The Circadian Rhythm 5K 10k Marathon

[George Payan]

The Circadian rhythm how does it effect runners training from waking up, warming up, to competing at 100%

The term for the built-in, approximately 24-hour rhythmic cycle that governs things like waking up, sleeping, and other biological processes is the Circadian Rhythm.

Key Rhythmic Cycles

1. Circadian Rhythm: This is the 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. The word "circadian" comes from the Latin circa (about) and dies (day).

2. Ultradian Rhythms: These cycles are shorter than 24 hours, such as the cycle of 90-minute sleep stages (REM/Non-REM) or the cycles of hormone pulses, feeding, and resting that occur throughout the day.

3. Infradian Rhythms: These cycles are longer than 24 hours, such as the human female menstrual cycle (28 days) or the seasonal cycles of weight gain/loss and mood changes.

The aspect of aging is not a periodic rhythm like the others but rather a progressive, non-cyclic process dictated by the passage of time and regulated by a separate group of genetic and cellular mechanisms.


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:

1. The Afternoon/Early Evening Peak (Optimal Performance Window)

For most people, peak physical performance occurs in the late afternoon or early evening (typically between 4:00 PM and 8:00 PM). This is when several circadian-regulated factors align to maximize running ability:

Physiological Factor, Circadian Rhythm Peak Impact on Performance

Core Body Temperature Peaks in late afternoon Crucial: Higher temperature increases muscle elasticity, joint mobility, nerve
conduction velocity, and enzyme activity, making muscles more powerful and less
prone to injury.
Hormone Levels (Cortisol/Testosterone) Testosterone: Levels often
peak in the late afternoon.
Cortisol: Tapers down
from a morning peak. 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.
Neuromuscular Function, 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. 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 in this window.

2. The Morning (The Warm-up Challenge and Endurance Advantage)

Performance is generally lowest in the early morning because core body temperature is at its lowest point.

Training Component Circadian Effect in the Morning Strategic Application

Warming Up 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. Runners must dedicate extra time to their dynamic
stretching and light jogging before hitting race
pace.
Endurance 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. Many large marathons are held in the morning to
beat the heat, and the body can be trained to
perform well at this time.
Race Simulation 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. 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.

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):

1. Optimal Time of Day (Morning vs. 2-5 PM)
Generally, there are physiological and practical trade-offs for each time slot:

Time Slot Potential Advantages Potential Disadvantages

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.

2. 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.

Training Frequency Potential Advantages Potential Disadvantages

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 Workouts 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

1. 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.

2. 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.

3. 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).