Personal Dev Health¶
12 cards — 🟢 5 easy | 🟡 5 medium | 🔴 2 hard
🟢 Easy (5)¶
1. Why does a fixed wake time matter more than a fixed bedtime for sleep quality?
Show answer
Your circadian clock is anchored by morning light exposure and wake timing, not bedtime. A fixed wake time stabilizes your entire sleep-wake rhythm; bedtime naturally adjusts as sleep pressure builds. Variable wake times create "social jet lag" — the Monday morning equivalent of flying across time zones. Allowed flexibility: +/- 30 minutes on weekends. More than that destroys the anchor and takes 3-4 days to re-establish.2. What is the correct light exposure pattern for healthy circadian rhythm, and what is the phone problem?
Show answer
Morning (first 30 min after waking): bright light — go outside for 10 minutes even on cloudy days (~10,000 lux). Evening (2-3 hrs before bed): dim, warm light — allow melatonin to rise. In bed: darkness. The phone problem: screens are 100-200 lux — dim by sunlight standards, but bright by pre-industrial evening standards. Both blue-light spectrum and cognitive engagement from scrolling suppress melatonin and delay sleep onset.3. How should on-call rotations be managed to minimize sleep disruption and accelerate recovery?
Show answer
Before on-call: bank sleep (go to bed 30-60 min earlier). During on-call: if paged for <1 hour, return to sleep immediately — no phone scrolling after. If paged for >2 hours: accept you are sleep-deprived, nap next day (20 min before 3 PM). Morning after: keep the wake anchor (max 30 min sleep-in — the anchor is more important than one day's comfort). After rotation: get a full night's sleep first night off, do fallback tasks not deep work.4. What is a "coffee nap" and why does it work?
Show answer
Drink coffee immediately before a 20-minute nap. Caffeine takes ~25 minutes to enter the bloodstream, so you wake up from the nap refreshed just as the caffeine onset begins — getting the benefit of both simultaneously. Nap timing: between 1-3 PM (natural circadian trough), exactly 20 minutes (avoid entering deep sleep which causes grogginess). This is also called a "nappuccino" and has solid research support.5. What are the three training buckets and the minimum useful dose for each per week?
Show answer
(1) Strength (builds muscle, bone density, metabolic health): 2x/week, 30-45 min — weights, bodyweight, resistance bands. (2) Conditioning (cardiovascular health, endurance): 3x/week, 20-30 min — walking counts. (3) Mobility (joint range of motion, injury prevention): daily, 10-15 min — stretching, yoga, joint circles. A complete program touches all three; proportion depends on goals and current state.🟡 Medium (5)¶
1. What happens to REM sleep when total sleep time is cut short, and why does this matter for engineers?
Show answer
REM sleep is concentrated in the last cycles of the night. Cutting sleep short (alarm at 5 AM when your body wants 7 AM) disproportionately cuts REM. REM loss impairs memory consolidation, emotional regulation, and creative problem-solving — exactly what engineering work requires. Alcohol also suppresses REM even when it helps you fall asleep faster, making it a net negative for sleep quality.2. What is the half-life of caffeine and what does it imply for daily caffeine strategy?
Show answer
Caffeine has a half-life of 5-6 hours. 50% of the caffeine from a 2 PM coffee is still active at 8 PM. Rules: delay first caffeine 60-90 minutes after waking (cortisol naturally rises on waking, making early caffeine add tolerance without benefit), last caffeine 8-10 hours before bed, cap at 400mg/day (~4 cups coffee). Do not use caffeine to compensate for sleep debt — it masks fatigue without resolving the cognitive impairment.3. What is the typical daily energy curve and how should task types be matched to energy levels?
Show answer
Peak (2-4 hours after waking, usually 8 AM-12 PM): hard cognitive work — architecture decisions, debugging complex issues, writing RFCs, code review. Trough (1-3 PM, nearly universal circadian dip): low-stakes admin — email, Slack catch-up, meetings, organizing. Rebound (4-6 PM): routine skilled work — code implementation, PR reviews, pair programming. Rule: protect your peak hours from interruptions and meetings.4. What is the relationship between training stress and adaptation, and why is recovery not optional?
Show answer
Training is stress applied on purpose. Adaptation (getting stronger, fitter) happens during the rest period after training, not during the workout itself. Training without adequate recovery is just damage accumulation. The limiting factor for most people is joint and connective tissue tolerance (which adapts slower than muscle), not muscular strength. This is why minimum effective dose beats maximum tolerable dose.5. What is Rate of Perceived Exertion (RPE) and how should it be used to regulate training intensity?
Show answer
RPE is a 1-10 scale for how hard a session or set felt, accounting for sleep, stress, and nutrition. Most training sessions should be RPE 5-7. RPE 8+ every session means overtraining. If the same workout's RPE is climbing over weeks, you are accumulating fatigue — take a deload week. RPE is subjective by design: it captures the variables that objective load calculations ignore.🔴 Hard (2)¶
1. Why does sleep deprivation impair self-assessment at the same rate as it impairs cognitive performance?
Show answer
As sleep debt accumulates, both cognitive performance and the accuracy of self-assessment of that performance degrade together. You lose the ability to judge your own impairment at the same rate you become impaired — this is the same mechanism as normalization of deviance in ops systems. This is why sleep-deprived engineers think they are performing fine when they are making more errors, missing details, and making slower decisions.2. Why does a wind-down routine work through consistency rather than relaxation, and what are its key components?