No. 5 [Elite Reaction Time]

On September 8, 2025, Carlos Alcaraz defeated Jannik Sinner in four sets to win his second U.S. Open, earning his sixth Grand Slam championship and returning to the top of the ATP rankings.

Tennis demands complete athletic versatility, and at the highest level, lightning-fast reaction time becomes one of the most critical skills for success.

Today, we examine the neurophysiological processes that support the complex process of reaction time.

The Physiology in Action

Reaction time reflects how efficiently the nervous system converts sensory input into motor output. This process draws on dynamic interactions across multiple brain regions, neurotransmitter systems, and physiological states.

Neural Circuits and Brain Areas

Reaction time tasks activate a distributed network that includes multiple areas of the brain, including the primary motor and premotor cortices, supplementary motor area, basal ganglia, cerebellum, and sensory cortices. Sensory signals are rapidly processed and forwarded to motor planning regions, where appropriate responses are selected and executed. The basal ganglia play a central role in sequence learning and decision-making, while the cerebellum refines timing and coordination, particularly for adaptive or sequential tasks.

Neurophysiological Stages

The transition from stimulus to response unfolds in several steps:

Detection and Processing: Sensory cortices (visual, somatosensory) register incoming stimuli. 

Motor Preparation and Execution: In the brain, the motor cortex, premotor cortex, and supplementary motor area coordinate to plan and initiate movement. Greater corticospinal excitability correlates with quicker responses.

Excitation–Inhibition Balance: GABA-mediated inhibition fine-tunes motor cortical excitability, preventing premature actions. Elevated GABA levels can paradoxically support faster responses by enhancing control and precision.

Oscillatory Activity and Variability

Brain activity can be measured through a variety of wave frequencies (for example, alpha, beta, and delta frequencies). These waves have a rhythm, and these rhythms in the alpha, beta, and delta bands shape reaction time by regulating cortical excitability and synchronizing neural ensembles. The phase and amplitude of oscillations before stimulus onset predict trial-to-trial differences, with specific phases favoring faster responses.

The Vitality Plan 

Great achievement doesn’t happen by chance. Finding ways to support the physiology required to realize these feats is paramount. 

Lifestyle: Sleep. Strive to get 8 to 10 hours of sleep for optimal recovery and adaptation. Sleep has been shown to support reaction time. (source)

Supplement: L-theanine. Supplement with at least 200 mg of theanine 1 hour prior to activity. Theanine supports attention and reaction time. (source)

Nutrition: Consume fatty fish. Eat at least two servings of fatty fish a week. Omega-3 fatty acids found in fatty fish, especially DHA, support reaction time. (source)

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