REF-1297 · Doma et al., 2023 · Journal of Strength and Conditioning Research · Paper · PubMed

Does the second gym session hurt my running less than the first?

Yes: across 20 studies, soreness, strength loss and running cost at 24-48 h were smaller after a second multi-joint bout. Versus bout 1, not fresh legs.

Main caveat: Read from the abstract only; the included studies, their sizes, exercises, inter-bout intervals, effect estimates per study, confidence intervals and…
fairly strong evidenceMeasured on non-athletes and recreational people

Doma, Matoso, Protzen, Singh and Boullosa pooled studies in which healthy adults did the same muscle-damaging multi-joint exercise twice (multiarticular exercise with eccentric contractions; the abstract names no exercise) and outcomes were measured 24-48 h after each bout. Twenty studies qualified.

At both 24 h and 48 h, soreness and creatine kinase were higher after the first bout than after the second (p < 0.001; SMD 0.51 to 1.23); muscle strength and vertical jump were lower after the first bout (p ≤ 0.05; SMD −0.27 to −0.40); and in running-economy protocols oxygen uptake and perceived exertion were higher after the first bout (p < 0.05; SMD 0.28 to 0.65).

The results did not change when intensity or volume differed between the two bouts. The authors conclude that a single bout of commonly performed exercises with eccentric contractions protects against muscle damage from the next one.

Our reading: this is the pooled case for familiarity as one thing that sets how much a lift shadows the next run — the first one or two sessions of a block cost more than the same session a few weeks later — but it cannot say how many hours the second bout still needs, because it never compares either bout with an unexercised baseline in the abstract.

Protocol

Eligibility (abstract): (a) healthy male and female adults; (b) multiarticular exercise used to cause muscle damage across 2 bouts; (c) outcomes compared at 24-48 h after the first and the second bout; (d) at least one of creatine kinase (CK), delayed-onset muscle soreness (DOMS), muscle strength or running economy.
Appraisal and analysis: study quality with the Kmet tool; forest plots giving standardised mean differences (SMD); alpha 0.05.
Studies: 20 after screening. The abstract does not give the total number of participants, their sex split or training status, the exercises used, the interval between bouts, the databases searched or heterogeneity statistics.
Familiarity: by design the first bout is the unaccustomed exposure; whether any included sample was already training the exercise is not stated.
Time points: 24 h (T24) and 48 h (T48) after each bout; no 6-h or 72-h outcome in the abstract.
Funding and interests: not stated in the abstract or the PubMed record; the full text could not be read.

Key Results

First bout vs second bout, same people, same exercise (abstract; SMD direction as reported):

OutcomeTime pointFirst bout vs secondSMDp
Markers — DOMS and CK24 h and 48 hhigher after the first0.51 to 1.23< 0.001
Performance — muscle strength and vertical jump24 h and 48 hlower after the first−0.27 to −0.40≤ 0.05
Running-economy test — oxygen uptake and RPE24 h and 48 hhigher after the first0.28 to 0.65< 0.05
Moderators — a change in intensity or volume between bouts—did not affect the meta-analyses——
Confidence intervals, heterogeneity (I²), the number of studies per outcome and the number of running-economy studies are not given in the abstract.
No result is reported against a pre-exercise baseline, so the residual cost after the second bout cannot be read from the abstract.

Mechanisms

Measured: the second bout produced a smaller rise in soreness and CK and smaller strength, jump and running-economy decrements than the first at 24 and 48 h.
Authors' interpretation: a single bout of multi-joint exercise with eccentric contractions provides protection against exercise-induced muscle damage in subsequent bouts (the repeated bout effect, REF-549), and this held even when the second bout differed in intensity or volume.
Inference: the time-course studies in this batch only partly fit — after a third lifting bout RPE, VE/VCO2 and time to exhaustion improved while oxygen uptake did not differ between bouts (REF-1299), and cyclists' net efficiency was higher in the second-bout week but already before that lift (REF-1304) — so the protection of the next endurance session may lie more in effort than in oxygen cost.
Inference: a repeated-bout design without a control arm cannot separate protection from test familiarisation (running-economy and jump tests often improve on repetition); the effect sizes may contain some of both.

Practical Application

Does the second gym session hurt my running less than the first? Yes: across 20 studies, soreness, strength loss and running cost at 24-48 h were smaller after a second multi-joint bout. Versus bout 1, not fresh legs.
Plan the first one or two strength sessions of a block as the expensive ones (inference from this meta-analysis and REF-1299): after them, keep quality endurance further away; once the session is familiar, the shorter gap in SYNTH-31 applies. How many repeats make a session familiar is not tested here; SYNTH-31 sets the base's practice definition.
A change in load between bouts did not remove the protection — the pooled effect was unaffected by changes in intensity or volume between bouts (abstract; the direction of the change, the number of studies and the power of this test are not given). Inference, not tested here: a first session of a block at reduced volume should buy the protection at a lower cost (REF-549 for the repeated bout effect).
This paper sets no hours. It compares two bouts at 24 and 48 h; how long the second bout still shadows a hard run comes from the time-course studies (REF-1298, REF-1299, REF-1300, REF-1304).

Limitations

Read from the abstract only; the included studies, their sizes, exercises, inter-bout intervals, effect estimates per study, confidence intervals and heterogeneity could not be checked.
Within-person bout-to-bout comparisons without control arms; test learning and season or fitness change between bouts are not separated from protection (inference).
Mostly marker outcomes; the endurance outcome is a running-economy test, not a time trial, and no cycling outcome is named.
Healthy adults, probably unaccustomed at bout 1 (inferred); not trained endurance athletes who lift regularly.
Funding and conflicts of interest: not stated in the abstract or the PubMed record.
How this entry was checked and changed
Why this level

a meta-analysis, but of 20 small within-person repeated-bout studies; participant numbers, heterogeneity and confidence intervals are not in the abstract, and the full text is not open (a James Cook University repository copy listed by OpenAlex is restricted). Held below A because the pooled studies compare a first and a second exposure in the same people without a control arm, and because it was read from the abstract only