Human physical performance follows a circadian rhythm with peak efficiency occurring in the late afternoon or early evening, and this peak can be shifted through habitual training at non-preferred times.

Study: Differential Time-of-Day Effects of Caffeine Capsule and Mouth Rinse on Physical Performance and Volleyball-Specific Skills in Adolescent Male Volleyball Players

The study found that athletes perform best in the late afternoon, just like the claim says. It also showed that caffeine can help them perform better in the morning, suggesting that performance timing isn’t fixed and can be changed by outside factors — which supports the idea that training at different times might shift your peak too.

Study: Circadian rhythm effect on physical tennis performance in trained male players

This study found that tennis players hit harder, jump higher, and run faster in the late afternoon than in the morning — so their bodies naturally perform better later in the day. But it didn’t test whether training in the morning could move that peak time.

Study: Circadian Rhythms, Regular Exercise, and Cognitive Performance in Morning-Trained Dancers

People who usually feel sluggish in the morning but train every day at that time eventually get better at it — their body adapts. This study shows dancers who trained in the morning improved their focus and reaction time, proving you can shift your peak performance time by training regularly at a new time.

Study: Circadian Rhythm and Physical Fatigue Separately Influence Cognitive and Physical Performance in Amateur Athletes

This study found that athletes perform best physically in the evening, which matches the idea that our bodies are strongest in the late afternoon or early evening. It doesn't prove that training at other times can change this peak, but it shows the peak exists.