Researchers from Romania, Tunisia, Turkey, and Qatar, investigated whether casein timing, either immediately post-exercise or shortly before sleep, differentially affects 24-hour recovery of anaerobic performance after high-intensity resistance exercise in trained soccer players.
The study compared the effects of sustained overnight amino acid availability versus immediate post-exercise support on explosive power, fatigue resistance, and agility to determine which timing strategy best supports recovery.
The researchers noted that results could support athletes in having the flexibility to “choose the timing of casein ingestion based on their specific performance goals, recovery needs, and daily schedules.”
Does casein protein timing matter for soccer recovery?
Casein protein can offer specific advantages for muscle recovery because it digests slowly and provides a sustained release of amino acids for up to eight hours.
After exercise, muscles become more sensitive to amino acids and insulin, creating a short window in which protein intake maximizes acute anabolic signaling.
Before sleep, protein ingestion can help counteract the prolonged overnight decline in amino acid availability and help sustain muscle protein synthesis.
In soccer players, higher protein intake has been associated with faster recovery of strength, sprinting, and jumping performance, as well as quicker normalization of oxidative stress markers.
Previous research in athletes has concluded pre-sleep casein can enhance overnight muscle protein synthesis, strength gains, reduce fatigue, and enhance performance. Post-exercise casein has been found to accelerate recovery of performance and muscle strength during congested schedules.
Pre-sleep vs post-workout casein protein intake
The researchers enrolled 24 highly trained athletes aged 18–25 years with more than three years of competitive experience to participate in the randomized controlled trial.
Participants were randomly assigned to a pre-sleep casein group, a post-exercise casein group, or a control group, and all completed pre-tests, a standardized high-intensity resistance training session, and post-tests.
The post-exercise group consumed 30 g of micellar casein shortly after training, the pre-sleep group consumed the same dose before bedtime, and the control group received no supplement. Researchers supervised supplementation and all testing occurred at the same time of day to control circadian effects.
A dietitian supervised a standardized soccer-specific diet throughout the study, while participants recorded all food intake using validated food records and portion-size references.
Researchers measured anthropometrics, countermovement jump (CMJ), agility (Illinois Agility Test), and anaerobic performance (RAST) using validated field-based instruments and protocols. Participants completed multiple trials for each test, and the researchers analyzed the best performance.
Results indicated pre-sleep casein intake produced greater improvements than control in countermovement jump (CMJ) height and repeated sprint mean power, whereas post-exercise casein intake significantly improved repeated sprint peak power, mean power, and fatigue resistance compared with control.
Although pre-sleep casein showed a trend toward faster intermittent agility test performance, this did not remain significant after correction for multiple comparisons. Direct comparisons between the two supplementation strategies revealed no significant differences.
Within-group analyses showed consistent performance declines across all measures in the control group. In contrast, both casein groups attenuated these declines, particularly for CMJ performance, which improved significantly in both intervention groups.
The researchers noted that because casein digests slowly, it provides a prolonged release of amino acids overnight, which supports muscle adaptation. On the other hand, post-exercise casein intake benefits recovery and performance, as its slow digestion and high leucine content stimulate muscle protein synthesis, help maintain muscle function, reduce fatigue, and support recovery during periods of intense training or competition.
The researchers advise that pre-sleep intake may better support explosive strength, whereas post-exercise intake may better enhance peak power and fatigue resistance.
As neither timing strategy proved superior overall, both approaches offer meaningful benefits.
“Future research should examine the long-term adaptations associated with different casein timing strategies across diverse training modalities and athletic populations, with particular emphasis on mechanisms underlying muscle protein synthesis, hormonal regulation, and recovery biomarkers,” they wrote.
Journal: Nutrients; doi: https://doi.org/10.3390/nu17243938; “Casein Supplementation Timing and Exercise Performance in Soccer Players: Pre-Sleep vs. Post-Exercise Intake—A Randomized Controlled Trial.” Authors: Bayrakdaroğlu, S. et al.
