REF-757 · Siegl A, Kösel E, Tam N, Koschnick S, Langerak NG, Skorski S, et al. — 2017 · International Journal of Sports Medicine, · Paper · PubMed
Two days after an ultramarathon, trained runners on a standard submaximal treadmill test showed a lower heart rate at the same speeds, 7 bpm faster 60-s heart-rate recovery and higher RPE
Fatigue that looked like fitness on every heart-rate number
Protocol
Fourteen trained runners completed the Lamberts Submaximal Running Test one week before and two days after an ultramarathon, with muscle soreness and the DALDA stress questionnaire.
Key Findings
After the race: submaximal heart rate lower at 70% (−3 bpm) and 85% of peak treadmill speed (P < 0.01).
RPE higher at 60% (+2 units) and 85% (+1 unit) of peak speed.
60-s HRR significantly faster (+7 bpm, P < 0.001).
Soreness and DALDA stress symptoms higher (P < 0.01).
The authors describe acute fatigue and overreaching as producing counterintuitive responses: lower submaximal heart rate and faster HRR, with higher RPE.
Practical Application
Never read a lower heart rate or a faster recovery on a fixed-load test as improvement unless RPE on the same test is unchanged or lower and the preceding days were not a heavy load. Here all three heart-rate signals "improved" two days after an ultramarathon.
The rule transfers to running: a pace-clamped test behaves like the power-clamped cycling version.
Limitations
n = 14, single event, a very large acute load; the size of the effect after an ordinary hard week is unknown.
No performance test to confirm a performance decrement.