Does a single session of eccentric knee extension reduce strength and increase creatine kinase in young men?

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Leans yes
Eccentric Training & CK Response2 min readUpdated May 25, 2026

What the Evidence Shows

We analyzed one assertion on this topic and found that a single session of eccentric knee-extension exercise is associated with a temporary drop in knee strength—about 10%—and a 100% increase in creatine kinase, a blood marker often linked to muscle stress or damage, in healthy young men. These changes do not appear to last, as they return to normal after three weeks of continued training [1].

The evidence we’ve reviewed so far consistently shows this pattern: after one intense session focused on lengthening the muscle under load—what’s called eccentric contraction—strength dips and muscle damage markers rise. Creatine kinase is not a direct measure of injury, but it signals that muscle fibers are under unusual stress, which is common after unfamiliar or intense exercise. The fact that strength and markers return to baseline after repeated sessions suggests the body adapts quickly.

We did not find any studies that contradicted this pattern. However, the analysis is based on only one assertion, and we have no details on the exact exercise protocol, sample size, or individual variability among participants. It’s also unclear whether these findings apply to women, older adults, or people with prior training experience.

What this means for someone trying this exercise: if you’re new to eccentric knee work, expect to feel weaker and possibly sore for a day or two afterward. That’s normal. Your body will adjust with consistent practice. Don’t push through sharp pain, but mild discomfort and temporary strength loss are common and likely part of the adaptation process.

Evidence from Studies

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Supporting (1)

A single session of eccentric knee-extension exercise transiently reduces maximal isometric and dynamic knee extension strength by approximately 10% and doubles serum creatine kinase levels in fit young males, indicating acute muscle damage, but these effects recover fully within 3 weeks of training.

Partly Substituting Whey for Collagen Peptide Supplementation Improves Neither Indices of Muscle Damage Nor Recovery of Functional Capacity During Eccentric Exercise Training in Fit Males.
study
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Contradicting (0)
No contradicting evidence found
Primary Studies (1)

Partly Substituting Whey for Collagen Peptide Supplementation Improves Neither Indices of Muscle Damage Nor Recovery of Functional Capacity During Eccentric Exercise Training in Fit Males.

DOI: 10.1123/ijsnem.2023-0070

Update History

Published
May 25, 2026·Last updated May 25, 2026
  • May 25, 2026New topic created from assertion