Acute pre-exercise oral intake of cacao polyphenols attenuates central fatigue development during sustained low-intensity ankle dorsiflexion exercise in healthy young male adults.
Morikawa I, Ono A, et al. • Physiological reports • 2026
Acute cacao polyphenol ingestion attenuates the decline in central motor drive and autonomic stress responses following strenuous exercise, without altering performance or peripheral recovery, supporting its potential as a nutritional strategy for modulating central fatigue.
Key Findings
Results
Voluntary activation percentage (VA%) was significantly higher in the cacao polyphenol condition compared to placebo immediately after the task and 1 minute post-task.
Study design: double-blind, randomized, crossover study in 19 healthy young male adults
VA% showed a significant condition × time interaction (p = 0.027)
VA% significantly decreased from before to immediately after the task and 1 min post-task in both conditions (p ≤ 0.002)
CP condition had significantly higher VA% values than placebo immediately after and 1 min post-task (p ≤ 0.037)
VA% reflects central motor drive, indicating that CP attenuated central fatigue development
Results
Salivary chromogranin A increased significantly after exercise in the placebo condition but not in the cacao polyphenol condition.
Chromogranin A showed a significant condition × time interaction (p = 0.039)
In the placebo condition, chromogranin A significantly increased from baseline to 1 min post-task (p < 0.001)
In the CP condition, chromogranin A did not significantly increase from baseline to 1 min post-task (p = 0.083)
Chromogranin A is a marker of autonomic/sympathoadrenal stress response
Measurements were taken at baseline and 1 min post-task
Results
Cacao polyphenol ingestion did not significantly affect exercise task failure time, MVIC torque, doublet torque, or electromyographic activity.
Participants performed sustained isometric ankle dorsiflexion at 25% of maximal voluntary isometric contraction (MVIC) torque until task failure
MVIC torque and doublet torque did not show significant condition × time interactions
Electromyographic activity did not differ significantly between conditions
These findings indicate CP did not alter exercise performance or peripheral neuromuscular recovery
Assessments were made before, immediately after, and during recovery at 1 and 5 min post-task
Results
Only VA% and chromogranin A showed significant condition × time interactions among all neuromuscular and physiological measures assessed.
Condition × time interactions were significant for VA% (p = 0.027) and chromogranin A (p = 0.039)
Salivary α-amylase was also measured but did not show a significant condition × time interaction
MVIC torque, doublet torque, and EMG activity did not show significant condition × time interactions
This pattern of selective effects supports central rather than peripheral mechanisms of CP action
Conclusions
The study concluded that acute cacao polyphenol ingestion attenuates central fatigue without modifying peripheral fatigue or exercise performance.
Acute CP ingestion was administered orally prior to exercise in a single-dose paradigm
The exercise task was sustained low-intensity ankle dorsiflexion (25% MVIC) until task failure
Central fatigue was operationally defined via VA%, which reflects voluntary neural drive to the muscle
Authors suggest CP may serve as 'a nutritional strategy for modulating central fatigue'
Peripheral fatigue indicators (doublet torque) were unaffected, supporting a central-specific mechanism
What This Means
This research suggests that consuming cacao polyphenols — natural compounds found in cocoa — before exercise can help preserve the brain's ability to drive muscles during prolonged effort. In this study, 19 healthy young men performed a sustained low-intensity ankle exercise until they could no longer continue, on two separate occasions: once after taking a cacao polyphenol supplement and once after taking a placebo. The researchers measured how well the nervous system was activating the muscles (called voluntary activation), along with markers of physical fatigue and stress in saliva. After exercise, those who had taken the cacao polyphenol supplement showed better preservation of the brain-to-muscle signal — a measure called voluntary activation — compared to those who took the placebo, suggesting less 'central fatigue' (fatigue originating in the brain and nervous system rather than the muscles themselves).
The study also found that a stress marker in saliva called chromogranin A — which reflects activation of the body's stress response system — rose significantly after exercise in the placebo group but not in the cacao polyphenol group. However, the supplement did not change how long participants could exercise, how much force their muscles could produce, or direct measures of muscle fatigue. This means the cacao polyphenols appeared to specifically influence the brain and nervous system aspects of fatigue, not the physical condition of the muscles themselves.
This research suggests that a single dose of cacao polyphenols taken before exercise may help reduce the mental and neurological component of fatigue and blunt the body's stress response to demanding physical activity. While these findings are preliminary and based on a small, specific population (healthy young men), they add to growing evidence that dietary compounds in cocoa may have meaningful effects on how the nervous system responds to exercise stress.
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Morikawa I, Ono A, Osada Y, Fujii Y, Natsume M, Osakabe N, et al.. (2026). Acute pre-exercise oral intake of cacao polyphenols attenuates central fatigue development during sustained low-intensity ankle dorsiflexion exercise in healthy young male adults.. Physiological reports. https://doi.org/10.14814/phy2.71095