← Sage hub · Strength hub · Hormesis timing · Surfer

Sage — Strength · Mitophagy

Capacity II of IV — Mitophagy

This page owns clearing damaged mitochondria. Sleep and Restore Phase are part of the lever. No invent fasting/drug mitophagy protocols.

Nocturnal half of Axis 2

Mitophagy as the nocturnal half of Axis 2

A larger fleet of damaged mitochondria is not health. It is a high-ROS, low-ATP liability. Mitophagy—PINK1/Parkin, BNIP3/NIX, FUNDC1, AMPK-ULK1—is the quality-control half of biogenesis. The dual-pathway week creates the signal on Days 3 through 6. Conversion of that signal into a cleaner fleet happens in the recovery phase of those same days and especially overnight: falling feeding-driven mTOR, rising AMPK tone in the fast, melatonin, growth-hormone pulses, darkness.

This is why the feeding window and the four-hour pre-sleep empty gut are not separate diet tips. They are the mitophagy protocol. Eating into the night after a 500 m day keeps mTOR on when the damaged reticulum should be sorted. Placing a strong antioxidant or ETC shuttle immediately before the sprint can blunt the ROS language the session was meant to speak. The recovery phase is not off. It is when Axis 2 becomes a better mitochondrion rather than merely a tired one.

Axis 2 context

Axis 2 — Metabolic stress to AMPK-SIRT1-PGC-1-alpha to biogenesis and mitophagy

Deep cellular energy depletion—rising AMP/ADP:ATP, calcium flux, and a controlled ROS pulse—activates AMPK and SIRT1. Those sensors recruit PGC-1-alpha, NRF1/2, and TFAM. Nuclear-encoded mitochondrial genes rise. mtDNA replication follows. The network remodels: fission during the effort, fusion and segregation afterward, mitophagy of units that cannot hold membrane potential.

The protocol's distinctive claim on this axis is depth over duration. A single continuous all-out effort of approximately two minutes can produce AMPK phosphorylation and PGC-1-alpha mRNA responses comparable to repeated shorter sprints when total high-intensity duration is matched. A maximal 500 m on the erg is, for most trained adults, a 90 to 120 second effort. That is long enough to empty phosphocreatine, drive glycolysis hard, and force a large drop in energy charge, and short enough that residual fatigue does not usually destroy the next morning's repeat. Three such efforts across three mornings are three deep pulses, not one sloppy interval soup.

Adenylate charge: how a sprint turns ATP collapse into an AMP signal

Cells do not measure tiredness. They measure the adenine nucleotide pool. ATP, ADP, and AMP stand in a fast equilibrium that biochemists call the adenylate energy charge. In a recovered fiber the pool is mostly ATP. Work hydrolyzes ATP to ADP. As long as phosphocreatine and oxidative phosphorylation can rephosphorylate that ADP, AMP barely moves and AMPK stays quiet. The SIRT1-biogenesis axis is not listening yet.

When the effort is fast enough and hard enough that phosphocreatine is emptied and ATP use outruns resynthesis, ADP accumulates. Adenylate kinase—myokinase in muscle—then runs the salvage reaction that is the hidden engine of this protocol: two ADP become one ATP and one AMP. That reaction does two things at once. It donates a last emergency ATP so the fiber can keep making force for a few more seconds. And it produces AMP, which is the amplified alarm. AMP rises out of proportion to the fall in ATP. A modest drop in energy charge becomes a large relative rise in AMP because the kinase stoichiometry turns a pair of ADP into a new AMP molecule that was not there before.

AMP binds the gamma subunit of AMPK and makes the kinase a better substrate for LKB1. Phosphorylated AMPK is the workhorse of Axis 2. It phosphorylates ULK1 and thereby opens the autophagy and mitophagy gate. It restrains ACC and shifts fuel use. It activates PGC-1-alpha by phosphorylation and, over a slightly longer arc, raises NAD+ through Nampt. That NAD+ rise is how the AMP world talks to SIRT1. SIRT1 is not an AMP receptor. It is an NAD+-dependent deacetylase. Deep depletion therefore reaches SIRT1 by a two-step relay: AMP to AMPK to a higher NAD+/NADH ratio, then SIRT1 deacetylation of PGC-1-alpha. Deacetylated, phosphorylated PGC-1-alpha coactivates NRF1/2 and the mitochondrial transcriptional program, including TFAM and mtDNA replication. The same AMPK pulse that starts mitophagy of depolarized units is the pulse that licenses building replacements.

This is why the 500 m and its cousins are built to be brief and honest rather than long and merely uncomfortable. Easy aerobic work keeps ATP nearly constant; adenylate kinase barely runs; AMP does not spike; AMPK and SIRT1 receive a whisper. Gray-zone intervals raise heart rate and sweat without driving the 2 ADP to AMP plus ATP reaction hard enough to matter. A maximal 90-to-120-second erg piece, a hill of the same depth, or a true Tabata that actually dies in the last rounds empties the creatine-P buffer, forces adenylate kinase, and writes AMP onto AMPK. The 2000 m is a longer version of the same logic with more aerobic wrapping. It still has to be maximal or the AMP story collapses back into ordinary respiration.

There is a cost. AMP that is not remade into ADP and ATP can be deaminated to IMP. That is part of why these sessions feel like a hole in the floor and why they need a night and, in this week, a final rest day before the next high-tension session. The protocol is not trying to live in low energy charge. It is trying to visit it deeply, briefly, and then let the nocturnal program turn an AMP spike into more and cleaner mitochondria.

The 2000 m maximal test is a longer pulse. It is both a field VO2 max assay and a strong metabolic stimulus. It sits on Day 3, after the post-ARX rest day, so the first metabolic session of the week arrives when the mTOR adaptive window has been protected and the trainee is not still neurologically cooked from accommodating resistance. It is the bridge session: hard enough to speak SIRT1, long enough to speak aerobic machinery, objective enough to become a metric.

Seven-day map note

Mitophagy

Nights of Days 3 through 6, and the entirety of Day 7. Fission during the effort; fusion, segregation, and clearance in the fasted dark. Protected by the four-hour pre-sleep rule and by not blotting the ROS signal with pre-session antioxidants. Optional methylene blue belongs after, if at all.

Neighbors

• Biogenesis — build after clear.
• Fuel timing — night empty-enough supports mitophagy weather.
• Hormesis timing — do not load through restore.

A working hypothesis, open to correction and revised as new evidence arrives. Last revised October 17, 2026.

Coach — Mitophagy · Strength hub

Related on Surf Wax: Urolithin A.