If you've ever dragged yourself out of bed for a morning run or gym session only to find it feels unusually difficult, you are not alone. A recent report explains the compelling scientific reasons behind this common phenomenon, confirming that morning exercise often feels more challenging for a host of biological reasons.
The Body's Internal Clock and Peak Performance
The primary culprit is your body's natural circadian rhythm. This internal clock governs numerous physiological processes over a 24-hour cycle, including those critical for physical exertion. Most people hit their peak for strength and endurance much later in the day, typically between 4 pm and 7 pm. During these afternoon and early evening hours, your body is primed for action.
In contrast, the early morning presents a less-than-ideal physiological landscape for a tough workout. One key factor is your core body temperature, which is at its lowest shortly after you wake up. A warmer core temperature, which you naturally have later in the day, improves muscle flexibility, increases nerve conduction speed, and enhances overall metabolic function, making exercise feel easier and more efficient.
Key Factors Making Morning Workouts Tough
Several specific bodily states contribute to the morning struggle. Alongside a lower core body temperature, you also contend with higher insulin levels in the morning. This can affect how your body manages blood sugar, potentially leaving you with less readily available energy for your muscles.
Furthermore, the signalling from your nervous system to your muscles is less efficient in the morning. This means the commands from your brain to contract and move your muscles are not as sharp or rapid as they are later on, resulting in a perceived lack of power and coordination.
Your individual sleep pattern, or chronotype, also plays a significant role. If you are a 'night owl', your body's natural peak performance window is shifted even later, making a 7 am spin class feel particularly gruelling compared to an early bird.
Adaptation and the Bigger Picture for Health
The good news is that the human body is remarkably adaptable. While you may never match your afternoon personal best in the morning, you can train your body to perform better at earlier hours over several weeks of consistent routine.
Perhaps the most important takeaway is that the fundamental health and fitness benefits of exercise are not diminished by the time of day you choose to do it. Whether you sweat at dawn or dusk, you are still boosting your cardiovascular health, building strength, and improving your mental wellbeing. The consistency of your routine matters far more than the clock.
The original analysis, reported by Hunter Bennett on Friday 07 November 2025, provides a scientific backbone to a feeling known by many dedicated fitness enthusiasts across the UK.
