While a morning weight training workout can be an invigorating start to your day, some people prefer to pump iron in the evening. While your time restrictions and personal preference for the time of day you choose to lift weights might come into play when scheduling your workout, science actually points to the afternoon hours as the best time of day for a weightlifting session.
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The concept of circadian rhythms explain why an afternoon workout is best for the body. Circadian rhythms are like an internal body clock, controlling sleep patterns, blood pressure and even mood. Because of this, working out in the afternoon might be more productive and beneficial than earlier in the day. “The reason for that is your muscle strength is at its peak, its highest, “ explains neurologist Dr. Phyllis Dee on CNN.com. “You're going to be less likely to injure yourself. It's also a time when people are most awake and alert."
Circadian rhythms also control body temperature. Temperature peaks in the late afternoon and reaches its lowest point very early in the morning, around 4 a.m. and temperature fluctuates by as much as 1 degree Farenheit throughout the day. Research continues to find that muscle strength peaks in the afternoon and correlates to one's peak body temperature, according to Lean Bulk. A 2005 study in "Medicine & Science in Sports & Exercise" found that maximal performance is generally improved by the end of the afternoon, at the peak of the body temperature curve.
While afternoon is scientifically the best time for a weight-training session, what “afternoon” is can vary by the individual, depending on what time he wakes up in the morning. The best time may be anywhere from early afternoon to early evening, according to Lean Bulk. Understanding your circadian rhythms can help you determine your peak performance time. You can do this by recording your body temperature every two hours for about a week. When it’s at its highest is when you should schedule your workout.
A 2000 study in the "American Journal of Physiology" showed that a women's circadian rhythm does slightly change as hormones fluctuate throughout their monthly cycles, so the best time for a woman’s aerobic workout may be different than for a man. However, a 1991 study in the "Canadian Journal of Sport Sciences" found that women still experience the same increased anaerobic performance in the afternoon as men, so mid-day weight-lifting workouts are also best for women.