Physical Training Sept 2005
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The Effect of Stretching Duration on the Flexibility of Lower Extremities in Junior Soccer Players

Theodorou Ioannis, Galazoulas Christos, Zakas Nikolaos, Vergou Aikaterini, Vamvakoudis Efstratios

Aristotle University of Thessaloniki
Department of Physical Education and Sports Sciences
Thessaloniki, Greece

Dr. Galazoulas Christos,
Department of Physical Education and Sports Science,
Aristotle University of Thessaloniki,
Thessaloniki 540 06, Greece.
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The effect of different duration passive stretching sessions as well as the effect of multiple stretching sessions in acute stretching protocols has not yet been thoroughly examined. The purpose of the present study was to investigate the effect of stretching sessions differing in duration, as well as the effect of multiple stretching sessions on the lower extremities range of motion (ROM) in a set total amount of time spent in stretching of junior soccer players. The subjects comprised of thirteen junior soccer players aged 14.3 ±1.3 years who participated in four different passive stretching protocols. All protocols lasted for a total of 60 seconds each, however, each protocol differed in the duration of the stretches performed. Three of the stretching protocols consisted of multiple stretches of different duration each and the forth protocol comprised of continuous stretching, serving as the control protocol. ROM was determined during hip flexion, extension, and abduction, knee flexion and ankle dorsiflexion for both the right and the left side of the body, using a flexometer and a goniometer. A mixed within - and between - subjects analysis of variance (ANOVA) with repeated measures revealed similar ROM values between both sides for all the examined joints. No significant differences were observed among the stretching protocols. Further statistical analysis of the data indicated significant improvements after stretching exercises in all flexibility protocols. These findings suggest that one 60-second passive stretch on the lower extremities muscles produced the same effect as two 30-second, four 15-second and twelve 5-second stretches over a single flexibility training session in junior soccer players.

Key words: Flexibility, Stretching duration, Range of motion, junior soccer players.


Flexibility is an indisputable component of fitness, defined as the ability to move a joint through a normal range of motion without producing stress to the musculotendinous unit (Chandler et al. 1990). Stretching is important because it contributes to various physical benefits, including improved flexibility (Borms et al., 1987; Smith, 1994), athletic performance (Handel et al., 1997; Worrell et al., 1994), running economy (Godges et al., 1989), injury prevention (Smith, 1994; Worrell et al., 1994; Hartig and Henderson, 1999; Witvrouw et al., 2001; Witvrouw et al., 2003), promotion of healing, and possibly decreased delayed-onset of muscle soreness (Buroker and Schwane, 1989). Although evidence to support the above beliefs is still limited, stretching is widely used.

Several different stretching protocols have been proposed in scientific literature in order to regain or retain flexibility and avoid possible reduction in the range of motion which could impair the functional activities of the muscle. Numerous researchers have compared stretching techniques in an attempt to determine which protocol is the most effective in increasing joint range of motion (Sady et al., 1982; Smith, 1994).
Thus, three stretching techniques have been developed in order to enhance flexibility; ballistic stretching, static or passive stretching, and proprioceptive neuromuscular facilitation. All three methods have been shown to increase ROM immediately after stretching (Sady et al., 1982; Smith, 1994). However, ballistic stretching does not appear to be widely supported in literature and its use is infrequent (Sady et al., 1982). This is due to the rapid and forceful nature of the method that could theoretically exceed the extensibility limits of a muscle (Bandy and Irion, 1994). Moreover, the rapid increase in tension via myostatic stretch reflex can strain or rupture the tissue.

Several authors have proposed that the proprioceptive neuromuscular facilitation techniques are superior to the other stretching methods for improving flexibility (Shellock and Prentice, 1985; Sady et al., 1982). However, these techniques may require an experienced practitioner to administer them safely, reducing their suitability for most coaches and sports performers. 

Contrarily, static stretching has become the most widely used method for increasing ROM because of the simplicity of execution and the reduced risks for muscle injury (Sady et al., 1982; Bandy and Irion, 1994). While most of the scientists agree that this method can improve joint flexibility with the incorporation of passive stretching, limited research in examining the optimal time a stretch should be sustained, is available.
Numerous studies have investigated the duration required for a static stretching effort to be effective in the improvement of ROM. According to Moffatt (1993), the effective duration varies from 5 to 60 sec, but justifications for these propositions are absent (Entyre and Abraham, 1986). Other studies compared three different techniques of stretching (dynamic, static, PNF) and Hardy and Jones (1986) performed 6 sec of stretching whereas Entyre and Lee (1988) suggested that stretching efforts should last for 9 sec each. Gajdosik (1991) applied the 15 sec duration in stretching, whereas Raab and his associates (1988) used 20 sec stretching efforts. Smith (1994) based on a review of the literature suggested that the stretches should be held for 15 to 20 seconds.

The changes in human muscle flexibility as a result of different duration static stretching efforts have been investigated in several studies. Borms and his associates (1987) compared the results of static stretching on the coxo-femoral flexibility using 10, 20 and 30 sec efforts. Bandy and Irion (1994) compared the results of static stretching performing 15, 30 and 60 sec efforts in a program that took place 5 times a week and lasted for 6 weeks. However, they only examined the duration of a static stretching in one single stretching effort and not in multiple efforts. Taylor et al. (1990) suggested that the largest lengthening in the muscle-tendon unit takes place after 4 stretching repetitions. Further repetitions could only produce little further improvement in the ROM. Multiple stretching efforts where examined by Bandy (1997) and Feland (2001) and their associates, using a 6 weeks program in which the subjects were adults aged 21-39 years old and people aged more than 65 years old, respectively. Bandy et al. (1997) managed to find significant improvement in the ROM of the hamstring muscles, irrespectively of whether the stretching repetitions were one or three for 30 or 60 sec. Feland et al. (2001) suggested that when the stretching efforts were applied 4 times and lasted for 60 sec, ROM was improved significantly more compared to a 4 times repetition of 15 or 30 sec.

However no effort was made in the above research to investigate the total fit time of the stretching session. This factor may have an impact on the improvement observed in the ROM, since the duration of a single stretching effort of 60 sec is greater than one of 10 or 30 sec. However, the large duration required for the improvement of ROM may be prohibitive for people performing passive stretching and especially in athletes, as a lot of time is spent, which eventually might be against their training program.

Given that athletes and especially soccer players apply passive stretching in their training, it would prove helpful to examine whether multiple stretching efforts in a specified time can produce positive changes in the ROM of either limb of the soccer players, in a stretching session.
The aim of the present study was to compare the effects of different duration stretching efforts as well as the effect of multiple stretches in different total duration, on the passive ROM during hip flexion, hip extension, hip abduction, knee flexion and ankle dorsiflexion while controlling the total amount of the time spend in a stretching session in junior soccer players.


Thirteen soccer players aged 14.3 ±1.3 years old, (mean height 175.0
±6.0cm, mean body mass 65.6 ±3.3kg) who had been training for 4.0 ±0.5 years, volunteered to participate as subjects in the study. Subjects performed 4 different stretching protocols for the lower extremities with passive stretching for a total of 60 sec. Τhe first protocol comprised of one single stretching effort of 60 sec (1x60s). The second protocol consisted of 2 efforts for 30 sec each (2x30s). Τhe third protocol comprosed of 4 efforts of 15 sec each (4x15s), while the last protocol consisted of 12 efforts of 5 sec each (12x5s). The first protocol served as the control treatment and the next three protocols as the experimental treatments. The order in which the protocols were exercised was random so that the results were not affected by the learning factor. All subjects agreed to maintain their normal exercise and activity levels for the duration of the study. Subjects were healthy with no history of musculoskeletal or neurological disease. A sports medicine accredited doctor examined them physically before the beginning of the measurements. All subjects as well as their parents were informed of the nature, purpose and possible risks involved in the study before giving their informed written consent for participation.

Five ROMs of the lower extremities (hip flexion, hip extension, hip abduction, knee flexion and ankle dorsiflexion with knee flexed) were measured. The measurements were taken before and immediately after the performance of each stretching protocol. Hip abduction was measured with a specially constructed double protractor goniometer, and the other movements were measured with a Myrin flexometer (Lic Rehab. 17183 Solna, Sweden). This flexometer is a modification of the Leighton flexometer, and consist of a circular scale with a weighed pointer controlled by gravity attached to the centre. All flexibility measurements were made according to the Ekstrand et al. (1982) method. The coefficient of variation for the method of goniometric measurements was high (1.9

All measurements except ankle dorsiflexion were made on an adjustable bench. The initial and final positions of each movement were passively measured starting from a 0 point, as defined by the American Academy of Orthopaedic Surgeons (1965). Maximal flexibility was defined as the point where the joint attained to end-range. Two persons performed the measurements. A tester who was responsible for the maximal passive movement of the examined joint and an observer who was responsible for the actual ROM measurement, Throughout the experiment the same experimenter was assigned the same task. Both tester and observer were experienced and familiar with the measurement of joint ROM. Ranges were passively measured in lower extremity joint once on the right-side and once on the left-side. All pre-test and post-test measurements were taken at approximately the same time of day. No warming-up exercises were performed prior to the initial flexibility measurements, and none of the subjects undertook any training program or other type of exercise during the 48 hours prior to the measurements. The reliability coefficient of each measurement was high and has been reported elsewhere (Zakas et al. 2003).

All subjects performed the 4 flexibility-training protocols in four different training sessions. Each training session was separated by at least 1 week from the next, for each subject. The stretching exercises for all flexibility-training protocols consisted of passive lengthening of the muscles. Starting from a maximum elongation, passive elongation of the muscle or muscle groups, without causing pain, maintained for 60, 30, 15 or 5 sec at the position of maximum lengthening proportionately flexibility-training protocols performed. The working muscle groups should be adductors, iliopsoas, hamstrings, quadriceps and soleus for both sides. Prior to the implementation of every flexibility-training protocol active warming-up took place via continuous jogging (120-130 bpm) for 10 min, performed in a normal stride. Briefing sessions were co-ordinated  in which visual demonstrations and individual assistance were provided to ensure all subjects were confident in the requirements of the program and competent in the execution of the stretches.

The first flexibility training protocol took place for 60 sec only one time (1x60s) for both body sides and all examined muscle groups. Τhe second protocol comprised of 2X30 sec stretches that took place first for the one side and then for the other side of the body. Τhe third protocol comprised of 4X15 sec stretches and was also performed for each side of the body, whereas the fourth protocol consisted of 12X5 sec stretches that were performed for both body sides. Recovery between the sets in the treatment protocols lasted for 10 sec. All four treatment protocols performed the warming-up and the stretching exercises identically, under the direct supervision and guidance of the investigators. The players that did not complete the treatment protocols were exempted from the study (2 players). 

Statistical analysis

A mixed within- and between- subjects 4x2x2 ANOVA model with repeated measurements over the tests was applied for each depended variable. The first repeated factor was the test which had 2 levels (pre, post). The second repeated factor was the side which also had 2 levels (right side, left side). The treatment protocol was set as the between subjects factor which comprised of 4 levels (1x60s, 2x30s, 4x15s and 12x5s). When significant different values were found, a Scheffe post hoc analysis was applied to determine the significance of the relationship of the means. In addition, when significant interactions were noted, these were further broken down using analysis of simple main effects. Statistical significance was accepted at the 95% level (p<.05).


The analysis of the main effects revealed no significant differences between the two body sides or between the treatment protocol groups, except for the joint flexibility (hip flexion, F1,48=156.89, p=000, hip extension, F1,48=130.80, p=000, hip abduction, F1,48=65.53, p=000, knee flexion, F1,48=47.56, p=000, ankle dorsiflexion, F1,48=84.71, p=000), indicating that the range of motion differs among the joints of the lower extremities. ROM was higher during knee joint flexion and smaller during ankle joint dorsiflexion. Additionally, no significant interactions were observed between the joint x treatment protocol group, the side x treatment protocol group, the joint x side or the joint x side x treatment protocol group.

A further analysis using a paired t-test for each treatment protocol group in each flexibility joint movement, showed no significant differences in the joint ROM between the two body sides of the junior players. Thus, only the results of the right side will be presented.  

A significant increment was observed for all joint ROMs (p<.01 to p<.001) immediately after the performance of all four flexibility training protocols of the treatment groups (Table 1). Hip flexion was increased by 8.3 to 10.2 degrees, hip extension by 5.9 to 6.8 degrees, hip abduction by 2.7 to 5.5 degrees, knee flexion by 3.3 to 4.7 degrees and in ankle dorsiflexion the increments varied from 1.8 to 4.6 degrees.

  Table 1


According to the results, significant improvement in the ROM of the lower extremity joints is produced after the muscles undergo passive lengthening for a total of one minute irrespectively of whether this lengthening is performed once or using multiple stretches in sets of one minute.
This study cannot be directly compared to the results of others due to the differences in methodology. However, the increases in ROM after the completion of acute condition stretching exercises in different duration concurs with the findings of Madding et al. (1987) who compared passive strengthening of 15, 45 and 120 sec during hip abduction to one single stretching session. Madding and his associates also found improvements in joint ROM irrespectively if the passive lengthening of the muscles lasted for 15 or 120 sec. It seems that under acute conditions the critical factor for the increment in joint ROM might be the lengthening of the muscles and not the time that they should be kept in the lengthening position or the number of the repeated efforts.

In short-term flexibility conditions Bandy et al. (1997) found significant improvement in the hamstring flexibility whether the passive stretching was performed one time or three times for half or one minute in a 6 week stretching program, that took place 5 times per week. Important improvements were also suggested by Roberts and Wilson (1999) in the passive ROM of hip flexion, knee flexion and extension irrespectively of whether the passive stretching was repeated 9 times for 5 sec or 3 times for 15 sec a 5 weeks program.

It is accepted that during stretching exercises joint flexibility is affected by the extensibility of connective tissue. Sapega et al. (1981) as well as Warren et al. (1976) demonstrated that tissue temperature can significantly influence the extensibility of connective tissue and, therefore, affect joint flexibility. Until now, research has focused on the influence of the increased temperature of muscles on the improvement of flexibility as a result of stretching exercises. It is believed that a general 5-min warming-up session should take place first during every training session in order to make the best of all muscles (Beaulieu, 1981), due to its viscosity decrement (Shellock and Prentice, 1985). In the present study the soccer players performed several stretching exercises after a 10-min warming-up procedure. Therefore, it is reasonable to assume that the improvements in joint flexibility immediately after each stretching protocol were due to the muscle elongation that occured during stretching, especially since the general training session proceeded. However, further investigation is required in order to completely clarify the warming up contribution to the increments of joint ROM during stretching.

No data collected in the present study could suggest a specific mechanism explaining the results. Connective tissue is comprised of collagen, elastin, and ground substances which are the structures that tend to limit ROM (Wright and Johns, 1960). Among these myogenic restrictive factors, neurogenic constrains, joint constraints, skin, subcutaneous connective tissue, and frictional constraints are included (Hutton, 1992). During stretching, only neurogenic and myogenic restrictions might exist during voluntary control in the acute setting. Most of the emphasis on stretching exercises used in rehabilitative medicine and athletic training has been placed on the neurogenic component by employing stretching techniques that are presumed to promote the level of inhibition to the muscle undergoing stretch. It seems that in the acute stretching session, the gains on flexibility might be due to neurogenic and myogenic adaptations, whereas during short-term stretching programmes, the gains on flexibility might be due to myogenic adaptations. However, further research is necessary to provide information on the exact mechanisms involved in improving flexibility during acute stretching settings.


We propose that a stretching session with passive lengthening lasting for 60 sec can constitute an important stimulus for the improvement of lower extremity joints ROM in junior soccer players. All stretching efforts appear effective whether they are performed only once or in sets. Results from the present study might prove useful for players who desire to increase their flexibility, as well as for clinicians who incorporate passive stretching sessions in rehabilitation programs and for coaches who incorporate the same type stretching exercises as part of their training sessions.


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Physical Training Sept 2005