The dominant conversation around energy management is built on the wrong unit of measurement.

Most high performers think about energy as a quantity,  something to be accumulated through sleep, topped up with caffeine, and burned through the day. When it runs low, the instinctive response is to add more: more stimulants, more sleep pressure at the weekend, more aggressive intervention at the first sign of a crash.

This framing isn't entirely wrong and coordinates very much with the life we've become accustomed to. Sleep debt is real. Stimulant effects are real. But it misses a more fundamental variable, one that determines not just how much energy you have, but whether the energy you generate is available at the right time and in the right sequence.

That variable is circadian amplitude.

Amplitude describes the height of the wave,  not whether your circadian clock is running, but how strongly it oscillates. A clock with high amplitude produces steep, well-defined transitions: a sharp cortisol rise in the morning, a clear temperature peak in the afternoon, a pronounced melatonin onset at night. A clock with low amplitude produces a flattened, blurred version of the same signals.

You are technically functioning, but the peaks are lower, the troughs are shallower, and the transitions between states are sluggish.

Low amplitude is not the same as being misaligned. Your clock can be reasonably well-timed and still be weak. And a weak clock produces a characteristic pattern that most high performers will recognise: a slow, unresponsive morning; a flat, effortful afternoon; and a paradoxical difficulty switching off at night. Not because sleep is broken. Because the rhythm has lost its signal strength.

For many people, the energy problem is not a fuel problem. It is an amplitude problem.

The Mechanism

To understand amplitude, you need to understand how the circadian system generates its signal.

The central clock is housed in the suprachiasmatic nucleus (SCN) of the hypothalamus,  a paired structure of approximately 20,000 neurons that functions as the body's master oscillator [1]. The SCN does not simply track time. It generates a rhythmic signal that is broadcast outward to peripheral clocks in virtually every organ and tissue in the body, including the liver, muscle, adrenal gland, and prefrontal cortex.

This signal is rhythmic because it is produced by a self-sustaining molecular feedback loop. A core set of clock genes,  CLOCK, BMAL1, PER1, PER2, CRY1, CRY2, form interlocking positive and negative feedback cycles that take approximately 24 hours to complete. The transcription factors CLOCK and BMAL1 drive expression of the Period (PER) and Cryptochrome (CRY) proteins; once those proteins accumulate sufficiently, they feed back to suppress their own production, creating an oscillation [2]. This is the molecular engine of circadian time.

In the world of watches, we would be considered grand complications. 

Amplitude, in this context, refers to how robustly this oscillation is maintained.

Physiologically, high amplitude is associated with large, consistent swings in clock gene expression, tight coordination between the SCN and peripheral clocks, and strong downstream hormonal and metabolic rhythms. The cortisol awakening response (CAR), the well-characterised surge in cortisol that occurs within 30–45 minutes of waking, is one of the most operationally significant expressions of circadian amplitude.

It mobilises glucose, primes the immune system, activates arousal pathways, and sets up the neurological readiness state for the morning window [3]. A strong CAR reflects a robust circadian signal. A blunted CAR, which is documented in individuals with chronic sleep disruption, irregular schedules, and elevated allostatic load, reflects a weakened one [4].

What this looks like across a full day is most clearly understood visually. The chart below shows strong versus weak amplitude across five key biological markers across the waking day.

The core difference is compression. In the weak state, every signal is pulled towards the middle, peaks are lower, troughs are shallower, and the transitions between states become gradual rather than defined.

The most diagnostically important changes are:

Cortisol flattens most dramatically. The cortisol awakening response, that sharp surge in the first 30–45 minutes of waking, is blunted or absent. This is the signal that primes morning alertness, mobilises glucose, and activates cognitive readiness [3]. Without a strong CAR, the morning simply does not start.

Alertness never fully peaks. Rather than a clear morning window of high-quality focus, you get a prolonged, effortful ramp that plateaus below where it should be, making the afternoon decline feel catastrophic even though it is proportionally similar.

Melatonin onset is delayed and gradual. Instead of a steep, well-timed rise as light drops, the onset creeps up slowly, the biological signal to wind down is weak, which is why tired but wired is the characteristic evening state of low-amplitude individuals [5]. The system cannot cleanly switch to recovery mode.

Temperature loses its range. The robust rise and fall that drive physical readiness in the afternoon and facilitate sleep onset at night are compressed into a narrow band that barely shifts across the day [6].

Sleep pressure still builds linearly, adenosine accumulation is largely independent of circadian amplitude, but without the strong amplitude of the other signals, the system cannot efficiently cash in on that pressure at night [7]. You feel tired, but your sleep quality is poor.

The practical result is what most high performers describe as chronic functional fatigue: never really on, never really off, and requiring force to move between states.

This is not three separate problems. It is one problem, low amplitude, expressing itself at three different points across the 24-hour cycle.

Crucially, amplitude is not fixed. It is a dynamic property of the system, and it is highly sensitive to the quality and consistency of the inputs the circadian clock receives — in technical language, its zeitgebers, or time-givers.

The primary zeitgeber is light. The SCN receives direct photic input via melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs), which are maximally sensitive to short-wavelength (approximately 480nm, blue-range) light [8]. Morning light exposure activates this pathway, suppresses residual melatonin, reinforces the phase of the cortisol rise, and critically helps maintain the oscillator's amplitude by providing a strong, consistent entraining signal. When this signal is weak, delayed, or inconsistent (as it typically is in people who wake in dark environments, work indoors, or travel across time zones), the circadian system's amplitude gradually erodes.

Secondary zeitgebers include temperature, physical activity, feeding timing, and social interaction. Each of these inputs acts as a secondary cue that either reinforces or disrupts the master signal. When secondary zeitgebers are consistently mistimed,  irregular meals, sedentary behaviour, late-night feeding,  they can conflict with the photic signal and reduce the coherence of the peripheral clock network, effectively widening the gap between what different organs think the time is [9]. This internal desynchrony is associated with metabolic impairment, cognitive blunting, and mood dysregulation even in the absence of gross misalignment or significant sleep deprivation [10].

The picture that emerges is this: circadian amplitude is not a fixed trait. It is a maintained property, and it requires consistent, appropriately timed inputs to sustain it. Modern schedules,  irregular wake times, indoor environments, artificial light at night, compressed and irregular feeding — systematically erode those inputs. The result is a biology that is technically running, but not running well.

Application

Recovering and protecting circadian amplitude is a sequenced problem. It requires the right inputs at the right points across the day, morning, afternoon, and evening, because amplitude is not rebuilt in a single window. It is the cumulative product of how well each phase of the 24-hour cycle is managed.

Morning: activate cleanly

The most evidence-supported lever for initiating amplitude recovery is morning light exposure. Bright, short-wavelength light in the first 30–60 minutes after waking provides the strongest entraining signal to the SCN, reinforces the cortisol awakening response, and suppresses residual melatonin with precision timing that cascades forward through the rest of the day [11]. Outdoor light or a light therapy lamp of at least 10,000 lux for 20–30 minutes, at a consistent time each morning, is the practical standard. Timing matters more than duration.

Evidence level: well-established; light as a primary zeitgeber is robust across animal and human studies.

Wake-time consistency compounds this effect. Irregular sleep-wake timing, including the social jet lag common among high performers who sleep later on weekends, is associated with blunted cortisol rhythms, reduced subjective alertness, and measurable mood consequences, even when total sleep time is adequate [12]. Maintaining wake time consistency, including on rest days, is one of the most underutilised amplitude protection strategies.

A stimulant strategy also matters here: a measured caffeine and L-theanine combination that produces a more controlled arousal profile than caffeine alone and reduces the sharp sympathetic activation that can erode downstream recovery quality [13].

Evidence is established for caffeine timing and sleep disruption; the caffeine-theanine combination is evidence positive but emerging for amplitude-specific outcomes. 

Afternoon: sustain without spiking

The afternoon window is where amplitude erosion most visibly expresses itself in functional terms. As the chart above shows, core body temperature and alertness should still be supporting output well into the afternoon in a high-amplitude system. In the weak-amplitude state, those signals have already declined toward the middle of the range, which is why the post-lunch period feels cognitively flat, emotionally thin, and prone to poor decision-making, even when total sleep the previous night was reasonable.

The common response is another caffeine spike. This is a category error. Adding stimulation to a stability problem does not fix the stability problem; it borrows briefly from the evening recovery window, compressing the melatonin onset that amplitude restoration depends on, and makes tomorrow's afternoon slightly worse than today's. It also erodes the quality of the primary cycles of sleep 

The more precise intervention is cognitive sustainment: supporting attentional stability and working memory through non-stimulant nootropic pathways rather than escalating arousal. The cholinergic system, which governs sustained attention and information processing, does not benefit from more stimulation; it benefits from the neuroenergetic substrate that allows it to hold signal quality across a demanding afternoon [14]. This is the role the afternoon phase of any serious performance system should be performing: not pushing harder, but preserving the quality of the output window that already exists.

Evidence level: established for cholinergic mechanisms in sustained attention; afternoon stimulant escalation consequences are well-documented.

Evening: downregulate with intention

The third expression of amplitude is the one most people treat as a separate problem. Tired but wired is not a sleep disorder. It is a state-transition failure. The biological machinery of melatonin onset and parasympathetic shift is present, but when amplitude is low, those signals are insufficient to override the residual activation the nervous system is carrying from the day. Work does not stop just because the laptop closes. Cognitive load, unresolved arousal, and late caffeine all delay the transition that amplitude restoration during sleep depends on.

Evening downregulation is not about sedation. It is about creating the conditions under which the downregulation signal the body is already generating can actually land. The practical levers are the cessation of artificial blue-spectrum light exposure, the elimination of late stimulant inputs, a reduction in cognitive and emotional activation in the 60–90 minutes before sleep, and, where appropriate, nutritional support for the parasympathetic shift and melatonin-pathway function. When the evening transition is managed well, sleep architecture improves, the depth of the overnight biological repair cycle increases, and tomorrow's cortisol awakening response is stronger [15]. Amplitude is rebuilt primarily during this phase, which is why an unmanaged evening undermines every other intervention in the protocol.

Implications

Amplitude is an invisible variable. You cannot feel it directly. What you feel is its downstream effects, the quality of your morning activation, the depth of your afternoon productivity window, the ease of your sleep onset, the rate at which you recover from travel or disruption.

When the amplitude is high, those transitions feel natural. You wake ready, you focus cleanly, you recover efficiently. When the amplitude is low, the same transitions require force. The morning needs more caffeine to start. The afternoon needs more stimulation to sustain. The night needs more chemical assistance to close. This is the escalation pattern that characterises a significant proportion of high-performance individuals, not because they are undisciplined, but because the underlying biological signal has been quietly weakened by the structural demands of modern schedules.

At scale, this matters beyond individual performance. Organisations running teams with irregular schedules, significant travel loads, or high-demand time-sensitive outputs are operating on a substrate of eroded circadian amplitude without typically naming it as such. Downstream costs, reduced cognitive function, elevated mood dysregulation, reduced recovery efficiency, and increased all-cause health risk are documented across the shift work and social jet lag literature [10, 16]. They are almost entirely unmanaged, because most corporate wellness frameworks have no mechanism for addressing timing quality as a distinct variable.

The reframe is straightforward but commercially important: energy is not just a quantity problem. It is a timing and amplitude problem. And amplitude is recoverable, with the right inputs, at the right time, applied consistently.

The HMN24 System

The HMN24 product range is structured directly around this three-phase amplitude architecture.

RISE is designed for the morning activation window, supporting the cortisol awakening response with a measured caffeine and L-theanine combination, nootropic support for cholinergic function, and the neuroenergetic cofactors that make the sleep-to-wake transition cleaner and more sustained. It is not a stimulant product. It is a morning-state product, timed to work with the biology of the transition rather than override it.

FLOW addresses the afternoon stability problem. Rather than defaulting to stimulant escalation when focus declines, FLOW is formulated to support cognitive endurance and sustained attentional output through the circadian window where amplitude-eroded individuals most visibly lose performance quality. The goal is not a second peak, it is a more stable second half.

PRE-SLEEP supports the evening downregulation transition,  the phase that most performance protocols ignore entirely, and the one that determines how well amplitude is restored during sleep. By supporting the parasympathetic shift and the conditions for clean melatonin onset, PRE-SLEEP is not treating sleep as an isolated problem. It treats the evening transition as the biological foundation for the following morning's cortisol response.

Together, these three products are not a supplement stack. They are a 24-hour amplitude management protocol. Each phase sets up the next. A stronger morning creates a more stable afternoon. A managed afternoon reduces the activation load the evening has to clear. A clean evening transition rebuilds the amplitude that makes tomorrow's morning stronger.

Your rhythm can be protected. That is what HMN24 is built to do.

References

1. Reppert, S.M. and Weaver, D.R. (2002) 'Coordination of circadian timing in mammals', Nature, 418, pp. 935–941. https://doi.org/10.1038/nature00965

2. Takahashi, J.S. (2017) 'Transcriptional architecture of the mammalian circadian clock', Nature Reviews Genetics, 18(3), pp. 164–179. https://doi.org/10.1038/nrg.2016.150

3. Clow, A., Thorn, L., Evans, P. and Hucklebridge, F. (2004) 'The awakening cortisol response: methodological issues and significance', Stress, 7(1), pp. 29–37. https://doi.org/10.1080/10253890410001667205

4. Wust, S., Wolf, J., Hellhammer, D.H., Federenko, I., Schommer, N. and Kirschbaum, C. (2000) 'The cortisol awakening response — normal values and confounds', Noise & Health, 2(7), pp. 79–88.

5. Gooley, J.J., Chamberlain, K., Smith, K.A., Khalsa, S.B., Rajaratnam, S.M., Van Reen, E., Zeitzer, J.M., Czeisler, C.A. and Lockley, S.W. (2011) 'Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans', Journal of Clinical Endocrinology & Metabolism, 96(3), pp. E463–E472. https://doi.org/10.1210/jc.2010-2098

6. Okamoto-Mizuno, K. and Mizuno, K. (2012) 'Effects of thermal environment on sleep and circadian rhythm', Journal of Physiological Anthropology, 31(1), p. 14. https://doi.org/10.1186/1880-6805-31-14

7. Borbély, A.A., Daan, S., Wirz-Justice, A. and Deboer, T. (2016) 'The two-process model of sleep regulation: a reappraisal', Journal of Sleep Research, 25(2), pp. 131–143. https://doi.org/10.1111/jsr.12371

8. Berson, D.M., Dunn, F.A. and Takao, M. (2002) 'Phototransduction by retinal ganglion cells that set the circadian clock', Science, 295(5557), pp. 1070–1073. https://doi.org/10.1126/science.1067262

9. Dibner, C., Schibler, U. and Albrecht, U. (2010) 'The mammalian circadian timing system: organization and coordination of central and peripheral clocks', Annual Review of Physiology, 72, pp. 517–549. https://doi.org/10.1146/annurev-physiol-021909-135821

10. Fishbein, A.B., Knutson, K.L. and Zee, P.C. (2021) 'Circadian disruption and human health', Journal of Clinical Investigation, 131(19). https://doi.org/10.1172/JCI148286

11. Viola, A.U., James, L.M., Schlangen, L.J.M. and Dijk, D.J. (2008) 'Blue-enriched white light in the workplace improves self-reported alertness, performance and sleep quality', Scandinavian Journal of Work, Environment & Health, 34(4), pp. 297–306. https://doi.org/10.5271/sjweh.1268

12. Roenneberg, T., Allebrandt, K.V., Merrow, M. and Vetter, C. (2012) 'Social jetlag and obesity', Current Biology, 22(10), pp. 939–943. https://doi.org/10.1016/j.cub.2012.03.038

13. Haskell, C.F., Kennedy, D.O., Milne, A.L., Wesnes, K.A. and Scholey, A.B. (2008) 'The effects of L-theanine, caffeine and their combination on cognition and mood', Biological Psychology, 77(2), pp. 113–122. https://doi.org/10.1016/j.biopsycho.2007.09.008

14. Jasielski, P., Piędel, F., Piwek, M., Rocka, A., Petit, V. and Rejdak, K. (2020) 'Application of citicoline in neurological disorders: a systematic review', Nutrients, 12(10), p. 3113. https://doi.org/10.3390/nu12103113

15. Engert, V., Efanov, S., Dedovic, K., Dagher, A. and Pruessner, J. (2010) 'Cortisol awakening response and stress vulnerability', Psychopharmacology, 214(1), pp. 261–268. https://doi.org/10.1007/s00213-010-1918-4

16. Kivimäki, M., Jokela, M., Nyberg, S.T., Singh-Manoux, A., Fransson, E.I., Alfredsson, L. and Virtanen, M. (2015) 'Long working hours and risk of coronary heart disease and stroke: a systematic review and meta-analysis', The Lancet, 386(10005), pp. 1739–1746. https://doi.org/10.1016/S0140-6736(15)60295-1