energy cycles

ultradian rhythms, 90-minute focus cycles, and working with your biology instead of against it.

the 90-minute rhythm

nathaniel 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.

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

peak phases are for demanding work: complex coding, architecture decisions, hard writing, research-workflow that requires deep comprehension.
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.
second peak (afternoon): smaller than the morning peak but real. good for a second focus block if the morning block was protected.
evening: variable. sometimes good creative energy, sometimes nothing. not reliable enough to plan around.

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 focus 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 emotional state:

low energy amplifies the inner critic. when i'm depleted, self-judgment gets louder and harder to notice.
unprocessed emotions drain energy. something i'm avoiding acts like a background process consuming CPU.

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.