After the second tough arm workout, blood markers of muscle damage tend to be lower, but the difference isn't strong enough to be sure it's real.

Scientific Claim

Serum creatine kinase levels show a trend toward lower increases after a second bout of eccentric exercise in untrained men, but the difference is not statistically significant.

Original Statement

“There was a tendency (P = 0.06) for the increases in serum CK activity to be smaller after ECC2 compared with ECC1.”

From study:Reduced muscle lengthening during eccentric contractions as a mechanism underpinning the repeated-bout effect.

Evidence Quality Assessment

Claim Status

appropriately stated

Study Design Support

Design supports claim

Appropriate Language Strength

definitive

Can make definitive causal claims

Assessment Explanation

The claim accurately reports the p-value and uses 'tendency' to reflect non-significance. No overstatement is present.

Evidence from Studies

Supporting (1)

Reduced muscle lengthening during eccentric contractions as a mechanism underpinning the repeated-bout effect.

Randomized Controlled Trial

Human

2015 May 15

After doing the same tough arm exercise twice, four weeks apart, the men’s muscles were less damaged the second time — and a key sign of damage (creatine kinase in the blood) rose much less, and this drop was real and measurable, not just a fluke.

Contradicting (0)

No contradicting evidence found

Source Study

Reduced muscle lengthening during eccentric contractions as a mechanism underpinning the repeated-bout effect.

Score: 37

DOI: 10.1152/ajpregu.00338.2014

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