Many physiological problems are described in terms of deficiency: too little oxygen, too few nutrients, insufficient ATP, impaired mitochondrial function.
But while working across nutrition, environmental stress, metabolic dysfunction and recovery, I kept encountering a different problem.
Sometimes the resources appeared to be there, yet the biological system behaved as if they were not fully available.
That observation eventually led us to ask a deceptively simple question:
What if the problem is not always a lack of energy, but difficulty moving energy through the system at the rate required?
That question became the starting point for our Perspective, Bioenergetic Impedance: A Network Physiology Framework for Stress Adaptation, Maladaptation, and Recovery, published in Frontiers in Network Physiology.
From energy shortage to constrained throughput
The idea did not begin with a new term. It grew from trying to make sense of a recurring clinical and physiological pattern.
Under stress, organisms do not simply consume more energy. They reorganize how resources are allocated. Some processes are protected, others are suppressed, substrates are rerouted, inflammatory and neuroendocrine pathways are activated, and mitochondrial metabolism changes to accommodate the altered demand.
Many of these responses are adaptive.
The difficulty begins when the stressor persists, recovery is incomplete, or the energetic machinery cannot return efficiently toward its previous state.
At that point, simply asking whether enough glucose, fatty acids, oxygen or nutrients are present becomes insufficient. The more important question may be whether those resources can actually be transported, processed, oxidized and coordinated across tissues without accumulating bottlenecks.
This is what we came to call bioenergetic impedance: a time-dependent constraint on energetic throughput and recovery relative to demand.
The word “impedance” was chosen deliberately. It does not imply that energy has stopped moving. Rather, it describes resistance to efficient energetic flow when demand and processing capacity become mismatched.
Stress adaptation is not automatically pathology
One of the most important distinctions we wanted to preserve was the boundary between adaptation and maladaptation.
A rise in glycolysis, inflammatory signaling, lactate production, substrate rerouting or mitochondrial stress does not by itself constitute bioenergetic impedance. These can all be useful responses.
The question is whether they resolve.
An adaptive response should help the system absorb a challenge and subsequently recover. But when compensatory mechanisms must remain active, they may become increasingly costly. What initially preserved function can eventually create a new constraint.
This led us to think about stress physiology as a trajectory:
constraint → compensation → propagation → network reorganization → recovery or lock-in.
The temporal dimension became critical. The same biological response could be beneficial during an acute challenge but maladaptive when it persists after the original demand has passed.
In this sense, recovery is not simply what happens after physiology. Recovery is part of the physiology.
Why network physiology became essential
Another important step was realizing that energetic constraints cannot be understood solely at the level of a single organelle or tissue.
A local energetic disturbance does not remain local.
Cells communicate through metabolites, reactive oxygen species, cytokines, mitochondrial signals, endocrine factors and autonomic pathways. Signals originating from one tissue can alter substrate allocation, vascular regulation, immune activity and metabolic priorities elsewhere.
The organism therefore responds to local energetic pressure by reorganizing the wider network.
This is where the network physiology perspective became especially useful.
Instead of asking whether a particular pathway is “up” or “down,” we can ask how a local constraint changes coordination between systems.
Does compensation in one tissue shift energetic burden elsewhere?
Does an unresolved mitochondrial constraint alter immune activity?
Does chronic resource redistribution preserve short-term function at the expense of long-term reserve?
Bioenergetic impedance is therefore less a description of one molecular defect than a framework for studying how energetic constraints propagate through biological networks.
Peer review made the framework sharper
The peer-review process substantially improved the paper.
An early risk was that bioenergetic impedance could become too broad—that almost any sign of metabolic dysfunction might be interpreted as evidence of impedance.
The reviewers pushed us to establish clearer boundaries.
Inflammation is not impedance. Mitochondrial dysfunction is not automatically impedance. Lactate elevation is not impedance. Metabolic rerouting is not impedance.
These findings may reflect, contribute to, or compensate for a constraint, but they cannot establish the higher-order construct on their own.
That distinction forced us to make the framework more falsifiable.
A useful test of bioenergetic impedance should require independent evidence of a mismatch between demand and energetic capacity, followed prospectively through recovery. The strongest evidence would come from trajectories showing delayed resolution, residual displacement, altered network organization or reduced tolerance to a subsequent equivalent challenge.
A standardized physiological challenge—for example exercise—illustrates the idea well. Two people may look similar at rest. After the same challenge, however, one may rapidly restore physiological variables and retain normal tolerance to a second challenge, while the other remains displaced for longer and shows diminished adaptive capacity.
The difference may lie not in baseline energy availability, but in the dynamics of energetic processing and recovery.
From exposure-related malnutrition to a broader framework
Part of the conceptual background came from our earlier work on exposure-related malnutrition, which examines how chronic environmental and physiological stress may alter nutrient transport, metabolism and resource allocation even when conventional nutrient intake appears adequate.
Bioenergetic impedance expands that idea beyond nutrition.
It asks whether apparently different conditions—metabolic disease, chronic inflammation, environmental stress, exercise intolerance and perhaps aspects of ageing—may sometimes share a more general physiological architecture: energetic demand repeatedly exceeding the system's ability to process, redistribute and recover.
This remains a hypothesis-generating framework, not a claim that one mechanism explains all chronic disease.
Its value will depend on whether it produces testable predictions that outperform simpler descriptions.
The question that now interests us most
The paper ultimately left us with a different way of thinking about resilience.
Resilience may not simply mean possessing large energetic reserves. A system can have substantial resources and still struggle if those resources cannot be mobilized and processed efficiently.
Perhaps a better question is:
How much demand can a biological network absorb, how quickly can it reorganize, and how completely can it return?
That shifts attention from static measurements toward trajectories.
The next challenge is therefore empirical: standardized perturbations, repeated measurements and longitudinal tracking of recovery.
If bioenergetic impedance proves useful, its contribution may be less about adding another biomarker and more about changing what we measure.
Instead of asking only how much energy is available, we may also need to ask how well energy can flow—and whether the system can recover after being challenged.