Skip to main content

Table 4 Nitrate meta-analysis and sub-group analyses

From: Effect of food sources of nitrate, polyphenols, L-arginine and L-citrulline on endurance exercise performance: a systematic review and meta-analysis of randomised controlled trials

 

k

n

SMD (95% CIs)

p

I2 (%)

Overall

81

956

0.15 [0.12, 0.18]

<0.001

6.4

Design

  

Qb: 2.37

0.121

 

Crossover

76

856

0.14 [0.11, 0.17]

<0.001

0

Parallel

5

100

0.36 [0.08, 0.64]

0.011

32

Blinding

  

Qb: 1.29

0.544

 

Single blind

8

77

0.11 [-0.002, 0.22]

0.054

0

Double blind

71

857

0.16 [0.12, 0.19]

<0.001

0

Unclear

2

22

0.07 [-0.14, 0.29]

0.519

60

Supplementation duration

  

Qb: 3.05

0.084

 

Acute

38

437

0.12 [0.06, 0.17]

<0.001

13

Multiple days

43

519

0.18 [0.13, 0.22]

<0.001

9

Sex1

  

Qb: 6.94

0.031

 

Male

59

658

0.16 [0.12, 0.20]

<0.001

0

Female

4

48

0.0 [-0.12, 0.11]

0.988

0

Mixed

16

229

0.15 [0.09, 0.21]

<0.001

0

Performance level

  

Qb: 8.78

0.032

 

PL12

1

14

-0.29 [-0.69, 0.11]

0.156

-

PL2

23

290

0.24 [0.12, 0.35]

<0.001

52

PL2 females

-

    

PL2 males:

17

181

0.24 [0.11, 0.36]

<0.001

52

GXT

3

34

0.16 [-0.14, 0.46]

0.300

80

IGXT

1

14

0.22 [0.01, 0.44]

0.040

 

ITTE

1

12

0.47 [0.03, 0.91]

0.038

 

TT

4

47

0.01 [-0.28, 0.29]

0.975

53

TTE

8

74

0.39 [0.21, 0.57]

<0.001

27

PL3

15

154

0.18 [0.12, 0.24]

<0.001

0

PL3 females

-

    

PL3 males:

15

154

0.18 [0.12, 0.24]

<0.001

0

GXT

2

17

0.1 [-0.27, 0.47]

0.612

53

ITT

2

20

0.17 [0, 0.35]

0.592

0

TT

8

82

0.17 [0.1, 0.24]

<0.001

0

TTE

3

35

0.26 [-0.18, 0.69]

0.249

71

PL4

8

87

0.03 [-0.14, 0.2]

0.762

0

PL4 females

1

14

0.02 [-0.37, 0.42]

0.912

-

PL4 males:

7

73

0.03 [-0.16, 0.22]

0.787

0

GXT

1

12

2.17 [-1.8, 6.14]

0.289

-

TT

6

61

0.02 [-0.17, 0.22]

0.825

0

PL5

6

57

-0.02 [-0.22, 0.17]

0.821

0

PL5 females

1

12

-0.01 [-0.43, 0.42]

0.980

-

PL5 males:

5

45

-0.03 [-0.25, 0.19]

0.808

0

ITTE

1

9

-0.07 [-0.56, 0.42]

0.801

-

TT

4

36

-0.02 [-0.27, 0.23]

0.882

0

Exercise mode

  

Qb: 2.29

0.825

 

Cycling

53

625

0.17 [0.12, 0.22]

<0.001

22

Hand cycling

4

39

0.02 [-0.21, 0.26]

0.859

0

Incline walk/run

1

14

-0.29 [-0.69, 0.11]

0.156

-

Kayaking

2

14

0.13 [-0.02, 0.28]

0.093

0

Rowing

2

20

0.09 [-0.24, 0.42]

0.604

0

Running

15

196

0.14 [0.07, 0.21]

<0.001

19

Swimming

4

48

0.12 [0.004, 0.23]

0.042

0

Test type

  

Qb: 10.29

0.059

 

GXT

15

176

0.15 [0.02, 0.27]

0.023

59

IGXT

2

50

0.13 [0.03, 0.22]

0.008

0

ITT

4

44

0.13 [0.002, 0.27]

0.046

0

ITTE

2

21

0.21 [-0.02, 0.39]

0.244

60

TT

39

436

0.12 [0.07, 0.16]

<0.001

0

TTE

19

229

0.31 [0.20, 0.42]

<0.001

29

Test duration

  

Qb: 2.89

0.577

 

<5 mins:

11

104

0.16 [0.08, 0.23]

<0.001

0

TT

8

70

0.12 [0.04, 0.21]

0.005

0

TTE

3

34

0.32 [0.07, 0.56]

0.011

29

5-10 mins:

24

276

0.18 [0.09, 0.27]

<0.001

31

TT

11

112

0.12 [0.02, 0.22]

0.016

7

TTE

13

164

0.29 [0.13, 0.44]

<0.001

40

10-30 mins:

12

122

0.16 [0.04, 0.28]

0.007

41

TT

9

91

0.12 [-0.004, 0.23]

0.058

41

TTE

3

31

0.44 [0.16, 0.73]

0.002

0

30-60 mins:

5

60

0.08 [-0.11, 0.28]

0.397

0

TT

5

60

0.08 [-0.11, 0.28]

0.397

0

>60 mins:

4

51

0.00 [-0.21, 0.21]

0.986

0

TT

4

51

0.00 [-0.21, 0.21]

0.986

0

Overall (TT & TTE)

56

613

0.15 [0.11, 0.19]

<0.001

2

  1. 1 Sex not specified in two trials. Abbreviations – GXT, graded exercise test; IGXT, intermittent graded exercise test; ITT, intermittent time-trial; ITTE, intermittent time to exhaustion; k, number of trials; LCI, lower confidence interval; n, pooled sample size; PL, performance level; Qb, between-group Q-statistic; SMD, standardised mean difference (Hedge’s g); TT, time-trial; TTE, time to exhaustion; UCI, upper confidence interval
Back to article page

Journal of the International Society of Sports Nutrition

ISSN: 1550-2783

Contact us