Biohacking techniques for sleep, training, and daily performance

Originally published on October 16, 2019

Biohacking techniques can help shape sleep, training, and daily energy when they are tied to feedback from your body. In Episode 044 of the WHOOP Podcast, Ben Greenfield, coach, author, and Ironman triathlete, explains how he builds a full day around fasted movement, nasal breathing, focused work blocks, recovery naps, and a tightly managed bedtime routine.

Recorded at the Spartan World Championships in Lake Tahoe, the conversation is most useful when read as a system instead of a list of hacks. Greenfield also shares which metrics he believes matter most, including sleep, HRV, blood glucose, and inflammation, and why measuring habits can change behavior.

Note: This article covers WHOOP 3.0. For the latest hardware, see WHOOP.

To listen to Episode 044 of the WHOOP Podcast in full, head to the WHOOP Podcast on YouTube.

What does a data-driven morning routine actually look like?

A data-driven morning routine starts with repeatable inputs before the day gets noisy. For Greenfield, that means beginning with gratitude and reading, then moving into hydration, mobility, coffee, and a fasted workout window.

He said the first minutes of the day are reserved for a gratitude journal, a short reading practice, and one specific prompt about who he can help that day. Only after that does he shift into physical prep. Coffee comes later, often after 15 minutes of foam rolling, mobility work, and deep nasal breathing. He also said he keeps mornings light on reactive tasks, choosing reading and research before email or notifications.

The same structure carries into food timing. Greenfield said he keeps a daily 12-16-hour intermittent fast, drinks coffee black, and prefers to train before his first meal. That routine creates a consistent testing ground for habits that can later show up in sleep, Recovery, and perceived readiness.

Greenfield put the food timing piece plainly

"I always every day do a 12-16-hour intermittent fast."

What you should take away

• A repeatable morning routine can make training and recovery easier to compare from day to day.
• Greenfield uses gratitude, reading, mobility, and black coffee before reactive work.
• A 12-16-hour fasting window is one way Greenfield keeps his morning routine consistent.
• Fasted training only makes sense when it fits your schedule, energy, and recovery patterns.

If you want to hear Greenfield unpack his fasted mornings and mobility routine, listen to the full episode on Spotify.

How can nasal breathing change a workout?

Once the day is structured, Greenfield pays close attention to how he breathes during effort. His view is that nasal breathing can support better control of carbon dioxide, reduce unnecessary sympathetic drive, and make training feel more focused.

Greenfield tied the idea to oxygen delivery. He pointed to the Bohr effect, the relationship between carbon dioxide and oxygen release into tissue, and argued that breathing through the nose can help preserve the carbon dioxide levels that support that process. He also said nasal breathing humidifies air and tends to promote more diaphragmatic breathing, which may help keep the body calmer during training.

That matters most in workouts where people usually default to chest breathing and rushing. Greenfield described nasal breathing as part of a wider attention practice, where breath becomes a steady cue for pacing, body awareness, and post-workout calm. For WHOOP members who want another conversation on breath and the autonomic nervous system, there is a related episode with Jordan Shallow on breathing and HRV.

Greenfield's explanation was specific:

"When you have high levels of CO2, oxygen dissociates more readily into tissues."

What you should take away

• Greenfield uses nasal breathing to stay more controlled during training.
• His rationale is that higher carbon dioxide tolerance can support oxygen delivery into tissue.
• Nasal breathing also slows airflow, humidifies air, and may support more diaphragmatic breathing.
• A breathing change is easier to judge when you compare it against WHOOP Recovery and sleep trends.

If you want to hear Greenfield go deeper on nasal breathing and carbon dioxide tolerance, watch the full episode on YouTube.

How much training is enough for strength and endurance?

Breathing is one part of the training equation, and Greenfield also thinks many people overspend time in the gym. His answer is a minimal effective dose approach, where training stays hard and purposeful without turning into hours of volume.

He described his main session as concurrent strength and endurance work, usually around 60 minutes with very little rest. A typical day might combine loaded carries, pull-ups, rowing, burpees, assault bike work, or running. He also said he keeps two movement sessions in a day, one hard and one parasympathetic, such as a walk, easy swim, or sauna session.

The key idea is that more time is not always more productive. Greenfield argued that very short bouts of muscular work can still do the job when effort is high enough. He also prefers hard training later in the day when schedule allows, because he believes grip strength, testosterone, post-workout protein synthesis, and body temperature all peak later than they do in the morning. That fits closely with other WHOOP conversations about training load and recovery, including Don Saladino on under-resting and training dose.

Greenfield summarized the strength side with a clear number:

"Two to three minutes of time under tension for a muscle group is enough to initiate hypertrophy and muscle maintenance."

What you should take away

• Greenfield favors hard, condensed training over long sessions filled with low-value volume.
• His default structure is one hard session and one easy, parasympathetic movement session each day.
• He believes two to three minutes of time under tension can be enough for a muscle group when effort is high.
• Later-day hard training may feel better for some people because body temperature and strength traits tend to be higher.

If you want to hear Greenfield unpack minimal effective dose training and concurrent workouts, listen to the full episode on Spotify.

Which recovery habits does Greenfield use to protect sleep?

If training dose is the stress side of the equation, sleep habits are the recovery side. Greenfield's sleep setup is built around cutting friction before bed and keeping the bedroom cool, dark, and quiet.

His routine starts well before lights out. He described family dinner and evening reading as part of the downshift, then said his bedroom uses red incandescent bulbs instead of bright LED lighting. He also wears red blue-light-blocking glasses at night, uses blackout curtains, diffuses lavender, and runs a cooling pad that circulates 55-degree water under the bed. Earlier in the day, he also protects recovery with a 20-45 minute post-lunch nap.

Greenfield treats sleep supplements as secondary to environment, but he did give specific numbers. He said he often takes 60-80 milligrams of CBD and uses a sleep formula developed by Dr. Kirk Parsley. He also said THC seems to disrupt his deep sleep. For people thinking about the timing side of sleep, there is a related WHOOP conversation with Dan Churchill on nutrition and sleep timing.

On supplementation, Greenfield was specific:

"I take about 60 to 80 milligrams of CBD, and I take a few capsules of this supplement called Sleep Remedy."

What you should take away

• Greenfield protects sleep by changing light, temperature, and evening stimulation before reaching for supplements.
• A 20-45 minute nap is one of his regular recovery tools.
• His bedroom setup includes red light, blackout conditions, lavender, and a 55-degree cooling system.
• Greenfield said CBD helped his deep sleep more than THC in his own tracking.

If you want to hear Greenfield go deeper on bedtime routines, CBD, and sleep environment, watch the full episode on YouTube.

Which health metrics does Greenfield think are most worth tracking?

Those routines matter more when they are measured, which is why Greenfield keeps coming back to a short list of metrics. His first tier is sleep and HRV, followed by overall heart rate, step count, blood glucose, and inflammatory markers.

Greenfield said tracking changes behavior as much as it explains it. He gave simple examples, taking a short walk before bed to hit a step goal, protecting sleep more carefully because he can see the data, and watching how different inputs change HRV. That matches the core idea behind WHOOP, which turns signals from your body into daily views of Sleep, Recovery, Strain, and heart rate. If you want a deeper overview of how those measurements work, see Episode 051 on what WHOOP measures.

Outside WHOOP, Greenfield said he would add regular blood glucose tracking, including hemoglobin A1c, and quarterly checks of inflammatory markers such as C-reactive protein, fibrinogen, and homocysteine. He specifically named the Dexcom G6 as a useful continuous glucose monitor. He framed glycemic variability and inflammation as the two variables he would focus on if he had to narrow the field.

Greenfield stated his priorities directly:

"Sleep and HRV, which in my opinion are the two top metrics to track."

What you should take away

• Greenfield ranks sleep and HRV at the top of his personal tracking list.
• Step count and overall heart rate are simple metrics that can still change daily behavior.
• Greenfield also values blood glucose, hemoglobin A1c, and inflammatory markers such as C-reactive protein, fibrinogen, and homocysteine.
• WHOOP is most useful when you use data to compare habits against Sleep, Recovery, and Strain over time.

If you want to hear Greenfield unpack sleep, HRV, blood glucose, and inflammation tracking, listen to the full episode on Spotify.

The bottom line

• Greenfield structures his mornings around gratitude, reading, mobility, and a delayed first meal so the start of the day stays consistent.
• Greenfield said a 12-16-hour intermittent fast helps keep his morning routine and training window predictable.
• Nasal breathing is one of Greenfield's main tools for controlling pace, attention, and perceived stress during training.
• Greenfield believes many people can get enough stimulus from shorter, harder sessions instead of adding more low-value volume.
• Greenfield balances hard training with an easier daily movement session such as walking, swimming, or sauna time.
• Greenfield protects sleep with environmental changes first, including red light, cooler temperatures, and less evening stimulation.
• Greenfield ranked sleep and HRV as his top metrics, then added heart rate, step count, blood glucose, and inflammatory markers.
• WHOOP data becomes more useful when it helps you compare a specific behavior, such as bedtime light exposure or a fasted workout, against Sleep and Recovery trends.

Frequently asked questions about things discussed in this episode

How does WHOOP measure sleep and HRV?

WHOOP measures sleep and HRV continuously and turns those inputs into daily Sleep and Recovery insights in the WHOOP app. Your overnight patterns make it easier to see whether habits such as later caffeine, alcohol, travel, or bedtime light exposure line up with better or worse recovery.

What does WHOOP do for people experimenting with fasting or morning workouts?

WHOOP helps you compare fasting or morning workouts against Recovery, sleep quality, heart rate, and Strain trends over time. Your data can show whether a routine that feels productive is also sustainable for your body.

How does WHOOP help track breathing or stress-related changes?

WHOOP helps track the downstream effects of breathing or stress-management habits by showing how they line up with Recovery, resting heart rate, and sleep metrics. Your patterns across several days are more useful than a single workout feeling easier or harder.

What does WHOOP show about daily activity outside formal training?

WHOOP shows the load from formal workouts and the broader context around them, including sleep, recovery, and daily heart rate trends. Your step count and overall Strain can help explain why a day felt harder even when the workout itself looked ordinary.

How does WHOOP fit with blood glucose or lab testing?

WHOOP fits well beside blood glucose or lab testing because it gives daily physiological context between those longer-interval checks. Your Sleep, Recovery, and heart rate trends can help you decide which behaviors are worth testing further with a continuous glucose monitor or lab panel.

What does WHOOP help you learn about bedtime routines?

WHOOP helps you learn which bedtime habits line up with better sleep by making patterns visible across nights. Your data can highlight whether cooler temperatures, lower light exposure, or fewer evening stimulants are connected to stronger Recovery the next day.

For this kind of routine-heavy experiment, WHOOP is most useful when one behavior, such as nasal breathing or a post-dinner walk, can be checked against what your body did overnight.