Mártély 6-Hour Run – March 1, 2026
After sixty days of zero-carbohydrate diet, the body is no longer operating in the classic “early ketosis” phase. At this point, the essence of adaptation is not whether ketones are measurable in the blood, but how stable the entire system remains under load. The 6-hour run put exactly that stability to the test.
The lead-up was far from ideal. The previous week still included an ultra-distance recovery phase, followed by kettlebell sessions—including 2 × 16-minute OALC with 18 kg. This type of work isn’t simple muscle labor: it demands continuous shoulder stability, grip strength, elevated heart rate, and intense mental focus, creating significant neuromuscular stress. Then came the 6-hour run on top of that.
Starting conditions weren’t helpful either. Sleep was poor—tossing and turning until 2 a.m., early wake-up. Morning fasting ketones were 0.3 mmol/L, which in traditional interpretation might suggest elevated cortisol and uncertain energy availability. Many would view this as metabolic instability. Reality showed otherwise.
Fueling remained simple throughout: salt and water. During the run, the watch “went crazy,” so for long stretches there was no pace or distance feedback—running “blind.” In ultra, that’s a serious mental challenge, as pacing without feedback becomes far more uncertain. Nevertheless, movement stayed controlled the entire time.
Actual distance covered: 59.4 km, with an average heart rate of 126 bpm. The truly telling number, however, wasn’t the average—it was the stability of the heart rate. There was no unwarranted drift; the same pace didn’t require progressively higher cardiac effort. The system operated in dominant aerobic mode, without metabolic stress response.
The post-run ketone level of 2.0 mmol/L was a key signal. This isn’t just a “high ketone value”—it’s proof that even at the end of the effort, the liver was still actively producing ketones while the energy system hadn’t depleted. Important distinction: high post-run ketones don’t necessarily mean more fat was burned overall; they mean ketone production and utilization remained in dynamic balance, and by the finish, production outpaced current usage. This is one of the hallmark patterns of adapted sports ketosis.
Despite the mid-week nervous-system load, there was no central collapse. Poor sleep didn’t translate into performance drop. Low starting ketones didn’t cause energy shortage. No “wall” appeared, no glycogen crisis, no sudden energy crash. Reserves remained in the tank—at ultra distances, that has strategic value.
The reduction in heart-rate drift deserves special attention. In the same pace, a rising heart rate over time isn’t merely cardiovascular—it’s a metabolic stress response. In carbohydrate-dominant metabolism, declining glycogen stores trigger stress-hormone elevation, increased sympathetic activity, and the circulation works harder to maintain energy delivery. That shows up as drift.
In fat-adapted mode, the situation is fundamentally different. Mitochondrial capacity increases, enzyme systems for fatty-acid oxidation become more efficient, fatty-acid transport stabilizes. Fat as an energy substrate is essentially an unlimited store, so the body doesn’t perceive dropping glycogen as an acute threat. The stress-hormone response is blunted, autonomic nervous-system balance remains more stable, parasympathetic tone stays stronger even under load. Heart rate doesn’t “run away.”
This doesn’t mean there’s no fatigue. Muscle fatigue, mechanical stress, and mental challenge are all present. The difference is that the energy system doesn’t collapse. In carb-dependent running, heart-rate drift is often the anteroom to “the wall.” In an adapted fat-based system, reduced drift is a sign of sustainable operation.
The functional carnivore approach isn’t about high blood ketone levels—it’s about a stable energy system. About the fact that load doesn’t disrupt metabolism but integrates with it. That the system isn’t fragile, but load-bearing.
On the road to Ultrabalaton, this is real progress. It’s not the first 60 kilometers that matter—it’s how stable the system remains in the 4th, 5th, 8th, or 12th hour. When conditions are suboptimal—sleep deprivation, nervous-system fatigue, technical failure—and the energy economy still holds, then it’s no longer the circumstances in control. It’s the system.