Heinz V;  University Medicine Berlin, Berlin, Germany.
Pilz N; Fesseler L; Lindner T; Malotka L; Opatz O; Blottner D;
Anosov O; Patzak A; Fahling M; Bothe TL

Scientific Reports. 16(1), 2026 May 19.
Headings by Dr Older

Background A ubiquitously available and accurate non-invasive ventilatory threshold
assessment (NIVA) would substantially improve real-world performance
assessment evaluation in both clinical and elite sports settings. We
hypothesised that ECG-derived ventilatory phase analysis achieves
reference-standard accuracy for second ventilatory threshold (VT2)
determination.
Methods 74 healthy adults performed stepwise cardiopulmonary
exercise testing with simultaneous lactate sampling to retrieve VT2 and
lactate-based (Dmax; LT2) thresholds. Threshold agreement was evaluated
for heart rate (HR) and exercise load (W) between VT2, LT2, age-estimated
HR (HR-Est) and NIVA.
Results In 66 assessable datasets, NIVA and VT2 yielded
equivalent threshold estimates for HR (- 0.46 bpm; 90% CI [- 2.10;1.17])
and exercise load (0.46 W; 90% CI [- 2.35; 3.27]). VT2 and HR-Est diverged
(HR – 7.22 bpm, p < 0.001; load – 6.26 W; p < 0.001). LT2 was available in
58 subjects and differed from both VT2 (p < 0.001) and NIVA (p < 0.001).
Correlations supported these findings, with close associations between VT2
and NIVA (HR r = 0.84; load r = 0.96). NIVA derived a high-intensity
performance threshold from ECG signals with reference-standard fidelity
and showed close agreement with CPET-derived VT2.
Conclusions Its performance and
accessibility make it attractive for frequent reassessment of a
VT2-aligned threshold without the need for spiroergometry or lactate
measurements. Validation across devices, protocols, populations, and
real-world signal conditions is warranted.