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Table 4 GRADE analysis

From: Effects of Upper-Body Plyometric Training on Physical Fitness in Healthy Youth and Young Adult Participants: A Systematic Review with Meta-Analysis

Outcome

N° studies (sample size)

Risk of bias in studies

Risk of publication bias

Inconsistency

Imprecision

Certainty of evidence

Maximal strength performance

13 (n = 363)

No downgrade (median PEDro score: 6)

Downgrade by 1 level (Egger's two-tailed test, p < 0.001)

Downgrade by 1 level (25% < I2 < 75%)

Downgrade by two levels (n < 800; very large CIs crossing the null effect)

Very low

Medicine ball throwing

17 (n = 819)

No downgrade (median PEDro score: 6)

No downgrade (no suspected risk of publication bias)

Downgrade by 1 level (25% < I2 < 75%)

Downgrade by one level (very large CIs crossing the null effect)

Low

Sport-specific throwing

10 (n = 291)

No downgrade (median PEDro score: 6)

Downgrade by 1 level (Egger's two-tailed test, p = 0.029)

Downgrade by 1 level (25% < I2 < 75%)

Downgrade by two levels (n < 800; very large CIs crossing the null effect)

Very low

Muscle volume

3 (n = 78)

No downgrade (median PEDro score: 6)

Not applicable (< 10 studies)

No downgrading (I2 < 25%)

Downgrade by two levels (n < 800; very large CIs crossing the null effect)

Low

  1. Risk of bias in studies: downgraded by one level if the median PEDro scores were moderate (< 6) or by two levels if they were poor (< 4)
  2. Low risk of indirectness was attributed by default due to strict eligibility criteria
  3. Risk of publication bias (assessed only if ≥ 10 studies were available for the comparison): downgraded by one level if there was suspected publication bias
  4. Inconsistency: judgments were downgraded by one or two levels when the impact of statistical heterogeneity (I2) was moderate (≥ 25%) or high (> 75%)
  5. Imprecision: one level of downgrading occurred whenever < 800 participants were available for a comparison [81] and/or if there was no clear direction of the effects (including large ranges for the 95% confidence interval, even if the overall meta-analysis presents a clear average direction). When both were observed, certainty was downgraded by two levels
  6. Note: for outcomes not meta-analytically analysed, a very low certainty of evidence was considered present
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