Table 1.

Characteristics of included studies.

Study ID	Study Design	Participants	SS protocols	DS protocols	Outcomes	Follow-up Period	Main Results, P value
Webright, W. G. 1997	RCT parallel	n (SS) = 15 (6 M 9 F) n (DS) = 11 (6 M 5 F) Healthy subjects with limited right hamstring flexibility (minimum of 15° loss of active knee extension) Age (SS) = 21.2 (3.65) Age (DS) = 21.8 (3.16)	Modified hurdler's position on the floor, flexed from the hip until a stretch sensation was felt in the posterior thigh, knee, and/or calf, avoiding cervical flexion, sustained for 30 s, twice daily, 6 weeks.	Sitting slumped on a sturdy object with feet do not reach the floor. Keep the right foot maximally dorsiflexed. Then, the knee was extended to end range for 1 s. Then lowered the leg and relaxed the foot in plantar flexion. Repeated 30 times, twice daily, 6 weeks.	Knee flexion ROM with the femur maintained in 90° of hip flexion	Immediately after the stretch	No significant difference in pre-test to post-test measures of knee ROM between the SS and DS groups. P > 0.05
Bandy, W. D. 1998	RCT parallel	n (SS), n (DS) = 19 Subjects with hamstring inflexibility (30° loss of active knee extension) Age (SS) = 24.63 (2.38) Age (DS) = 25.53 (4.86)	Standing, left foot planted on the floor, stretch the hamstring by raising right leg with the knee fully extended. Then flexed forward from the hip, maintaining the spine in a neutral position, sustained for 30 s, five times a week for 6 weeks.	Lying supine and holding the hip in 90° of flexion, actively extended the leg (5 s), and held the leg at the end of knee extension for 5 s, and slowly lowered the leg (5 s), repeat 6 times, 5 sessions a week for 6 weeks.	Knee extension ROM with the femur maintained in 90° of hip flexion	Immediately after the stretch	Both SS and DS could increase hamstring flexibility, but a 30-s SS was more effective than DS, for enhancing flexibility. P < 0.05
Herman, S. L. 2008	RCT parallel	n (SS) = 10 M n (DS) = 10 M Collegiate wrestlers Age (SS) = 19.5 (0.3) Age (DS) = 20.3 (0.3)	Step forward with the left leg and reach toward the left foot by bending the waist (Trunk remains straight). Both knees are slightly bent, and the arms are straight on either side of the forward leg. Repeat on the opposite side. Each SS was held for 30 s and performed only once, lasted 15 min, 5 times a week for 4 weeks.	Reach high overhead. Squat and reach between the legs, allowing the back to flex, but keeping the heels down. Return to the starting position. Perform at a slow cadence. Perform 1 repetition of each exercise, lasted approximately 15 min, 5 times a week for 4 weeks.	SR	Immediately after the stretch	Those two stretching methods showed similar effects in improving flexibility of the hamstrings. P > 0.05
O'Sullivan, K. 2009	RCT crossover	n (SS), n (DS) = injured (16 M, 2 F), uninjured (16 M, 2 F) Previously hamstring injured and uninjured university students Age (SS), Age (DS) = injured 21 (2), uninjured 21 (1)	The participant placed their leg on an elevated surface with their knee extended and their ankle plantarflexed, then lean forward from the hip, with their spine in neutral until a stretch was felt in the posterior thigh. This position was held for 30 s and repeated 3 times.	Each participant was instructed to swing the leg to be stretched forward into hip flexion whilst keeping their knee extended and their ankle plantarflexed and then swing back into slight hip extension, lasted for 30 s, and repeated 3 times.	Passive Knee Extension ROM with the femur maintained in 90° of hip flexion	Immediately after the stretch and after a 15-min rest	ROM after SS was greater than after DS (p < 0.001). After 15 min, there was a significant decrease in ROM for static stretching. (p < 0.001)
Amiri-Khorasani, M. 2011	RCT crossover	n (SS), n (DS) = 18 M Professional adult soccer players with no history of major lower limb injury Age (SS), Age (DS) = 19.22 (1.83)	Stretching hamstrings for 15s on each leg until approached the end of the ROM but within the pain threshold.	Stretching hamstrings for 30s at a rate of approximately 1 stretch cycle per second or unilaterally for 15s.	ROM of the hip in the follow-through kicking phase	After a 2-min rest after the stretch	There was a significant difference after DS compared with SS during the follow-through phase. (p < 0.01)
Behm, D. G. 2011	RCT crossover	n (SS), n (DS) = 10 M (young) and 7 M (middle-aged) Subjects participating in recreational or fitness activities 2–4 times per week Age (SS), Age (DS) = 22 (1.4) (young), 46.3 (6.5) (middle-aged)	In a standing position, flexing their hip, and placing their heel with an extended leg on a 50 cm high platform, then reaching forward with their arms towards the extended leg; 4 repetitions and held at the point of discomfort for 30s each.	Walking lunges: lunging motions with hip flexion and knee flexion of the front leg); 4 repetitions in total for 30 s each and achieving the highest ROM possible for all DS.	SR	Immediately after the stretch and after a 10-min rest	There were no significant differences between the SS and DS immediately after the stretch (P > 0.05), but SS was greater than DS after 10 min (P < 0.05).
Perrier, E. T. 2011	RCT crossover	n (SS), n (DS) = 21 M Recreationally active university students Age (SS), Age (DS) = 24.4 (4.5)	Supine with both legs fully extended, raising one leg, using the hands to support both above and below the knee. Only a small amount of knee flexion was allowed. 2 repetitions of 30 s each for each lower extremity.	Step into single leg Romanian dead lift; Walking diagonal lunges; High knee pulls (knee to chest, on toe); Straight leg strides (back and forth-no walk-rest 20 s between reps); Each exercise was performed twice.	SR	Immediately after the stretch	There was no difference in flexibility between SS and DS. P > 0.05
Silveira, G. 2011	RCT crossover	n (SS), n (DS) = 12 (5 F 7 M) University students with a variety of sporting backgrounds and free of any bony or soft tissue injury Age (SS), Age (DS) = 24.8 (6.8)	In a supine position, lying on an exercise treatment bench with a Velcro sling passing around the ankle to flex the hip and stretch the hamstrings. The stretch was held for 15 s to the terminal range of discomfort or tightness felt in the back of the thigh. 75 s for each stretch.	The dominant leg was flexed at the hip in a forward kicking action, 5 sets of 7 or 8 forward leg swings or kicks, total 225 s; Dominant leg swung across the midline of the body towards the opposite shoulder to stretch the hamstring.	Active SLR	Immediately after the stretch	No difference in flexibility between SS and DS was investigated. P > 0.05
Samson, M. 2012	RCT crossover	n (SS), n (DS) = 19 (10 F 9 M) University students and staff involved in recreational or competitive sports Age (SS), Age (DS) = 22.2 (3.3) (F), 27.8 (8.4) (M)	Supine, hip flexion to maximum ROM with legs partially abducted and knees slightly flexed. Each stretch was repeated for 3 sets of 30s and held at the point of mild discomfort.	All stretches were performed dynamically to full ROM at a moderate speed of approximately 1 Hz (approximately 30 repetitions per set)	SR	Immediately after the stretch	The SS condition increased sit and reach ROM more than the dynamic condition. (p < 0.05)
Morrin, N. 2013	RCT crossover	n (SS), n (DS) = 10 F Dancers Age (SS), Age (DS) = 27 (5)	Sit upright on the floor, flex one knee and slide the heel until it touches the inner side of the opposite thigh. Keep the extended leg straight and bend at the hips and lower torso onto the extended thigh. Each stretch was completed twice, and each repetition was held for 30s.	With hands on hips, walk around the room while extending alternate legs forward in a parallel grand battement fashion. Each stretch was completed twice, and each repetition was held for 30s.	Active SLR	Immediately after the stretch	SS displayed significantly greater changes than DS. (p < 0.05)
Chen. 2015	RCT parallel	n (SS), n (DS) = 12 M Students with limited passive straight-leg elevation (hip flexion ROM of less than 80°) Age = 20.6 (2.4)	Lunge position, rotating the trunk and using the hand to reach gently to the opposite toes of the dominant leg with the knee extended to stretch the hamstrings to the point of discomfort without pain, maintained for 15 s, followed by 15s of rest, total 6 sets.	Raise the arms horizontal to the floor, then actively swing the dominant leg forward with hip flexion and knee extension to allow the toes to approach the hands. 15 rhythmic repeated movements per set for 6 sets, with 15s of rest between sets.	Passive SLR; Myotonometer for hamstrings stiffness	Immediately after the stretch	There was no significant difference in ROM between SS and DS. (P > 0.05) Hamstrings stiffness decreased significantly more in DS than in SS. (P < 0.05)
C Kurt. 2015	RCT crossover	n (SS), n (DS) = 24 M Well-trained combat athletes Age (SS), Age (DS) = 22.7 (3.3)	Sit on the ground. Legs are straight out in front. Bend forward and keep the back straight. Each limb for 20s and rested for 20s between exercises.	Kick leg up then out straight as high as possible. Try to touch the toe with the contralateral hand. Then, perform it with the other leg. Each exercise lasted for 15s, two sets with 30s inter-set and inter-exercise rest intervals.	FGD	At the 15th second and the 2nd, 4th, 6th, 8th, 10th and 15th minute after the stretch.	There was no difference in flexibility between SS and DS at the 15th second and the 2nd, 4th, 6th, 8th, 10th and 15th minute after the stretch. P > 0.05
Chaouachi, A. 2015	RCT crossover	n (SS), n (DS) = 14 M Healthy highly trained rowers Age (SS), Age (DS) = 18 (2)	Unilateral supine, hip flexion straight leg with eight repetitions of 30s each to the point of discomfort, with 20s rest between repetitions. The same researcher helped in achieving the desired ROM for each subject.	Eight sets of 30s of unilateral hip flexion kicking actions through a full ROM, with 20s rest between sets, approximately 1s for hip flexion and 1s for the return to the starting point (hip extension).	Hip flexion ROM with knee extended	After 1-min and 10-min rest of stretch	There were no significant between the two interventions of SS and DS. P > 0.05
Su, Hsuan 2016	RCT crossover	n (SS), n (DS) = 20 (5 M 15 F) College students Age (SS), Age (DS) = 21.43 (1.48)	In a supine position, keep left leg on the floor and right knee extended, slowly raise right leg toward the chest using hands or a towel. Hold the position for 30s, then change to the left leg. Hold the position for 30s, then change to the left leg.	Standing, kick one leg forward with knee extended. Step forward and kick the other leg forward with knee extended. Repeat each movement for 1 min. Both movements were performed 3 times for a total of 6 min.	SR	After 5 min rest of stretch	Statistically insignificant difference was found in hamstrings flexibility. (P > 0.05)
Matsuo, S. 2019	RCT crossover	n (SS), n (DS) = 16 M Healthy young men Age (SS), Age (DS) = 22.2 (1.2)	Standing and placing the right heel (with an extended leg) on a platform (50 cm high), then reached forward with their arms toward the extended leg. Ten 30s sets of SS were performed with a 20s rest period between each set.	Standing upright beside parallel bars and held a parallel bar with his left hand with knee extended and swung their right leg up to the anterior aspect of their body. Each exercise was performed 5 times slowly to practice, and then 10 times as quickly as possible without bouncing. Ten 30-s sets of DS (15 repetitions of the DS movement in each set) were performed with a 20s rest period between each set.	ROM; PT at the onset of pain. Passive Stiffness	Immediately after the stretch	The effects of stretching do not appear to differ between the two stretching methods. (P > 0.05)
Zhou, Wen-Sheng 2019	RCT crossover	n (SS), n (DS) = 11 Elderly people absence of conditions possibly affecting hip joint flexion or extension Age (SS), Age (DS) = 63.2 (7.13)	Adopting a forward flexion position while sitting in a chair, and to stretch the hamstrings by adopting a forward lunge position. Each set included six 30-s long repetitions, with 30s of rest between repetitions.	Standing with left foot while holding onto the back of a chair. Each set containing fifty repetitions performed to the rhythm of a metronome, and with 30 s of rest between sets. In total, 3 sets were performed, and the DS trial covered 130s (43.6 s × 3 sets).	Measurement of ROM of passive hip flexion	Immediately after and at 60 min after completing the stretch	Hip flexion ROM at 0 min showed no significant difference between DS and SS. However, DS had a better sustained effect than that provided by SS at 60 min, p < 0.05).
Fakhro, M. A. 2020	RCT parallel	n (SS), n (DS) = 32 M Football players Age (SS), Age (DS) = 24.7 (4.1)	In a supine position, the tested limb was in full knee extension and the foot, in a relaxed position, and moved up passively by the assessor to a point of slight pain or discomfort at the posterior aspect of the thigh, held for 30s and performed 3 times for a total of 1 min and 30s, 15 min after a match or training.	Participants swung their tested leg actively into hip flexion while keeping their knee fully extended and their ankle fully plantar flexed until a stretch was felt in the posterior thigh. This was repeated over 30s at the end of the participant's warm-up phase.	Passive SLR	15 min after the first intervention and after four weeks	SS was showed to be superior to the DS in short (15min) and long-term hamstring extensibility (4 weeks). ( P < 0.05)
Ferreira-Junior, Joao B. 2021	RCT parallel	n (SS) = 14 n (DS) = 13 College students engaged in moderate physical activity Age (SS) = 21.1 (2.1) Age (DS) = 21.3 (1.7)	Stood with one leg stretched on a bench while the other leg supported their body mass. Then, lean forward at the waist with the arms reaching for the toes with both knees extended; Seated and maintained one leg stretched while the other one was fully extended. Then, subjects lean forward and held the stretch position by actively contracting the muscles in opposition to the muscle being stretched for 20s to the threshold of mild discomfort. 15s rest period between each set and each stretching exercise. The total time was approximately 80 s, 2 days per week for 8 weeks.	Stood upright, swung upward by flexing the hip and while maintaining the leg in the extended position. Standing upright, hip was flexed until the thigh of the stretched leg was parallel to the ground. Then, the subject extended their leg. 15 repetitions through a challenging ROM to the same threshold of mild discomfort. There was a 15s rest period between each set and each stretching exercise. The total time was approximately 80s, 2 days per week for 8 weeks.	Biceps femoris muscle thickness	One week after the last training session	There was no significant differences in muscle thickness (SS 6.0 (3.5) mm; DS (6.7 (4.1) mm) across groups. (p > 0.05)
Lee, Jin Hyuck 2021	RCT parallel	n (SS) = 25 (11 M 14 F) n (DS) = 21 (8 M 13 F) Patients with patellofemoral pain and had <141° of knee extension angle during the hamstring flexibility test Age (SS) = 27.2 (7) Age (DS) = 25.1 (9.2)	Sitting or standing, the affected leg was maintained in a straightened position with ankle dorsiflexion. The foot was grasped using the ipsilateral hand or a towel, with the contralateral hand keeping the affected knee straight, with a slight trunk forward flexion. Repeated for 3 sets, with a holding time of 15s, twice a day and 12-week follow-up.	Supine, the affected leg was maintained at 90° flexion of the hip and knee. The distal thigh was grasped by a towel; then, active knee extension through contraction of the quadriceps. Standing, repeated hip flexion with the knee extended, 3 sets, 15 repetitions with a 1-s holding time, twice a day and 12-week follow-up.	Knee extension ROM with the femur maintained in 90° of hip flexion	After the 12-week follow-up	There were no differences in hamstring flexibility between the two groups. P > 0.05
Siebert, T. 2022	RCT crossover	n (SS), n (DS) = 14 M Male sport students with diverse sport experience Age (SS), Age (DS) = 23.7 (1.3)	Flexed the hip slowly until a pain score of 8. If this threshold was reached, SS was performed for 30s. In case of reduced pain, the hip angle was further increased. After 30s, the leg was released followed by the resting period, repeated 3 sets, 30s rest between each stretching.	Be like the protocol of SS. The subject gave feedback to the assessor how far the hip could be flexed. Within 30s, the assessor flexed the hip slightly rhythmically about 10–12 times, repeated 3 sets, 30s rest between each stretching.	ROM of hip flexion	5 min after the intervention	No significant difference was observed between SS and DS in terms of hamstring flexibility. (p > 0.943)
Gunaydin, G. 2020	RCT parallel	n (SS), n (DS) = 14 Healthy individuals Age (SS) = 24.07 (3.20) Age (DS) = 22.57 (2.06)	Supine on the bed and one leg was fixed to the bed with a belt. Hold the ends of the exercise band wrapped around the foot with two hands. Then raise the leg as high and straight as he/she could, and stretch for 15s, 6 weeks, 3 days a week and 10 repetitions per day.	Supine, hold the exercise band wrapping around the sole of the foot with two hands. Then, raise the leg as high and straight as possible and contract the quadriceps for 2s and then relaxed, 6 weeks, 3 days a week and 10 repetitions per day.	Passive knee extension ROM with the femur maintained in 90° of hip flexion	Three days after the last stretching (6 weeks)	The flexibility increase in the DS was higher than the SS group. P < 0.001
Vasileiou 2013	RCT crossover	n (SS), n (DS) = 22 M Healthy, amateur soccer players Age (SS), Age (DS) = 21.9 (3.2)	Stretching one leg forward with the toes pointing up while bending the opposing leg. Reaching to touch forward knee with head. Twice each and for 10s each.	Moving each leg front to back with knee extended. 10 repetitions for each leg and repeated two times.	ROM of hip flexion	Immediately after the stretch	No differences found between trials (SS or DS). P > 0.05
Zmijewski, P. 2020	RCT crossover	n (SS), n (DS) = 13 F Healthy female handball players Age (SS), Age (DS) = 22.1 (3.2)	Sitting, extend a single leg and flex the other leg until the foot was in contact with the thigh. Flexed forward from the waist, keeping the back flat. Each stretch was held to the point of slight discomfort (not pain) for 20s per muscle group followed by a 10s passive rest period in a neutral position. Each stretch was repeated three times for each limb in alternating order.	12 sets of leg swings (in 3 successive sets) including a set of 20s anterior or posterior leg swings in a standing position, followed by a 10s passive rest interval in a neutral position. Each set of stretches (around 14–18 swings in one set/muscle group) was repeated three times for each limb in alternating order.	SR	Immediately after the stretch	Athletes demonstrated a similar increase in ROM for the DS and SS protocols. P > 0.05
Amber Magner 2012	RCT crossover	n (SS), n (DS) = 9 (5 M 4 F) Recreationally trained subjects and participated in a variety of sport backgrounds Age (SS), Age (DS) = 24 - 56	Standing Stretches: feet together, bend over at the waist keeping back straight; Sitting Stretches: double leg hamstring stretch: seated keep back of knees on ground and bend at the waist forward reaching to touch toes; Single leg hamstring: bend right leg to the inside of left leg, leaving left leg straight in front, bend at waist forward to touch toes. Repeat procedure with left leg bent and right forward. Static stretches were held for 12s, and the same stretch was duplicated on the opposite limb being stretched, lasting 10 min.	Jog, Back pedal, Jog down, Skipping, High knees, Butt kicks, High knees down, Skipping, Carioca, walking sumo squats, Defensive slides, Frankenstein walks, Heel walks/toe walks, Wall assisted leg throws-facing wall, Wall assisted leg throws-side to wall, Frankenstein-keeping legs straight swing one at a time high up in front with your hands stretched out and chest high, lasting 10 min.	SR	Immediately after the stretch	No differences found between trials (SS or DS). P > 0.05
Philip Ford 2007	RCT parallel	n (SS), n (DS) = 8 Physically active individuals Age = 22.1 (3.04)	In a seated position, the treatment leg was fully extended at the knee with the left hip externally rotated and flexed, then flexed the trunk toward the right leg, to the point of mild discomfort without pain in the posterior aspect of the knee and thigh. This position was repeated 5 times for 30s with a 10s rest period between each stretch.	In a seated position, each subject grabs the side of the treatment table with the trunk in slight flexion and to actively extend the right knee, to the point of mild discomfort without pain, repeated 10 times and held in that position for a period of 10s with a relaxation period of 10s.	Active Knee Extension ROM	Immediately, 3-min, 7-min, 12-min, 18-min, 25-min, after the stretch	SS was showed to be superior to the DS, 3-min, 7-min, 12-min, 18-min, 25-min, after the stretch (P < 0.05), but not immediately after the stretch. (P > 0.05)
Jesus López 2013	RCT parallel	n (SS) = 11 (4 M 11 F) n (DS) = 9 (5 M 4 F) Healthy, active students Age = 21.79 (2.45)	A series of 10 repetitions of the following cycle: passive elongation of the hamstring muscle group to maximum ROM, holding the position for 10s; then relaxation of the muscles in the initial position for 5s, while trying to increase the ROM in each repetition, a total stretching time of 100s per session and per leg making a total working time of 6 min, 2 sessions per week for 9 weeks.	Four series of 12 repetitions of the following cycle: initial active stretching (by contraction of the flexor muscles of the hip), the motion being assisted by gently stretching the hamstring passively until the maximum ROM was reached, holding the position for 2s, then returning to the initial position, with a total stretching time of 96s per session and per leg and a total working time of 8 min, 2 sessions per week for 9 weeks.	Active and passive SLR	Immediately after the stretch	There were no significant post-test differences between DS and SS. (P > 0.05)
Cem Kurt 2016	RCT crossover	n (SS), n (DS) = 20 Professional football players Age (SS), Age (DS) = 25.3 (4.3)	Standing hamstring stretch. 5 min of SS (6 different unilateral SS exercises [1 × 20s hold for each extremity, 10 s interval between exercises] and one bilateral exercise [2 × 20s hold])	Walking hamstring kicks, walking lunges, lateral walking lunges, power high knee, dynamic hip flexor, leg swing towards the opposite side and explosive hip flexion mobility. 5 min of DS [7 different DS exercises (2 × 20s, with 10s between exercises)].	FGD	Immediately after the stretch	The difference between SS and DS was insignificant. P > 0.05

SR = Sit and Reach test. SLR = Straight Leg Raise test. FGD = Finger Ground Distance. ROM = Range of Motion. PT = Passive Torque. SS = Static Stretching. DS = Dynamic Stretching. M = Male. F = Female.