How does sleep influence your chances of exercising the next day? According to a new study (Leota et al., 2025) led by researchers at Monash University’s Sleep and Circadian Rhythms Research Program, the answer may hinge on what time you go to bed.

To explore how sleep duration and timing affect next-day physical activity, first author Josh Leota and colleagues analyzed data from two large-scale wearable sensor studies that tracked bedtimes and daily movement in more than 100,000 people. These massive datasets offered an unprecedented look at real-world sleep and exercise habits.

The researchers found a strong link between bedtime and how active people were the following day. Specifically, those who went to bed earlier were far more likely to engage in moderate-to-vigorous physical activity (MVPA) compared to night owls.

The sweet spot appeared to be a 9 p.m. bedtime: People who turned in three hours before midnight logged about 30 more minutes of MVPA per day than those who went to bed at 1 a.m. Even modest shifts mattered. For those with an average bedtime of 11 p.m., turning in just 30 minutes earlier (at 10:30 p.m.) was associated with more next-day activity.

What This Study Adds to the Sleep–Exercise Conversation

It’s well established that regular physical activity improves sleep quality and that good sleep improves athletic performance. But this study addresses a surprisingly understudied question: Does your bedtime predict how active you’ll be tomorrow? By using objective data from wearables instead of notoriously unreliable self-reports, researchers were able to tease out the distinct roles of sleep duration (how long you sleep) and timing (what time you go to bed and wake up).

It turns out both matter, but sleep timing may be more influential than previously thought. The study found that even on nights when people maintained their typical sleep duration, an earlier bedtime still led to more energy and higher levels of next-day physical activity.

“Rather than just promoting sleep and physical activity independently, health campaigns could encourage earlier bedtimes to naturally foster more active lifestyles,” Leota said in a June 2025 news release.

Why Do Earlier Bedtimes Boost Physical Activity?

This observational study found a correlation, not a definitive cause-and-effect relationship. Nevertheless, several evidence-based guesses may explain why “early birds” tend to be more active than “night owls”:

Circadian alignment: Earlier bedtimes better align your sleep-wake cycle with your internal circadian rhythm. This synchrony can leave you feeling more refreshed and energized in the morning, making it easier to lace up your sneakers for a workout.
More morning opportunity: Waking earlier gives you more uninterrupted time to fit in a workout before the demands of 9-to-5 routines take over. Early risers often use this “protected time” for unfettered exercise.
More consistent routines: Earlier bedtimes may reflect a generally more structured lifestyle, which often includes healthy daily habits, such as regular exercise and sticking to a fitness routine.
Mood and motivation: Lack of sleep is linked to irritability, low energy, and reduced motivation. People who get enough sleep tend to feel more optimistic and proactive, making the idea of a workout feel more doable and enjoyable.

Is This Just Another Argument for Becoming a Morning Person?

Not quite. The researchers were careful to point out that their goal is not to convince everyone to wake up at dawn. Instead, their findings offer a subtle, powerful way to nudge your next-day behavior in a healthier direction. Your personal chronotype—whether you’re a morning lark or a night owl—is largely determined by your genetics.

The key takeaway isn’t to change your natural chronotype, but to recognize that an earlier bedtime, relative to your baked-in sleep patterns, can significantly increase both sleep hygiene and exercise adherence. That said, the researchers also found that people who consistently got enough sleep, regardless of their bedtime, were still more active than those living with untreated insomnia or chronic sleep deprivation.

How to Use This Research in Your Daily Life

You don’t need a wearable or a strict 9 p.m. bedtime to benefit from this science. Here are three simple, actionable tips:

Reverse-engineer your bedtime. Count back 7–8 hours from when you need to wake up, and aim to start winding down about 30–60 minutes before that.
Dim the lights and screens. Blue light exposure after dark can delay melatonin production, making it harder to fall asleep early.
Rethink your morning routine. Even a brisk walk, light yoga, or 10-minute bodyweight workout can count as MVPA. The key is to build movement into your day before it slips away.

Take-Home Message

If you’ve been struggling to stick to a workout routine, the solution might not be in your gym bag—it might be in your bed. So tonight, why not conduct a simple n = 1 experiment? Hit the sack a little earlier than usual and observe the results. See if you wake up feeling more eager to move than if you’d burned the midnight oil. Your personal data may just reinforce the science.