Table 1

Definitions of physical exercise interventions and non-exercise comparators

Type	Definition
Intervention
Strengthening	Exercises to increase the power or endurance of cervical musculature, without a specific focus on deep cervical flexors.
Stretching	Static or isometric exercises focussed on muscle lengthening, optionally includes passively added (over)pressure.
Motor control	Exercises to increase the control and coordination of deep cervical musculature, specifically flexors. Most commonly achieved with the craniocervical flexion action.
Proprioception	Exercises to increase the proprioceptive and kinesthetic control of head, neck and eye movements. Examples of proprioceptive training include cervical joint repositioning and gaze direction exercises. While craniocervical flexion exercises also have a proprioceptive component, their primary aim is to improve control of the craniocervical flexion movement and the deep cervical muscles.65 For this reason we opted to keep these as distinct exercise types.
Balance	Exercises aimed at improving postural balance.
Prescribed physical activity	General exercises such as walking, cycling, rowing, aimed at improving overall physical activity.
Yoga/Pilates/Tai Chi/Qigong	Exercises following traditional principles with a physical component.
Range of motion	Exercises aimed at improving range of motion, performed actively without a stretching (static, overpressure) component.
Strengthening+motor control	A combination of strengthening and motor control exercises as described above.
Strengthening+stretching	A combination of strengthening and stretching exercises as described above.
Prescribed physical activity+strengthening	A combination of prescribed physical activity and strengthening exercises as described above.
Multimodal	A combination of three or more of the above-mentioned exercise types.
Control
No treatment/information/sham	No active treatment, no prescribed physical exercise, no physical/manual therapy. Control interventions may include: information, general advice to stay active (without specific exercise instructions), limited pain education, sham.