Energy envelope maintenance among patients with myalgic encephalomyelitis and chronic fatigue syndrome (2017) O'connor et al.

For me, it doesn't make any difference how good or bad I'm feeling, or how long I've been resting-my 'energy envelop' has remained the same for the last 16 years.

If I go over, I'm cooked.

 

Whilst travelling on the M25 over the Christmas break, and the inevitable variable speed limits, it occurred to me that these speed limits are analogous to pacing. If you just leave traffic flow to its own devices, and there is some partial restriction to the flow, I'm pretty sure you end up with "pressure waves" in the traffic flow, akin to gas flow. I suspect the traffic density peaks and troughs quite a distance back from the source, with the traffic speed thereby oscillating. The speed limits effect is probably to preemptively dampen out the oscillatory behaviour, so the overall pace of the traffic ends up much more even, albeit slower than drivers would otherwise be able to in the peaks. The damping effect needed varying according to prevailing conditions. Speed limits are not damping in the strictest sense, but achieve a damping effect.

If you think of traffic flow as akin to energy flow (which in a way it is anyway), and pacing as a means by which PwME preemptively even out the rate at which they consume energy before they overcook things and go into boom-and-bust mode, then I think there is a similarity.

Just a rough analogy, nothing more.

 

'Energy Envelope' is a euphemism, at best in a more literal sense it would mean ATP budget before you force not only ATP > ADP, but ADP > AMP. Where AMP is not available to recycle but dumped from the body. Glucose budget as well as another energy source. Degree of mitochondrial dysfunction could effect both budget and rate of production / recovery.

Metabolic byproducts may create a burden as the ability to clear them is impaired, lactic acid in muscles and brain, the flaring by exertion of disease processes, severity being the constellation of processes and how low the threshold of activation / exacerbation. Cytokines and other illness effects are elevated.

System defects mean 'using the machine' causes damage from use and the damage accumulates, pushing the machine past 'idle' increases the rate of damage, possibly to critical levels that permanently increase the defects and reducing 'machine' function. Running the machine sparingly and carefully will extend both serviceable lifespan and useful function. The limits are mostly known by operator experience and both known and unknown factors can vary these limits, best to operate well within known operational limits.

This is more complex than a low sluggish or limited charge battery or 'spoon' analogy.

 

The notion of an 'envelope' is well known in engineering, and no doubt plenty of other disciplines. The notion of a "performance envelope" is often used, or for aircraft/pilot a "flight envelope". The point is there can be a myriad of different parameters affecting performance, flight capability, etc. Which of these parameters are relevant may vary according to what is actually happening at the time, and then it will be particular combinations of those relevant parameters that govern the limiting effect. So in straight and level flight it might primarily be engine power and altitude; in a steep dive it might be whether the wings can actually remain attached to the fuselage; in a tight turn it may be whether the pilot remains conscious; etc.

The point is that whatever the limiting factors are at any given operating point, there will be a limit, within some multi-dimensional space (lots of parameters), and the 'envelope' gives those limits.

For PwME, their energy-uptake limits will likely be affected by various thing; the dominance of those things may well vary according to what is going on for the person at any particular moment. Although probably very complex to scientifically analyse, I suspect PwME develop a natural skill at sensing where their limits are, and/or will be looking ahead. My wife seems very skilled at this. The notion of an 'energy envelope' really is about a PwME staying within their energy-uptake limits. This also involves preemptive action, because there is delay between cause and effect; ill-advised action taken now, can push someone outside their energy envelope later, when it's too late to undo their causative action.

Edit: The 'natural skill' I refer to is pacing of course.

 

I took this to mean the individuals with higher levels of available energy were able to drive themselves deeper into a hole of PEM.

Maybe individuals with lower available energy who think they are staying within their energy envelope really aren't. Perhaps aiming to underexert is needed to avoid overexertion.

Uhh, OK, if you say so. Were you a physics major? Or chemistry (fluid dynamics)?

But it is too d***ed cold to put air in the tires so that the low tire pressure warning light will go off. The tires are just going to have to manage as best they can. (I am not driving very far or very fast.)

 

No . Just a modestly qualified engineer, with some (but not deep) understanding of control theory.