOTE -->\n  <footer class=\"bp-bdc-footer\">\n    <strong>Note<\/strong>: this content aims to explain mechanisms.\n    It is not a medical diagnosis or a treatment prescription.\n  <\/footer>\n\n  <p class=\"bp-bdc-copyright\" style=\"font-size:.85em;color:#6b7280;margin-top:16px;\">\n    \u00a9 Gil Ayache. The concepts, diagrams, terminology and principles presented on this page are a work\n    protected by copyright. They are made available to Blue Portance under an intellectual property licensing\n    agreement, without transfer of economic rights or authorship.\n  <\/p>\n\n\n<\/section>\n\n\n","protected":false},"excerpt":{"rendered":"<p>Blue Portance \u2192 Knowledge Base \u2192 Expert Guides \u2192 Living Flows \u2192 Continuous-Flow Organization \u2192 Biological Rhythms 9. Biological Rhythms: Alternation, Pulsation and Renewal Knowledge Base \u2013 Expert Guide: Continuous-Flow Organization Blue Portance Knowledge Base \u00b7 Non-commercial reproduction permitted with source attribution Living systems do not operate in a perfectly uniform regime. 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