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+# energy cycles
+
+ultradian rhythms, 90-minute focus cycles, and working with your biology instead of against it.
+
+## the 90-minute rhythm
+
+nathiel kleitman (the same researcher who mapped sleep cycles) proposed the basic rest-activity cycle (BRAC): a roughly 90-minute oscillation between higher and lower alertness that runs throughout the day, not just during sleep.
+
+the pattern: ~70 minutes of rising alertness and focus, followed by ~20 minutes of lower alertness where the body wants rest. during the peak phase, concentration and cognitive performance are naturally higher. during the trough, your brain is pushing toward daydreaming, distraction, and rest.
+
+the research is mixed — some studies find the 90-minute cycle clearly, others don't. but the underlying principle is solid: attention and cognitive capacity fluctuate in cycles throughout the day. you are not a machine that runs at constant output.
+
+## working with cycles, not against them
+
+the implications for [[deep-work]]:
+
+- **peak phases are for demanding work**: complex coding, architecture decisions, hard writing, [[research-workflow]] that requires deep comprehension. this is when [[flow-triggers]] are most likely to fire.
+- **trough phases are for shallow work**: email, admin, reviews, routine tasks, [[spaced-repetition]] reviews in mochi. fighting the trough with willpower is inefficient — you'll produce worse work while burning more energy.
+- **transitions need breaks**: the shift between peak and trough is the natural break point. trying to power through without a break extends the trough and delays the next peak.
+
+## my energy map
+
+through tracking (inconsistently, honestly), i've noticed rough patterns:
+
+- **first peak (morning)**: strongest focus window. this is where the most important [[critical-path]] work should go. protecting this window from meetings and messages is the highest-leverage scheduling decision i can make.
+- **post-lunch dip**: the most reliable low-energy period. perfect for admin, reviews, or a walk. trying to do [[deep-work]] here is fighting biology.
+- **second peak (afternoon)**: smaller than the morning peak but real. good for a second deep work block if the morning block was protected.
+- **evening**: variable. sometimes good creative energy, sometimes nothing. not reliable enough to plan around.
+
+## the 90-minute block in practice
+
+combining the ultradian research with [[deep-work]] time-blocking:
+
+1. block 90 minutes of uninterrupted focus time
+2. during the block: phone away, notifications off, single task only
+3. after 90 minutes: take a real 15-20 minute break. not checking email — actual rest (walk, stretch, stare at the wall)
+4. assess energy: if another peak is coming, do another block. if not, switch to shallow work.
+
+the break quality matters enormously. scrolling social media during a break is stimulation, not recovery. see [[distraction-management]] — the "break" needs to actually restore cognitive resources.
+
+## energy management vs time management
+
+this is maybe the biggest practical insight from all of this: time management is necessary but not sufficient. an hour of high-energy focus produces more than three hours of low-energy grinding. see [[operation-optimization]] — optimizing when you work matters as much as optimizing how you work.
+
+the implication: a shorter workday with well-timed deep work blocks often produces more than a long day of constant low-grade effort. this is counterintuitive when the culture values hours worked, but the output doesn't lie.
+
+## energy and emotions
+
+there's a bidirectional relationship between energy and the inner work:
+
+- low energy amplifies [[the-inner-critic]]. when i'm depleted, the critic gets louder and harder to notice.
+- unprocessed emotions drain energy. something i'm avoiding (see [[welcoming-emotions]]) acts like a background process consuming CPU.
+- [[self-acceptance]] is harder when tired. the default shifts toward self-judgment.
+
+this is why [[resets]] aren't optional luxuries. they're maintenance. running on empty doesn't just reduce output — it degrades the quality of your thinking, your relationships, and your relationship with yourself.
+
+## sleep as the foundation
+
+all of this is moot without adequate sleep. ultradian rhythms assume a well-rested baseline. sleep-deprived, the peaks are lower, the troughs are deeper, and the cycles are harder to detect. no amount of time-blocking or environment design compensates for insufficient sleep.
+
+this is probably the most boring and most important insight in this entire wiki: sleep more. everything else works better when you do.
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