Author Correction: Efficacy of resistance training in hypoxia on muscle hypertrophy and strength development: a systematic review with meta-analysis

indicated a medium effect on CSA for longer inter-set rest intervals and a small effect for moderate hypoxia and moderate loads favoring RTH. Moreover, a moderate effect for longer inter-set rest intervals and a trivial effect for severe hypoxia and moderate loads favoring RTH was found on 1RM. Evidence suggests that RTH employed with moderate loads (60–80% 1RM) and short (≤ 60 s) to longer inter-set rest intervals (≥ 120 s) respectively enhances muscle hypertrophy and strength compared to normoxia.

In the Abstract, "Subanalyses indicated a medium effect on CSA for longer inter-set rest intervals and a small effect for moderate hypoxia and moderate loads favoring RTH.Moreover, a moderate effect for longer inter-set rest intervals and a trivial effect for severe hypoxia and moderate loads favoring RTH was found on 1RM.Evidence suggests that RTH employed with moderate loads (60-80% 1RM) and short (≤ 60 s) to longer inter-set rest intervals (≥ 120 s) respectively enhances muscle hypertrophy and strength compared to normoxia." now reads: "Subanalyses indicated a small effect on CSA for shorter inter-set rest intervals, moderate hypoxia and moderate loads favoring RTH.Moreover, a medium effect for longer inter-set rest intervals and a trivial to small effect for severe hypoxia and moderate loads favoring RTH was found on 1RM.Evidence suggests that RTH employed with moderate loads (60-80% 1RM) enhances both hypertrophy and strength.Hypertrophy appears to benefit from shorter (≤ 60 s) inter-set rest intervals during RTH while greater gains in strength are achieved with longer rest intervals (≥ 120 s)." In the Method section, under the subheading 'Data extraction and study outcomes ' ,   In  In the Results section, under the subheading 'Study characteristics' , "Three studies employed the use of low-loads (20-50% of 1 RM) 3,7,8 , and 3 implemented heavy-load training programs (> 80% of 1 RM) 38,43,45 ; the remainder of the studies employed moderate-load programs (60-80% 1RM) 15,41,44 ." now reads: "Four studies employed the use of low-loads (20-50% of 1 RM) 3,7,8,47 , and 3 implemented heavy-load training programs (> 80% of 1 RM) 38,43,45 ; the remainder of the studies employed moderate-load programs (60-80% 1RM) 15,41,44 ." And, "Six studies used short inter-set rest intervals (< 60 s) 3,[6][7][8]44,47 , 3 used moderate inter-set rest intervals (> 60-< 120 s) 39,41,46 and 5 used long inter-set rest intervals (≥ 120 s) 5,15,21,40,42 . (Tabl 1). " now reds: "Seven studies used short inter-set rest intervals (≤ 60 s) 3,[5][6][7][8]44,47 , 3 used moderate inter-set rest intervals (> 60-< 120s) 39,41,46 and 4 used long inter-set rest intervals (≥ 120 s) 15,21,40,42 . (Tabl 1)." Additionally, in the Results section, under the subheading 'Meta-analyses.Effect of RTH on muscle hypertrophy' , "Subanalysis indicated a small effect on CSA benefiting RTH with the use of moderate hypoxia (SMD = 0.32 [− 0.08, 0.73]; Figure 3A) and moderate loads (SMD = 0.30 [− 0.05, 0.65]; Figure 3B) and a medium effect for longer inter-set rest intervals (SMD = 0.56 [0.05; 1.08]; Figure 3C)." now reads: "Subanalysis indicated a small effect on CSA benefiting RTH with the use of moderate hypoxia (SMD = 0.32 [− 0.08, 0.73]; Figure 3A) and moderate loads (SMD = 0.32 [− 0.08, 0.73]; Figure 3B) and a small effect for short inter-set rest intervals (SMD = 0.21 [− 0.05; 0.47]; Figure 3C)." Furthermore, in the Results section, under the subheading 'Meta-analyses.Effect of RTH on strength development' , "Subanalysis of the length of the inter-set rest interval showed a medium effect favoring RTH with the use of longer inter-set rest intervals (SMD = 0.67 [0.36; 0.98]; Figure 8C).A trivial effect was observed favoring RTH with the use of moderate loads (SMD = 0.18 [0.02, 0.34]; Figure 8B) and severe hypoxia (SMD = 0.16 [− 0.10, 0.43]; Figure 8A)." now reads: "Subanalysis of the length of the inter-set rest interval showed a medium effect favoring RTH with the use of longer inter-set rest intervals (SMD = 0.63 [0.14; 1.12]; Figure 8C).A trivial effect was observed favoring RTH with the use of moderate loads (SMD = 0.20 [0.01, 0.40]; Figure 8B) and severe hypoxia (SMD = 0.24 [− 0.11, 0.58]; Figure 8A)." And, "Heterogeneity between studies was found to be low for 1RM between environmental conditions (I 2 = 18.7%)" now reads: "Heterogeneity between studies was found to be low for 1RM between environmental conditions (I 2 = 13.2%)." In the Figures, Panels (B) and (C) in Figure 3 and Figure 8  show a small to medium beneficial effect of RTH on strength development and CSA improvements compared to the same training protocol under normoxic conditions.However, the inter-set rest period impact on CSA was highly influenced by the results of a single study and thus should be interpreted with some caution 5 .Moreover, the use of moderate hypoxia showed a small beneficial effect on CSA compared to severe." now reads: "In this regard, our findings indicate that the use of moderate training loads and longer inter-set rest intervals show a trivial to medium beneficial effect of RTH on strength development compared to the same training protocol under normoxic conditions.However, the inter-set rest period impact on CSA was highly influenced by the fact that only one study employed rest intervals longer than 60 s 46 ; thus, this finding should be interpreted with some caution.Moreover, the use of moderate loads and hypoxia showed a small beneficial effect on CSA compared to low loads and severe hypoxia." In the Discussion section, under the subheading 'Effect of RTH on muscle hypertrophy' , "A pooled analysis of all studies did not show a beneficial effect for RTH on muscle hypertrophy compared to equivalent training in normoxia (SMD < 0.17).Intriguingly, although short inter-set rest intervals (60-120 s) have been shown to maximize metabolite accumulation, subanalysis of studies indicated that the use of longer inter-set rest intervals with RTH had a moderate benefit on CSA changes (SMD = 0.56 [0.05; 1.08]).Longer inter-set rest periods (> 120 s) are proposed to extend the capacity to maintain intensities of load and volume during training 49,52 , which in turn may have superseded any potential benefits of metabolic stress on hypertrophic adaptations.The interaction between environmental conditions and rest period length is not clear and further research is needed to elucidate the underlying mechanisms for this finding." Vol:.( 1234567890 now reads: "A pooled analysis of all studies did not show a beneficial effect for RTH on muscle hypertrophy compared to equivalent training in normoxia (SMD < 0.17).Subanalysis of studies indicated that the use of shorter inter-set rest intervals with RTH had a small benefit on CSA changes (SMD = 0.21 [− 0.05; 0.47]).However, longer interset rest periods (> 120 s) also are proposed to extend the capacity to maintain intensities of load and volume during training 49,52 , which in turn could supersede any potential benefits of metabolic stress on hypertrophic adaptations.The paucity of studies with moderate and long inter-set rest intervals in this meta-analysis clouds interpretation of the interaction between environmental conditions and rest period length.Further research is needed to elucidate the underlying mechanisms." In the Discussion section, under the subheading 'Effect of RTH on strength development' , "Pooled analysis of all studies did not indicate that RTH increased maximal strength to a greater magnitude than the same training under normoxia (p = 0.14); although the direction of the interaction favored RTH, the point estimate indicated minimal benefits on this outcome (SMD = 0.  "Only 1 of the 3 included studies that employed long inter-set rest intervals 42 showed a clear benefit of hypoxia for strength development (Figure 8.C), which only would partially support this beneficial effect." And, "In contrast, our results revealed that longer rest periods produced moderate gains in 1RM after RTH compared to RTN (SMD = 0.67 [0.36; 0.98]; p < 0.001).This discrepancy may be due to the use of untrained samples in 3 of the studies 5,21,42 ." now reads: "In contrast, our results revealed that longer rest periods produced moderate gains in 1RM after RTH compared to RTN (SMD = 0.63 [0.14; 1.12]).This discrepancy may be due to the use of untrained samples in 2 of the studies 21,42 ." Additionally, in the section of 'Practical Applications' , "The subgroup analysis revealed 2 conditions under which the use of RT in hypoxia may be of benefit: 1) training programs that employ loads between 60-80%1RM and inter-set rest intervals ≥ 120 s show greater increases in muscle strength and CSA compared to normoxia; and 2) moderate hypoxia seems to be more suitable for improvement in muscle hypertrophy compared to severe hypoxia, while this covariate does not appear relevant to gains in 1RM." now reads: "The subgroup analysis revealed 2 conditions under which the use of RT in hypoxia may be of benefit: 1) training programs that employ loads between 60-80%1RM, inter-set rest intervals of ≤ 60 s and moderate hypoxia show greater increases in muscle CSA; 2) training programs that employ loads between 60-80%1RM and inter-set rest intervals ≥ 120 s show greater increases in strength; however, the severity of hypoxia does not appear relevant to gains in 1RM." The original Article has been corrected.
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Figure 3 .Figure 8 .
Figure 3. Forest plot of the standardized mean differences of the resistance training program betweenconditions (hypoxic [H] group vs. normoxic [N] group) on CSA, subanalysed by: (A) severity of the hypoxia; (B) training load; and (C) interset rest interval.Δ: mean differences between post-pre in H and N or between H-N; n: sample size; Spre: mean baseline standard deviation; Std.MD: standard mean difference; RE: random effect's model; CI; confidence interval; FiO 2 : fraction of inspired oxygen; 1RM; 1 repetition maximum; Q: test statistic for the test of heterogeneity; df: degrees of freedom; p: p value; I 2 : I 2 test; τ 2 : tau 2 test; Z: z value.

Figure 8 .
Figure 8. (continued) Table 1, the methodology for Fashi and Ahmadizad and Nishimura et al. were incorrect.The correct and incorrect methodologies appear below.
contained errors and have been updated.The legends are not affected.The original Figures3 and 8and accompanying legends appear below.
"However, subanalyses of data, which considered previously identified potential biases (training load, inter-set rest interval and severity of the hypoxia), suggest a small to medium advantage in the use of moderate training loads and longer inter-set rest period in RT at moderate hypoxia on muscular adaptations (seeFig 3, 5 & 8)." now reads: "However, subanalyses of data, which considered previously identified potential biases (training load, inter-set rest interval and severity of the hypoxia), suggest a trivial to medium advantage in the use of moderate training loads and short to longer inter-set rest period in R T at moderate hypoxia on muscular adaptations (seeFig 3, 5  & 8)."And, "In this regard, our findings indicate that the use of moderate training loads and longer inter-set rest intervals