Table 2.

Chronic Effects of FR on Flexibility and Performance.

Author	Participants		Duration	Protocol		Measures		Result
	FR	CON	Flexibility	Performance	Flexibility	Performance
Aune et al. 2018 [20]	23 male and female top-division soccer players		4 weeks	daily FR on gastrocnemius (3 × 60 s)	daily single-leg heel drop exercise (3 × 15 repetitions)	DFROM	maximal isometric plantar flexion torque drop RSI	DFROM: FR ↔ CON	plantar flexion torque: FR ↔ CON drop RSI: FR ↔ CON
Guillot et al. 2019 [21]	30 male professional rugby players		6 weeks	FR20: unilateral FR for hip extensors, hip adductors, knee extensors, and plantar flexors (1 × 20 s for 15 sessions) FR40: same FR intervention with FR20 but executed for 1 × 40 s	cycling task at 50% Vo2Max	side split active flexed/straight leg raise hip extension	not available	All dependent variables: FR20 > CON FR40 > CON	not available
CON–control group; Vo2Max–maximal oxygen consumption; DFROM–dorsiflexion range of motion; RSI–reactive strength index.
Author	Participants	Duration	Protocol		Measures			Result
			FR	CON	Flexibility	Performance		Flexibility	Performance
Hodgson et al. 2018 [22]	23 recreationally -active males and females	4 weeks	FR3: 3 days/week of alternating FR for quadriceps and hamstrings for 4 × 30 s FR6: same FR protocol with FR3 but performed for 6 days/week	regular training routine	active and passive hip flexion ROM	neuromuscular efficiency during a lunge single leg CMJ knee flexor and extensor MVIC pain pressure threshold of biceps femoris and rectus femoris		active and passive hip flexion ROM: FR3 ↔ CON FR6 ↔ CON	all dependent variables: FR3 ↔ CON FR6 ↔ CON
Ikutomo et al. 2020 [28]	74 male and female patients with osteoarthritis	11–12 weeks	home exercise program with 10-min FR for gluteus, hamstrings, and quadriceps of the affected leg	home exercise program	not available	hip pain VAS Haris Hip Score JHEQ		not available	hip pain VAS: FR < CON Haris Hip Score and JHEQ: FR > CON
Junker & Stöggl 2015 [24]	26 recreationally- active males	4 weeks	3 days/week of 3 × 30–40 s hamstring FR for both limbs	regular training routine	Stand-and- Reach Test	not available		Stand-and-Reach Test	Stand-and -Reach Test: FR > CON
MVIC–maximal voluntary isometric contraction; VAS–visual analog scale; JHEQ–Japanese Orthopedic Association Hip Disease Evaluation Questionnaire.
Author	Participants	Duration	Protocol		Measures			Result
			FR	CON	Flexibility	Performance		Flexibility	Performance
Junker & Stöggl 2015 [23]	25 recreationally- active males and females	8 weeks	Twice a week, unilateral/bilateral FR for gluteus, quadriceps, hamstrings, illiotibial band, and calf muscles (3 × 30–50 s)	regular training routine	Stand-and-Reach Test	Bourban Trunk Muscle Test standing long jump single leg, triple hop for distance Y-Balance Test knee flexor and extensor MVIC		Stand-and-Reach Test: FR > CON	all dependent variables: FR ↔ CON
Kiyono et al. 2020 [25]	30 healthy males and females	5 weeks	thrice a week, unilateral FR for gastrocnemius (3 × 30 s)	regular training routine	DFROM	DFROM passive torque Haris Hip Score JHEQ muscle stiffness		not available	Haris Hip Score and JHEQ: FR > CON DFROM passive torque and muscle stiffness: FR6 ↔ CON
Author	Participants	Duration	Protocol		Measures			Result
			FR	CON	Flexibility	Performance		Flexibility	Performance
Morton et al. 2016 [26]	20 recreationally- active males	4 weeks	once a day, bilateral FR for hamstrings (4 × 60 s) followed by static stretching of hamstrings (4 × 45 s),	once a day static stretching of hamstrings (4 × 45 s)	passive knee extension ROM	knee extensor MVIC		Passive knee extension ROM: FR ↔ CON	knee extensor MVIC: FR ↔ CON
Smith et al. 2019 [27]	44 male and female university students	6 weeks	FR: twice a week, unilateral FR for gastrocnemius (3 × 30 s) FR + SS: FR with twice a week, static stretching for gastrocnemius (3 × 30 s)	Twice a week, static stretching for gastrocnemius (3 × 30 s)	DFROM	not available		DFROM: FR ↔ CON FR + SS ↔ CON	not available