Table 1.

Overview over measurements across the three questionnaires

Concept	Indicator	Questionnaire T 0 T 1 T 2			Instrument
Personal characteristics	Sex, age, ethnic background, education, employment	X
Life prospects	Subjective health	X	X	X	2 items from SF-36
	Problem behaviour	X	X	X	SDQ
	School or employment status	X	X	X
	Functioning at school or work	X	X	X
Self-regulation skills	Planning	X	X	X	Planning subscale SRL-SRS
	Self-monitoring	X	X	X	Self-monitoring subscale SRL-SRS
	Effort	X	X	X	Effort subscale SRL-SRS
	Reflection	X	X	X	Reflection subscale SRL-SRS
Sense of coherence	Sense of coherence	X	X	X	Orientation to Life Questionnaire (SOC-13)
Sport participation	Frequency and duration	X	X	X	RSO
	Type of sport	X	X	X	RSO
	Membership sport/fitness club	X	X	X	RSO
	Sport as part of treatment plan		X
Sport climate	Motivational sport climate		X	X	MCSYS

Note. SDQ: Strengths and Difficulties Questionnaire; SRL-SRS: Self-Regulation of Learning Self-Report Scale; RSO: Richtlijn Sportdeelname Onderzoek; MCSYS: Motivational Climate Scale for Youth Sports.