REF-313 · Andonian P, Viallon M, Le Goff C, de Bourguignon C, Tourel C, Morel J, Giardini G, Gergelé L, Millet GP & Croisille P, 2016 · PLoS ONE, · Paper · PubMed
Shear-Wave Elastography Assessments of Quadriceps Stiffness Changes prior to, during and after Prolonged Exercise: A Longitudinal Study during an Extreme Mountain Ultra-Marathon
In 50 runners of a 330 km / +24,000 m race, quadriceps shear modulus FELL at the finish (3.56 → 3.31 kPa) and had only partly recovered 48 h later (3.45 kPa)
Participants
n=50 volunteers participating in an extreme mountain ultra-marathon (330 km, +24,000 m elevation)
Protocol
Real-time shear-wave elastography (SWE) of the most superficial quadriceps heads (rectus femoris, vastus medialis, vastus lateralis) at 4 time points: before the race, halfway, at the finish, and after recovery (+48 h)
Blood biomarker levels measured in parallel (the abstract does not name the markers or report their relation to stiffness)
Key Results
Quadriceps shear modulus decreased significantly at the finish: 3.31 ± 0.61 kPa vs 3.56 ± 0.63 kPa at baseline (p < 0.001)
Partial recovery at +48 h: 3.45 ± 0.6 kPa (p = 0.002 vs baseline)
The decrease held across all muscle heads and for each head individually: rectus femoris p = 0.003, vastus medialis p = 0.033, vastus lateralis p = 0.001
First study to track muscle stiffness through a prolonged extreme endurance event with SWE
Mechanism
The authors' interpretation: the drop in stiffness may result from quadriceps overuse under the supra-physiological stress of the distance and elevation, and may be linked to the development of inflammation and muscle swelling. Prolonged endurance load made the muscle SOFTER — the opposite direction from the acute stiffening seen after short eccentric bouts (Pournot 2016 REF-315, Kong 2018 REF-317).
Practical Application
In 50 runners of a 330 km mountain ultra, resting quadriceps stiffness fell about 7% at the finish (3.56 → 3.31 kPa) and had only partly returned 48 h later (3.45 kPa) — extreme endurance softens the muscle rather than tightening it, and 48 h is not enough for the tissue to normalise
The direction matters for reading the body: a soft, swollen quad after a very long day is the endurance signature; a tight, stiff muscle in the following days is the eccentric/strength-work signature (Kong 2018 REF-317)
SWE can track this objectively; Inference, not tested: perceived recovery and tissue recovery need not coincide — the study did not measure perception
Not from this paper; the base's own practice: after a multi-day or ultra event plan more than 48 h before the next loaded session; this study shows incomplete tissue recovery at 48 h but did not measure when it completes
Limitations
Extreme event (330 km) — may not extrapolate to standard training
No control for terrain, nutrition or sleep deprivation
SWE at rest only — no active-muscle assessment; recovery tracked only to +48 h
How this entry was checked and changed
Why this level
regraded 2026-09-27 from B+: uncontrolled pre-post, n=50
Content correction 2026-09-27
"Blood biomarkers (CK, myoglobin)" and "stiffness decrease correlated with biomarker elevation" -> the abstract only says blood biomarker levels were measured; marker names and any correlation are not in the abstract; removed.
Sport running -> trail running (mountain ultra); Level B+ -> B (uncontrolled pre-post, n=50); gravel line replaced by labelled house practice.