Table 1. Methodological characteristics of the individual studies.

Study	Sport	Sample (n, sex; age)	Tier	Study design	SSG format	Training regimen	Field / area	Task constraints	Neuromuscular	Physiological	Biochemical/ Endocrine	Timing
(Alashti et al., 2021)	Soccer	24 M; 17.1 ± 1.1	T2	Quasi-experimental + control	2v2; 4v4	2v2: 8×2 min/1 min; 4v4: 4×4 min/2 min	2v2: 20×25 m; 4v4: 28×35 m	Stop-ball; no GK; coach encouragement	—	HR, %HRmax, RPE	BLa, GH, IGF-1	Pre, post
(Ascondo et al., 2024)	Wheelchair basketball	13 M; 28.8 ± 9.2	T3	Repeated measures (5 wk)	4v4	4 bouts per session; 1×/wk ×5	28 × 15 m	Wheelchairs; SCI vs non-SCI	Acceleration capacity	HR, RPE (muscular/resp.), tympanic temp	—	End of each bout
(Baseri et al., 2022)	Soccer	24 M; 22.3 ± 2.6	T3	Crossover (recovery after SSG)	3v3 + 4 support players	4×4 min; 3-min passive rest	18×20 m (60 m2/plyr)	ball-possession; 4 neutrals; coach encouragement; spare balls	20 m sprint	HRV (SDNN, lnRMSSD), HR, RPE, Hooper	—	Pre, post-SSG, post-recovery, 48 h
(Bekris et al., 2022)	Soccer	22 M; 22.3 ± 3.9	T3	Controlled trial	3v3	8×3 min; 3-min active recovery	20 × 25 m	No GK; standard rules	SJ, 20 m sprint	HR, RPE	CK, IL-6, Cortisol, Testosterone, BLa	Pre, post, 24/48/72 h
(Bonato et al., 2020)	Soccer	32 M; 24 ± 6	T2	RCT (SSG vs HIIT)	4v4	4×4 min; 3-min active recovery; evening (20:00)	36×24 m	ball-possession; coaches’ encouragement; HR monitored	—	Sleep (actigraphy: AST, SE, SL, IT, MT, FI); HR	Salivary Cortisol; Cortisol Awakening Response	PRE, POST (cortisol); POST1 & POST2 nights (sleep)
(Chmura et al., 2019)	Soccer	18 M; 17.2 ± 0.8	T2	Randomized (2 groups)	1v1	6×30 s/2 min vs 6×45 s/3 min	10×15 m	Maximal effort; coach encouragement	—	—	Serum TT, FT, Cortisol	Rest, post, +15, +30 min
(Clemente et al., 2017)	Soccer	6 M; 20.3 ± 4.8	T2	Within-subject	1v1; 3v3	1v1: 3×2 min; 3v3: 2×3 min (1:1.5)	1v1: 10×15 m; 3v3: 19×24 m	Small goals	SJ, CMJ	HR, RPE, GPS load	—	Pre and post bouts
(Dellal et al., 2015)	Soccer	22 M; 24.3 ± 4.2	T5	Within-subject	2v2; 3v3; 4v4	2v2: 4×2 min; 3v3: 4×3 min; 4v4: 4×4 min	2v2: 20×15 m; 3v3: 25×18 m; 4v4: 30×20 m	With and without GK	—	HR recovery (parasympathetic)	—	1-3 min post
(Dello Iacono et al., 2017)	Handball	12 M; 19.3 ± 0.4	T4	Counterbalanced	3v3	Two sessions 5 d apart; 5×3 min/1 min rest	40×20 m	contact vs no-contact; Contact allowed vs prohibited; multiple balls; 20 s attack limit	Upper/lower neuromuscular performance	HR-derived internal load	IL-6	Pre, post
(Iturricastillo et al., 2018)	Wheelchair basketball	13 M; 31 ± 9	T3	Experimental	4v4	4×4 min separated by 2 min of passive recovery	28×15 m (standard court)	Wheelchairs	Muscle function	HR, RPE (methods compared)	—	During/after SSG
(Johnston et al., 2014)	Rugby league	23 M; 19.1 ± 0.8	T3	Cross-over, counterbalanced	6v6	2×8 min halves; 72 h apart	30×70 m	contact vs no-contact; Contact bouts every 50 s in contact game	Upper/lower power	GPS, HR, RPE	CK	Pre, post, 12/24 h
(Karadağ et al., 2024)	Soccer	28 M; 24.9 ± 4.6	T2	Between-groups	2v2; 4v4; 8v8	2v2: 3×4 min; 3v3: 3×4 min; 8v8: 3×4 min /3 min passive rest for all	2v2: 20x25 m; 3v3: 30x35 m; 8v8: 40x45 m	Standard rules	—	HR, RPE	BLa	Pre, post, +30 min
(Kryściak et al., 2023)	Soccer	20 M; 17.2 ± 0.8	T2	Parallel groups	1v1	6×30 s vs 6×45 s	10×15 m	Standard rules	—	HR, GPS EL, RPE	BLa, pH, HCO3-, BE	Rest, post each bout, +15/+30 min
(Madison et al., 2019)	Soccer	10 M; 23 ± 5	T3	Counterbalanced cross-over	3v3; 4v4	6×4 min/90 s	20×15 m (300 m2) vs. 40×25 m (1000 m2)	Standard rules	NordBord hamstring isometric torque	HR, GPS EL	—	Pre, post
(Martínez-Serrano et al., 2023)	Soccer	34 M; 17.1 ± 0.8	T3	Observational (in-season)	4v4+3; 6v6+2GK; 7v7+3; 10v8	Multiple sessions	6v6+2GK: 40×40 m; 7v7+3: 90×60m; 10v8: ¾ of the field	Not detailed	MVIC (KE; posterior chain)	RPE, EL (distance, HSR, acc/dec)	—	BL, post-SSG, +6 h, +24 h
(Mascarin et al., 2018)	Soccer	13 W; 18.8 ± 0.8	T3	Single-group repeated	4v4	4×4 min/3 min	120 m2 per player	end-line invasion scoring	—	HRV (RMSSD, LF/HF, pNN50)	CK, LDH, T, C	Pre, +10 min, 24/48/72 h
(McLean et al., 2016)	Soccer	12 M; 21 ± 3	T2	Cross-over	3v3	6×2 min; rec 30 s vs 120 s	20×15 m	Standard rules	—	HR, RPE, GPS distance/speed; VL-NIRS	—	Continuous per bout
(Mitrotasios et al., 2021)	Soccer	8 M; 18.4 ± 1	T4	Observational	4v4 + 2 GK	6×4 min/ 3 min rest	30×20 m	Coach encouragement; multiple balls	—	HR	CK, LDH, T, C; enzymes/lipids profile	Pre, post
(Modena and Schena, 2024)	Soccer	12 M; 18.3 ± 0.7	T2	Observational	3v3; 6v6	4×4 min/ 2 min	3v3: 30×20 m (100 m2/plyr); 6v6: 60×40 m (200 m2/plyr)	Small goals (2×1 m); ball always available	CMJ; sprint; DOMS	RPE; TQR; GPS EL (distance, speed, acc/dec)	—	Pre, post, 24 h
(Hidalgo de Mora et al., 2024)	Soccer	14 M; 17.1 ± 0.6	T2	Within-subject	7v7 + GK	(a) 3×8 min/5 min; (b) 6×4 min/2 min (large); (c) 6×4 min/2 min (small)	68×40 m (194 m2); 40×34 m (97 m2)	GK present	Vertical jump; sprint; kick velocity	—	—	Pre, post
(Papanikolaou et al., 2021)	Soccer	10 M; 21.7 ± 2.1	T3	Repeated measures	4v4; 8v8	4v4: 6×4 min/180 s; 8v8: 3×8 min/90 s	4v4: 20×25 m; 8v8: 70×65 m	No GK; 2-touch limit; ball-possession; standardized warm-up/cool-down	MVIC (KE/KF); CMJ; 30 m sprint; DOMS	HR; BLa; RPE; GPS EL	CK	BL, 1-3 h, 24/48/72 h
(Calderón Pellegrino et al., 2020)	Soccer	16 M; 16.9 ± 0.32	T3	Pre-post	4v4	8 min	125, 150, 250, and 300 m2	Standard play	Sprint count; accelerations	HR; GPS EL	—	Pre, post-RSA
(Ravier and Marcel-Millet, 2020)	Handball	14 M; 25.4 ± 4.9	T4	Repeated measures	3v3 + GK	2×8 min; internal 30 s play/30 s rest; 2-min inter-period	40×20 m	Modified rules; immediate GK restart; coaches return balls	—	HR, HRR; HRV (RMSSD/HF); time-varying RMSSD	—	Pre, post, +10 min
(Sansone et al., 2019)	Basketball	12 M; 21 ± 2	T3	Randomized, repeated measures	3v3	Long: 3×4 min/2 min; Short: 6×2 min/1 min	15×14 m	Offense vs defense tactical tasks	—	%HRmax; PlayerLoad; RPE	T; C	Pre, post
(Sjokvist et al., 2011)	Soccer	20 W; 20.3 ± 2.3	T3	Repeated measures	4v4	4×4 min/3 min active	32×22.5 m	With vs without ball	CMJ; 5BT; 20 m sprint	HR; S-RPE	—	BL, 24/48/ 72 h
(Skala and Zemková, 2023)	Soccer	16 M; 13.6 ± 0.5	T2	Pre-post	4v4 + GK	30 min continuous	40×25 m	Standard rules	CMJ; Planned/Reactive agility; Go/ No-Go	HR; GPS EL	—	Pre, post
(Sparkes et al., 2018)	Soccer	16 M; 21 ± 2	T4	Repeated measures	4v4 + GK	6×7 min/2 min	24x29 m	Standard rules	CMJ (JH); PPO	HR; RPE; GPS EL	CK; BLa; T; C	Pre, 0 h, +2 h, +24 h
(Sparkes et al., 2020a)	Soccer	12 M; 21 ± 2	T3	Repeated measures (single vs double day)	4v4 + GK	6×7 min/2 min; + RT 2 h later on double day	24×29 m	Standard rules	CMJ (JH); PPO	Mood disturbance	T; C	Pre, 0 h, +24 h
(Sparkes et al., 2020b)	Soccer	14 M; 22.1 ± 3.1	T3	Repeated measures (order)	4v4 + GK	6×7 min/2 min; RT 2 h apart (SSG+ RT vs RT+SSG)	24×29 m	Standard rules	CMJ (JH); PPO	Mood disturbance	T; C	Pre, 0 h, +2 h, +24 h
(Sparkes et al., 2022)	Soccer	12 M; 21 ± 2	T3	Reliability (wk-to-wk)	4v4 + GK	6×7 min/ 2 min	24×29 m	Standard rules	CMJ (JH); PPO	GPS EL	T; C	Pre, post
(Trecroci et al., 2020)	Soccer	9 M; 17.7 ± 0.5	T3	Crossover (SST vs AR) in MD+2	4v4	4×3 min; 3-min rest; + tactical drills	18×24 m	No GK reported	MVF knee extensors/flexors (isometric)	RSA (5×30 m); HR; GPS EL; RPE	—	BL (-72 h), 0 h post-match, +72 h post-match
(Trecroci et al., 2021)	Soccer	9 M; 17.7 ± 0.5	T3	Crossover (SST vs AR) in MD+2	4v4	4×3 min SSG (3-min rest) + tactical drills	18×24 m	No GK reported	—	Perceptual: soreness (VAS); TQR	CK; CRP; IL-6; WBC, Neut, Lymph, Mono; Cortisol	BL (-72 h), 0 h post-match, +72 h post-match

Tier 2 (T2): Trained/Developmental; Tier 3 (T3): Highly Trained/National level; Tier 4 (T4): Elite/International level; Tier 5 (T5): World-class; SSG: Small-sided game; GK: Goalkeeper; RS: Repeated sprints; CT: Circuit training; RT: Resistance training; EL: External load; HSR: High-speed running; GPS: Global Positioning System (tracking); HR: Heart rate; HRR: Heart rate recovery; %HRmax: Percent of maximal heart rate; HRV: Heart rate variability; RMSSD: Root-mean-square of successive differences; pNN50: Percentage of NN intervals differing >50 ms; LF/HF: Low-/High-frequency power ratio; NIRS: Near-infrared spectroscopy; VL-NIRS: Vastus lateralis NIRS; RPE: Rating of perceived exertion; S-RPE: Session RPE; TQR: Total quality of recovery; DOMS: Delayed-onset muscle soreness; CMJ: Countermovement jump; SJ: Squat jump; PPO: Peak power output; MVF: Maximal voluntary force; MVIC: Maximal voluntary isometric contraction; NR: not reported; NordBord: Nordic hamstring strength device; KE/KF: Knee extensors/flexors; RSA: Repeated sprint ability; VAS: Visual analogue scale; BLa: Blood lactate; CK: Creatine kinase; LDH: Lactate dehydrogenase; IL-6: Interleukin-6; CRP: C-reactive protein; GH: Growth hormone; IGF-1: Insulin-like growth factor-1; T: Testosterone; TT: Total testosterone; FT: Free testosterone; C: Cortisol; CAR: Cortisol awakening response; WBC: White blood cell count; Neut: Neutrophils; Lymph: Lymphocytes; M: men; Mono: Monocytes; pH: Acid.base measure; HCO..: Bicarbonate; BE: Base excess; AST: Actual sleep time; SE: Sleep efficiency; SL: Sleep latency; IT: In-bed time; MT: Movement time; FI: Fragmentation index; MD+2: Match day plus two; BL: Baseline; ACC/DEC: Accelerations/decelerations; m2/player: Square meters per player; SCI: Spinal cord injury; IWBF: International Wheelchair Basketball Federation; W: women; YYIRTL1: Yo-Yo Intermittent Recovery Test Level 1.