Study | Indices | Male | Female |

Shiota et al. [22] | R_{5} | R_{5}=8.67158−3.841167·log(h) | R_{5}=8.67158−3.841167·log(h) |

R_{20} | R_{20}=5.841867−2.546561·log(h) | R_{20}=5.841867−2.546561·log(h) | |

X_{5} | X_{5}= −2.343672−0.000097a+1.018597·log(h) | X_{5}= −2.343672−0.000097a+1.018597·log(h) | |

AX | Not available | Not available | |

Newbury et al. [20] | R_{5} | R_{5}=1.1672−0.0017a−0.007h+0.0043w | R_{5}=0.768−0.00064a−0.00276h |

R_{20} | R_{20}=0.9216−0.0013a−0.0049h+0.0027w | R_{20}=0.4821+0.00034a−0.00125h | |

X_{5} | X_{5}= −0.3593+0.00013a+0.0016h | X_{5}= −0.4689−0.00092a+0.00245h | |

AX | Not available | Not available | |

Brown et al. [18]^{#} | R_{6} | log(R_{6})=3.18955−0.01617h+0.00882w | log(R_{6})=3.88965−0.01944h+0.00812w |

R_{19} | log(R_{19})=2.89318−0.01445h+0.00789w | log(R_{19})=3.25796−0.01519h+0.00605w | |

X_{6} | exp(X_{6})= −1.23047+0.01286a−0.00013712a^{2}+0.01098h−0.00323w | exp(X_{6})= −1.36295+0.00845a−0.0001035a^{2}+0.01282h−0.00449w | |

AX | Not available | Not available | |

Aarli et al. [24] | R_{5} | ln(R_{5})=3.02−0.023h | ln(R_{5})=2.68−0.026h+0.012w |

R_{20} | ln(R_{20})=1.52−0.016h | ln(R_{20})=1.26−0.017h+0.009w | |

X_{5} | ln(−X_{5})=3.57−0.033h | ln(−X_{5})=3.85−0.041h+0.014w | |

AX | ln(AX)=12.0−0.074h | ln(AX)=10.8−0.074h | |

Schulz et al. [23] | R_{5} | 5th quantile: R_{5}=1.0685571−0.0022403a−0.004312h | R_{5}=0.5012224+0.0002940a−0.0037866h+0.0045199w |

50th quantile: R_{5}=0.9861137−0.0001223a−0.0055278h+0.0029891w | R_{5}=0.7887960+0.0015118a−0.0046594h+0.0029768w | ||

95th quantile: R_{5}=0.6683472+0.0029051a−0.0026280h | R_{5}=0.1926787+0.0004133a+0.0016756h | ||

R_{20} | 5th quantile: R_{20}=0.6342369−0.0019656a−0.0021069h | R_{20}=0.5970057−0.0006897a−0.0030934h+0.0016623h | |

50th quantile: R_{20}=0.7722257−0.0006446a−0.0037120h+0.0013924w | R_{20}=0.4505645+0.0001251a−0.0020488h+0.0017939w | ||

95th quantile: R_{20}=1.1824320−0.0003590a−0.0048639h | R_{20}=0.8177947−0.0003549a−0.0025771h | ||

X_{5} | 5th quantile: X_{5}= −0.5568254−0.0004762a+0.0025397h | X_{5}= −0.5446960−0.0018068a+0.0029323h | |

50th quantile: X_{5}= −0.4670275−0.0003344a+0.0027755h−0.0010424w | X_{5}= −0.3313017−0.0007541a+0.0022090h−0.001413w | ||

95th quantile: X_{5}= −0.2058333+0.0006944a+0.0006944h | X_{5}= −0.1831886+0.0003607a+0.0005743h | ||

AX | 5th quantile: AX=0.0430162+0.0012195a−0.0002327h | AX=1.0968758−0.0001349a−0.0077805h+0.0048793w | |

50th quantile: AX=1.7584772+0.0027451a−0.0132469h+0.0077552w | AX=1.7909627+0.0110077a−0.0168559h+0.0104360w | ||

95th quantile: AX=2.2955939+0.0161916a−0.0139157h | AX=2.7124098+0.0173679a−0.0227368h+0.0152978w | ||

Oostveen et al. [16]^{¶,+} | R_{5} | ln(R_{5})=5.327−0.00381a−3.032h+0.01390w | ln(R_{5})=2.591+0.00279a−1.461h+0.0121w |

R_{20} | ln(R_{20})=3.540−0.0033a−1.824h+0.00888w | ln(R_{20})=2.482+0.00135a−1.122h+0.00695w | |

X_{5} | ln(4−X_{5})=2.683+0a−0.703h+0.0019w | ln(4−X_{5})=2.373+0.0015a−0.607h+0.00312w | |

AX_{5} | ln(AX_{5})=9.730+0a−6.107h+0.02122w | ln(AX_{5})=5.490+0.00960a−4.122h+0.02836w | |

Ribeiro et al. [21]^{#,¶} | R_{6} | ln(R_{6})=2.964−0.002a−1.545h+0.009w | R_{6}=8.164−0.006a−3.563h+0.014w |

R_{20} | ln(R_{20})=2.196−0.002a−0.970h+0.005w | R_{20}=9.142−0.005a−3.811h+0.003w | |

X_{6} | exp(X_{6})= −1.082+0a+0.983h−0.003w | X_{6}= −5.293+0a+2.759h−0.007w | |

AX | Not available | Not available | |

De et al. [19]^{#} | R_{5} | R_{5}=10.035+0.008a−0.057h+0.036w | R_{5}=9.697−0.046h+0.033w |

R_{19} | R_{19}=8.077−0.040h+0.02w | R_{19}=8.683−0.038h+0.019w | |

X_{5} | X_{5}= −3.334−0.004a+0.018h−0.009w | X_{5}= −4.40+0.02h | |

AX | Not available | Not available | |

Moitra et al. [15]^{¶} | R_{5} | ln(R_{5})= −0.30+0.003a−0.83h+0.01w | ln(R_{5})=0.003+0.004a−0.66h+0.007w |

R_{20} | ln(R_{20})= −0.14−0.001a−0.99h+0.01w | ln(R_{20})=0.164+0.0003a−0.92h+0.007w | |

X_{5} | X_{5}= −0.23−0.002a+0.15h−0.002w | X_{5}= −0.60−0.004a+0.37h−0.001w | |

AX | ln(AX)= −0.20+1.24ln(a)−2.98h+0.01w | ln(AX)= −2.33+0.76ln(a)−0.004h+0.004w | |

Berger et al. [17]^{¶,+} | R_{5} | ln(R_{5})=2.07069−1.05124h+0.03337·BMI | ln(R_{5})=2.22395−0.98351h+0.02903·BMI |

R_{20} | ln(R_{20})=1.95570−0.81148h+0.02042·BMI | ln(R_{20})=2.01077−0.72768h+0.02009·BMI | |

X_{5} | ln(X_{5}+4)=0.10509+0.82626h−0.01775·BMI | ln(X_{5}+4)=0.29066+0.73387h−0.01984·BMI | |

AX | ln(AX)=4.36142−3.47450h+0.08784·BMI | ln(AX)=4.67153−3.31633h+0.06719·BMI |

Reference equations developed by included studies for R_{6}, R_{19} and X_{6} instead of R_{5}, R_{19} and X_{5}, respectively were considered. Respiratory resistance (R_{rs}) and respiratory reactance (X_{rs}) measured in kPa·L^{−1}·s^{−1} and AX measured in kPa·L^{−1} unless otherwise indicated. Age (a), height (h), weight (w) and body mass index (BMI) measured in years, cm, kg and kg·m^{−2}, respectively, unless otherwise indicated. Shiota *et al*. [22] developed unisex reference equations. Schulz *et al*. [23] developed reference equations for the 5th, 50th and 95th quantiles. For Oostveen *et al*. [16] the equations for AX_{5} are included. R_{5}: resistance at 5 Hz; R_{20}: resistance at 20 Hz; X_{5}: reactance at 5 Hz; AX: reactance area; R_{6}: resistance at 6 Hz; R_{19}: resistance at 19 Hz; X_{6}: reactance at 6 Hz. ^{#}: R_{rs} and X_{rs} measured in cmH_{2}O·L^{−1}·s^{−1} and AX measured in cmH_{2}O·L^{−1}; ^{¶}: height measured in metres (m); ^{+}: R_{rs} and X_{rs} measured in hPa·L^{−1}·s^{−1} and AX measured in hPa·L^{−1}.