Which Should Be Prioritized: Sleep or Exercise?—The "Real Data" from 70,000 People Shows the Reason to "Sleep First"

1. "Both Sleep and Exercise Are Important," Yet There's a Lack of "Time" in Reality

In health discussions, it usually ends with these recommendations:
"Get plenty of sleep" and "Exercise moderately."

Both are correct.
However, with work, house chores, childcare, commuting, social media, schedules, stress... the reality of 24 hours is tough.

In response, the study covered by n-tv aimed to directly address the question, "On days when you can't do both, which should you prioritize?"n-tv.de

2. Study Details: Verified with Over 70,000 People and About 28 Million Days of "Objective Data"

The strength of this study lies in the fact that it uses daily records "collected by devices" rather than surveys (self-reports).
The research team (Flinders University, Australia) integrated and analyzed the following data:

• Subjects: 70,963 people

• Period: January 2020 - September 2023

• Data: Sleep (sensor under the mattress) + Steps (wrist health tracker)

• Analysis Scale: About 28 million person-days

• Items Observed: Sleep duration, sleep efficiency (percentage of time in bed spent sleeping), time to fall asleep, steps the next day, etc.Nature+1

Instead of "feeling like I exercised" or "feeling like I slept well yesterday," the study examined the relationship between sleep and activity using real daily numbers in a "bidirectional" manner.Nature

3. First Shock: Only About 13% Can Achieve the Recommended "Sleep + Exercise"

The benchmarks set by the study (generally recommended levels) are:

• Sleep: 7-9 hours

• Activity: More than 8,000 steps a day

However, those who could "regularly" meet both were only 12.9%.Nature+1

In other words, the "ideal set" often seen in health information is actually difficult for many people to achieve in reality.
The researchers themselves suggest that "general health recommendations may be difficult to balance in real life."n-tv.de+1

Furthermore, the combination of **short sleep (less than 7 hours) and low activity (less than 5,000 steps)** was also 16.5% (introduced as about 17% in the n-tv article).
This combination is emphasized in the study as a "dangerous simultaneous deficiency" that is likely to be linked to health risks.Nature+1

4. Core Conclusion: The Stronger Impact Was "Sleep → Next Day's Activity"

This is the most important point of this study.

The study roughly indicated the following:

• Good sleep (especially high-quality sleep) → Tendency to walk more the next day

• Walking a lot → Doesn't necessarily mean sleeping well that night (small impact)n-tv.de+1

Based on this, n-tv summarizes that the daily priority should be "when in doubt, prioritize sleep."n-tv.de

5. Improving "Sleep Quality" Increases Steps the Next Day (and It's Dose-Responsive)

In the study, sleep efficiency was used as an indicator of sleep quality.Sleep Efficiency.
It was shown that the higher the sleep efficiency, the more steps were taken the next day (dose-response = the better, the more likely to increase).Nature

This is intuitively understandable.
If your sleep is shallow and you remain tired, your motivation to act decreases.
Conversely, if you sleep deeply and recover, you'll become a "body capable of walking and moving."

Researchers cite factors such as fatigue, motivation, and performance as reasons why sleep supports the next day's activities.Fatigue, Motivation, Performance.n-tv.de+1

6. Caution on "6-Hour Sleep Allows for the Most Walking": It's Not Necessarily the "Optimal Health Solution"

The summary section of the paper presents some numbers that can be easily misunderstood.
It states that "the number of steps the next day is maximized with about 6 hours of sleep" (e.g., +339 steps compared to 8 hours of sleep).Nature

However, this is not a story of "it's okay to imitate this directly."

The reason is simple:With shorter sleep, the waking time increases, making it easier to accumulate steps..
In fact, this study also showed that the effect size diminishes when adjusted for awake duration.Nature

In other words,
"The shorter you sleep, the healthier you are!" is not the case.
Instead, "In real data, the relationship between sleep and steps is not a simple straight line."
.

From a health perspective, 7-9 hours of sleep for adults is generally widely recommended.National Sleep Foundation+1

7. Has the Recommendation for Exercise Become "Unnecessary"? → Of Course Not

What should not be misunderstood here is that the study is not saying "you don't need to exercise,"

but rather "Getting enough sleep tends to be the foundation that triggers exercise (daily activity)."

This is a proposal for prioritization.n-tv.de+1

The fact that lack of exercise is bad for health is repeatedly emphasized by organizations like the WHO.
The WHO recommends for adults150 minutes or more of moderate-intensityor75 minutes or more of high-intensity exercise per week (or an equivalent combination).World Health Organization+1

However, in reality, the pressure of "I have to exercise" on a tired day can have the opposite effect.
In such cases, first, re-establish your sleep.
As a result, the amount of activity the next day increases, and a lifestyle closer to exercise returns—this sequence is "realistic," according to the message.n-tv.de+1

8. Limitations of the Study: Not a Universal Conclusion (But Still Useful)

Every study has its limitations, and this one is no exception.

• The data may be biased towards people who use specific sleep sensors and wearables (purchasers)

• Sleep trackers may tend to "overestimate" actual sleep time

• As an observational study, it cannot be 100% confirmed that sleep causes increased activityn-tv.de+1

Nevertheless,the scale of "over 70,000 people, daily, objectively measured"is powerful, and at the very least, it convincingly demonstrates the reality that the strategy of "neglecting sleep and only focusing on exercise" is likely to fail.Nature+1

9. Practical Ideas for "Prioritizing Sleep