Circadian rhythm
Sleep Hormone Performance
Circadian rhythm is your internal 24-hour clock. It shapes when you get sleepy, when you feel awake, how melatonin and cortisol behave, when you get hungry and when your body can perform at its best. For hardgainers that means: fragmented sleep times and constant jet lag eat your progress, a stable rhythm works like a quiet performance booster in the background.
Note
Term and system context
Short definition “Circadian” means “about a day” (Latin circa = about, dies = day). Your body runs a whole set of rhythms that roughly repeat every 24 hours:
- Sleep–wake cycle: When you usually get sleepy and wake up.
- Hormone curves: for example cortisol high in the morning, melatonin rising in the evening.
- Body temperature: Nadir during the night, rising during the day, often peaking in late afternoon.
- Metabolism and digestion: Insulin sensitivity, digestive readiness and appetite fluctuate across the day.
The master clock sits in the suprachiasmatic nucleus (SCN) in the hypothalamus. It responds mainly to light signals through the eyes, but also to social cues (getting up, work, training) and meal timing.
For hardgainers the circadian rhythm is a framework for sleep, eating and training:
- Stable rhythm → better sleep quality, more MPS, better mood and training performance.
- Chaotic rhythm → foggy head, fluctuating appetite, worse recovery, more “I feel weird” sessions.
Typical day curve – your internal clock at a glance
The exact curve is individual and depends on your chronotype (lark vs night owl), but rough patterns are similar for most people.
| Time window | Typical state | Practice for hardgainers |
|---|---|---|
| Early morning (approx. 06:00–09:00) |
Cortisol peak, waking up, body temp rising | Get light into your eyes (daylight), light movement, first water; avoid heavy doomscrolling. |
| Late morning (approx. 09:00–12:00) |
High alertness, focus often strong | Deep work, studying or job tasks – optionally a small meal that does not knock you into a food coma. |
| Afternoon (approx. 14:00–18:00) |
Body temp high, nervous system alert | For many an ideal window for strength training: good performance, lower injury risk. |
| Late evening (approx. 20:00–23:00) |
Melatonin rises (if light is low), body temp drops | Dim the lights, reduce screentime, avoid a huge meal right before bed. |
| Night | Recovery, growth hormone pulses, MPS phases | Minimise disturbances (light, noise), keep the bedroom cool, prioritise sleeping through. |
Important: This is a model, not a religion. You do not have to train at 4 p.m. to grow. But: consistent rhythm beats chaos. If you sleep, eat and train at roughly the same times, your body learns to bring performance to those slots.
Guardrails for hardgainers – sleep, light and meals
- Relatively fixed bedtime: Aim for ±1 hour around your standard time – including weekends. Example: Going to bed between 22:30 and 23:30 instead of Mon 22:00, Fri 03:00, Sun 01:00.
- Use light properly: Morning: get daylight into your eyes as early as possible (window/daylight lamp). Evening: reduce bright artificial light and cold screen light, use night-shift modes if needed.
- Caffeine cutoff: No caffeine 6–8 hours before sleep – especially if you are sensitive. That late pre-workout can hurt your sleep more than the extra reps help.
- Regular meals: Distribute your calories for TDEE and lean bulk roughly across 2–4 main meals per day – plus training near a carb-containing meal.
- Train in your high: If possible, train in a window where you feel awake and strong (for many between 15:00 and 19:00). If not, the rule is: consistent training time > perfect training time.
- Clean up your sleep environment: Dark, cool, quiet, no Netflix home office in bed. The bed is for sleep (and sex), not for endless scrolling.
Practice – 7-day reset of your circadian rhythm
-
Day 1 – status check:
Log for 3–5 days:
- Bedtime, wake-up time (including snooze marathons).
- Caffeine times, training times, last bigger meal.
- Subjective sleepiness (for example 1–5 scale) and training performance.
-
Day 2–3 – set anchor points:
Decide on three things:
- Fixed wake-up window (for example 06:30–07:00).
- Fixed bedtime (for example 22:30–23:00).
- Roughly fixed training time (for example 17:00–19:00, 3–5x/week).
-
Day 3–7 – implement hygiene:
- Get light in the morning (window, short walk outside, lamp if needed).
- Last big meal about 2–3 hours before sleep.
- Respect your caffeine cutoff; no “just this one energy drink” at 20:00.
- Evening 30–60 minutes “wind-down” without heavy social media or big arguments.
-
Week 2 – fine-tuning:
- If you are not sleepy at night: Increase stimuli earlier in the day (movement, light) and lower stimulation in the evening. Do not keep shifting bedtime later.
- If you feel like a zombie in the morning: Remove early phone use in bed, stop constantly shifting your wake-up time and slightly increase total sleep duration instead.
- If training always feels “sluggish”: Shift training time 1–2 hours earlier or later and observe whether performance and drive improve.
“5–6 hours of sleep are enough for muscle growth.”
Short sleep can feel “fine” in everyday life, but your body pays for it in the background: shortened deep sleep phases, disrupted circadian rhythms and a less stable interplay of cortisol, testosterone, growth hormone (GH) and insulin.
For hardgainers this means: lower training performance, poorer nutrient partitioning and worse adaptation to training stimuli – even if the training looks good “on paper”. Circadian rhythm is the frame in which sleep duration and quality can actually work. Target range for most people: 7–9 hours per night, as consistent as possible in timing and routine.
Studies and evidence (PubMed)
If you want to dig deeper into research on circadian rhythm, sleep and metabolism, these are solid starting points:
- A Narrative Review of the Impact of Sleep on Athletes: Sleep Restriction Causes and Consequences, Monitoring, and Interventions (Hatia et al., 2024) – overview of sleep quality, sleep restriction and performance in athletes (including effects on physical and cognitive performance).
- Sleep Disturbances and Metabolic Syndrome in Shift Health Care Workers: A Systematic Review (Cairns et al., 2025) – systematic review on sleep disturbances, shift work, circadian disruption and metabolic syndrome / cardiometabolic risk.
- Time-of-day-specific strength training effects in male adolescents (Souissi et al., 2002) – classic paper on time-of-day effects in strength training: training time, circadian rhythm and strength/performance parameters.
Note: These articles are primarily written for a specialist audience and are methodologically demanding. They do not replace individual sleep diagnostics, but help to better understand the role of a stable circadian rhythm for health, metabolism and performance.