This study used a standing one-legged hamstring stretch (3). Decoster et al. (4) found that stretching position (i.e., supine, seated, standing) did not make a difference with regard to ROM gains. The single stretch was deemed effective as a comprehensive stretching program because previous studies found that a single stretch is effective at significantly increasing ROM about a joint (1,2,4-7,15,18). All subjects were instructed on the appropriate stretching procedure prior to the start of the study. First, each subject assumed an upright posture with both feet facing forward. The leg to be stretched was extended and placed on a surface at or slightly below hip level. Subjects were then instructed to keep their back straight, while they hinged forward at their hips, until slight to moderate discomfort was felt in the back of their thigh of the leg being stretched (Figure 1). Subjects were instructed to maintain this position of discomfort throughout the entirety of the stretch.
The stretching protocol during the initial 4 weeks of the study called for both groups to stretch their hamstrings 30 seconds, rest for 10 seconds, and then stretch for another 30 seconds (1-5). This same procedure was then repeated for the contralateral leg. Stretching was performed 2 times per day, with a minimum of 4 hours between stretches. The total stretching time was 2 minutes per leg per day. Stretching was performed daily (i.e., 7 days per week) for the initial 4 weeks of the study. The final 4 weeks of the study had the standard group cease all hamstring stretching, whereas the intermittent group continued the stretching protocol 2 or 3 days per week. Prior to the start of the study, subjects were instructed to keep a log of the times that they stretched to monitor adherence to the stretching program.
A hip ROM measurement of each subject was taken prior to the start of the study (PRE). Hip ROM thereafter was measured at the end of each week of this 8-week study. Hence, all subjects were measured a total of 9 times over the course of this study. Measurements of both right and left lower extremities were recorded, but only measurements of the right lower extremity were analyzed.
For the measurement process, a passive straight leg raise (SLR) was used to measure hip ROM (2). Subjects laid supine on a standard plinth with their knees bent over the edge. One investigator then applied a passive ROM force to each lower extremity (1 at a time) until a firm end feel was noted or when the subject requested to stop. A second investigator then used a standard 12-inch goniometer (Jamar, Miami, Florida) to measure hip flexion using the procedure outlined by Norkin (10) (Figure 2). Both of these investigators were blinded as to which group a subject was in. The second investigator then reported the ROM measurement to the third investigator, who recorded this value. Subjects were not made aware of their hip ROM measures. The third investigator documented all ROM measurements and had sole access to these records. All 3 investigators performed the same duties throughout the duration of this study.
Reliability of the measurement procedure was estimated prior to the beginning of this study. The measuring investigators, prior to the start of the study, measured right lower-extremity hip ROM on a sample of healthy individuals (n = 15). Hip ROM was measured twice in the same day to determine intrarater reliability. The second measurement occurred in a random order, approximately 20 minutes after the initial measurement. Intraclass correlation coefficients (ICC) (2,1) were determined and demonstrated that the investigators provided reliable data with this technique (ICC = 0.95, CI95 = 0.91, 0.97).
Descriptive statistics were generated for subject details. To test for the possible interaction between stretching protocol and time, a 2-factor analysis of variance (ANOVA) was used. The 2 factors included time (repeated factor of 9 time points) and condition (i.e., standard stretch and intermittent stretch). In the absence of any interaction, the main effects were then tested with ANOVA. If the interaction was significant, separate paired t-tests were run to compare group differences. Planned contrasts were used to test for differences between each time period (e.g., Week 1 to Week 2, Week 2 to Week 3, etc.) for the 2 groups. A p-value of 0.05 was established as the criteria for statistical significance.
The 2-way ANOVA found a significant interaction between group and time, with the hip ROM values of the intermittent group and standard group diverging during the final 4 weeks of the study (Figure 3). Mean hip ROM significantly increased (p < 0.05) for both groups from the PRE measurement to Week 4. The mean hip ROM of the standard group increased from 71.4 ± 18.5 degrees to 90.6 ± 20.5 degrees. The mean hip ROM of the intermittent group increased at a similar rate from 68.6 ± 15.7 degrees to 89.1 ± 16.8 degrees. The hip ROM at Week 4 was not different between the 2 groups (p > 0.05). During the final 4 weeks of the study, mean hip ROM significantly decreased (p < 0.05) for the standard group from 90.6 ± 20.5 degrees to 83.9 ± 20.3 degrees. However, the mean hip ROM for the intermittent group did not decrease during the final 4 weeks. In fact, the intermittent group demonstrated a trend toward increasing ROM from 89.1 ± 16.8 degrees to 93.2 ± 14.9 degrees (Table 2). Finally, the intermittent group's hip ROM was significantly greater than that of the control group (p < 0.05) by the end of Week 8.
Figure 3 illustrates the rate of gain and loss in ROM between the 2 groups over the 8-week period. A consistent weekly gain in ROM is noted during the first 4 weeks; however, the change from week to week was not statistically significant when tested with the planned contrasts. A significant change is not detected until a comparison is made between PRE and Week 4. In addition, during the final 4 weeks of the study (i.e., cessation time and intermittent time), the change in ROM for the standard group (cessation) was not significant on a week-to-week basis until comparing Week 4 with Week 8.
The results of this study, which are similar to those found by Wallin et al., indicate that intermittent stretching (i.e., 2 or 3 days/week) will maintain ROM gains made during an initial stretching program. Both of our groups (standard and intermittent) gained similar ROM during the first 4 weeks of the study. However, the intermittent group maintained ROM and demonstrated a possible trend to gain ROM during the final 4 weeks of the study. The standard group lost significant motion during the final 4 weeks. At the conclusion of the 8 weeks, the intermittent group demonstrated significantly greater hip ROM than the control group (Figure 4). Our study differs from that of Wallin et al. in that our standard group ceased all stretching, whereas all groups in the Wallin et al. study continued stretching, even during the intermittent period. Hence, our study demonstrates that, in the absence of at least intermittent stretching (i.e., 2-3 days/week), ROM gains will be lost when stretching is discontinued.
Stretching can cause viscoelastic changes to occur in muscles. Elastic changes occur following a single stretch. However, these changes are temporary, and the muscle will return to its original length once the stretching load is removed (11). This may account for why ROM decreases following a single stretch (5,6,13). Willy et al. (16) noted that following several weeks of stretching, increases in musculotendinous length and stretching tolerance can occur. These increases may be a result of the plastic elongation of tissues. Plastic changes are hard to achieve but can lead to permanent elongation of tissues (11). Thus, the muscle will not return to its original length once the stretching load has ceased (14). This may explain the accumulative effects of stretching and demonstrate how ROM may be maintained following a stretching program. Intermittent stretching may therefore help to prevent ROM from decreasing by keeping the muscles in the plastic elongation state.
Our study also examined the weekly changes in ROM during a stretching program. Although we found significant gains at the end of a 4-week stretching program, the weekly gains, although notable, were not significant on a week-to-week basis. Only after a full 4 weeks were we able to document a significant change in motion. The same is noted for the cessation period. During this time, the standard group lost a significant amount of ROM by the end of the 4-week cessation period. However, the week-to-week changes were not statistically significant. This indicates that the rate of gain/loss over a 4-week stretching program and subsequent 4-week cessation period likely occurs consistently over the time period. Our limited sample size likely contributed to the lack of significance between weeks.
From a clinical and practical perspective, the results of this study are pertinent because patients/clients may be more likely to adhere to their stretching exercise programs if they are educated that they will be able to begin a maintenance program (i.e., intermittent) once their ROM goal is attained. Patients/clients also may be more likely to adhere to their maintenance stretching program because this program will not be as time consuming as the initial program but will still be as effective. In the case of patients, this in turn may lead to a decreased risk of reinjury following discharge from therapy. Athletes may also benefit from this knowledge, especially during the off-season, when ROM gains need to be maintained. However, it is essential for clinicians and coaches to educate their patients and athletes on the potential benefits of intermittent stretching.
Several limitations were associated with this study. This study used a sampling of convenience to recruit subjects, and all subjects were healthy and free of injury. Future studies might attempt to recruit a more diverse subject population including those with specific musculoskeletal injuries/dysfunction and subjects of different age. Finally, collection of all subject stretching logs, although attempted, was not feasible. The intermittent group stretched either 2 or 3 days per week during the final 4 weeks; however, we do not have an accurate account of the final percentage of days stretched.
Future multiweek studies are needed to study the effects of intermittent stretching, following an initial stretching program, because there is a current lack of research in this area. Future studies may also look at a strictly intermittent stretching program rather than a daily program. The effects of intermittent stretching for durations longer than 1 month should be assessed to determine whether ROM gains continue to be maintained. Different muscles may be studied to see if there are any differences between muscle groups. Finally, our study used healthy individuals, aged 18 to 50 years old. Therefore, the results can only be applied to this population of individuals.
The results of this study indicate that, following a daily stretching program of 4 weeks duration, the gains made during this program can be sufficiently maintained with an intermittent stretching (i.e., 2 or 3 days/week) program. Once ROM goals have been attained with a daily stretching program, ROM can be maintained, provided the individual continues to stretch 2 to 3 days per week. These findings may help to increase adherence to home exercise programs and maintenance programs. With this potential increased rate of adherence, this may lead to a decreased rate of reinjury following discharge from therapy. This may also allow athletes to maintain their ROM gains, during the off-season, which may help to prevent injury as well. Clinicians, coaches, patients, and athletes can consider the use of intermittent stretching to maintain ROM gains following an initial stretching program.
This study was funded by Koroshi, Inc. (Toledo, Ohio) to provide compensation to subjects for their time. The authors do not have a professional relationship with Koroshi, Inc. We also wish to thank Steve Benesh, PT, MSPT; Kristin Orwig, PT, MSPT; Justin Wilson, PT, MSPT; Michelle Gellar, PT, MSPT; and Pam Spradlin, PT, MSPT for their assistance with data collection.
1. Bandy, WD and Irion, JM. The effects of time on static stretch on the flexibility
of the hamstring
muscles. Phys Ther
74: 845-850, 1994.
2. Bandy, WD, Irion, JM, and Briggler, M. The effect of static stretch and dynamic range of motion
training on the flexibility
of the hamstring
muscles. J Orthop Sports Phys Ther
27: 295-300, 1998.
3. Cipriani, D, Abel, B, and Pirrwitz, D. A comparison of two stretching protocols on hip range of motion
: Implications for total daily stretch duration. J Strength Cond Res
17: 274-278, 2003.
4. Decoster, LC, Cleland, J, Altieri, C, and Russell, P. The effects of hamstring
stretching on range of motion
: A systematic literature review. J Orthop Sports Phys Ther
. 35: 377-387, 2005.
5. Depino, GM, Webright, WG, and Arnold, BL. Duration of maintained hamstring flexibility
after cessation of an acute static stretching protocol. J Athl Train
35: 56-59, 2000.
6. Deweijer, VC, Gorniak, GC, and Shamus, E. The effect of static stretch and warm-up exercise on hamstring
length over the course of 24 hours. J Orthop Sports Phys Ther
33: 727-733, 2003.
7. Guissard, N and Duchateau, J. Effect of static stretch training on neural and mechanical properties of the human plantar-flexor muscles. Muscle Nerve
29: 248-255, 2004.
8. Hall, CM and Broday, LT. Therapeutic Exercise: Moving Toward Function
. (2nd ed.) Baltimore: Lippincott Williams and Wilkins, 2005. pp. 129.
9. Malliaropoulos, N, Papalexandris, S, Papalada, A, and Papacostas, E. The role of stretching in rehabilitation of hamstring
injuries: 80 Athletes follow up. Med Sci Sports Exerc
36: 756-759, 2004.
10. Norkin, C and Joyce, D. Measurement Joint Motion: A Guide to Goniometry
. (2nd ed.) Philadelphia: F.A. Davis Company, 1995.
11. Prentice, WE. Therapeutic Modalities for Physical Therapists
. (2nd ed.) New York: McGraw-Hill, 2002. pp. 203-225.
12. Rubley, MD, Brucker, JB, Knight, KL, Ricard, MD, and Draper, DO. Flexibility
retention 3 weeks after a 5-day training regime. J Sport Rehabil
10: 105-112, 2001.
13. Spernoga, SG, Uhl, TL, Arnold, BL, and Gansneder, BM. Duration of maintained hamstring flexibility
after a one-time, modified hold-relax stretching protocol. J Athl Train
36: 44-48, 2001.
14. Starring, DT, Gossman, MR, Nicholson GG Jr, and Lemons, J. Comparison of cyclic and sustained passive stretching using a mechanical device to increase resting length of hamstring
muscles. Phys Ther
68: 314-320, 1988.
15. Wallin D, Ekblom, B, Grahn, R, and Nordenborg, T. Improvement of muscle flexibility
. A comparison between two techniques. Am J Sports Med
13: 363-268, 1985.
16. Willy, RW, Kyle, BA, Moore, SA, and Chleboun, GS. Effect of cessation and resumption of static hamstring
muscle stretching on joint range of motion
. J Orthop Sports Phys Ther
31: 138-144, 2001.
17. Worrell, TW, Smith, TL, and Winegardner, J. Effect of hamstring
stretching on hamstring
muscle performance. J Orthop Sports Phys Ther
18. Zebas, CJ and Rivera, ML. Retention of flexibility
in selected joints after cessation of a stretching exercise program. Exerc Physiol
1: 181-191, 1985.
Keywords:© 2009 National Strength and Conditioning Association
flexibility; hamstring; range of motion