Ultradian Rhythms for Sustainable Productivity

The Problem with Continuous Focus

As principal engineers and technical leaders, we’re often expected to maintain focus for extended periods - reviewing architecture proposals, debugging complex systems, leading design discussions. The conventional wisdom says “focus for 8 hours,” “grind through,” or “power through the afternoon slump.”

But this approach fights biology. Your brain isn’t designed for continuous high-intensity work. It operates in natural cycles called ultradian rhythms - 90-120 minute waves of energy and alertness that repeat throughout the day. Understanding and working with these rhythms, rather than against them, can dramatically improve both productivity and sustainability.

What Are Ultradian Rhythms?

Ultradian rhythms are biological cycles shorter than 24 hours that regulate various physiological and mental processes. The most relevant for knowledge work is the Basic Rest-Activity Cycle (BRAC), discovered by sleep researcher Nathaniel Kleitman in the 1960s.

Key characteristics:

Duration: 90-120 minutes of high alertness followed by 20-30 minutes of lower energy
Continuous: Operate throughout day and night (also govern sleep stages)
Biological: Driven by hormones, neurotransmitters, and metabolic processes
Individual variation: Exact timing varies by person, but pattern is universal

During each ultradian cycle:

Ascending phase (30-40 min): Energy and focus increase
Peak phase (30-40 min): Maximum cognitive capacity
Descending phase (20-30 min): Energy and focus decline
Trough phase (20-30 min): Recovery period, body signals need for rest

The Science Behind Ultradian Rhythms

Neurobiological basis:

Prefrontal cortex depletion: Sustained focus depletes glucose and neurotransmitters in the prefrontal cortex
Adenosine accumulation: Metabolic byproduct builds up during mental work, creating fatigue
Stress hormones: Continuous work elevates cortisol, impairing memory and decision-making
Restorative processes: Rest periods allow clearing of metabolic waste and neurotransmitter replenishment

Research findings:

Violating ultradian rhythms correlates with increased errors, reduced creativity, and decision fatigue
Elite performers across domains (musicians, athletes, chess players) naturally work in ~90-minute cycles
Medical residents working continuous shifts show impaired judgment equivalent to blood alcohol of 0.05%

How to Work with Ultradian Rhythms

1. Design 90-Minute Work Blocks

Structure your day around 90-minute focused work sessions aligned with natural energy peaks.

Implementation:

Start time tracking: Notice your natural energy patterns for 1-2 weeks
Schedule important work: Place cognitively demanding tasks during morning/mid-morning peaks
Set boundaries: Protect 90-minute blocks from meetings and interruptions
Use timers: Set a gentle reminder at 90 minutes to check in with your energy

Example schedule for a principal engineer:

08:00-09:30  Deep architecture work (designing systems, code review)
09:30-10:00  Break: walk, coffee, light email
10:00-11:30  Technical writing or mentoring
11:30-12:00  Administrative tasks, light planning
12:00-13:00  Lunch + extended break
13:00-14:30  Meetings or collaborative work
14:30-15:00  Break: walk outdoors if possible
15:00-16:30  Learning, prototyping, experimentation
16:30-17:00  Wrap-up, planning tomorrow

2. Take Strategic Recovery Breaks

The 15-20 minute break between cycles isn’t wasted time - it’s essential for cognitive restoration.

Effective break activities:

Movement: Walking (especially outdoors), stretching, light exercise
Nature exposure: Even looking at nature images reduces cortisol
Social connection: Brief conversation with colleague (non-work topics)
Mindfulness: Meditation, breathing exercises, or simply closing eyes
Napping: 10-20 minute power nap during afternoon trough

Ineffective break activities:

Scrolling social media (doesn’t restore attention)
Email or Slack (still uses prefrontal cortex)
Complex problem-solving (defeats the purpose)
News consumption (increases stress hormones)

3. Align Task Difficulty with Energy Levels

Match the cognitive demands of tasks to your position in the ultradian cycle.

Peak energy (peak of cycle):

System design and architecture decisions
Complex debugging and root cause analysis
Learning new technologies or frameworks
Writing technical proposals
Difficult conversations or negotiations

Moderate energy (ascending/descending phases):

Code review with clear context
Mentoring and pairing sessions
Documentation writing
Participating in meetings
Refactoring familiar code

Low energy (trough phase):

Administrative tasks (timesheets, expense reports)
Organizing notes and documentation
Light email processing
Planning and organizing future work
Passive learning (watching conference talks)

4. Monitor Ultradian Trough Signals

Your body signals when it’s entering a trough phase. Learn to recognize and respect these signals rather than pushing through with caffeine.

Common trough signals:

Difficulty maintaining focus
Increased error rate
Craving snacks or caffeine
Physical restlessness
Yawning or eye strain
Mind wandering
Frustration with simple tasks

When you notice these signs:

Save your work and note where you are
Step away from the screen
Take a 15-20 minute break
Return refreshed for the next cycle

5. Optimize Environment for Cycles

Structure your physical and digital environment to support ultradian rhythm work.

Physical environment:

Lighting: Bright light during work blocks, dimmer during breaks
Temperature: Slightly cool (68-70°F) during focus, comfortable during breaks
Noise: Use focus blocks for deep work, breaks for ambient noise/music
Ergonomics: Adjust sitting/standing throughout the day

Digital environment:

Notification blocking: Turn off during 90-minute blocks
Tool switching: Minimize context switches within blocks
Break automation: Apps like Time Out or Stretchly enforce breaks
Calendar blocking: Mark focus blocks as busy

Application for Technical Leaders

For Individual Contributors

Morning (Highest cognitive capacity):

08:00-09:30: Architecture design, algorithm optimization
10:00-11:30: Complex debugging or system design

Afternoon (Moderate capacity):

13:00-14:30: Code review, collaboration
15:30-17:00: Documentation, learning

For Managers and Tech Leads

Protect your team’s ultradian rhythms:

No-meeting blocks: Reserve 08:00-11:30 for deep work
Meeting clustering: Schedule meetings in the 13:00-15:00 window
Break culture: Model taking breaks, don’t reward continuous work
Async communication: Use Slack/email for non-urgent items

Design meetings around rhythms:

90 minutes max: Even for important discussions
Breaks in long sessions: 10 min break after each 90 min
Energy-appropriate timing: Important decisions in morning peaks

Common Pitfalls

Caffeine override: Using caffeine to push through troughs creates dependency and disrupts natural rhythms
Inconsistent timing: Working late one day, early the next prevents rhythm stabilization
Guilt about breaks: Viewing breaks as lazy rather than essential
Digital breaks: Checking Slack during breaks doesn’t allow cognitive recovery
Ignoring weekend rhythms: Completely different schedule on weekends disrupts weekly patterns

Measuring Success

Track these metrics to validate ultradian rhythm adoption:

Productivity metrics:

Code review quality and speed
Bug introduction rate
Time to complete complex tasks
Decision quality (track decisions revisited)

Wellbeing metrics:

Energy levels at end of day
Sleep quality
Stress and anxiety levels
Sustainable pace (can you maintain this weekly?)

Advanced Techniques

1. Strategic Napping

A 10-20 minute nap during the afternoon trough (14:00-15:00) can reset the ultradian cycle and provide a second wind.

Napping best practices:

Keep it short (10-20 min) to avoid sleep inertia
Use timer to prevent oversleeping
Find dark, quiet space
Don’t feel guilty - NASA research shows 26-minute naps improve performance by 34%

2. Ultradian-Aligned Learning

For mastering complex topics (new programming languages, system design patterns):

Study in 90-minute blocks with full breaks
Interleave topics across different blocks
Review during troughs (passive consolidation)
Sleep between sessions (overnight consolidation)

3. Meeting Energy Management

When you must attend back-to-back meetings:

Active participation: Engage fully during your peak cycles
Note-taking: During descending phases, focus on documentation
Bathroom breaks: Use transitions between meetings for micro-breaks
Protect one cycle: Keep at least one 90-min block meeting-free daily

Conclusion

Ultradian rhythms aren’t a productivity hack - they’re biological reality. You can either fight your biology with caffeine and willpower (leading to burnout), or work with it for sustainable high performance.

The key shift is reframing breaks from “wasted time” to “essential recovery.” A principal engineer who works three focused 90-minute cycles with proper breaks will outperform one who grinds for 8 hours straight, makes more errors, and burns out within months.

Start small: Track your energy for one week, then design one 90-minute focus block with a proper break. You’ll likely find it produces better work than hours of continuous effort. From there, gradually restructure your day around these natural rhythms.

Reflection Questions

When during the day do you feel most mentally sharp? When do you hit energy troughs?
How do you currently spend your “break” time? Does it restore your focus?
What would need to change in your schedule to protect 90-minute focus blocks?
How could you restructure meetings to align with ultradian rhythms?
What signals does your body send when it needs recovery?

2025-11-04

../