REF-316 · Lall PS, Alsubiheen AM, Aldaihan MM & Lee H, 2022 · International Journal of Environmental Research and Public Health, · Paper · PubMed

Differences in Medial and Lateral Gastrocnemius Stiffness after Exercise-Induced Muscle Fatigue

In 35 healthy young adults, 3 × 50 eccentric calf contractions raised RESTING stiffness of both gastrocnemius heads immediately, at 24 h and at 48 h, while stiffness DURING maximal contraction fell in the medial head; the medial head changed more than the lateral

Blimited evidenceMeasured on recreational peopleWritten before October 2026, being re-checked

Participants

n=35 healthy young adults

Protocol

Muscle fatigue protocol: 3 sets of 50 eccentric contractions of the calf muscles of the dominant leg
Stiffness of the medial (MG) and lateral (LG) gastrocnemius measured with shear-wave elastography (SWE) and a MyotonPRO simultaneously, at rest and during maximum voluntary contraction (MVC)
Time points: before, immediately after, 24 h and 48 h after the protocol

Key Results

Resting stiffness of MG and LG increased significantly immediately, at 24 h and at 48 h after fatigue (p < 0.05) compared with baseline
During MVC, MG stiffness DECREASED (p < 0.05) while LG stiffness did not change (p > 0.05)
The change in MG stiffness was significantly greater than in LG (p < 0.05) — the medial head was more affected by the eccentric fatigue than the lateral
The abstract reports both instruments were used simultaneously; it does not report their agreement

Mechanism

Eccentric work raised the passive (resting) stiffness of the calf for at least 48 h while lowering the stiffness the medial head could generate during a maximal contraction. Inference, not tested (the abstract offers no mechanism): a muscle that is stiffer at rest but less stiff when contracting is one that has lost force-generating capacity while its passive tissue is swollen or tightened — "tight but weak".

Practical Application

In 35 healthy young adults, 150 eccentric calf contractions made both gastrocnemius heads stiffer at rest for at least 48 h, while the medial head became LESS stiff during maximal contraction — resting stiffness and contracting stiffness moved in opposite directions
The medial gastrocnemius changed more than the lateral, so the medial head is the one to watch after eccentric calf loading (downhill running, plyometrics)
Inference, not tested: after eccentric calf work a "tight" calf at 24-48 h is not a sign of readiness; the same muscle produced less stiffness under load
Not from this paper; the base's own practice: MyotonPRO is used as a field stiffness tool in the base's stiffness entries (Kong 2018 REF-317, Basti 2021 REF-325); this abstract does not validate it against SWE

Limitations

Isolated eccentric calf exercise — not whole-body endurance
Young, untrained population
48 h follow-up only
How this entry was checked and changed
Why this level

regraded 2026-09-27 from B+: uncontrolled pre-post, n=35

Content correction 2026-09-27
"MyotonPRO and SWE showed concordant results — validates field-portable measurement" -> the abstract says only that the two were measured simultaneously; no agreement result; removed/relabelled.
"MG recovers slower than LG" -> the abstract says MG was more affected (greater change), not that it recovered more slowly; reworded.
Level B+ -> B (uncontrolled pre-post, n=35).