Summary of "Ученые выяснили, когда лучше тренироваться"
Core message
Time of day matters for some health and performance outcomes. Midday–evening exercise (roughly 12:00–23:00) generally associates with better metabolic outcomes (lower odds of obesity and type 2 diabetes) than activity concentrated in the morning. Night‑time activity (during habitual sleep hours) is associated with worse metabolic outcomes. For athletic performance (strength, power, speed, coordination) many controlled studies show better results in the afternoon/evening than in the early morning. Chronotype and warm‑up/adaptation strongly influence these effects. Caveat: most population findings are observational associations (not proof of causation). Regular activity at any time is better than none; diet remains the main driver of weight loss.
Part A — Key study (International Journal of Obesity; German National Cohort)
Study overview
- Large population‑based German cohort; accelerometer sub‑study with ~61,000 participants aged 20–75.
- Objective measurement: thigh‑mounted accelerometer worn continuously for one week (advantage over self‑report).
- Study design: cross‑sectional (associations, not definitive causation).
- Analyses adjusted for age, sex, education, smoking, alcohol, night work, sleep duration and chronotype (mid‑sleep proxy); many subgroup and sensitivity analyses were performed.
Time windows and exposure
- Day divided into approximate windows:
- Morning: ~06:00–12:00
- Daytime: ~12:00–18:00
- Evening: ~18:00–midnight (~23:00)
- Night: after midnight (habitual sleep hours)
- For each window participants were ranked into quartiles of activity (Q1 = lowest activity; Q4 = highest).
- Main comparisons: Q4 vs Q1 within each window.
Main results (associations with obesity and type 2 diabetes)
- Obesity (Q4 vs Q1):
- Morning (high): ≈29% lower odds (OR ≈ 0.71)
- Daytime (12:00–18:00; high): ≈64% lower odds (OR ≈ 0.36) — largest effect
- Evening (18:00–~23:00; high): ≈55% lower odds (OR ≈ 0.45)
- Night (high): ≈58% higher odds (OR ≈ 1.58)
- Type 2 diabetes:
- Morning: ≈20% lower odds
- Daytime: ≈53% lower odds (largest benefit)
- Evening: ≈44% lower odds
- Night: ≈43% higher odds
- These patterns persisted after adjusting for chronotype and across subgroups; authors emphasize that the results are associative but consistent with known physiology.
Proposed mechanisms from the study and related literature
- Muscle mitochondrial and oxidative metabolism peak in the afternoon, improving glucose and fat use.
- Insulin sensitivity declines toward evening/night; afternoon/evening exercise engages insulin‑independent pathways (e.g., AMPK) to improve glycemic control.
- Physical activity is a powerful zeitgeber; activity at night can conflict with endogenous circadian rhythms and, combined with artificial light and late eating, cause circadian desynchronization → altered hormones (leptin, cortisol), higher glucose, insulin resistance.
- Night activity may therefore harm metabolism via circadian misalignment and altered hormonal/metabolic responses.
Part B — Performance, chronotype, mechanisms and practical implications
Evidence on performance timing
- Best evidence: randomized crossover studies (same individuals tested at different times).
- Strength, explosive power and short high‑intensity efforts: consistently better in afternoon/evening vs early morning. Reported effects range from small to large (some tasks show ~17–30% differences).
- Endurance: smaller but measurable improvements in afternoon/evening (e.g., faster cycling times).
- Team sports, accuracy and reaction speed: generally better later in the day.
- Chronotype effects:
- Morning types (larks) tend to perform better in the morning.
- Evening types (owls) tend to perform better later; forcing owls into early‑morning high‑intensity work can reduce performance by ~20–30%.
- Adaptation: habitual training at a given time reduces the time‑of‑day disadvantage — the body partially adapts when sessions are consistent.
Mechanisms for diurnal performance differences
- Body temperature: peaks late afternoon/evening; warmer muscles increase power (~2–5% per °C) and improve elasticity and enzyme kinetics.
- Neuromuscular/CNS activation: lower motor cortex excitability and motor unit recruitment in early morning reduce maximal force and coordination.
- Hormonal milieu: blunted catecholamine/adrenal response in the morning; melatonin residuals in owls can depress arousal; cortisol’s role is complex.
- Subjective factors: perceived exertion is higher at non‑preferred times, affecting motivation and adherence.
Practical recommendations & actionable steps
If metabolic health is your primary goal
- Prefer daytime (12:00–18:00) activity when possible; evening (18:00–~23:00) is the next best option.
- Avoid regular, intense activity during habitual sleep hours. If unavoidable (shift work), be aware of higher metabolic risk and try to mitigate circadian disruption.
If morning is your only option (or you prefer mornings)
Do it — morning exercise is much better than inactivity. To mitigate morning limitations: 1. Allow a lead‑in: wake 2–4 hours earlier when possible rather than jumping straight into high‑intensity work. 2. Use bright light on waking (natural sunlight if possible) to increase alertness and shift circadian phase. 3. Consider eating before training if it improves performance (fasting cardio does not reliably improve long‑term fat loss). 4. Perform an extended active warm‑up (12–20+ minutes of dynamic activity) to raise core and muscle temperature and prime CNS. 5. Use music, dynamic movement and short high‑intensity warm‑ups to increase catecholamines. 6. Consider passive heating (hot shower, warmer clothing) if facilities are cold. 7. Caffeine taken ~1–2 hours before exercise can provide a modest boost.
If you regularly train at the same (suboptimal) time
- Consistency helps — regular training at the same hour promotes physiological adaptation.
- Schedule key sessions or competitions at your chronotype‑preferred time if possible.
For weight loss
- Diet (caloric restriction) is the primary lever. Exercise supports energy expenditure and metabolic health but is typically secondary for pure weight loss.
For highly sedentary people or those with limited time
- Increase movement across the day: exercise “snacks,” short walks, under‑desk stepping. Daytime movement is highly beneficial and can offset long sitting periods.
For older adults or fall‑prone individuals
- Prioritize resistance/strength training to preserve muscle mass and include balance training to reduce fall risk. Coordination work alone may be insufficient.
For shift workers / jet lag
- Circadian desynchronization increases metabolic and cardiovascular risk. Try to stabilize schedules, optimize light exposure and meal timing, and keep regular activity to reduce harm.
Limitations and practical nuance
- The major population study is cross‑sectional: the findings are associations, not definitive proof of causation.
- Chronotype varies between individuals; recommendations should be personalized.
- Ceiling/marginal effect: very high daytime activity can offset lower activity at other times — if you are already highly active during the day, extra evening/morning sessions add little metabolic benefit.
- Late‑evening workouts can be glycemically beneficial relative to morning workouts, but very late workouts combined with late eating and light exposure may cause circadian misalignment and harm.
Other practical tips
- If you have an important morning event, wake earlier to allow physiological systems to mobilize.
- Keep training time consistent to promote adaptation.
- Track your own performance and perceived exertion across morning/afternoon/evening for several weeks to identify your pattern.
- Small daily changes (walking the dog, short walks, under‑desk steppers) add up and improve health outcomes.
Speakers and sources mentioned
- Irina Yakutenko — biologist and science journalist (presenter).
- International Journal of Obesity study: analysis of the German National Cohort accelerometer sub‑study (~61,000 participants; thigh accelerometers).
- German National Cohort.
- Numerous randomized crossover and interventional performance studies (time‑of‑day and chronotype effects).
- Broader circadian physiology literature (mitochondrial rhythms, insulin sensitivity, hormonal rhythms, circadian desynchronization and shift‑work harms).
Bottom line
If your goal is metabolic health (lower obesity and diabetes risk) and you can choose, favor midday/afternoon or evening activity rather than concentrating activity only in the morning; avoid habitual activity during sleep hours. If morning is the only option, do it — but use bright light, appropriate food, longer active warm‑ups and consistent timing to reduce the morning deficit. For peak performance, schedule key sessions and competitions at your chronotype‑preferred time or use warm‑up and adaptation strategies to reduce time‑of‑day differences.
Category
Educational
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