For building muscle and lifting heavier weight, the afternoon and early evening tend to outperform the morning in controlled studies.
A narrative review of circadian regulation in sport, published in 2025 in MDPI's Clocks & Sleep, points to three biological reasons: core body temperature, hormonal patterns and neuromuscular readiness all peak in the late afternoon.
The pattern is not new to researchers, but the mechanism is becoming clearer.
The 2025 review synthesizes work showing that peak performance on many sport indicators lands close to the daily peak in core body temperature, which for most people arrives in the late afternoon.
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What changes between morning and evening
Warmer muscle contracts faster and stretches further.
A 2025 editorial in Frontiers in Sports and Active Living notes that body temperature reaches its peak in the late afternoon and correlates with maximum performance in strength and power sports.
The hormonal balance shifts too. In a 2016 study published in PLoS ONE, researchers tracked resistance-trained men through matched morning and evening sessions.
Cortisol, a catabolic stress hormone, was about 43 percent lower before exercise and 41 percent lower after exercise in the evening compared with the morning. The evening sessions also produced a larger rise in IGFBP-3, a marker linked to muscle protein signaling.
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The authors concluded that evening resistance training appears to augment some markers of hypertrophic potential.
Nerve signaling follows a similar rhythm. Nerve conduction velocity and muscle elasticity both rise as the day progresses, which helps explain why baseline strength scores tend to be higher in the evening than in the morning.
What long-term training studies actually show
Acute markers are one thing. What happens across months of training is another. A 24-week trial of 42 young men, published in Applied Physiology, Nutrition, and Metabolism, compared combined strength and endurance sessions performed either between 6:30 and 10:00 a.m. or between 4:30 and 8:30 p.m.
The evening groups showed a somewhat larger increase in the cross-sectional area of the vastus lateralis, one of the main quadriceps muscles.
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A broader picture comes from a systematic review and meta-analysis of eleven studies published in Chronobiology International in 2019.
Across the pooled data, muscle size increases were similar regardless of when people trained, though baseline strength was consistently greater in the evening.
In other words, the biology tilts toward the afternoon, but the effect on long-term muscle growth is modest and not seen in every study.
The habit effect is real
There is one caveat that changes how any of this should be applied. Athletes tend to perform best at the time of day they habitually train.
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The body adapts to the schedule it is given, and consistent morning trainees narrow the gap over weeks and months.
The 2025 Clocks & Sleep review argues for personalized scheduling based on individual chronotype rather than a one-size hour, and the 2019 meta-analysis reached a similar practical conclusion: the time of day for strength and hypertrophy training should be based on personal preference.
What to do with this
If your schedule is flexible and your goal is maximum strength, shifting training to somewhere between mid-afternoon and early evening is a reasonable experiment.
If mornings are the only slot that fits your life, the research is clear that consistent training at any hour still delivers most of the benefit. What matters most is doing it, and doing it on a schedule the body can lock onto.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.