The term Circadian Rhythm, approximately 24-hour rhythmic cycle that governs biological processes.
Circadian Rhythm is a 24-hour cycle that regulates the sleep-wake cycle, hormone release, body temperature, and metabolism. It is primarily controlled by the suprachiasmatic nucleus (SCN), a cluster of cells in the hypothalamus of the brain, and synchronized by exposure to light and darkness.
1. The circadian rhythm significantly impacts a runner's training and race-day performance by regulating several key physiological factors throughout the 24-hour cycle.
It essentially dictates when your body is most biologically primed for certain types of effort.
Here is a breakdown of how the circadian rhythm affects a runner choosing the time to workout and compete:
For most people, peak physical performance occurs in the late afternoon or early evening (typically between 2:00 PM and 8:00 PM). This is when several circadian-regulated factors align to maximize running ability:
Physiological Factor: Core body temperature. Hormone Levels (Cortisol/Testosterone). Neuromuscular Function
Circadian Rhythm Peak: Peaks in late afternoon: Testosterone.
Cortisol: Tapers down from a morning peak. Peaks in the evening. Faster reaction time, higher jump height, and greater muscular power/strength are observed, which are critical for the explosive component of a sprint finish or hill climb. Respiratory function airway resistance is lowest, and lung function (like FEV 1) is generally highest.
Impact on Performance: Crucial: Higher temperature increases muscle elasticity, joint mobility, nerve conduction velocity, and enzyme activity, making muscles more powerful and less prone to injury. The favorable ratio (higher T, lower C) supports anabolism (muscle repair/growth) and maximal effort, while the morning spike in cortisol is useful for waking up but can impede long-term performance if elevated. Impact on Performance: Leads to more efficient oxygen exchange, making maximal aerobic effort feel slightly easier.
Application: Hard workouts, like speed work, track intervals, or high-intensity tempo runs, are often most effective and yield the best adaptations when performed.
2. The Morning
Performance is generally lowest in the early morning because core body temperature is at its lowest point.
Training Component: Warm up; Endurance; Race Simulation
Circadian Effect in the morning: More difficult: With lower core temperature and stiffer connective tissue, the warm-up needs to be longer, more thorough, and more dynamic to effectively raise muscle temperature and prevent injury. Less Affected: While strength and speed are lower, long-distance endurance performance (like marathon time-trials) is less consistently affected by circadian variation than pure strength/power is. Essential for early races: Training runs must be done at the scheduled race time (e.g., 7 AM) to phase-shift the body's clock, so the athlete is mentally and physically ready to perform at 100% when the gun goes off.
Strategic Application: Runners must dedicate extra time to their dynamic stretching and light jogging before hitting race pace. Many large marathons are held in the morning to beat the heat, and the body can be trained to perform well at this time. Consistent morning training synchronizes the body''s feeding, hydration, and muscle firing patterns to the competition time.
3. Individual Chronotype (The "Lark" vs. "Owl" Effect)
The concepts above apply to the average person, but a runner's chronotype (their natural preference for morning or evening activity) is a huge factor:
Morning Types ("Larks"): These runners naturally wake up early, are more alert in the morning, and often exhibit an earlier peak in their physiological
functions. They will likely see less performance drop-off in a morning race compared to an "Owl."
Evening Types ("Owls"): These runners naturally stay up late and perform best later in the day. They have the most to gain from pushing their training
and warm-ups later and will experience the largest performance deficit in an early morning race.
Comparing Workout and Competition Times
The choice of training or racing time depends on whether a runner prioritizes maximizing performance or fitting the run into their schedule.
Early Morning (The "Waking Up" Window)
While many runners choose this time for its convenience (cool temperatures, clear schedule), it's generally the least optimal window for peak performance.
Pros for Training: Cooler temperatures in summer, less interference with work/social life, good for establishing routine.
Cons for Performance: Lowest Core Body Temperature: Muscles are stiff and less pliable, requiring a longer, more thorough warm-up to prevent injury.
Reaction Time and Grip Strength: Lower compared to later in the day.
Oxygen Use: Slightly less efficient.
Recommendation: If training in the morning, focus on aerobic base miles or lighter workouts. Always warm up thoroughly.
Late Afternoon / Early Evening (The "Peak" Window)
This window aligns with the body's natural readiness for strenuous activity, making it the best time for speed work and competition.
Pros: for Training/Competing: Everything listed in the table above—optimal strength, power, flexibility, and lung function.
Cons: for Training: Higher air temperatures (in summer), potentially more scheduling conflicts, and for some, an intense workout too late can interfere with sleep onset.
Recommendation: Schedule your most intense workouts (interval training, tempo runs, long runs, race-specific pace work) during this window. If a race is scheduled for the morning, training in the afternoon is still beneficial, but you may want to occasionally practice race-pace efforts in the morning to adapt your body.
Key Takeaway for Runners
To truly maximize performance for a key race, a runner should aim to schedule their hardest training sessions to occur at the same time of day as the competition. This helps the body's internal clock (circadian rhythm) adjust and ensures the body is fully "primed" at the required time.
Coaching Implication: A smart training plan will consider the athlete's race time and their chronotype to strategically schedule key workouts at the time when 100% effort is required.
after waking up early in the morning running double workout, one in the morning and the other workout after lunch between 2-5 pm or working out one workout per day is it better for a runner to train and run his/her miles train in the morning or after lunch 2-5 pm. Is it better to train once or twice a day?
This is a classic runner's dilemma, and the answer isn't a simple one-size-fits-all, as it depends on your specific goals, training volume, and body's response.
Here is a breakdown of the considerations for both the timing of the run and the number of daily sessions (singles vs. doubles):
4. Optimal Time of Day (Morning vs. 2-5 PM)
Generally, there are physiological and practical trade-offs for each time slot:
Early Morning Consistency: Easier to fit in before other commitments derail your plan. Race Prep: Simulates common race start times (marathons, etc.). Fat Burning: Running fasted (if desired) can promote greater fat oxidation. Mental Boost: Establishes a positive, productive start to the day. Lower Performance: Core body temperature and muscle flexibility are lowest, which can make hard workouts feel slower/harder. Requires a thorough warm-up. Injury Risk: Muscles are "cold," potentially increasing injury risk without a proper warm-up.
Afternoon (2-5 PM) Peak Performance: Core body temperature and hormone levels (like testosterone) are often at their highest, which is scientifically
linked to peak strength, power, and endurance performance. Better for Speed/Quality: Muscles are warmed up from the day's activity, making speed work and tempo runs generally more productive. Less Consistency: Life/work commitments, fatigue, and procrastination are more likely to interfere with your run. Heat: In warmer months, this time slot can be the hottest part of the day, negatively affecting performance.
The Verdict on Time:
For speed work, threshold runs, and generally aiming for peak performance in a single session, the 2-5 PM window is often physiologically superior.
For consistency, race-day simulation, and getting the mileage done, the morning is often the most practical and beneficial time.
Best Strategy: Many high-level runners mix it up, doing key speed/quality work in the afternoon and easy/recovery runs in the morning.
5. Single vs. Double Workouts (Once vs. Twice a Day) The decision to run once or twice a day primarily revolves around total weekly volume and recovery.
Single Workout Greater Specificity: A single, longer run provides a sustained stimulus that is crucial for endurance (e.g., marathon training). Simpler: Requires less time planning, less post-run prep (showering, etc.), and less frequent fueling. Higher Impact Stress: Running all your mileage in one session can be more taxing on the musculoskeletal system, increasing injury risk at high volumes. Recovery: Takes longer to replenish glycogen stores after a long single session.
Double Workout Boosted Volume: Allows experienced runners to safely increase weekly mileage without excessively long single sessions that beat up the body. Enhanced Recovery: Shorter runs are less fatiguing, and the double stimulus can increase blood flow (aiding recovery) and provide a "double-shot" of beneficial hormones (like growth hormone). Metabolic Benefits: Trains the body to better utilize fat and manage glycogen when running in a somewhat depleted state (if the second run is well after the first).
Time Consuming: Requires more dedication to logistics (two warm-ups, two cool-downs, two showers, etc.). Beginners: runners or those with low base mileage, as the extra fatigue can lead to injury. Sacrifice Long Run: Cannot replace the long, continuous effort needed for true endurance development.
The Verdict on Frequency:
For most amateur runners building a base or training for shorter races (5k/10k) with typical mileage (e.g., 20-50 miles per week), single runs are
usually sufficient and often better for maximizing adaptation and minimizing injury risk.
For high-mileage runners (e.g., over 60 miles per week) or those needing to boost volume, doubles are a highly effective tool to accumulate more
mileage with less single-session strain.
Final Recommendation
6. If you are running a high weekly volume (e.g., 60+ miles): Incorporating doubles is likely beneficial. A common strategy is to do your easy, shorter run in the early morning and your primary workout (speed, tempo, or medium-long run) in the 2-5 PM window for optimal performance.
7. If you are running a moderate weekly volume (e.g., 20-50 miles): Stick to a single workout per day. The best time is the one you can stick to most consistently. If you are focusing on a key workout like speed, the afternoon may yield better results, but getting the run done in the morning is often the key to consistency.
8. For a long run (crucial for endurance): This should always be a single, continuous effort and is best placed on a day when you can dedicate the time (often a weekend morning).
The Circadian Rhythm 5K 10k Marathon
Moderator: George Payan