How exercise, sleep, and nutrition shape brain health and performance

Podcast episode originally published on June 14, 2022

Brain health and performance are shaped by trainable inputs, especially exercise, sleep, hydration, and nutrition. In this episode of the WHOOP Podcast, Global Head of Human Performance, Principal Scientist at WHOOP Dr. Kristen Holmes talks with neurophysiologist Louisa Nicola about how those inputs affect reaction time, accuracy, motivation, recovery, and long-term cognitive health.

Nicola came to this work after a cycling accident pushed her from elite triathlon into neurophysiology and the study of how the brain adapts under stress. This article covers six questions from that conversation, including how the brain ages, why resistance training deserves more attention, how dehydration changes decision-making, why sleep loss raises the cost of hard training, and how WHOOP data can help you spot trends before poor recovery turns into poor performance.

For Nicola’s full discussion of exercise, sleep, and brain performance, listen to Episode 177 of the WHOOP Podcast with Louisa Nicola on Spotify.

How does the brain age, and what can you do about it?

Brain aging starts earlier than many people expect, and Nicola argues that it is influenced by daily behavior. Her core idea is simple: the brain responds to inputs, and those inputs can either support performance or speed decline.

Nicola’s view grew out of her own experience. After a serious bike crash ended a period of high-level triathlon training, she was introduced to electroencephalography, or EEG, and saw how intensely the brain could respond even during imagined performance. That moment shifted her from endurance sport into neurophysiology. From there, she began to frame high performance as a brain-first problem. In her language, the brain is the hardware, and the mind reflects what that hardware can support.

In the episode, Nicola says there are about 12 theories of brain aging, but three stand out in her work. The first is age-related white matter change, which refers to structural changes in the tissue that contains many of the brain’s myelinated nerve fibers. The second is reduced dopamine receptor activity in the frontal lobe, which she links to lower drive and motivation with age. The third is neurodegeneration itself, the steady decline in cognitive function that begins as part of normal aging.

Nicola’s practical point is that the brain is affected by the same behaviors people often treat as separate categories: how they train, how they sleep, and how they eat. That is why her company, Neuro Athletics, works across three domains: exercise, neurophysiology and sleep, and nutrition. In her telling, those are not separate habits. They are overlapping inputs that shape how the nervous system functions day to day.

For a related WHOOP discussion on how the brain builds and updates internal models, read Episode 262 of the WHOOP Podcast with Dr. Lisa Feldman Barrett.

Nicola frames the scope this way:

"There’s around 12 theories of how our brain ages, and there’s 3 that really stand out to me."

What you should take away

• Brain aging is influenced by daily behavior, especially exercise, sleep, and nutrition
• Nicola focuses on three main drivers of decline: white matter changes, lower dopamine receptor activity, and neurodegeneration
• Her working model treats the brain as hardware that shapes how well the rest of the system can perform

Is resistance training better than aerobic exercise for brain health?

Nicola’s answer is yes, with an important caveat. She still values easy aerobic work, but she believes resistance training delivers a stronger direct signal for structural and functional brain benefits.

That argument starts with aerobic exercise. Nicola points to a 1999 mouse study on running and hippocampal neurogenesis, which reported that daily aerobic activity increased the formation of new neurons in the hippocampus. She also cites a 2017 paper that she says linked daily aerobic activity with delaying Alzheimer’s disease by 20 years. In Nicola’s view, those findings matter because they established an early connection between movement and the aging brain.

Her bigger emphasis, though, is what happens when people lift heavy. Nicola points to a 2019 systematic review by Herold and colleagues, which she says found stronger brain-related benefits from resistance training than from aerobic work alone. She also references a 2021 trial in people with mild cognitive impairment , where six months of resistance training was associated with new connections in hippocampal subregions.

The mechanism is where Nicola spends most of her time. Endurance work is closely associated with brain-derived neurotrophic factor, or BDNF, a growth factor linked to plasticity and neuron survival. Resistance training adds another layer. Nicola says lifting releases myokines, muscle-derived signaling proteins, along with hormones such as insulin-like growth factor 1, or IGF-1. She also highlights irisin, a signaling molecule that can cross the blood-brain barrier and is thought to affect memory, processing speed, and other cognitive functions.

Her rule of thumb for people who care about brain aging is practical. Aim for resistance training at least three days per week, and lift heavy enough that six repetitions feels close to the limit. She still keeps zone 2 work in the week, about two hours of easy aerobic work, partly because of its relationship to mitochondrial function and healthy aging.

WHOOP has explored a related question in Episode 200 of the WHOOP Podcast with Dr. Tommy Wood, which also focuses on exercise and cognitive function.

Nicola gets specific about loading parameters:

"If you go and do bench press or a squat at 70% of your one repetition max, you’re going to get a massive influx of IGF-1."

What you should take away

• Nicola argues that resistance training gives the brain a stronger growth signal than aerobic exercise alone
• Aerobic work is still useful, especially for mitochondrial function and healthy aging
• A practical resistance-training target is three sessions per week at roughly 70% of one-repetition max
• In Nicola’s framework, heavy lifting supports brain health through myokines, IGF-1, and irisin

If you want Nicola’s full explanation of resistance training, BDNF, IGF-1, and brain aging, listen to the full episode on Spotify.

How do nutrition and hydration affect brain performance?

Nicola treats brain nutrition as an individual question first, then a general one. The individual layer includes genetics, blood work, training load, and head-impact exposure. The general layer starts with fats, water, and electrolytes.

In the episode, Nicola says her team uses blood analysis and genetic testing so recommendations match the person in front of them. She gives APOE4 as an example. A person carrying that allele may have a higher risk profile for Alzheimer’s disease, which would change how her team thinks about diet, sleep, and exercise. She makes the same point for athletes in contact sports. If a player is absorbing frequent head impacts, Nicola wants the nutrition plan to serve a clear neuroprotective role.

That is where omega-3s enter the discussion. Nicola emphasizes docosahexaenoic acid, or DHA, the omega-3 fatty acid that is especially important in brain tissue. She mentions fish sources such as sardines, mackerel, and salmon roe, and says that some athletes in high-impact sports supplement aggressively. Her own example is 2 grams of EPA and 2 grams of DHA per day. She also mentions work from researcher Dominic D’Agostino, which she connects to ketones, traumatic brain injury, and ketogenic diets.

Hydration is where Nicola becomes even more practical. She says even 2% dehydration can impair cognitive performance, including decision-making and reaction to stimulus. Her explanation centers on the sodium-potassium pump, the cellular mechanism neurons use to generate and propagate electrical signals. Sodium, potassium, calcium, phosphorus, and magnesium all help support the movement of charges that let brain cells communicate.

Nicola’s coaching language is clear: people do not need to be visibly drenched in sweat to care about electrolytes. The brain uses them every day. She gives 2.5 liters of fluid as a bare minimum and notes that larger or more active people may need more. She personally targets around 3 liters per day and adds electrolytes even when sweat loss feels modest.

For another WHOOP discussion of individual nutrition, food timing, and behavior change, see Episode 157 of the WHOOP Podcast with Dr. Hazel Wallace.

Nicola summarizes the hydration threshold in one line:

"Just a mere 2% of dehydration can affect your cognitive performance."

What you should take away

• Nicola treats brain nutrition as a personalized question shaped by genetics, blood work, and sport demands
• DHA-rich foods and omega-3 supplementation are central to her approach for brain support
• Even mild dehydration can reduce decision-making speed and reaction time
• Electrolytes matter for brain signaling because neurons rely on ion movement to communicate

Why does sleep loss hurt endurance, accuracy, and immunity?

Nicola’s answer is that sleep loss changes both perception and physiology. In her framework, poor sleep makes effort feel harder, reduces precision, and shifts recovery biology in the wrong direction.

She starts with athletes in season. During heavy travel stretches, especially in playoffs, circadian rhythm disruption can stack on top of training load. Nicola says injuries often cluster during those periods, and she sees sleep as one of the missing explanations. She then points to a sleep-deprivation study in 11 male subjects. In that protocol, subjects completed a 30-minute self-paced treadmill test after 30 hours without sleep. Nicola says the main effect was higher perceived exertion. Oxygen consumption and temperature regulation were not the main story. The limiting factor was how hard the effort felt.

From there, she moves to precision. Nicola references research in basketball players showing worse jump-shot and free-throw accuracy with sleep loss. She adds a dart-throwing result that found a 53% drop in accuracy after one night with only five hours of sleep. For athletes, that means poor sleep can show up as worse technical execution long before it shows up as a dramatic drop in effort.

Her strongest claim comes from a paper in Proceedings of the National Academy of Sciences. Nicola says a week of six hours of sleep per night changed the expression of about 3% of the genome, which she translates into hundreds of altered genes. She specifically says the sleep-restricted group showed higher expression in genes related to tumor growth and lower expression in genes related to immunity. Nicola uses that finding to argue that chronic short sleep is more than a mental fog problem. It is a biological stressor.

WHOOP has covered sleep and long-term cognition from another angle in Episode 49 of the WHOOP Podcast with Dr. Richard Isaacson, which discusses sleep patterns and Alzheimer’s prevention research.

Discussing the gene-expression finding, Nicola puts it starkly:

"They showed that with this sleep deprivation of 1 week of 6 hours a night of sleep, they upregulated the genes responsible for tumor growth, and they downregulated the genes responsible for immunity."

What you should take away

• Sleep loss can reduce endurance performance by making effort feel harder
• Short sleep can hurt accuracy in skill-based tasks such as shooting and target work
• Nicola links six-hour sleep schedules to gene-expression changes tied to worse immune function
• Travel, late schedules, and playoff-style calendar stress can raise injury risk by disrupting sleep

To hear Nicola connect sleep loss to endurance, accuracy, and immune biology in her own words, listen to the full episode on Spotify.

How can WHOOP help you track stress and recovery trends that affect the brain?

Nicola treats WHOOP as a trend tool first. She uses HRV, sleep data, and week-to-week patterns to see when stress is accumulating and when the nervous system is ready for more work.

In the episode, Nicola says all of her athletes use WHOOP and that she reviews the weekly reports on the back end. Her goal is to see how the Neuro Athletics protocol is affecting the person over time. That means she is not hunting for a perfect single day. She wants a pattern. Are sleep metrics improving month to month? Is HRV holding steady during travel? Is an athlete recovering well enough to absorb another hard session?

The most concrete example comes from Nicola herself. After travel from New York to Los Angeles while dealing with allergies, she says her HRV dropped to 120 from a usual level around 180. For her, that shift was a clear sign to back off. In her coaching logic, a low HRV suggests higher physiological stress. Pushing a hard run into that state would add more strain, make it harder to wind down, and reduce the odds of a good night of deep and REM sleep.

That is where WHOOP becomes useful for people outside professional sport too. HRV, or heart rate variability, refers to the variation in time between successive heartbeats. WHOOP measures it during sleep, when the body is in a more stable state, and places it alongside other sleep and recovery signals. Nicola’s point is that the number only becomes useful when it is interpreted against your own baseline.

If you want the basics of how sleep, strain, and recovery fit together, Episode 51 of the WHOOP Podcast on what WHOOP measures is a useful starting point.

Nicola describes her review process this way:

"I’m not looking at every single day what’s your HRV. I’m looking at trends."

What you should take away

• Nicola uses WHOOP to follow trends in HRV and sleep, not to obsess over one isolated reading
• HRV is most useful when compared with your own baseline and recent context, such as travel or illness
• A low-HRV day can be a cue to reduce training stress rather than force a hard session
• WHOOP becomes more useful when the data leads to a clear decision about recovery and workload

What daily habits help protect brain performance over time?

Once Nicola identifies a trend, she tries to change the environment that produced it. Her daily habits are straightforward: cool the body, darken the room, finish eating early enough, reduce late light exposure, and respect what caffeine and alcohol do to sleep stages.

Nicola says the sleep environment is the hub. She wants athletes in a cold, dark room because the body needs to cool down to fall asleep and stay asleep. For hot sleepers, she recommends temperature control at the mattress level. She also wants a fully blackout room so light does not disrupt sleep late in the night or early in the morning.

Her preferred schedule is equally direct. Lights out at 10:00 p.m., wake time around 6:00 a.m. That target is less about ritual for its own sake and more about total time in bed. Nicola says a lot of low REM or low slow-wave sleep problems come back to a basic issue: people are simply not asleep long enough.

She adds a few daytime rules that support the night. Finish the last meal by about 7:30 p.m. if bedtime is 10:00 p.m. so digestion and the thermal effect of food do not keep body temperature elevated. Reduce bright light exposure after 8:00 p.m. Get stress out of the head and onto paper before evening. Avoid caffeine after noon. Treat alcohol as a sleep disruptor, especially for REM sleep.

The larger theme is consistency. Nicola wants people to stop treating sleep like the leftover part of training. In her model, sleep is where the benefits of good exercise and good nutrition get consolidated.

For Nicola’s full discussion of sleep environments, meal timing, caffeine, and alcohol, listen to Episode 177 of the WHOOP Podcast with Louisa Nicola on Spotify.

Nicola explains the temperature piece clearly:

"In order to fall asleep and stay asleep, our core body temperature needs to drop at least 2 degrees."

What you should take away

• A cold, dark, quiet sleep environment gives the brain a better chance to reach deep and REM sleep
• Earlier meal timing can help the body cool down before bed
• Caffeine after noon and alcohol in the evening can disrupt sleep quality even when total sleep time looks acceptable
• Consistent time in bed is one of the simplest ways to support brain recovery

The bottom line

• Brain aging is influenced by daily behavior, especially sleep, exercise, hydration, and nutrition
• Nicola argues that resistance training may provide a stronger brain-growth signal than aerobic exercise alone, partly through myokines, IGF-1, and irisin
• Easy aerobic training still matters for mitochondrial function and healthy aging, and Nicola keeps about two hours of zone 2 work in the week
• Mild dehydration can impair cognitive performance, and Nicola uses electrolytes as part of brain-focused hydration rather than treating them as a sweat-only tool
• Omega-3 intake, especially DHA, is central to Nicola’s neuroprotective nutrition strategy for people who care about brain performance
• Short sleep can raise perceived exertion, reduce shooting accuracy, and shift immune-related biology in an unfavorable direction
• WHOOP is most useful for brain-related decisions when HRV and sleep are read as trends against your own baseline
• A cold, dark sleep environment, earlier meal timing, and lower evening light exposure are simple habits that can support better brain recovery

Frequently asked questions about things discussed in this episode

How does WHOOP measure HRV in a way that is useful for brain-related recovery decisions?

WHOOP measures HRV during sleep, when your body is relatively stable, so changes in the trend can help show when travel, illness, stress, or heavy training may be affecting nervous system recovery.

What does WHOOP do for sleep tracking when brain performance is the goal?

WHOOP records sleep duration, sleep need, sleep consistency, and related recovery signals, which helps you see whether the brain is getting enough time and regularity to recover well.

How can WHOOP help you decide whether to push hard or back off?

WHOOP combines sleep and physiological signals into daily Recovery guidance, which can help you recognize when low HRV and poor sleep may make hard training less productive.

What does WHOOP show about the effect of alcohol on recovery?

WHOOP often shows alcohol as worse sleep quality, lower HRV, and poorer next-day recovery, which matches Nicola’s point that ethanol disrupts REM sleep and can affect more than one night.

How does WHOOP help you monitor the effect of travel or schedule disruption?

WHOOP makes travel disruption visible through changes in sleep timing, HRV, resting heart rate, and recovery trends, all of which can help explain why training feels harder after flights or late nights.

What can WHOOP tell you about hydration and brain performance?

WHOOP does not measure hydration directly, but shifts in resting heart rate, HRV, sleep quality, and strain tolerance can help you spot when poor hydration may be adding physiological stress.

What does WHOOP track that matters for resistance training and zone 2 work?

WHOOP tracks Strain, sleep, Recovery, HRV, and resting heart rate, which helps you see whether your weekly mix of lifting and easy aerobic work is building adaptation or accumulating fatigue.

For people trying to protect brain performance, WHOOP can make the cost of short sleep, mistimed training, travel, and poor hydration visible before those factors show up as slower thinking or worse recovery.