Caffeine improved the peak force of maximum voluntary contraction (the maximum force a muscle voluntarily produces in a single static contraction) to levels observed by others in the evening.
It also had positive effects on some aspects of bench press, back squat and recall performance. However, caffeine did not affect mood, tiredness, or other cognitive performance measures.
“The current findings provide important recommendations and interventions for athletes who have high training/competition demands,” wrote researchers from the UK, France, and India. “Based on our results, the effectiveness of acute (1–1.5 h) CAFF [caffeine] supplementation in a healthy population who are not high habitual users of CAFF is strong.”
How the time of day affects training
Athletes often train or compete in the morning, when muscle strength and power have been shown to be lower than in the early afternoon or evening.
Skeletal muscle tissue has an internal circadian clock that coordinates timed gene expression in the muscle, affecting key muscle processes such as hypertrophy, metabolism, and repair. Studies show that muscle strength peaks between 4 p.m. and 8 p.m., for example, with a 5 to 6% increase in grip strength and a 4 to 13% increase in knee strength.
Cognitive performance is another key aspect of athletes’ success and can vary by time of day. Previous research has demonstrated that mood, fatigue and motivation may be poorer in the morning than in the evening.
With these effects in mind, the researchers assessed how caffeine, an extensively researched ergogenic aid, affects morning strength and power output, as well as cognitive performance.
Study details
Researchers randomly assigned 14 recreationally active males aged 18 to 30 who did not regularly consume more than 150 mg of caffeine per day to three groups: caffeine (300 mg or 2.8–4.3 mg/kg body weight), a placebo or a no-pill control group.
A week before the study, the participants completed one maximum repetition (1RM) for bench press and back squat, two familiarization sessions of cognitive and strength performance tests, and a 7-day food diary.
On the day of the study, the participants arrived at 7 a.m. in a fasted state and took their assigned intervention as a pill 1 hour before taking their tests. They completed the same tests above again and performed maximum voluntary contraction on an isometric chair (MVC) without and with stimulation.
MuscleLab linear encoders were used to record power, velocity, and acceleration, and the participants were questioned about the rate of perceived exertion and effort.
The findings revealed that the caffeine group showed better results on MVC peak force, average velocity, and mean propulsive velocity in the bench and back squat, as well as on muscle activation and auditory recall, compared with the control and/or placebo group.
“Early morning ingestion of caffeine improved MVC to levels observed by others in the evening, as well as some aspects of bench press, back squat and recall performance,” the researchers concluded, noting that the results may give “some evidence that caffeine may offset the diurnal variation in this measure.”
They also noted that caffeine had “had no effect on core temperature, mood, tiredness, alertness or other measures of cognitive performance.”
The researchers called for further studies in male and female populations who consume varying amounts of caffeine habitually to measure its effects on cognitive and strength measures.
Source: Nutrients; doi: 10.3390/nu18060954; “Effects of Caffeine Ingestion on Morning Cognitive and Muscle Strength Measures in Males: A Standardized Approach.”Authors: J.P.S. Agulhari et al.
