The Effect of Acute Physical Exercise on NK-Cell Cytolytic Activity: A Systematic Review and Meta-Analysis

Publication: Contribution to journalJournal articlesResearchpeer-review


Background: Data on changes in natural killer cell cytolytic activity (NKCA) in response to acute physical exercise are contradictory.
Objective: The aim of this systematic review, meta-analysis and meta-regression is to (1) examine the effect of acute physical exercise on NKCA, (2) shed more light on the moderating factors, and (3) test the assumption of NKCA suppression subsequent to performing sports.
Methods: Two comparisons of NKCA were performed: (1) pre- versus post-exercise and (2) pre-exercise versus recovery. Data were acquired through a systematic search of MEDLINE (via PubMed), Scopus, and SportDiscus. Studies were eligible for inclusion if the effect of acute physical exercise was assessed including a passive control group and reporting NKCA prior to and immediately after the trial, and during the first 2 h of recovery. To better explain between-study heterogeneity, a moderator analysis was conducted.
Results: Pooled estimate from 12 studies reporting 18 effect sizes show that NKCA is largely elevated by acute physical exercise (Hedges’ g = 1.02, 95% CI 0.59–1.46, p < 0.01). Meta-regressions reveal that this effect is larger for endurance versus resistance exercise and increases with the intensity of exercise (both p < 0.01), whereas the blood material used in the assay (p = 0.71), and the quantitative change in NK-cell count (R2 = 0%, p = 0.55) do not play a significant role. Physical exercise does not affect the level of NKCA after the recovery period (g = 0.06, 95% CI − 0.37 to 0.50, p < 0.76).
Conclusions: This work provides solid evidence for elevated NKCA through performing sports which returns to baseline during the first 1–2 h of recovery, but not below the pre-exercise values providing counterevidence to the assumption of temporarily reduced NKCA. Remarkably, the functional change in NKCA exists independently from the quantitative change in NK-cell count.
Original languageEnglish
JournalSports medicine
Issue number3
Pages (from-to)519-530
Number of pages12
Publication statusPublished - 03.2021

Research areas and keywords

  • Exercise
  • Humans
  • Killer Cells, Natural


Dive into the research topics of 'The Effect of Acute Physical Exercise on NK-Cell Cytolytic Activity: A Systematic Review and Meta-Analysis'. Together they form a unique fingerprint.