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ORIGINAL

The effect of dynamic stretching on hamstrings flexibility
with respect to the spino-pelvic rhythm
Kiyotaka Hasebe1,2, Yu Okubo3, Koji Kaneoka2, Kohei Takada4, Daisuke Suzuki5, and Koichi Sairyo6
1Faculty of Sports Science, Waseda University, Mikajima, Tokorozawa, Saitama, Japan, 2Department of Rehabilitation, Teikyo University
Mizonokuchi Hospital, Mizonokuchi, Takatsu - ku, Kanagawa, Japan, 3Faculty of Health and Medical Care, Saitama Medical University,
Moroyama - machi, Iruma - gun, Saitama, Japan, 4Department of Rehabilitation, The Cancer Institute Hospital Of Japanese Foundation For
Cancer Research, Ariake, Kouto - ku, Tokyo, Japan, 5Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tennodai,
Tsukuba, Ibaraki, Japan, 6Department of Orthopedics, the University of Tokushima, Kuramoto, Tokushima, Tokushima, Japan

Abstract : Objectives : To ascertain the dynamic stretch effects of flexibility of the hamstrings on lumbar spine
and pelvic kinematics. Background : Tight hamstrings are positively correlated with low back pain. However,
it is unclear how flexibility of the hamstrings affects spino-pelvic rhythm. Methods : Twelve healthy men participated in the study. The straight leg raising (SLR) angle, finger floor distance (FFD), and spino-pelvic rhythm
was measured before and after the 6-week stretching protocol. The forward bending task was divided into 4phases. The paired t-test was used to determine significant differences before and after the FFD, SLR angle,
lumbar motion, and pelvic motion, and spino-pelvic rhythm in each phase (p 0.05). Results : After 6 weeks ofstretching, significant improvements were seen in the FFD with maximum forward bending and in the SLR angle.
Total pelvic rotation was also significantly increased in contrast to total lumbar flexion. A decreased spino-pelvic
ratio was seen in the final phase. Conclusion : Dynamic stretching could change the spino-pelvic rhythm to apelvis-dominant motion, indicating that flexible hamstrings are important for preventing low back pain. J. Med.
Invest. 63 : 85-90, February, 2016
Keywords : FFD, SLR angle, spinal mouse, low back, lumbo-pelvic rhythm

INTRODUCTION
Low back pain is one of the most common symptoms in the general population. In fact, more than 80% of people experience lowback pain at least once in their life (1). Tight hamstrings correlatestrongly with low back pain (2-5). Esola et al. reported that spinopelvic rhythm (lumbar motion/pelvic motion) contributes to low
back pain, and that the spino-pelvic rhythm is disturbed by tighthamstrings (2).
It is reported that the spino-pelvic complex has a range of motion of 110!: 40!in the lumbar spine and 70!in the hip joint (2).
During forward bending of the trunk, lumbar spine movement isdominant during the initial phase ; lumbar spine movement andpelvic movement are similar during the middle phase ; and pelvic
movement is dominant during the ending phase. Esola et al. measured spino-pelvic rhythm in healthy subjects and in subjects witha history of low back pain. In the back pain group, the lumbar segment moved more than the pelvis during forward bending of thetrunk, suggesting that greater lumbar motion can induce overloading of the lumbar spine and consequently cause low back pain (2).
Tight hamstrings can restrict hip movement, thereby increasing
lumbar spine motion (6, 7) and causing back pain due to their influence on spino-pelvic rhythm during forward bending (8). Recently, Hasebe et al. (9) measured spino-pelvic rhythm in healthy
subjects with various grades of hamstrings tightness and foundincrease pelvic motion in subjects with flexible hamstrings thanin those with tight hamstrings. They also stated that improving hamstrings flexibility is important for reducing lumbar loading during

activities in daily life. Thus, it is reasonable to assume that decreased
lumbar loading would decrease the incidence of such mechanicalstress-induced lumbar disorders. Therefore, a possible means of
reducing lumbar loading through physical therapy is improving
the flexibility of the hamstrings.
Previous studies investigating the spino-pelvic rhythm after
hamstrings stretching had mainly used static stretching (10). Dynamic stretching is another method that aims to improve the capacity of an individual’s body to move instantaneously (11). It utilizes
gentle momentum of limbs, or a bouncing motion to move limbs
throughout the possible range of motion (12). It has been widely
performed as a warm-up for athletes before the training or games(11). There are various studies regarding dynamic stretching thatshowed positive effects of the same on power (13), jump performance (14), and sprinting (15). In addition, recent articles have indicated that dynamic stretching improved not only maximal strengthand power performance but also balance and agility. This indicatesthat dynamic stretching is more appropriate than static stretchingfor activities that require balance, rapid change of running direction (agility), and movement time of the upper extremities (16).
To the best of our knowledge, no report has yet investigated theeffect of dynamic stretching on spino-pelvic rhythm. Investigating
how the lumbo-pelvic rhythm changes when hamstring flexibility
improves through dynamic stretching may help prevent the development of lower back pain. Therefore, the aim of this study is toclarify the influence of dynamic stretching of hamstrings on spinopelvic rhythm. Our hypothesis is that improving the flexibility of
the hamstrings would be beneficial for pelvic motion through reducing lumbar motion.

Received for publication November 30, 2015 ; accepted December 11,
2015.
Address correspondence and reprint requests to Yu Okubo, RPT, PhD,
Faculty of Health and Medical Care, Saitama Medical University, 981
Kawakado, Moroyama - machi, Iruma - gun, Saitama 350 - 0496 Japan andFax : +81 - 49 - 295 - 5104.

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K. Hasebe, et al. Stretching for spino-pelvic flexibility

SUBJECT AND METHODS
Subjects
In total, 14 healthy men were recruited in the study. Exclusion
criteria included history of lumbar spine disorder, neurologicaldisorder, spinal surgery, or lower extremity surgery. Subjects were
excluded if they could touch their fingers to the floor in the finger
floor distance (FFD) test. Two of the participants performed stretching exercises regularly during the intervention period, so they were
excluded. Finally, we used the data of 12 participants for the data
analysis. The age, height, and body mass of the participants were
20.5!1.1 years (mean!SD), 170.1!5.9 cm, and 62.3!5.3 kg, respectively.
The purpose and protocol of the study was explained to eachparticipant, and a signed informed consent form was obtained prior
to participation. The study was approved by the Ethics Committeeof Saitama medical University. (approval number, 87)

Measurement Protocol & analysis
The straight leg raising (SLR) angle, FFD, and spino-pelvic
rhythm was measured before and after the 6-week stretching protocol and the results were compared to elucidate the effects ofstretching exercises on the spino-pelvic rhythm. To conduct image
analysis, four passive reflective markers were attached to the rightside of the participants at specific anatomical landmarks : the lateralepicondyle, greater trochanter, 7th rib, and 10th rib along the axillary line.
As a characteristic of hamstring flexibility, we measured the SLR
angle. Flexibility of the hamstring muscles through the SLR test
was measured at full hip flexion with the knee extended. The SLR
motions were filmed with a digital video camera (DCR-TRV30 ;Sony Corporation, Tokyo, Japan). The camera was positioned at
the same height as the bed and 3 m away from the right side ofeach subject. We analyzed the obtained images with the Image J
software (National Institutes of Health, USA), calculated the angle
between the line linking the 10th rib to the 7th rib and the line
linking the greater trochanter to the lateral epicondyle. The SLR
angle was measured twice, and the mean value was used.
We measured the FFD in both the upright standing position(x cm) and at the maximum forward bending posture with full
extension of the knee joint (y cm), such that we measured the total

finger movement with flexion (TFM ; x-y cm) by using a digital
FFD meter (T.K.K.5403 : Takei Scientific Instruments Co., Ltd,Tokyo, Japan). If the finger was extended below the level of thetable, the value was regarded as negative.
Spinal alignment was measured with a spinal mouse (Idiag AG,
Voletswil, Switzerland) in the following five positions : (1) upright
posture 0% TFM ; (2) forward bending 25% TFM ; (3) forwardbending 50% TFM ; (4) forward bending 75% TFM ; and forwardbending 100% TFM (Figure 1). The reliability of the spinal mousehas been well established (9, 17 -19). A spinal mouse enables measurement of the entire thoracic angle, from T1 to T12, and likewise,
the pelvic rotation motion (sacrum inclination angle) and the entire
lumbar angle from L1 to L5. In each position, the average value obtained through three measurements was used following analysis.
Changes in the angle of the thoracic and lumbar spine as wellas that of the pelvis were calculated for each step. The change frompositions 0% TFM to 25% TFM was designated as phase I, frompositions 25% TFM to 50% as phase II, from positions 50% to 75%
TFM as phase III, and from positions 75% TFM to 100% TFM asphase IV. The kyphotic angles were positive and lordotic angles
were negative. In each phase, the ratio of lumbar motion to pelvic
motion (L/P) was measured to understand the lumbo-pelvic
rhythm. When the L/P ratio was "1.0, the motion was consideredlumbar dominant ; when the L/P ratio was !1.0, the motion wasconsidered pelvis dominant.

Stretching exercise program
To stretch the hamstrings, we used a stretching machine (NeverTight-Ham, Hogrel Inc., Tokyo, Japan) as shown in Figure 2. Thismachine has been reported to be effective for active stretching oftight hamstrings (20). Theoretically active stretching is efficientfor gaining flexibility since the stretch utilizes reciprocal inhibition
from contraction of the quadriceps muscle. The stretching machine is designed to perform active stretching while lying on abench. Each subject performed 20 repetitions of knee extension
every second for 5 sets, with 1-min rest intervals between the sets,
3 days per week for 6 weeks.
The seat angle of the machine can be adjusted to four positions
based on the changing angle of the hip joint. (Figure 3). During theintervention period, the seat angle was changed by one stage every
1 week, which increased the strength of the stretch progressively.

Figure 1 : Posture and position of the subjects during measurement of the spino - pelvic rhythm. Spinal alignment was measured with a spinal mousein the following five positions : (1) upright posture 0% TFM ; (2) forward bending 25% TFM ; (3) forward bending 50% TFM ; (4) forward bending 75%
TFM ; and forward bending 100% TFM. TFM : total finger movement with flexion.

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Figure 2 : Stretching on the “Never - Tight - Ham” machine designed to perform active stretch in the lying position on a bench. In the stretchingposition, subjects contract the quadriceps muscles against resistance, which simultaneously relaxes the hamstrings through reciprocal inhibition.

Figure 3 : Seat angle of the machine. The seat angle can be adjusted to four positions according to the flexibility of the hamstrings. The angle atposition 4 is less than 90". Simply sitting on the bench produces deep hip joint flexion, which stretches the hamstrings.

each phase. In phase I, the thoracic spine showed the greatest flexion ; thereafter, it showed extension as trunk flexion progressedfrom phase II to phase IV. Movement of the lumbar spine in each
Statistical analysis
phase is depicted in Figure 7. The lumbar spine moved to a greater
Statcel 2 (OMS publishing Inc., Tokyo, Japan) was used for sta- extent in phases I and II, with significantly greater (p!0.05) movetistical analysis. The paired t-test was used to determine significant ment in phase I after stretching than before. In phases III and IV,
differences before and after the FFD, SLR angle, the total lumbar the movement was small, and further decreased significantly (p!
motion and pelvic motion, thoracic spine motion and lumbar spine 0.05) after stretching.
motion and pelvic rotation motion and L/P ratio in each phase. A p
Pelvic rotation is shown in Figure 8. The motion appeared to bevalue !0.05 was considered significant.
increased in all phases after stretching, with significant (p!0.05)
differences seen in phases III and IV. To understand lumbo-pelvic
rhythm, the lumbar movement to pelvic rotation (L/P) ratio was
calculated (Figure 9). The L/P value decreased from phases I to
RESULTS
IV both before and after the stretching protocol, indicating predomiAfter the 6 -week stretching protocol, all subjects showed in- nant use of the lumbar spine in the early stages and predominantcreased flexibility in the hamstrings. The FFD and SLR were sig- use of the pelvis in the late stages. The ratio in phase IV was 0.5!0.3
nificantly (p!0.05) improved, from 5.8!5.5 cm and 71.2!9.7" and 0.3!0.2 before and after stretching, respectively. The values
to -2.5!3.8 cm and 79.3!9.0", respectively (Figure 4). During full were less than 1.0, indicating that the motion was generated mainly
flexion (upright position to maximum forward bending position), from the pelvis in the final stage of bending the trunk forward. The
total pelvic motion was also significantly (p !0.01) increased, from values after stretching were significantly smaller (p!0.05) than
31.9!6.9"to 42.3!8.3"(Figure 5). On the other hand, no signifi- those before stretching, indicating that subjects had achieved efficant differences were observed between measurements for the cient use of the pelvis in phase IV.
lumbar motion. Figure 6 shows the thoracic spine movement inIn the fifth and sixth weeks of the intervention, the stretch was performed at the maximum angle.

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K. Hasebe, et al. Stretching for spino-pelvic flexibility

Figure 4 : Finger to floor distance and straight leg raising were significantly (p!0.01) improved after stretching.

Figure 5 : Total pelvic and lumbar spine angles before and after stretching. Total pelvic motion was significantly (p !0.01) increased, whereas total
lumbar spine angle was largely unchanged.

Figure 6 : Thoracic spine motion in each phase. Note the paradoxical
extension motion during trunk forward bending in phases II, III, and IV.

Figure 7 : Lumbar spine motion in each phase. In phase I, the movement

was greater (p !0.05) after stretching than before. In phases III and IV,
the movement was small before stretching but decreased significantly(p !0.05) after stretching.

DISCUSSION
After 6 weeks of dynamic stretching intervention in healthy men,
the SLR angle increased significantly, while the FFD decreased
significantly. After the intervention, FFD and SLR showed significant improvements, with a mean of approximately 7 cm and 8",
respectively, which indicates the improvement in hamstrings
flexibility. In a previous study, the effect of active static stretching
was investigated and FFD was seen to improve by 8.9 cm (21). The

improvement in the SLR angle was the same in both studies (9")(7), which suggests that this method is equally effective as thestatic stretch at improving flexibility. Ayala et al. reported that after
active static stretching intervention in healthy men with normal
hamstrings, the SLR angle increased to 10"(22). Therefore, we
believe that this stretching method was as effective as previously
studied methods at improving flexibility.

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Figure 8 : Pelvic rotation motion in each phase. In all phases, the motion
increased after stretching, and the difference was significant (p !0.05)
in phases III and IV.

Vol. 63 February 201689

deep flexion position of the hip joint. Dynamic stretching elevatesmuscle temperature (25) and stimulates the nervous system (26)
as well as improvement of the spino-pelvic rhythm in this study.
Therefore, dynamic stretching is considered to be more useful fora warm-up before sports activity than static stretching.
Tightness in the hamstrings can restrict pelvic forward movement, thereby increasing compensatory lumbar flexion. The resultof our study showed that the dynamic stretching intervention for
hamstring muscles can possibly improve pelvic mobility in the latephase of trunk forward bending (phase III and IV), leading to a reduction in compensatory lumbar flexion movement. It is therefore
logical that overcoming hamstrings tightness and improving flexibility will ensure greater mobility of the pelvis, leading to reduced
lumbar motion and mechanical loading during trunk motion. These
data indicate that flexible hamstrings are beneficial for preventing
low back pain by reducing lumbar loading.
There are several limitations of the current study. First, it is unknown whether there will be reduction in low back pain prevalenceor the vicious cycle of low back pain will be broken when lumbopelvic rhythm is improved by stretching the hamstrings. Second
point, we used only male subjects, because no studies have reported sex differences in spino-pelvic rhythm. Future studies
should include female subjects and examine the relationship between spino-pelvic rhythm and sexes.

CONCLUSION

Figure 9 : Lumbo - pelvic ratio before and after stretching. In phase IV,
the value after stretching was significantly smaller (p !0.05) than before
stretching, indicating that subjects gained efficient use of the pelvis.

Our results indicate that after 6 weeks of dynamic stretchingintervention in healthy men, the SLR angle significantly increased
and the FFD significantly decreased, which indicates improvement
in hamstrings flexibility. In addition, the dynamic stretching intervention for hamstring muscles can possibly improve pelvic mobility at the late phase of trunk forward bending (phase III and IV),
leading to a reduction in compensatory lumbar flexion movement
and change in the spino-pelvic rhythm.

CONFLICT OF INTEREST
None of the authors have any conflicts of interest to declare
The dynamic stretch on the hamstrings did not show significant
difference in the total variation of the lumbar motion, and only the
total variation of pelvic motion increased significantly. This result
suggested that improvement of the hamstrings flexibility significantly increased the pelvic anterior motion. Some previous studies
have investigated the effects of hamstrings stretching on the spinopelvic rhythm (10). However, although some studies reported thatstretching improved the flexibility of the hamstrings, and as a consequence, the pelvic anterior motion increased significantly (7),there was no report that the spino-pelvic rhythm significantly
changed. In this study, as the result of separately indicating thevariation in the lumbar spine angle in each phase, the pelvic angle
variation significantly increased in phase III and IV, and the lumbar
angle variation significantly decreased. Moreover, the L/P rate significantly decreased only in phase IV. Regarding the differing results of earlier studies with respect to no change in the spino-pelvic
rhythm, the difference of the stretching methods was likely thereason (7). Also, it might be that earlier studies used the static
stretch, which is the most used clinical method, but this study usedthe dynamic stretch. The dynamic stretch improves the specificflexibility of the movements, particularly when movements are
simulating actual motions (23, 24). In this study, as the dynamic
stretch was applied when the hip joint deep flexion posture was performed, it is possible that a change occurring in the spino-pelvic
rhythm of the late phase of anterior forward bending involved the

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