When Your Arms Give Out: What Exodus 17 and the Science of Fatigue Reveal About Training in Community in Raleigh
By Eric Johnson | CrossFit Full Armor | CrossFit Gym in Raleigh, NC
“When Moses’ hands grew tired, they took a stone and put it under him and he sat on it. Aaron and Hur held his hands up — one on one side, one on the other — so that his hands remained steady till sunset.” — Exodus 17:12
Moses was not weak. He was fatigued.
There is a difference, and Exodus 17 understands it with a precision that most people miss when they read the story. Moses was not failing because he lacked faith, character, or physical ability. He was failing because the human body has limits, and he had reached one. His arms were heavy. The stone under him was not a concession to weakness — it was wisdom. Aaron and Hur holding his hands was not charity — it was the difference between Israel winning and Israel losing.
The battle in the valley below was contingent on Moses’ arms staying raised. And Moses’ arms staying raised was contingent on the people beside him. Three men on a hill, two of them doing something the text almost passes over — and the outcome of the entire day turned on whether they showed up and held on.
Exercise science took a few thousand years to catch up. But it got there.
What Fatigue Actually Is
For most of the twentieth century, exercise scientists understood fatigue the way most people intuitively understand it — as a peripheral phenomenon. The muscles ran out of fuel, accumulated waste products, and stopped working. The body failed from the outside in. The solution was conditioning: build the aerobic engine, improve lactate threshold, train the muscles to sustain output longer before they broke down.
That model is not wrong. It is incomplete.
In the late 1990s, a South African exercise physiologist named Timothy Noakes began publishing research that fundamentally challenged the peripheral model of fatigue. His central governor theory proposed that fatigue is not primarily a muscular event — it is a neurological one. The brain, acting as a central governor, monitors the body’s physiological state continuously and imposes fatigue as a protective mechanism before the body reaches genuine physical failure. You do not stop because you cannot continue. You stop because your brain has decided that continuing is not safe.
The implication of this is significant. The ceiling you experience in a hard workout — the moment your arms want to come down, the moment you want to drop the bar, the moment the next rep feels genuinely impossible — is almost never your actual physical ceiling. It is your brain’s conservative estimate of where your ceiling is, set deliberately below the true limit to keep you safe.
You do not fail because your body gives out. You fail because your brain decides, based on incomplete information, that the risk of continuing is too high.
Noakes’ research showed that this estimate is not fixed. It is responsive. It changes based on environmental inputs, emotional state, perceived effort relative to expected effort, and critically — the presence and behavior of other people.
The Aaron and Hur Effect
In Exodus 17, Moses is not given more strength. He is given support. The stone does not change his capacity — it changes his position. Aaron and Hur do not replace him — they hold what he cannot hold alone. The outcome is not that Moses becomes superhuman. The outcome is that the limit he was about to reach is never actually reached, because external support changed what was possible.
This is a precise description of what the research on social support and performance has consistently found for the last thirty years.
A landmark study published in the Journal of Experimental Social Psychology found that people standing at the base of a hill estimated it as significantly steeper when they stood alone than when they stood next to a friend. The hill did not change. Their perception of what the hill required of them did. The central governor — the brain’s protective system — calibrated its estimate of the challenge differently based on whether support was present.
A follow-up study found that the longer the friendship, the more pronounced the effect. The brain does not simply respond to the presence of another body. It responds to the quality and depth of the relationship. People who trained alongside trusted partners consistently underestimated the difficulty of physical challenges relative to people who trained alone or alongside strangers.
This is not a motivational metaphor. It is a neurological mechanism. The presence of people you trust physically changes the signal your central governor sends — raising the threshold at which it imposes fatigue, extending the window of sustainable output, shifting the ceiling you experience before you reach your actual limit.
Aaron and Hur were not spectators. They were the reason Moses’ arms stayed up. The science has a name for what they did. It is called support — and it is biological.
Why This Is Not the Same as Motivation
It is important to be precise here because the word motivation gets used to cover too much ground. Motivation is a conscious experience — you feel inspired, you decide to try harder, you push through discomfort by choice. What Aaron and Hur provided was something different and deeper. Moses did not need to feel more motivated. He needed his arms held up. The support was physical, continuous, and unconditional. It did not require Moses to access a new level of willpower. It simply changed the physical reality of what he was being asked to sustain.
The research distinguishes these two things carefully. Motivational interventions — encouragement, coaching cues, positive reinforcement — produce real but modest performance improvements, typically in the range of 5 to 15 percent above baseline. Physical co-regulation — sustained presence, synchronized effort, the kind of support that does not require the struggling person to do anything additional — produces effects that are harder to quantify but consistently larger in magnitude and longer in duration.
The difference is the difference between someone on the sideline shouting encouragement and someone beside you on the rower pulling at the same pace. Both are valuable. Only one changes your physiology in real time.
What Happens When No One Shows Up
The other half of the Exodus 17 story is equally important and almost never discussed.
If Aaron and Hur had not been on that hill — if Moses had faced the battle alone — his arms would have come down. The text is not ambiguous. His hands were already heavy. He was already sitting on a stone. Without the people beside him, Israel loses.
Exercise science has documented the inverse of the support effect with equal consistency. Isolation during physical challenge does not simply return performance to baseline. It actively depresses it. Athletes training alone report higher perceived exertion for identical objective workloads compared to athletes training in the presence of others. The central governor, receiving no input that suggests external resources are available, becomes more conservative. The ceiling drops. The wall arrives earlier.
This is why the first week back after a training partner moves away, a gym closes, or a community dissolves feels harder than the workouts actually are. The weights did not get heavier. The runs did not get longer. The support structure that was silently holding your ceiling up is gone — and your brain, without that input, recalibrates downward.
You do not notice Aaron and Hur when they are there. You notice them immediately when they are not.
The Stone Under Moses
There is one detail in Exodus 17:12 that deserves its own attention. Before Aaron and Hur held Moses’ hands, they found a stone and put it under him so he could sit.
This is not a small thing. Moses had been standing. Holding his arms raised while standing requires the entire postural chain — legs, core, shoulders, the full load of the body bearing down on the working muscles. The stone changed the mechanical demand. By sitting, Moses reduced the postural load, freed the energy that had been going into simply staying upright, and made the remaining task — arms up — sustainable for hours rather than minutes.
In exercise science this is called load management. The principle is that performance over a long duration is not maximized by pushing hardest at every moment. It is maximized by making intelligent adjustments that preserve capacity for the moments that matter most. Elite endurance athletes manage load continuously — easing effort on the uphills, recovering on the downhills, arriving at the final kilometer with something left rather than nothing. The stone under Moses was the original load management intervention.
Aaron and Hur understood something that many well-intentioned people miss: helping someone is not always about adding to them. Sometimes it is about removing unnecessary burden so that what they actually need to do becomes possible. The stone did not make Moses stronger. It made the task smaller. Both matter.
The Hill Outside Your Gym in Raleigh
CrossFit Full Armor exists on Lead Mine Road in north Raleigh because we believe that what happened on that hill in Exodus 17 is still happening — in gyms, in training sessions, in the small acts of showing up for someone who is about to put their arms down.
Every class here is a version of the hill. There is a battle happening — against fatigue, against the voice that says the next rep is impossible, against the conservative estimate your brain makes about what you can sustain. And every person in the room who is still moving, still pulling, still pressing — every person who stays — is doing something neurologically real for the person beside them. They are raising the ceiling. They are being Aaron and Hur without knowing the name for it.
We track benchmarks here not because numbers are the point but because the record of what you have sustained — with the community around you, on the days your arms were heavy and someone was beside you — is worth keeping. It is evidence that the limit you thought was your limit was not your limit. That the ceiling your brain set was not the actual ceiling. That with the right people in the right room, you went further than you would have gone alone.
Raleigh is a city full of people training alone. On apps, in garages, in big box gyms where nobody knows your name or your last lift. They are capable people doing real work. And they are leaving something on the table every session — not because they lack discipline or desire, but because no one is holding their arms up.
The stone is the programming. Aaron and Hur are the community. The battle is yours. But you were never meant to fight it alone.
Come find your Aaron and Hur.
CrossFit Full Armor — 4312 Lead Mine Rd, Raleigh, NC 27612
— Eric Johnson, CrossFit Full Armor