Decoupling of internal and external workload during a marathon: An analysis of durability in 82,303 recreational runner

Barry Smyth, Ed Maunder, Samuel Meyler, Ben Hunter, Daniel Muniz

Research output: Contribution to journalArticlepeer-review


This study characterised the decoupling of internal-to-external workload in marathon running and investigated whether decoupling magnitude and onset could improve predictions of marathon performance.

The decoupling of internal-to-external workload was calculated in 82,303 marathon runners (13,125 female). Internal workload was determined as a percentage of maximum heart rate, and external workload as speed relative to estimated critical speed (CS). Decoupling magnitude (i.e., decoupling in the 35 40 km segment relative to 5-10 km segment) was classified as low (<1.1), moderate (≥1.1 but <1.2), or high (≥1.2). Decoupling onset was calculated when decoupling exceeded 1.025.

The overall internal-to-external workload decoupling experienced was 1.16±0.22, first detected 25.2±9.9 km into marathon running. The low decoupling group (34.5% of runners) completed the marathon at a faster relative speed (88±6% CS), had better marathon performance (217.3±33.1 min), and first experienced decoupling later in the marathon (33.4±9.0 km) compared to those in the moderate (32.7% of runners, 86±6% CS, 224.9±31.7 min, and 22.6±7.7 km) and high decoupling groups (32.8% runners, 82±7% CS, 238.5±30.7 min, and 19.1±6.8 km; all p <0.01). Compared to females, males’ decoupling magnitude was greater (1.17±0.22 vs. 1.12±0.16; p <0.01) and occurred earlier (25.0±9.8 vs. 26.3±10.6 km; p <0.01). Marathon performance was associated with the magnitude and onset of decoupling, and when included in marathon performance models utilising CS and the curvature constant, prediction error was reduced from 6.45% to 5.16%.

Durability characteristics, assessed as internal-to-external workload ratio, show considerable inter-individual variability, and both its magnitude and onset are associated with marathon performance.
Original languageEnglish
JournalSports Medicine
Publication statusAccepted/In press - 28 Mar 2022


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