Research Review By Demetry Assimakopoulos©

Date Posted:

February 2010

Study Title:

Active stretching improves flexibility, joint torque, and functional mobility in older women


Batista LH, Vilar AC, Ferreira JJA, Rebelatto JR & Salvini TF

Author's Affiliations:

Department of Physical Therapy of the Federal University of Sao Paolo, Brazil; Department of Physical Therapy of the Federal University of Praiba, Brazil

Publication Information:

American Journal of Physical Medicine & Rehabilitation 2009; 88: 815-822.

Background Information:

Deficits in muscle strength and range of motion are common in older adults due to a decrease in overall flexibility (6). Reduced flexibility is generally caused by shortening and increased rigidity of muscles (5), especially when compared to younger individuals (4). These viscoelastic changes in muscle fibers have deleterious functional consequences, such as aberrant gait patterns (12) and hampered ability to rise from a seated position, leading to a greater incidence of falls and loss of independence (11). Functional status can be assessed using the “timed up-and-go” (TUG) test. A decrease in muscular strength can lead to greater times in the TUG test (13).

Stretching is an exercise performed in clinical settings and physical fitness facilities used to increase range of motion. Research has shown that stretching can cause morphologic change in muscle fibres (9) and connective tissue (2), ultimately leading to an increase in overall muscle strength (7).

The researchers involved in this study hypothesized that active stretching programs can increase knee-flexor torque and flexibility, improve knee extensor torque and improve functional mobility of older adults. In addition to ascertaining this information, the researchers were interested in whether or not these physiological changes remained after the intervention.

Pertinent Results:

Flexibility: An increase in knee-extension ROM was seen (P=0.0001), although the gain was not completely maintained 4 weeks post-intervention.

Functional mobility: TUG test time improved, demonstrated by a decreased time which was maintained 4 weeks post-intervention.

Peak torque of knee flexors and extensors: there was a general increase in concentric and eccentric torque of the knee flexors and extensors (P=0.01 and .02; P=.02 and .01, respectively). Generally, these favorable changes were maintained 4 weeks post-intervention, except for concentric knee flexor torque.

Clinical Application & Conclusions:

The knee flexor stretching protocol (described in the methods section) has the potential to increase flexibility of the muscle group. In addition to this conclusion, stretching can increase the flexor and extensor torque, leading to an improvement in functional capacity in older adults. The most impressive discovery was that these physiological and functional changes were maintained for 4 weeks post-intervention. This indicates that older individuals’ neuromuscular systems can adequately adapt to a progressive stretching protocol.

Flexibility protocols implemented in older individuals likely result in increased viscoelasticity leading to an increase in extension ROM. There is experimental evidence that there may be an increase in sarcomere number oriented serially. However, this finding has not been observed in human subjects as yet.

Previous studies have shown that similar results can occur after a stretching intervention implemented every day for 6 weeks straight. This study showed that flexibility training twice a week for 4 weeks is as efficient as a 6 week training protocol. However, this is the first study to describe such findings.

The researchers attribute the increase in torque for both muscle groups to an increase in the activation threshold of golgi tendon organs. As a result of this, there will be a localized increase in the number of active motor units, leading to a generation of greater muscle tension (13). In addition, muscle hypertrophy as a result of stretching exercises has been seen in animal models (3). This could also be involved in the resultant increase in torque. Some research claimed that the combination of stretching and contraction can lead to greater effects on the adaptations seen in this study (8). Future research aimed at studying all of these hypotheses are needed, as many of them have only been observed in animals.

According to this group of researchers, it is conceivable that stretched muscles are stronger because both passive and active forces add to strength production. Previous research concluded that the increase in stored energy and ranges of motion after stretching is important because it can increase the elastic recoil capacity of a muscle (7). Assuming this, activities such as the TUG can become more efficient. However, this notion is not completely agreed upon in the fitness industry. Through the assessment of past research (10), the authors of this study concluded that the participants of this study showed similar TUG times as individuals roughly 10 years younger!

Study Methods:

Subjects: were taken from the participants of a geriatric revitalization program. These individuals participated in this program for 12 months before the study. Subjects were excluded if they had vascular, inflammatory disorders, lower limb musculoskeletal disorders or uncontrolled hypertension. The inclusion criteria were: having a flexibility deficit of >20 degrees, being 60-80 years of age, and attaining a doctor’s endorsement stating adequate health to perform exercise. 12 female subjects were finally included in the study – 5 males were excluded because of a lack of conformity to scheduled activities.

Assessment phases: There were 3 phases to this study, each lasting 3 weeks. A1 – period without intervention; B – time of stretching intervention; A2 – used to determine whether or not the physiological and functional adaptations had remained post-intervention. The periods without intervention (A1/2) were used as control periods for comparison with the intervention period. During this time, the subjects continued with their activities of the geriatric revitalization program. They were however, advised to not perform knee-flexor muscle stretching during the 12 weeks period.

Flexibility assessment goniometry: The patient is positioned supine with 90° of hip flexion. While maintaining this position with the assistance of physiotherapists and straps, the knee is then extended to the point of maximum stretch of the hamstring muscle group without pain. The researcher used a goniometer to measure this angle. This number was then subtracted from 180, because this is the resting angle of the hip joint. This measurement was done 3 times and the best of the 3 measurements were taken for statistical analysis.

Assessment of functional capacity: the TUG test. The subject begins seated. When instructed, the subject stands up. When they hear “go” they must walk along a 3m marked line as quickly as possible without running. From there, they must go around an obstacle, requiring them to perform a 180 degree turn. Subsequently, they make their way back to the chair and sit down in a controlled fashion as quickly as possible. This measurement was taken by the same examiner for all subjects. The test was performed 3 times. The shortest time was used for the statistical analysis.

Assessment of isokinetic torque of knee flexors and extensors: for the knee flexors, the subjects placed their foot on a chair and flexed the trunk while keeping the knees extended. To stretch the extensors, subjects flexed the knee and held the ankle to maximally stretch the quadriceps after a 5 minute warm up on a stationary cycle. The subjects sat in an isokinetic dynamometer machine with their hips at 90° of flexion. Extension torque was assessed via maximal voluntary contraction at 60 degrees of knee flexion, which was demarcated by the peak torque. 3 measurements were taken and the highest was used for statistical analysis. Each torque was held for 5 seconds and after 3 minutes the measurement was repeated. The same protocol was used for the flexor torque, only the knee was held at 30 degrees of flexion. Prior to the measurement, the subjects were familiarized.

Eccentric and concentric isokinetic torques of the muscle groups around the knee: were assessed with the knee at 60° of flexion. The hamstrings started the assessment at 90 degrees of flexion and went in a concentric to eccentric fashion, whereas the flexors initiated the test at 75 degrees of flexion and went in an eccentric to concentric motion. These were performed 5 consecutive times at 60 degrees per second with 3 minute intervals between series. All measurements were supervised by the same examiner.

Stretching program: the subjects stood in front of a stretcher. The therapist ensured a neutral spine through the use of a bar. The subjects were instructed to flex the knee and trunk until their hands touched the stretcher (never creating lumbar flexion). Subjects then extended the knee and performed an anterior pelvic tilt, which ensured proximal and distal stretching of the muscle. This position was maintained for 1 minute and was repeated 7 times. This was done twice a week for 4 weeks.

Study Strengths / Weaknesses:

  • The researchers took great control to isolate stretches and control measurements
  • Very creative stretching protocol
  • The subjects were active – there may have been more statistically significant results if they hadn’t been
  • Small subject group - could lead to fewer statistically significant results
  • No randomization or control group
  • The 2 measurements taken during the A1 phase can skew the statistics. Often, statistical significance was found when the results of the B timeline was compared to one A1 measurement and not the other.
  • Continued participation in the geriatric revitalization program could account for their results
  • Only females were included in the study

Additional References:

  • Coutinho EL, DeLuca C, Salvini TF. Bouts of passive stretching after immobilization of the rat soleus muscle increase collagen macromolecular organization and muscle fiber area. Connect Tissue Res 2006; 47: 1-9.
  • Coutinho EL, DeLuca C, Salvini TF. Bouts of passive stretching after immobilization of the rat soleus muscle increase collagen macromolecular organization and muscle fiber area. Connect Tissue Res 2006; 47: 1-9
  • Coutinho EL, Gomes AR, Franca CN. Effect of passive stretching on the immobilized soleus muscle fiber morphology. Braz J Med Biol Res 2004; 37: 1853-1861.
  • DeVita P, Hortobagyi T. Age causes redistribution of joint torques and powers during gait. J of Appl Physiol 2000; 88:1804-1811.
  • Gajosik RL, Linden DWV, Mcnair PT et al. Slow passive stretch and release characteristics of the calf muscles of older women with limited dorsiflexion range of motion. Clin Biomech 2004; 19: 398-406.
  • Gajosik RL, Linden DWV, Mcnair PT et al. Viscoelastic properties of short calf muscle-tendon units of older women: Effects of and fast passive dorsiflexion stretch in vivo. Eur J Appl Physiology 2005; 95: 131-139
  • Gajdosik RL, Vanden Linden DWV, Mcnair PJ et al. Effects of an eight-week stretching program on the passive-elastic properties and function of the calf muscles of older women. Clin Biomech 2005; 20: 973-983.
  • Goldspink G. Molecular mechanisms involved in the determination of muscle fiber 5 mass and phenotype. Adv in Exerc Sports Physiol 1999; 5: 27-39.
  • Gomes ARS, Cornachione A, Salvini TF et al. Morphological effects of two protocols of passive stretch over the immobilized rat soleus muscle. J Anat 2007; 210: 328-335
  • Isles RC, Choy NLL, Steer M, et al. Normal values of balance tests in women age 20-80. J Am Geriatr Soc 2004; 52:1367-1372.
  • Rebelatto JR, Castro AP, Paiva A. Effect of the adult revitalization program on the occurrence of falls among its participants. Rev Bras Fisiot 2007; 2: 383-389
  • Ringsberg K, Gerdhem P, Johansson J et al. Is there a relationship between balance, gait performance and muscular strength in 75 year-old women? Age Ageing 1999; 28: 289-293
  • Sanson MM, Meeuwsen IBAE, Crowe A et al. Relationships between physical performance measures, age, height and body weight in healthy adults. Age Aging 2000; 29: 235-242
  • Wilmore JH, Costill DLl. Physiology of Sport and Exercise, ed 2. Champaign, Human Kinetics, 1999