The Resting Heart Rate Signal

The foreword to Hans Selye — On AI opens with a number Segal did not see on any dashboard: the nine-beats-per-minute rise in his resting heart rate during the months he built Napster Station, wrote the book, and crossed three continents. The number is the specific, measurable signal that Selye's framework predicts and that contemporary wearable technology now makes accessible. Resting heart rate is a simple integrator of autonomic nervous system balance — persistent elevation indicates chronic sympathetic dominance, the hormonal signature of the late resistance phase. The signal is unreliable as a real-time measure (one night of poor sleep can move it) but highly reliable as a trend across weeks. What haunts Segal's account is not the elevation itself but its subjective invisibility: he felt he was operating at the peak of his career while his autonomic nervous system was recording the cost.