Table 4.

Characteristics of the single-arm studies included in the systematic review.

Reference	Participants Level	Intervention	Outcomes	Compliance Rate	Reliability /SWC	Results	Comments
Holcomb et al. 2007 [71]	12 female soccer players (age: 20 ± 0.8 years) NCAA 1st division	IG: Hamstring-emphasised RT Duration: 6 weeks Frequency: 2/week Session duration: Unable to determine Training components: Two of different exercises (single leg curls, straight leg dead lifts, good morning exercises, trunk hyperextensions, resisted sled walking and exercise ball leg curls) in addition to speed, agility and endurance training.	Functional and conventional H/Q ratio at 240, 180 and 60 °/s	NR	NR NR	↑ Functional H/Q (ESc = 1.13, p = 0.049). ↔ Conventional H/Q (ESc = 1.26, p = 0.172)	Supervisor not specified. Low sample. Results not stratified by velocities. Poor description of the intervention.
Brito et al. 2010 [61]	20 male soccer players (age: 22.3 ± 4,2 years) Sub-elite	IG: FIFA 11+ Duration: 10 weeks Frequency: 3/week Session duration: 20 min Training components: (1) Running, stretching and controlled contacts; (2) strengthening, plyometrics and balance; and (3) speed running and soccer-specific movements.	H/Qcon 60° and 180°, H/Qecc30° and Hecc30 °/Qcon180°(DCR) ratios in isokinetic tests in both limbs	73%	Acknowledges another reliability data/ NR	↑ H/Qcon60° (ESc = 0.11) and Hecc30°/Qcon180° (ESc = 0.39) in non-dominant limb (p < 0.05).	Supervisor not specified. 2 dropouts.
McCann et al. 2011 [76]	10 healthy female soccer players (age: 19.1 ± 0.9 years)	IG: Resistance and conditioning training Duration: 10 weeks (11 weeks for retention) Frequency: 4/week Session duration: ≈60 min Training components: Strength, endurance or RT twice a week (depending on the athletes’ weaknesses) and conditioning training (speed, quickness, plyometric and agility drills) twice a week.	Knee abduction and hip abduction angles, and knee flexion moment in a running stop jump.	NR	NR/ NR	↑ Hip abduction angle and knee flexion moment from pre- to post-intervention. ↓ Knee abduction angle from pre- to post-intervention and retention (Z = −2.29), and hip abduction angle and knee flexion moment from post-intervention to retention.	Supervisor: CSCS specialist. No descriptive data. Low cohort (n = 10). No information about training during retention.
Greska et al. 2012 [70]	12 female soccer players (age: 19.2 ± 0.8 years) NCAA 1st division	IG1: Strength focused RT Duration: 10 weeks Frequency: 4/week Session duration: ≈60 min Training components: 2 days of low volume of RT exercises with a self-selected rest interval and with augmented feedback (verbal and visual) in relation to the movement patterns and body positioning. 2 days of field conditioning focusing on speed, quickness, plyometric and agility drills. IG2: Endurance focused RT Duration: 10 weeks Frequency: 4/week Session duration: ≈60 min Training components: 2 days of high volume of RT exercises with a 30-s rest interval between each exercise and with augmented feedback (verbal and visual) in relation to the movement patterns and body positioning. 2 days of field conditioning focusing on speed, quickness, plyometric and agility drills. IG3: Maintenance focused RT Duration: 10 weeks Frequency: 4/week Session duration: ≈60 min Training components: 2 days of hybrid scheme between IG1 and IG2, performing strength-focused 1 day and endurance-focused the other day. 2 days of field conditioning focusing on speed, quickness, plyometric and agility drills.	Kinetic and kinematic variables during a stop-jump task	95%	NR/ NR	↓ Knee abduction angle at IC (d = 0.76, p = 0.007) ↑ Hip abduction angle at IC (d = 0.63, p = 0.007) and peak knee flexion (d = 0.99, p = 0.002) and maximum knee extension moment (ESc = 0.59, p = 0.022) at peak stance.	Supervisor: CSCS specialist. All participants measured together (not by group). Low sample. Inadequate and unbalanced group sizes. Differences in BW at baseline. Too much time required.
Lehnert et al. 2017 [74]	18 male soccer players (age: 17.1 ± 0.4 years) Czech 1st division	IG: Pre-season training with the inclusion of progressive eccentric hamstring exercises Duration: 10 weeks Frequency: from 1/week (from 1st to 4th) to 3/week (from 5th to 10th) Session duration: ≈5–15 min Training components: Strength training with a special focus on eccentric hamstring exercises such as the Nordic curl (from 1 set of 5 reps at the beginning of the program, to 3 sets of 8–12 repetitions by the 5th week)	Conventional and functional H/Q ratio at 60 °/s.	NR	NR/ NR	↑ Functional H/Q in ND (ESc = 0.62, p < 0.05). ↔ Conventional H/Q in D and ND (p > 0.05)	Supervisor not specified.
Oshima et al. 2018 [77]	8 male soccer players (age: 20.4 ± 0.5 years) Collegiate	IG: FIFA 11+ (part 2) Duration: 24 weeks (6 months) Frequency: ≥3/week Session duration: ≈10 min Training components: Three levels of difficulty of six exercises aiming to increase muscular strength (core and lower limbs), balance, muscle control (plyometrics), and core stability.	Postural sway for 60s: Length per time (LG) and environmental area (AR) (two-leg stance with eyes opened and then with eyes closed and single leg standing with eyes opened). Star excursion balance test (SEBT - 8 directions). H/Q ratio	NR	NR/ NR	↑ Anterior-lateral with D and medial, posterior-medial, and posterior with ND (ESc = 0.38–0.71) in SEBT. ↔ H/Q ratio in D (ESc = 0.20, p > 0.05) and ND (ESc = 0.44, p > 0.05)	Supervisor not specified. No p values reported. Low sample (n = 8)

CG—control group, ES—effect size, ESc—effect size calculated through Hedge’s g, IG—intervention group, NA—non-applicable, NR—non-reported, RT—resistance training, SWC—smallest worthwhile change, D—dominant, ND—nondominant, ↓—decrease, ↑—increase, ↔—no change.