Table 2

Characteristics of included articles: interventions

Author (year)	Design	Intervention programme	Intervention group	Comparison group(s)
*Schmidt et al* 27 (2013)** ^δ	NRCT	24 weeks; 2/week; 60 min.	ST: indoor; 4–6 players a side; 5×10 min SSG; 1.2 sessions/week completed; 82% HRmax.	CG: maintain daily lifestyle.
Andersen et al 28 (2014)^δ	NRCT	As above (see Schmidt et al, 2013).	As above (see Schmidt et al, 2013), but 1.5 sessions/week completed with average intensity of 83% HRmax.	As above (see Schmidt et al, 2013).
*Schmidt et al* 22 (2014)^α**	RCT	12 months; (month 1–4) 2/week, (month 5–12) 3/week; 1hour.	ST: outdoor/indoor; 3–5 players a side; supervised, (months 1–3) 3×15 min SSG, (months 3–12) 4×15 min SSG; 66% of all sessions completed.	RT: supervised, 5 UL and LL ex (two additional exercises added from week 25) and 5 min core training, (months 0–3) 3 sets/ex with 1.5 min rest, (months 3–12) 4 sets/ex with 3 min rest, (months 0–1) 16–20 RM, (months 2–12) 8–12 RM; 73% of all sessions completed.CG: maintain usual lifestyle.
Andersen et al 29 (2014)^α	RCT	16 weeks; 2/week; 1 hour.	As above (see Schmidt et al, 2014), but only played outdoors (4–6 players a side), 77.1% of all sessions completed with average intensity of ~82% HRmax.	As above (see Schmidt et al, 2014), but 74.1% of all sessions completed.
Helge et al 30 (2014)^α	RCT	As above (see Schmidt et al, 2014).	As above (see Schmidt et al, 2014), but only played outdoors with average intensity of ~82% HRmax.	As above (see Schmidt et al, 2014), but the rest interval for weeks 13–52 was 1.5 min.
Andersen et al 31 (2016)^α	RCT	As above (see Schmidt et al, 2014)	As above (see Schmidt et al, 2014).	As above (see Schmidt et al, 2014), but the rest interval for weeks 13–52 was 1.5 min.
Sundstrup et al 32 (2016)^α	RCT	As above (see Schmidt et al, 2014).	As above (see Schmidt et al, 2014), but 4–5 players a side with average intensity of ~82% HRmax.	As above (see Schmidt et al, 2014), but the rest interval for weeks 13–52 was 1.5 min.
*Uth et al* 33 (2014)^γ**	RCT	12 weeks; (weeks 1–8) 2/week, (weeks 9–12) 3/week; (weeks 1–4) 45 min, (weeks 5–12) 1hour.	ST: outdoor/indoor; 5–7 players a side; supervised, (weeks 1–4) 2×15 min and (weeks 5–12) 3×15 min SSG; 76.5% of all sessions completed; 84.6% HRmax.	CG: maintain daily lifestyle.
Uth et al 34 (2016)^γ	RCT	32 weeks; (weeks 1–8) 2/week, (weeks 9–12) 3/week, (weeks 13–32) 2/week; (weeks 0–4) 45 min, (weeks 5–32) 1 hour.	ST: supervised (weeks 1–4) 2×15 min SSG, (weeks 5–32) 3×15 min SSG; 46.2%–76.5% of all sessions completed.	As above (see Uth et al, 2014).
Uth et al 35 (2016)^γ	RCT	As above (see Uth et al, 2014).	As above (see Uth et al, 2014), but 3–7 players a side without reporting training intensity.	As above (see Uth et al, 2014).
*de Sousa et al* 36 (2014)^β**	RUT	12 weeks; (NC) 1/week; (NEP) 1/2 weeks; (SSG) 3/week; (NEP) 1 hour; (SSG) 40 min.	ST: outdoor/indoor; 3–7 players a side; 2×12 min SSG; >70% to >90% HRmaxDI: NC and NEP (cut 500–1000 kcal/day/subject).	DI: NC and NEP (cut 500–1000 kcal/day/subject).
de Sousa et al 37 (2017)^β	RUT	As above (see de Sousa et al, 2014).	As above (see de Sousa et al, 2014), but training was supervised.	As above (see de Sousa et al, 2014).
*Reddy et al* 38 (2017)**	RCT	12 weeks; 1/week; 1hour.	ST: outdoor; 5 players a side; walking soccer games; average 9.4 sessions completed; 76% HRmax.	CG: maintain daily lifestyle.

α, β,γ,δ: Studies based on the same trial.
As trial results are described in more than one paper, the bolded study represents the first published paper from a given exercise trial.
CG, control group; DI, dietary intervention; ex, exercise; HRmax, maximum heart rate; LL, lower limb; NC, nutritional counselling; NEP, Nutritional Education Programme; NRCT, non-randomised controlled trial; RCT, randomised controlled trial; RM, repetition maximum; RT, resistance training; RUT, randomised uncontrolled trial; SSG, small-sided games; ST, soccer training; UL, upper limb.