REF-320 · Cheng R, Wang Q, Xu L, Xu W, Zheng Y, Cui Y & Cao Y, 2026 · Sports Medicine Open, · Paper · PubMed

Assessing the Recovery of Muscle Fatigue Using Shear Wave Elastography

After eccentric elbow flexion at 90% 1RM in 35 athletes and 16 non-athletes, passive shear modulus rose immediately and was back to baseline by 48 h in male athletes and non-athlete males; there was NO main effect of group (athlete vs non-athlete) — only non-athlete females showed a different time course

Blimited evidenceMeasured on non-to trained athletesWritten before October 2026, being re-checked

Participants

n=51: 35 athletes and 16 non-athletes

Protocol

Fatigue induced by unilateral eccentric dumbbell elbow flexion at 90% of one-repetition maximum: 3 sets of 10 repetitions plus a final set to exhaustion
Passive shear modulus (G) by portable SWE at baseline, immediately post-exercise, 24 h and 48 h
Linear mixed-effects models for group and time, with arm dominance as a controlled factor

Key Results

G changed significantly over TIME (main effect, P < 0.001); neither group nor arm dominance had a main effect, and none of the interactions was significant (all P > 0.05)
Baseline: G in non-athlete females sat below that of athletes for the dominant arm and below that of male athletes for the non-dominant arm (P < 0.05, ES 1.05-1.39)
Immediately post: G rose in non-athlete females, non-athlete males and male athletes alike (P < 0.05, ES 0.43-1.34); dominant-arm G was greater in non-athlete males than in non-athlete females (ES 0.95)
24 h: compared with male athletes and non-athlete males, non-athlete females had higher G in the dominant arm and lower G in the non-dominant arm (ES 1.16-1.57); they were also the only group with a difference between limbs at 24 h (ES 1.14)
48 h: male athletes and non-athlete males were back at baseline G; in non-athlete females, dominant-arm G fell significantly from its 24 h value (ES 1.06)
Authors' conclusion: passive G is a valid, non-invasively monitorable indicator for tracking fatigue and recovery across populations

Mechanism

Passive shear modulus tracks the exercise-induced change in the muscle's resting state — up immediately after an eccentric bout, back down over 48 h. The abstract offers no tissue mechanism. The training-status story is weaker than it looks: with no main effect of group, the data do not show athletes recovering faster than non-athletes; the one distinct pattern belonged to non-athlete females (lower baseline, and a 24-h asymmetry between arms).

Practical Application

In 35 athletes and 16 non-athletes, eccentric elbow flexion at 90% 1RM raised passive shear modulus immediately, and it was back to baseline by 48 h in male athletes AND in non-athlete males — the mixed model found no main effect of athlete status, so this study does not show that trained people recover tissue stiffness faster
The subgroup that behaved differently was non-athlete females: lower baseline stiffness, and at 24 h a dominant/non-dominant arm asymmetry not seen in the other groups; by 48 h their dominant arm had dropped from the 24-h value
Portable SWE tracked the fatigue-recovery curve well enough for the authors to call it a valid monitoring indicator
Not from this paper; the base's own practice: allow 48 h before repeating heavy eccentric loading on the same muscle; this study's 48-h return to baseline in males is the anchor, and it did not measure beyond 48 h

Limitations

Eccentric arm exercise — not endurance-specific
Small non-athlete group (n=16); athlete level not specified in the abstract
48 h follow-up — longer timeline unknown
How this entry was checked and changed
Why this level

regraded 2026-09-27 from B+: uncontrolled pre-post in two non-randomised groups, n=51

Content correction 2026-09-27
"Athletes recover tissue stiffness faster than non-athletes" and "48 h sufficient for trained vs longer for untrained" -> the abstract reports NO main effect of group and a 48-h return to baseline in non-athlete males as well as male athletes; corrected. "Supports progressive training adaptation: as fitness improves, tissue recovery accelerates" removed.
Added the sex-specific results (baseline ES 1.05-1.39; 24-h asymmetry ES 1.14-1.57).
Level B+ -> B (two-group pre-post, n=51).