To reach peak physical performance, we often hear about new training plans, nutrition tips, and electrolytes. But there’s one performance booster you might be missing, and that’s sleep, according to Dr Matt Walker.

It’s the unsung hero of performance, and it’s not just for elite athletes. Sleep is crucial for performance, whether you’re training for a marathon or working out at the gym. Let’s explore why.

THE IMPACT OF LACK OF SLEEP ON PHYSICAL PERFORMANCE

Skimping on sleep harms our bodies and brains. This affects our athletic ability in many ways. Here’s how a lack of sleep undermines your performance:

1. REDUCED STRENGTH AND POWER

If you’ve been training hard, poor sleep can undo much of that effort. Studies show that a lack of sleep directly reduces your peak performance strength. If your vertical jump, bench press, or squat aren't where they should be, a lack of sleep could be holding you back.

2. IMPAIRED OXYGEN AND ENDURANCE

Your lungs play a key role in performing at your peak. They get rid of carbon dioxide and take in oxygen, which fuels your muscles.

A lack of sleep reduces this ability, making physical activities more exhausting. For endurance athletes, this can be devastating.

Picture this: you train hard for a 10K race. But by kilometre 7, your performance falls off a cliff because you didn’t sleep enough before the big day.

Research shows that not getting enough sleep can make you tire 15 to 30% faster.

3. DISRUPTED COOLING SYSTEM

Sweating is your body’s natural cooling mechanism. If you can’t cool down properly, your performance drops. Not getting enough sleep also affects how you sweat. This makes it harder for your body to cool down. As a result, your temperature goes up, and important functions can start to fail.

4. FASTER LACTIC ACID BUILD-UP

We all know the burn that comes with intense exercise; that’s lactic acid buildup. Lack of sleep speeds up lactic acid build-up in your muscles. This increases the risk of painful cramps and spasms, which can put you out of action completely. Ain’t nobody got that time for that.

5. INCREASED RISK OF INJURY

If there’s one point to hammer home, it’s this: meta-analyses of several studies show that both the quantity and quality of sleep affect your risk of injury. Athletes who sleep less are far more likely to sustain injuries over a season. For professional athletes, this is costly. For the rest of us, it’s equally frustrating and demotivating. In the long run, sleep seems to help prevent overreaching and even overtraining syndrome.

WHY SLEEP IS THE BEST RECOVERY TOOL

Sleep doesn’t prepare you for peak performance; it also helps your body recover and rebuild. During deep sleep, your body:

• Reduces inflammation in joints and tissues.
• Replenishes critical energy stores, such as glucose and glycogen, within your muscles.
• Repairs damaged muscle fibres, making you stronger and more resilient.

In other words, sleep is essential both before and after physical activity.

EXERCISE IMPROVES YOUR SLEEP

The relationship between sleep and exercise is like a beautiful reinforcing loop. While sleep boosts your physical performance, physical activity also improves your sleep.

Here’s what the science says about regular exercise and its impact on sleep quality:

• LONGER SLEEP DURATION: People who exercise regularly tend to sleep longer than those who do not.
• BETTER SLEEP QUALITY: People who exercise regularly wake up less often at night. This means they enjoy more continuous and uninterrupted sleep.
• DEEPER SLEEP: In midlife and later years, exercise helps promote deeper non-REM sleep (stages 3 and 4). This type of sleep is key for recovery.

Your timing of exercise is crucial. Intense workouts in the two hours before bed can make it hard to sleep. They boost your heart rate, release endorphins, and raise your body temperature. If you love evening workouts, try to finish a few hours before bed. This helps your body cool down and relax naturally.

IT’S NOT JUST PHYSICAL

Sleep improves more than just your body. It boosts your motor skills and muscle memory. These are key for mastering technique and precision in sports.

Think of it this way: practice doesn’t make perfect. Practice followed by sleep does. When you practice your golf swing, free kicks, or learn a new skill, your brain works during sleep. It helps to consolidate and strengthen those skills. Studies show that getting enough sleep can boost motor performance by up to 30% overnight. This improvement happens even without extra practice.

A good night’s sleep could be the key to going from good to great.

LESSONS FROM THE PROS

Some of the world’s best athletes know how important sleep is. They make it a priority in their training and recovery.

• LEBRON JAMES reportedly sleeps 11 to 12 hours a day. He combines night sleep with daytime naps. He’s said there’s no better form of recovery than sleep. King James says that quality sleep helps with “complete physical and emotional recovery.” This means he’ll be ready to perform "at the highest level the next day.”
• ROGER FEDERER, the Swiss Maestro and tennis legend, also sleeps 11 to 12 hours every day. He believes that prioritising sleep helps him stay consistent and prolongs his career.
• USAIN BOLT, the fastest human ever, famously woke up from a nap before breaking the 100m world record in 2009. He ran it in 9.58 seconds in Berlin. He has often napped before breaking the world record and before Olympic finals where he won gold. Daytime naps have enough sleep spindles to boost motor skill memory. They also help restore energy and reduce muscle fatigue.
• TOM BRADY is known for his disciplined routine. Which includes going to bed at 8:30 pm to ensure adequate sleep for optimal performance.
• MICHAEL PHELPS, the Olympic swimmer, emphasised the importance of sleep, reportedly getting at least 8 hours per night along with a 2-3 hour nap during training periods.
• SIMONE BILES in addition to 8 hours of nightly sleep, often takes a 1-2 hour nap after her morning training to help her muscles recover and lock in new motor skills.

If sleep matters that much to the best to ever do it, it’s a clear signal for the rest of us.

WHEN IS THE BEST TIME OF DAY TO BREAK A RECORD?

Turns out, our circadian rhythm, the body’s internal clock, plays a huge role in peak athletic performance.

Most world records in explosive sports, like sprinting, weightlifting, and swimming, are set in the late afternoon or early evening. Why? Because around 4–7 pm, the body reaches its biological prime:

• Core body temperature peaks → Looser muscles, faster reactions
• Cardiovascular efficiency improves → Better endurance
• Cognitive sharpness increases → Faster decision-making
• Grip strength & muscle power are highest

One study found that athletes performed up to 26% better in the evening compared to early morning.

This is why major competitions, like Olympic finals, often take place in the evening. When the stakes are high, you want every natural advantage.

But there’s a catch:

Some endurance records, like ultra-marathons, long swims, and cycling feats, are often set in the morning. This is when cortisol levels peak, helping athletes overcome fatigue.

While a power nap can help, long-term sleep deprivation wrecks performance.

One study published in the Asian Journal of Sports Medicine found that after just one night of poor sleep, athletes experienced:

• Reduced sprint speed by 3%
• Decreased strength output by 9%
• Slower reaction times by 15.4%

Even NBA teams that travelled across time zones and lost sleep had lower win rates. Eastern Conference teams struggled more when they travelled west with a win rate of just 36.2%. This was even clearer in late evening games when their bodies thought it was time to sleep. In contrast, players who slept for 8 hours or more had a shooting accuracy that was 9% higher.

MAKE SLEEP YOUR COMPETITIVE EDGE

In the race to optimise performance, we often look for complex solutions, the latest whatsits and whatnots. But sometimes, the simplest answers are the most effective. Sleep science is improving each year. The message is simple: sleep may be the best legal performance-enhancing drug we've got.

Sleep better. Perform better. It’s that simple.