Why does exercise increase your energy even when you already feel tired?
Exercise boosts energy because it triggers a flood of dopamine and serotonin in the brain — the neurochemicals directly associated with reward and happiness. According to Dr. Wendy Suzuki, neuroscientist at New York University, even a single 10-minute walk is enough to set off this full neurochemical response. You feel more alert and energized not despite the physical effort, but because of the chemical reward your brain delivers in response to it.
"Every single time you move your body, you are releasing literally a flood of neurochemicals in your brain. I'm not talking about run a marathon. I'm talking about even taking a walk, a 10-minute walk gets that flood of neurochemicals going."
— Wendy Suzuki, Neuroscientist, New York University · The Mel Robbins PodcastSuzuki adds a second layer to the explanation: the relationship between exercise and motivation is self-reinforcing. In study groups assigned to regular exercise, motivation to exercise actually grew over time — the more people moved, the more they wanted to move. This means the fatigue barrier people feel before exercising is real, but neurochemically temporary. The brain learns to anticipate the reward and begins to pull toward the behavior rather than resist it.
This insight was shared in a broader episode of The Mel Robbins Podcast dedicated to five science-backed tools for shifting mood quickly — each drawn from leading researchers who have appeared on the show. Suzuki's contribution focused specifically on movement as the fastest available lever for changing how your brain feels.
About Wendy Suzuki
Dr. Wendy Suzuki is a world-renowned neuroscientist and the Dean of the College of Arts and Science at New York University. Her research has centered on two major areas: the mechanisms of memory formation and the remarkable plasticity of the human brain — its capacity to change and improve in response to behavior and experience. She is particularly known for making neuroscience actionable, identifying the simple, everyday habits — including movement, attention, and social connection — that measurably improve focus, learning, memory, and overall brain performance. Beyond memory research, Suzuki has become a leading voice in the science of exercise and brain health, pioneering work that demonstrates how physical movement produces direct neurochemical changes in the brain, including the release of dopamine and serotonin. Her credibility on the specific question of why exercise energizes rather than depletes comes directly from this research: she has studied what happens at the neurochemical level when people move, and her findings consistently show that even minimal movement — a 10-minute walk — is sufficient to activate the brain's reward and mood systems.
See also
Dr. Suzuki explains that improved focus is the most commonly reported positive effect from studies of exercise on the brain. A single 10-minute walk can trigger a neurochemical response that meaningfully improves focus and attention, even in people who are not regular exercisers.
According to Dr. Wendy Suzuki, every time you move your body you release a flood of neurochemicals in your brain, including dopamine, serotonin, noradrenaline, endorphins, and growth factors — all triggered by as little as a 10-minute walk.