Sleep & Recovery: The Underrated Success Factor

Why Is Sleep So Important for Recovery?

Sleep is the most important factor for recovery. Training provides the stimulus, nutrition supplies the building blocks, but the actual adaptation happens during the rest phase.

What Happens During Sleep?

Hormonal Processes

• Growth Hormone (HGH): In young adults, a large secretory burst occurs shortly after falling asleep, coinciding with the first phase of deep sleep. In men, around 70% of daily secretion falls within early sleep; in women, this proportion is lower and varies more (Van Cauter et al., 1998).
• Testosterone: In a small study of 10 young, healthy men, daytime testosterone levels after one week of 5 hours of sleep per night were 10 to 15% lower than in the well-rested state (Leproult & Van Cauter, 2011).

What Happens When You Don’t Get Enough Sleep?

One night or more without sleep reduces athletic performance. Whether partial sleep restriction over 1 to 3 nights affects performance is unclear (Walsh et al., 2021). A small study by Mah et al. (2011) of 11 Stanford University basketball players, without a control group, examined how more sleep affects performance:

After 5 to 7 weeks of extended sleep (target: at least 10 hours in bed per night; on average, the players slept around 111 minutes longer than before):

• Sprint time: 0.7 seconds faster
• Free throw accuracy: +9%
• 3-point shooting: +9.2%
• Reaction time: significantly improved

Conversely, sleep deprivation shows negative effects:

• More injuries (Milewski et al., 2014: in a survey of 112 adolescent athletes, those who slept less than 8 hours per night on average had been injured 1.7 times more often than those who slept at least 8 hours)
• More hunger and appetite, especially for calorie-dense food (Spiegel et al., 2004: 12 young men, 2 days of restricted sleep)

How Many Hours of Sleep Do You Need?

The National Sleep Foundation recommends 7 to 9 hours of sleep per night for adults and 7 to 8 hours for older adults (Hirshkowitz et al., 2015). Sleep need varies from person to person. For physically active people, an individual approach that takes their self-perceived sleep need into account is recommended (Walsh et al., 2021).

Individual differences: Genetics influence sleep needs. A rare mutation in the DEC2 gene has been linked to a shorter sleep need (He et al., 2009).

How Can You Improve Sleep Quality?

1. Light Exposure

Morning: Light is the most important time cue for the internal clock. Morning light shifts the internal clock earlier, while evening and night light delays it (Blume et al., 2019).

Evening: Light from screens is suspected of disrupting sleep. In a study of 12 young adults (Chang et al., 2015), participants took on average just under 10 minutes longer to fall asleep after about four hours of reading on an iPad at maximum brightness than after reading a printed book, and their evening melatonin levels were 55% lower.

Recommendation: Limit screen time in the evening.

2. Temperature

The body lowers its core temperature to fall asleep: sleep is most likely to begin when core temperature drops. An environment that is too warm disrupts sleep, because in heat, periods of wakefulness increase while deep sleep and REM sleep decrease. With clothing or bedding, no significant difference in sleep was found in the range of 13 to 23°C (Okamoto-Mizuno & Mizuno, 2012).

3. Caffeine Timing

Caffeine has an average half-life of about 4 hours, varying individually between 2 and 8 hours (EFSA, 2015). In a study of 12 healthy adults, 400 mg of caffeine taken 0, 3, or 6 hours before habitual bedtime reduced objectively measured sleep time by 1.1 to 1.2 hours compared with placebo; in the sleep diary, the difference at 6 hours was not apparent (Drake et al., 2013).

Recommendation: Avoid caffeine in the hours before bedtime. Recommendations for the latest intake range from 4 to 11 hours before bedtime (Drake et al., 2013).

4. Consistency

The circadian rhythm benefits from regularity. Go to bed and wake up at the same time every day, including weekends.

A study by Phillips et al. (2017) on Harvard students found that inconsistent sleep times correlated with poorer academic performance, even with the same total sleep duration.

5. Avoid Alcohol

Alcohol can make it easier to fall asleep, but it disrupts the second half of the night and delays the first REM sleep. At moderate and high doses, the proportion of REM sleep decreases (Ebrahim et al., 2013).

Sleep Tracking

Wearables can create awareness of sleep patterns. However, the accuracy of sleep stage detection is limited (Chinoy et al., 2021). Use them as a rough indicator, not as an absolute measure.

More important than data are subjective indicators:

• Do you feel rested?
• How is your training performance?
• Do you need an alarm clock to wake up?

Strategic Napping

Short naps (5 to 15 minutes) can reduce sleepiness and improve cognitive performance. The effect sets in almost immediately and lasts 1 to 3 hours (Lovato & Lack, 2010).

Rules:

• No longer than 30 minutes (longer naps can briefly cause sleep inertia after waking)
• Ideally in the early afternoon
• Not as a substitute for nighttime sleep

Training and Sleep

Evening Training

Contrary to older recommendations, a meta-analysis of 23 studies in healthy adults shows that evening exercise does not negatively affect sleep (Stutz et al., 2019). After intense exercise that ends no more than 1 hour before bedtime, the time it takes to fall asleep, sleep duration, and sleep efficiency can suffer.

On Sleep-Deprived Days

On days with poor sleep:

• Reduce training intensity
• Consider reducing volume
• Watch for signs of injury

Conclusion

Sleep is not negotiable. For adults, 7 to 9 hours of sleep per night is the recommended range (National Sleep Foundation). Pay attention to daylight, a sleep environment that is not too warm, how you handle caffeine, and fixed sleep times.

Further reading

• Stress & Cortisol: How Chronic Stress Sabotages Your Fitness
• Recovery Myths: What Really Helps with Regeneration
• Strength Training for Beginners: The Key Fundamentals
• The Simple Principles of Nutrition
• Protein Calculator: Calculate Your Individual Needs

Sources:

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