Table 1 Study characteristics of included studies

Chiu and Lo [4]

Hong Kong

Cross-sectional

Total (n = 46)

Neck pain (n = 21)

Age: Mean (SD) (years)

Neck pain: 27.0 (9.5)

Gender: M/F

All participants: 24:22

Neck pain: 9:12

Mechanical neck pain

Disability: Not reported

Pain duration: Not reported

Intensity of pain: Not reported

Multi Cervical Rehabilitation (Hanoun Medical Inc., Ontario)

Cibulka et al. [3]

USA

Cross-sectional

Total (n = 51)

Neck pain (n = 37)

Age: Mean (SD) (years)

Neck pain: 22.8 (3.5)

Gender: M/F

All participants: 18:33

Neck pain: 14:23

Mechanical neck pain

Disability: Not reported

Pain duration: Not reported

Intensity of pain: Not reported

Handheld dynamometer (Microfet) (Hogan Health Industries, Salt Lake City, UT)

Jordan et al. [11]

Denmark

Not reported

Total (n = 199)

Neck pain (n = 119)

Age: Mean (SD) (years)

Not reported

Gender: M/F

All participants: 71:128

Neck pain: 31:88

Not reported

Disability: Not reported

Pain duration:

42 patients reported NP <3 years

40 patients reported NP >3 years

28 patients reported NP >5 years

9 patients reported NP >10 years

Intensity of pain: Median (IQR)

13 (8.30)

Strain gauge Dynamometer (Neck Exercise Unit, Follo, Norway)

O’Leary et al. [25]

Australia

Not reported

Total (n = 20)

History of neck pain (n = 12)

Age: Mean (range) (years)

Total: 27.9 (18–47)

Gender: M/F

All participants: 5:15

Not reported

Disability:

Mean (range)

History of neck pain

20.4 (10–46)

Pain duration: Not reported

Intensity of pain: Not reported

Isometric Dynamometer (NeckMetrix, UniQuest Pty Ltd, The University of Queensland, Brisbane, Australia)

Pearson et al. [26]

Canada

Cross-sectional, repeated-measures design

Total (n = 42)

Chronic WAD (n = 14)

Age: Mean ± SD (range) (years)

WAD:

36.6 ± 10.8 (24–58)

Gender: M/F

All participants: 24:18

WAD: 8:6

Whiplash

Disability

(NDI) (/50):

WAD (/50)

20.0 ± 6.9 (10–33)

Pain duration: Not reported

Intensity of pain at rest (/100mm):

Session 1–33.4 ± 18.8

Session 2–27.4 ± 20.7

Multi-Cervical Unit

(MCU, BTE Technologies, Inc.)

Scheuer and Friedrich [28]

USA

Non-randomized controlled trial

Total (n = 95)

Neck pain (n = 53)

Age: Mean (SD) (years)

Neck pain:

49.72 (10.74)

Gender: M/F

All participants: 26:69

Neck pain: 14:39

Not reported

Disability: Not reported

Pain duration: Not reported

Intensity of pain: Not reported

(Back Check 607) Multifunctional Measurement Unit (Dr. Wolff Sports & Prevention GmbH, Arnsberg, Germany)

Shahidi et al. [30]

USA

Repeated measures design

Total (n = 39)

Neck pain (n = 19)

Age: Mean (SD) (years)

Neck pain:

34.9 (9.9)

Gender: M/F

All participants: 20:19

Neck pain: 10:9

Not reported

Disability:

NDI (points): mean (SD)

Neck pain

14.4 (7.3)

Pain duration: Not reported

Intensity of pain: Not reported

Handheld dynamometer (FPIX 100kg load cell, Wagner Instruments, Greenwich, CT)

Vernon et al. [33]

Canada

Analytic survey

Neck pain (n = 24)

Age: Mean (SD) (years)

Neck pain:

Male: 39 (7)

Female: 36 (10)

Gender: M/F

Neck pain: 12:12

Mechanical neck pain syndrome

1. Whiplash-type cervical sprain/strain injury (n = 8)

2. Non-traumatic mechanical complaints related to postural or occupational strains (n = 16)

Disability: Not reported

Pain duration: Mean

1. Whiplash-type cervical sprain/strain injury: 22.5 weeks

2. Nontraumatic mechanical complaints related to postural or occupational strains: 110 weeks

Intensity of pain: Not reported

Modified sphygmomanometer dynamometer (Magnatec Co. Ltd., Concord, Ontario, Canada)

Ylinen et al. [37]

Finland

Cross sectional

Total (n = 42)

Neck pain (n = 21)

Age: Mean (SD) (years)

Neck pain: 44 (6)

Gender: M/F

No male

42 females

Non-specific neck pain

Disability: Mean ± SD

Vernon disability index: 13 ± 5

Pain duration: Mean (SD)

9 (6) years

Intensity of pain: (VAS)

54 ± 22mm

Strain gauge dynamometer (Kuntovaline Inc., Helsinki, Finland)