Why Most People Can't Hit Both Sleep And Exercise Goals, According To New Research

Study Reveals Only 1 In 8 People Meet Both Sleep and Activity Goals

More sleep means more energy for exercise, right? Not according to research tracking nearly 71,000 people across three years. The study reveals a surprising pattern. The relationship between sleep and next-day activity isn’t straightforward, with initial data showing peak activity after about six hours of sleep, though that shifts closer to seven hours when accounting for time awake.

Australian researchers analyzed roughly 28 million person-days of data from wearable devices worn between January 2020 and September 2023. Participants wore an under-mattress sleep sensor and a wrist tracker, giving scientists an unusually detailed look at how sleep and walking activity connect in everyday life.

Scientists from Flinders University discovered an inverted U-shaped relationship between sleep and next-day activity. In the initial analysis, people who slept six hours walked about 339 more steps the next day compared to eight-hour sleepers, while seven-hour sleepers took 237 more steps than those who slept eight hours. However, when researchers accounted for time spent awake, the peak shifted to around seven hours of sleep.

While the National Sleep Foundation recommends seven to nine hours nightly for adults, this research, published in Communications Medicine, reveals a more nuanced relationship between sleep duration and daily movement than previously understood.

Quality Beats Quantity for Next-Day Movement

Sleep efficiency (the percentage of time in bed actually sleeping) showed a clearer connection to next-day activity than duration. People with high sleep efficiency around 94% took 282 more steps the following day compared to those at 83% efficiency.

How long someone took to fall asleep mattered too. Taking 37 minutes to drift off meant 209 fewer steps the next day compared to falling asleep within 15 minutes.

Lead author Dr. Josh Fitton and colleagues from Flinders Health and Medical Research Institute used statistical models that could detect these curved relationships, which standard analyses might miss.

Most People Miss Both Sleep and Step Count Target

Only 12.9% of participants hit both the recommended sleep duration and more than 8,000 daily steps. Nearly 17% landed in a high-risk zone: less than seven hours of sleep combined with fewer than 5,000 steps daily, considered a sedentary lifestyle.

Three-quarters of participants (76.8%) failed to reach 8,000 steps per day. Almost everyone (99%) slept either under seven hours (43.2%) or seven to nine hours (55.9%). Less than 1% slept more than nine hours.

Participants were mostly male (82%), averaged 48 years old, and fell into the overweight category with a body mass index of 27.7. Daily step count averaged 5,521, below the threshold linked to better health outcomes.

Physical Activity Barely Affects Sleep

The reverse relationship was surprisingly weak. Someone walking 8,751 steps versus 3,090 steps showed virtually no difference in their sleep that night. When researchers accounted for waking hours, physical activity’s effect on sleep nearly disappeared.

This lopsided relationship suggests sleep-focused interventions might do more to boost physical activity than exercise programs do to improve sleep. Researchers controlled for age, body mass index, sex, day of the week, daylight hours, year, and location, and the core patterns remained consistent.

The Six-Hour Sweet Spot Holds Across Ages

The research examined three age groups: 19-33 years, 34-53 years, and 54+ years. Relationships between sleep and next-day activity stayed similar across ages, though older adults showed a slightly higher optimal sleep duration (around 6.5 hours) compared to middle-aged adults (5.5 hours).

Activity also varied by day and season. Saturdays saw peak movement, with roughly 400 more steps than Fridays. Fifteen-hour daylight periods correlated with about 300 additional steps compared to 10-hour days. Step counts rose about 400 daily from 2020 to 2022, probably reflecting pandemic restriction changes.

Rethinking Sleep and Activity Guidelines

The data came from the Withings Sleep Analyzer (an under-mattress sensor tracking sleep, heart rate, and breathing) and the Withings ScanWatch (a wrist-worn step counter). Each person contributed an average of 394 monitoring days, creating nearly 28 million person-days of information from 244 regions worldwide.

If only one in eight people can meet both sleep and activity targets simultaneously, current health guidelines might need adjustment. The findings don’t mean people should deliberately sleep less. Insufficient sleep increases risks for cognitive decline, mental health problems, weight gain, high blood pressure, inflammation, and early death.

The research points to practical strategies. For people struggling to balance sleep and activity, improving sleep quality rather than fixating on duration might work better. Getting to sleep faster and staying asleep once there appeared more beneficial for next-day activity than simply lying in bed longer.

Public health campaigns might get better results by addressing sleep first, since the study found stronger effects from sleep to activity than the reverse. For individuals, this could mean tackling sleep problems or improving bedtime routines before stressing about step counts.

Sleep and physical activity interact within each 24-hour cycle as connected health behaviors rather than separate ones. Future health guidelines should account for how these behaviors compete for time and influence each other across the day, rather than treating them as independent targets people should somehow achieve simultaneously.

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Disclaimer: This article is for informational purposes only and should not be considered medical advice. The study findings do not suggest that reducing sleep duration is beneficial. Inadequate sleep is associated with increased risks for cognitive decline, mental health issues, cardiovascular disease, and other health problems. Consult with a healthcare provider about sleep and physical activity recommendations appropriate for your individual circumstances.

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