Chronobiology is the scientific discipline that studies the rhythms and “internal clocks” of the human body (body-clocks), this is, our temporal organization as the alterations and mechanisms regulating it. These rhythms and clocks are sleep-wake cycles, mood and performance states.
Sports chronobiology is the area that investigates the moments of the day where we get our best performance. For example, some of us have a better performance in the morning than the afternoon, since our physiological and psychological functions fluctuate in relation to the different moments of the day. These variations also affect sports performance interfering in motor executions.
According to Reilly & Waterhouse (2009), the factors influencing sports performance would be:
- External factors: such as temperature, physical or psychological stimulation of the environment.
- Internal factors (physiological): as biological rhythm, lifestyle factors (psycho-biological) such as the preference of activities timetable, sleep patterns, and sleep inertia.
During the day there are normally two periods where our functional skiing capacity increases, which are from around 10 a.m. and 1 p.m., and from 3 p.m. to 5 p.m. Performance partially deteriorates after lunch even without having digested food. Cappaert (1999) proposes that peak performance is reached in the afternoon, coinciding with our body temperature apex.
Some authors mention that in sports with fine motricity and greater control as skiing, performance is better in the morning because of our lower arousal. Others emphasize that during mornings, short-term memory has greater reach and is consistent with the period of higher alert.
Also, several studies agree that it is during the afternoon when our performance reaches its peak along with body temperature. The significance of our body temperature follows the idea that the best results are obtained by an appropriate warm-up before skiing. In general, performance is lower in the first hours of the day and the last of the afternoon. I observed that most skiers experience a better mental and physical state in the morning until performance slowly decreases.
It has been investigated how circadian rhythm influences our physical performance due to hormonal changes and body temperature. Our functioning parameters such as body temperature, hormone concentration, blood pressure, and muscle strength are not constant throughout the day since they vary according to cycles that recur every day. The variable aspects are movement amplitude, muscle power, cardio-respiratory resistance, and muscular endurance. This has been proven because sports world records are normally reached in the afternoon, a time that coincides with the highest point of body temperature.
The alert state is an attentional control attitude that includes, among other aspects, selective attention, vigilance, and observation. The opposite is the fatigue state referring to the loss of desire and/or ability to continue with the activities.
Although these are generalizations, paying attention to our personal fluctuations in energy and alertness during different day times helps us to recognize and to adjust our performance patterns, optimizing skiing time.
Synchrony Effect
According to May & Hasher (1998), there would be a performance benefit by coordinating activities with the optimal daytime. These authors refer to the synchrony effect where our performance is optimal when activities coincide with peak stimulation periods of our own circadian rhythm.
According to this approach, optimal and non-optimal moments exist in daily skiing activities. During optimal moments, we tend to use more difficult decision patterns including analysis and evaluations. In non-optimal moments we are likely to have less control over our attentional process, the ability to ignore distractions and assess appropriate responses is reduced, there is a tendency to have difficulty in remembering and using simple and more accessible decision patterns.
Neuroscientific Framework Matrix for Skier’s Chronobiology
| Chrono-biology Concept | Neural Structure & Circuitry | Physiological / Endocrine Mechanism | Cognitive Control & Attentional Profile | Decision-Making Pattern | Bio-mechanical / Skiing Outcome |
| Circadian Performance Fluctuation | • Supra-chiasmatic Nucleus (SCN) • Hypothalamic-Pituitary Axis | Regulates the 24-hour rhythmic oscillation of core body temperature, blood pressure, and hormone secretion curves. | Cyclic modulation of wakefulness, altering mental energy and physical state across distinct diurnal periods. | Shifts from analytical processing to heuristic shortcuts based on internal clock alignment. | Inconsistent technical execution and variable motor capacity across different times of the day. |
| The Synchrony Effect | • Locus Coeruleus-Nore-pinephrine System • Frontoparietal Attention Network | Coordinates physical tasks with peak endogenous stimulation periods of the personal circadian pacemaker. | Maximal selective attention, heightened vigilance, and acute environmental observation. | Employs high-utility, complex decision patterns including deep structural analysis and alternative evaluations. | Optimal performance, smooth technical precision, and maximized environmental synchro-nization. |
| Non-Optimal Circadian Phase | • Thalamo-cortical Loops • Prefrontal Cortex (PFC) | Phase mismatch or trough in the circadian alertness cycle, leading to reduced neural firing rates. | Loss of top-down attentional control and decreased ability to ignore environmental distractions. | Relies on simple, highly accessible decision templates; impaired hazard and response assessment. | Sluggish, defensive skiing with high vulnerability to distraction-induced technical errors. |
| Post-Prandial Dip | • Para-sympathetic Nervous System • Ventromedial Hypothalamus | Endogenous circadian drop in metabolic activation and core temp trajectory, independent of active digestion. | Transient drop in cognitive arousal, localized mental fog, and a perceived loss of physical desire. | Reduced cognitive flexibility; slower evaluation of terrain hazards or line adjustments. | Temporary degradation of skiing capacity, slow reaction times, and poor coordination after midday. |
| Thermal Apex Performance | • Preoptic Area of the Hypothalamus | Reaches peak core body temperature in the late afternoon, mimicking the physiological effects of an aggressive warm-up. | High physiological arousal, accelerated neuromuscular signaling, and optimal alertness. | Highly proactive and aggressive line selection backed by rapid processing speeds. | Maximized movement amplitude, peak muscle power, and superior cardio-respiratory/muscular endurance. |
| Morning Low-Arousal Window | • Reticular Activating System (RAS) • Hippocampal Memory Circuits | Lower baseline sympathetic arousal combined with high morning short-term memory capacity. | Focused, clear-headed vigilance; crisp visual search development with minimal mental chatter. | Efficient application of newly learned technical elements and immediate tactical planning. | Enhanced fine motor control and highly precise edge manipulation due to minimized neuromuscular noise. |
| Dawn Sleep Inertia | • Brainstem Sleep-Inducing Centers • Anterior Cingulate Cortex | Incomplete clearance of nocturnal adenosine coupled with a lagging morning cortisol awakening surge. | Cognitive clouding, spatial disorientation, and low immediate motivation. | Delayed evaluation of slope hazards; slow, passive reactions to terrain changes. | Low muscular strength, stiff/reactive joint manipulation, and elevated injury risk on early runs. |
