. 2023 Mar 29;123(8):1655–1670. doi: 10.1007/s00421-023-05176-6

Table 2.

Linear mixed model estimates for acute responses to exhaustive interval training [95% confidence limits]

Dependent variable	Intensity prescription	Intercept	Interval coefficient_(a)	Interval coefficient_(b)	Interval coefficient_(c)	Inter-individual SD	Standard error of estimate	Inter-individual variability (%)	Residual variability (%)
Oxygen uptake (ml·kg⁻¹·min⁻¹)	70%Δ	50.3 [47.4–53.2]	N/A	N/A	N/A	6.6 [4.1–9.3]	2.2 [1.9–2.6]	89.7 [76.2–94.8]	10.3 [5.2–23.4]
85% $\dot{W}$ _max	50.5 [47.4–54.5]	N/A	N/A	N/A	7.4 [4.7–9.9]	2.4 [2.0–2.8]	90.7 [75.9–94.9]	9.3 [5.0–23.0]
120%TT	50.1 [45.9–54.2]	N/A	N/A	N/A	8.3 [5.4–10.9]	2.5 [2.0–3.1]	91.4 [80.6–95.4]	8.6 [4.5–18.8]
80%W'	51.2 [47.5–55.2]	N/A	N/A	N/A	8.2 [5.3–10.3]	2.4 [1.9–2.9]	92.3 [83.2–95.7]	7.7 [4.1–16.5]
Ratings of perceived exertion	70%Δ	13.8 [12.9–14.7]	1.6 [1.3–1.9]	– 0.08 [– 0.12 to – 0.06]	N/A	1.6 [1.0–2.2]	1.0 [0.8–1.2]	73.5 [49.4–84.9]	26.5 [14.8–48.2]
85% $\dot{W}$ _max	13.1 [11.5–14.6]	3.5 [2.2–4.9]	– 0.55 [– 0.94 to – 0.25]	0.03 [0.01–0.06]	1.4 [0.8–2.1]	1.2 [0.9–1.5]	57.3 [26.3–78.9]	42.7 [21.0–72.0]
120%TT	14.0 [12.7–15.2]	2.1 [1.6–2.5]	– 0.12 [– 0.16 to – 0.07]	N/A	2.3 [1.4–3.3]	1.0 [0.8–1.2]	83.8 [65.1–92.9]	16.2 [7.0–32.2]
80%W'	13.1 [11.2–14.6]	3.5 [2.3 – 4.8]	– 0.55 [– 0.90 to – 0.26]	0.03 [0.01–0.05]	1.4 [0.8–2.1]	1.2 [0.9–1.5]	57.3 [29.2–78.6]	42.7 [21.0–69.8]
Blood lactate concentration (mmol·L⁻¹)	70%Δ	4.4 [2.2–6.4]	5.0 [3.6–6.3]	– 0.9 [– 1.2 to – 0.6]	0.04 [0.03–0.06]	2.9 [1.9–3.9]	1.6 [1.3–1.8]	77.8 [57.2–87.6]	22.2 [12.2–42.8]
85% $\dot{W}$ _max	5.5 [3.6–7.1]	4.9 [3.8–6.1]	– 0.9 [– 1.1 to – 0.6]	0.05 [0.03–0.06]	3.1 [2.0–4.1]	1.1 [1.0–1.3]	87.8 [74.2–93.6]	12.2 [5.9–25.4]
120%TT	5.5 [3.1–7.8]	5.9 [4.0–8.0]	– 1.1 [– 1.7 to – 0.7]	0.06 [0.03–0.10]	3.3 [2.1–4.4]	1.6 [1.3–1.9]	79.7 [60.5–90.3]	20.3 [9.5–38.4]
80%W'	9.3 [7.2–11.1]	2.8 [2.0 – 3.4]	– 0.3 [– 0.4 to – 0.2]	N/A	3.2 [1.9–4.2]	1.7 [1.3–2.0]	78.5 [51.0–89.5]	21.5 [10.5–47.6]
Heart rate (beats·min⁻¹)	70%Δ	161 [154–168]	5 [3–7]	– 0.4 [– 0.6 to – 0.2]	N/A	12 [7–16]	6 [5–7]	77.0 [55.9–87.2]	23.0 [12.6–43.2]
85% $\dot{W}$ _max	157 [147–165]	10 [4–14]	– 1.9 [– 3.1 to – 0.6]	0.1 [0.0–0.2]	12 [8–17]	6 [5–7]	80.2 [61.4–90.0]	19.8 [9.7–37.5]
120%TT	161 [153–167]	5 [2–6]	– 0.3 [– 0.5 to – 0.1]	N/A	15 [9–21]	4 [3–5]	93.7 [85.6–97.1]	6.3 [2.8–14.3]
80%W'	164 [158–170]	4 [2–5]	– 0.3 [– 0.5 to 0.0]	N/A	11 [8–15]	5 [3–5]	85.3 [72.0–93.2]	14.7 [6.4–26.7]
Ventilation (L·min⁻¹)	70%Δ	125 [115–136]	9 [4–12]	– 0.6 [– 0.9 to – 0.1]	N/A	19 [13–26]	12 [9–13]	72.8 [50.8–83.5]	27.2 [16.1–47.3]
85% $\dot{W}$ _max	133 [120–146]	7 [2–12]	– 0.5 [– 0.9–0.0]	N/A	20 [12–27]	11 [9–13]	74.7 [49.2–87.2]	25.3 [12.8–48.8]
120%TT	131 [118–143]	9 [3–15]	– 0.7 [– 1.4 to – 0.2]	N/A	20 [14–29]	13 [10–15]	71.3 [49.0–86.8]	28.7 [12.9–49.5]
80%W'	138 [128–151]	7 [3–10]	– 0.5 [– 0.8 to 0.0]	N/A	22 [14–29]	9 [7–11]	84.2 [67.2–92.8]	15.8 [7.1–31.7]
Respiratory frequency (cycles·min⁻¹)	70%Δ	43 [38–48]	5 [3–6]	– 0.2 [– 0.3 to – 0.1]	N/A	12 [8–15]	4 [4–5]	87.9 [74.9–92.6]	12.1 [7.4–24.3]
85% $\dot{W}$ _max	45 [39–51]	5 [4–7]	– 0.4 [– 0.5 to – 0.2]	N/A	10 [7–13]	4 [3–4]	88.4 [72.6–93.3]	11.6 [6.5–25.5]
120%TT	39 [33–46]	13 [8–17]	– 2.2 [– 3.4 to – 1.1]	0.1 [0.0–0.2]	11 [7–14]	4 [3–4]	89.3 [78.0–95.0]	10.7 [5.0–21.0]
80%W'	43 [36–49]	9 [5–14]	– 1.4 [– 2.6 to – 0.5]	0.1 [0.0–0.1]	11 [7–15]	4 [3–4]	90.8 [80.2–96.1]	9.2 [3.8–18.7]
ΔStO₂ (%)	70%Δ	– 21.4 [– 24.5 to – 18.3]	– 0.4 [– 0.6 to – 0.1]	N/A	N/A	7.0 [4.3–9.5]	2.8 [2.3–3.2]	86.5 [68.9–93.2]	13.5 [6.7–30.1]
85% $\dot{W}$ ˙_max	– 20.9 [– 23.3 to – 17.9]	– 0.3 [– 0.5 to – 0.1]	N/A	N/A	5.1 [3.2–6.7]	1.4 [1.1–1.6]	93.2 [84.1–96.5]	6.8 [3.4–15.8]
120%TT	– 21.7 [– 25.5 to – 17.4]	1.5 [– 0.3–3.1]	– 0.4 [– 0.7 to – 0.1]	N/A	6.8 [4.1–9.9]	1.7 [1.3–2.1]	94.3 [85.1–97.6]	5.7 [2.2–14.9]
80%W'	– 19.4 [– 22.3 to – 16.6]	– 0.5 [– 0.7 to – 0.3]	N/A	N/A	5.7 [3.7–7.6]	1.3 [1.0–1.6]	95.3 [88.1–97.9]	4.7 [2.1–11.5]
Δdeoxy[heme] (µm)	70%Δ	84 [69–100]	1.5 [0.6–2.3]	N/A	N/A	32 [20–42]	10 [8–11]	91.4 [80.6–95.2]	8.6 [4.7–18.6]
85% $\dot{W}$ _max	80 [69–95]	1.1 [0.2–1.8]	N/A	N/A	21 [13–28]	6 [5–7]	92.7 [80.1–96.3]	7.3 [3.5–18.8]
120%TT	79 [64–91]	1.7 [0.3–3.0]	N/A	N/A	29 [19–39]	5 [4–6]	97.3 [93.0–98.9]	2.7 [1.1–7.0]
80%W'	82 [67–96]	1.9 [0.7–3.0]	N/A	N/A	32 [21–44]	6 [5–7]	96.3 [91.4–98.2]	3.7 [1.6–8.0]
Cadence (rev·min⁻¹)	70%Δ	102 [98–107]	– 2 [– 2 to – 1]	N/A	N/A	9 [6–12]	5 [4–6]	74.7 [53.6–85.3]	25.3 [14.7–45.6]
85% $\dot{W}$ _max	101 [97–105]	– 2 [– 2 to – 1]	N/A	N/A	8 [5–11]	6 [4–6]	74.3 [48.6–87.3]	25.7 [12.3–51.0]
120%TT	100 [94–104]	– 2 [– 3 to – 1]	N/A	N/A	9 [5–13]	6 [5–7]	68.9 [43.0–83.3]	31.1 [16.6–56.3]
80%W'	100 [95–105]	– 2 [– 3 to – 1]	N/A	N/A	9 [6–12]	5 [4–6]	77.0 [55.9–89.0]	23.0 [10.9–43.8]

Dependent variable

Intensity prescription

Intercept

Interval coefficient_(a)

Interval coefficient_(b)

Interval coefficient_(c)

Inter-individual SD

Standard error of estimate

Inter-individual variability (%)

Residual variability (%)

Oxygen uptake (ml·kg⁻¹·min⁻¹)

70%Δ

50.3

[47.4–53.2]

N/A

6.6

[4.1–9.3]

2.2

[1.9–2.6]

89.7

[76.2–94.8]

10.3

[5.2–23.4]

85%

\dot{W}

_max

50.5

[47.4–54.5]

N/A

7.4

[4.7–9.9]

2.4

[2.0–2.8]

90.7

[75.9–94.9]

9.3

[5.0–23.0]

120%TT

50.1

[45.9–54.2]

N/A

8.3

[5.4–10.9]

2.5

[2.0–3.1]

91.4

[80.6–95.4]

8.6

[4.5–18.8]

80%W'

51.2

[47.5–55.2]

N/A

8.2

[5.3–10.3]

2.4

[1.9–2.9]

92.3

[83.2–95.7]

7.7

[4.1–16.5]

Ratings of perceived exertion

70%Δ

13.8

[12.9–14.7]

1.6

[1.3–1.9]

– 0.08 [– 0.12 to – 0.06]

N/A

1.6

[1.0–2.2]

1.0

[0.8–1.2]

73.5

[49.4–84.9]

26.5

[14.8–48.2]

85%

\dot{W}

_max

13.1

[11.5–14.6]

3.5

[2.2–4.9]

– 0.55

[– 0.94 to – 0.25]

0.03

[0.01–0.06]

1.4

[0.8–2.1]

1.2

[0.9–1.5]

57.3

[26.3–78.9]

42.7

[21.0–72.0]

120%TT

14.0

[12.7–15.2]

2.1

[1.6–2.5]

– 0.12

[– 0.16 to – 0.07]

N/A

2.3

[1.4–3.3]

1.0

[0.8–1.2]

83.8

[65.1–92.9]

16.2

[7.0–32.2]

80%W'

13.1

[11.2–14.6]

3.5

[2.3 – 4.8]

– 0.55

[– 0.90 to – 0.26]

0.03

[0.01–0.05]

1.4

[0.8–2.1]

1.2

[0.9–1.5]

57.3

[29.2–78.6]

42.7

[21.0–69.8]

Blood lactate concentration (mmol·L⁻¹)

70%Δ

4.4

[2.2–6.4]

5.0

[3.6–6.3]

– 0.9

[– 1.2 to – 0.6]

0.04

[0.03–0.06]

2.9

[1.9–3.9]

1.6

[1.3–1.8]

77.8

[57.2–87.6]

22.2

[12.2–42.8]

85%

\dot{W}

_max

5.5

[3.6–7.1]

4.9

[3.8–6.1]

– 0.9

[– 1.1 to – 0.6]

0.05

[0.03–0.06]

3.1

[2.0–4.1]

1.1

[1.0–1.3]

87.8

[74.2–93.6]

12.2

[5.9–25.4]

120%TT

5.5

[3.1–7.8]

5.9

[4.0–8.0]

– 1.1

[– 1.7 to – 0.7]

0.06

[0.03–0.10]

3.3

[2.1–4.4]

1.6

[1.3–1.9]

79.7

[60.5–90.3]

20.3

[9.5–38.4]

80%W'

9.3

[7.2–11.1]

2.8

[2.0 – 3.4]

– 0.3

[– 0.4 to – 0.2]

N/A

3.2

[1.9–4.2]

1.7

[1.3–2.0]

78.5

[51.0–89.5]

21.5

[10.5–47.6]

Heart rate (beats·min⁻¹)

70%Δ

161

[154–168]

[3–7]

– 0.4

[– 0.6 to – 0.2]

N/A

[7–16]

[5–7]

77.0

[55.9–87.2]

23.0

[12.6–43.2]

85%

\dot{W}

_max

157

[147–165]

[4–14]

– 1.9

[– 3.1 to – 0.6]

0.1

[0.0–0.2]

[8–17]

[5–7]

80.2

[61.4–90.0]

19.8

[9.7–37.5]

120%TT

161

[153–167]

[2–6]

– 0.3

[– 0.5 to – 0.1]

N/A

[9–21]

[3–5]

93.7

[85.6–97.1]

6.3

[2.8–14.3]

80%W'

164

[158–170]

[2–5]

– 0.3

[– 0.5 to 0.0]

N/A

[8–15]

[3–5]

85.3

[72.0–93.2]

14.7

[6.4–26.7]

Ventilation (L·min⁻¹)

70%Δ

125

[115–136]

[4–12]

– 0.6

[– 0.9 to – 0.1]

N/A

[13–26]

[9–13]

72.8

[50.8–83.5]

27.2

[16.1–47.3]

85%

\dot{W}

_max

133

[120–146]

[2–12]

– 0.5

[– 0.9–0.0]

N/A

[12–27]

[9–13]

74.7

[49.2–87.2]

25.3

[12.8–48.8]

120%TT

131

[118–143]

[3–15]

– 0.7

[– 1.4 to – 0.2]

N/A

[14–29]

[10–15]

71.3

[49.0–86.8]

28.7

[12.9–49.5]

80%W'

138

[128–151]

[3–10]

– 0.5

[– 0.8 to 0.0]

N/A

[14–29]

[7–11]

84.2

[67.2–92.8]

15.8

[7.1–31.7]

Respiratory frequency (cycles·min⁻¹)

70%Δ

[38–48]

[3–6]

– 0.2

[– 0.3 to – 0.1]

N/A

[8–15]

[4–5]

87.9

[74.9–92.6]

12.1

[7.4–24.3]

85%

\dot{W}

_max

[39–51]

[4–7]

– 0.4

[– 0.5 to – 0.2]

N/A

[7–13]

[3–4]

88.4

[72.6–93.3]

11.6

[6.5–25.5]

120%TT

[33–46]

[8–17]

– 2.2

[– 3.4 to – 1.1]

0.1

[0.0–0.2]

[7–14]

[3–4]

89.3

[78.0–95.0]

10.7

[5.0–21.0]

80%W'

[36–49]

[5–14]

– 1.4

[– 2.6 to – 0.5]

0.1

[0.0–0.1]

[7–15]

[3–4]

90.8

[80.2–96.1]

9.2

[3.8–18.7]

ΔStO₂ (%)

70%Δ

– 21.4

[– 24.5 to – 18.3]

– 0.4

[– 0.6 to – 0.1]

N/A

7.0

[4.3–9.5]

2.8

[2.3–3.2]

86.5

[68.9–93.2]

13.5

[6.7–30.1]

85%

\dot{W}

˙_max

– 20.9

[– 23.3 to – 17.9]

– 0.3

[– 0.5 to – 0.1]

N/A

5.1

[3.2–6.7]

1.4

[1.1–1.6]

93.2

[84.1–96.5]

6.8

[3.4–15.8]

120%TT

– 21.7

[– 25.5 to – 17.4]

1.5

[– 0.3–3.1]

– 0.4

[– 0.7 to – 0.1]

N/A

6.8

[4.1–9.9]

1.7

[1.3–2.1]

94.3

[85.1–97.6]

5.7

[2.2–14.9]

80%W'

– 19.4

[– 22.3 to – 16.6]

– 0.5

[– 0.7 to – 0.3]

N/A

5.7

[3.7–7.6]

1.3

[1.0–1.6]

95.3

[88.1–97.9]

4.7

[2.1–11.5]

Δdeoxy[heme] (µm)

70%Δ

[69–100]

1.5

[0.6–2.3]

N/A

[20–42]

[8–11]

91.4

[80.6–95.2]

8.6

[4.7–18.6]

85%

\dot{W}

_max

[69–95]

1.1

[0.2–1.8]

N/A

[13–28]

[5–7]

92.7

[80.1–96.3]

7.3

[3.5–18.8]

120%TT

[64–91]

1.7

[0.3–3.0]

N/A

[19–39]

[4–6]

97.3

[93.0–98.9]

2.7

[1.1–7.0]

80%W'

[67–96]

1.9

[0.7–3.0]

N/A

[21–44]

[5–7]

96.3

[91.4–98.2]

3.7

[1.6–8.0]

Cadence (rev·min⁻¹)

70%Δ

102

[98–107]

– 2

[– 2 to – 1]

N/A

[6–12]

[4–6]

74.7

[53.6–85.3]

25.3

[14.7–45.6]

85%

\dot{W}

_max

101

[97–105]

– 2

[– 2 to – 1]

N/A

[5–11]

[4–6]

74.3

[48.6–87.3]

25.7

[12.3–51.0]

120%TT

100

[94–104]

– 2

[– 3 to – 1]

N/A

[5–13]

[5–7]

68.9

[43.0–83.3]

31.1

[16.6–56.3]

80%W'

100

[95–105]

– 2

[– 3 to – 1]

N/A

[6–12]

[4–6]

77.0

[55.9–89.0]

23.0

[10.9–43.8]

Formula: dependent variable = intercept + interval coefficient_(a) · x + interval coefficient_(b) · x² + interval coefficient_(c) · x³, where x = work interval number. ΔStO₂, changes from a resting baseline in muscle tissue oxygen saturation; Δdeoxy[heme], changes from a resting baseline in the concentration of deoxygenated heme compounds; N/A, not applicable (i.e., consider the coefficient as 0). See text for intensity prescription abbreviations