Flexibility is an important functional capacity affecting the efficacy of daily living activities and maintenance of an independent lifestyle in older adults (1,10). The practice of stretching seems to be a widely accepted means of trying to reduce injuries and improve performance in athletes (5,7,11). Range of motion (ROM) decreases with increasing age, a decline related to the aging process itself (24). In older people, it is an important variable with respect to both health and athletic performance (1). Mobility problems in older people may lead to falls, which in turn may result in hip fractures. Coaches therefore need to be aware of the most effective and efficient ways of achieving optimal increases in muscle length to improve the health of older people. The Position Stand of the American College of Sports Medicine states, “flexibility exercises should be incorporated into the overall fitness program sufficient to develop and maintain range of movement. These exercises should stretch the major muscle groups and be performed a minimum of 2–3 days a week. Stretching should include appropriate static and/or dynamic techniques.” Few studies have investigated the efficacy of passive vs. proprioceptive neuromuscular facilitation (PNF) training programs (3,8,14). We found only 1 study comparing the effects of static, active, and PNF stretching on flexibility in older people. Chow and Ng (3) concluded that active stretching, passive stretching, and PNF stretching training were associated with an increase in knee flexion range, with no statistically significant differences between the stretching exercises observed for persons aged 60–70 years. With respect to increasing hamstring flexibility, Funk et al. (8) studied the effects of both static and PNF stretching on hamstring torque for persons aged 18–23 years and concluded that either protocol was an effective method for increasing both concentric and eccentric hamstring torque. Lucas and Koslow (14) investigated the effects of static, dynamic, and PNF stretching techniques on the flexibility of the hamstring-gastrocnemius muscle in college women. The findings indicated that all 3 methods of flexibility training produced significant improvements.
Similar studies comparing the effects of passive vs. active stretching techniques have concluded that active stretching produces greater gain in knee extension for persons aged 20–28 years (16). To our knowledge, no studies have compared the efficacy of passive vs. PNF stretching techniques in older people.
The interventions designed to improve flexibility often lacked sufficient numbers of subjects, randomization, and control subjects and have failed to provide clear evidence for dose-response effects of exercises.
There is therefore a need for further research to determine the effects of different modes of stretching on shoulder and hip flexion in older people. The purpose of this study was to compare the efficacy of passive and PNF stretching training during a 13-week period on shoulder and hip flexion in older people.
It was based on the hypothesis that passive stretching and PNF are both associated with an increase in hip and shoulder flexion and that there are no differences between the stretching methods.
Experimental Approach to the Problem
A pretraining-posttraining intervention design was used with 3 equivalent groups: 2 experimental groups (PNF vs. passive) and 1 control group. The experimental groups performed 2 different flexibility training programs for 26 weeks, one using the PNF method and the other using the passive method. During the first 13 weeks, participants performed a shoulder joint flexibility training program (PNF vs. passive), and during the last 13 weeks, they performed a hip joint flexibility training program (PNF vs. passive). Participants carried out 2 nonconsecutive training sessions per week. Shoulder joint flexion was measured in all participants in the study at weeks 1 and 13, whereas hip joint flexion was tested at weeks 13 and 26. The control group did not perform stretching exercises during the intervention period. Our dependent variables were ROM in flexion (in degrees) measured in the shoulder and hip joints. Obtaining measures of ROM in flexion at 2 time points (pretest and posttest) during the training cycle enabled us to determine how these participants responded to a specific flexibility training program.
Each subject performed the tests at the same time of the day throughout the period of the study. Because the subjects were evaluated at a different time of the year, the ambient conditions were maintained constant during all the tests (temperature, 22–24°C).
A population sample of 54 older participants (39 women and 15 men) was recruited to the study and divided into 3 groups: passive (n = 18; age, 66.5 ± 6.5 years; height, 1.58 ± 0.09 m; body mass, 71.9 ± 15.5 kg), PNF (n = 18; age, 64.7 ± 4.0 years; height, 1.62 ± 0.08 m; body mass, 70.0 ± 10.6 kg), and control (n = 18; age, 66.4 ± 4.5 years; height, 1.61 ± 0.07 m; body mass, 68.5 ± 7.8 kg). The male participants were distributed evenly within each group (5 men per group). Subjects were volunteers from the physical activity program for older people run by the University of Córdoba (Spain) and all were healthy and physically active but not specifically trained. Their previous physical activity background was limited to walking and other normal everyday activities. Before participation, the experimental procedures were explained to all the participants, who gave their voluntary written informed consent and understood that they were free to withdraw from the study at any time. The study was conducted in accordance with the Declaration of Helsinki, and all procedures were approved by the Research Ethics Committee at the Córdoba University relative to human or animal research. None of the subjects had previously performed any flexibility training. All were given a medical examination before participation to assess their state of health and detect any medical condition that might result in injury during the study. Participants were excluded from the study if they fell into any of the following categories: (a) they were younger than 60 years or older than 70 years; (b) they recently had a shoulder or hip injury with no evidence of osteoporosis or arthritis or both; (c) their screening forms indicated previous cardiovascular, respiratory, or other major chronic diseases; (d) they had joint replacements or previous surgery that might have altered ROM ability/potential; or (e) they had undergone any type of surgery or sustained an injury that might constitute a risk during exercise.
Training Programs. During the first 13 weeks, the subjects trained 2 times per week on nonconsecutive days. Each training session included 2 flexibility exercises focused on the shoulder joint (Figures 1 and 2).
- Exercise 1. The subject lies in a supine position on a mat with the knees flexed. The legs are allowed to fall toward the side opposite the arm that is stretched out (Figure 1). With the help of an assistant, the shoulder is flexed to the maximum possible until stretch is felt.
- Exercise 2. The subject sits on a mat with his or her back resting against the assistant's knees, hands behind the neck, and elbows open (Figure 2). The assistant takes hold of each elbow and pulls it back until stretch is felt; the back should not be leaning and no pain should be felt.
- Over the next 13 weeks, 2 flexibility exercises focusing on the hip joint were performed (Figures 3 and 4).
- Exercise 3. The subject sits with one leg stretched out and the other flexed. The trunk is bent forward (Figure 3). The assistant places both hands on the lumbar region and pulls forward until the stretch is noticed.
- Exercise 4. The subject lies in a supine position with hands under one thigh, which the assistant helps to flex while the other leg remains stretched out on the mat (Figure 4).
The procedure used by the PNF group to perform the exercises was as follows: 6 seconds of passive stretching, 3 seconds of muscular contractions, and 2 seconds of relaxation. This sequence was repeated 3 times. Exercises performed by the passive group consisted of 10 seconds of stretching and 5 seconds of relaxation, also repeated 3 times.
Participants in all the training sessions were closely supervised by a qualified exercise leader (drawn from graduates in physical activity and sports sciences and physical therapy) to ensure that the proper technique was being used and to minimize the risk of injury. The leader demonstrated the exercises before the classes and supervised correct execution by participants and assistants. The leader also controlled the time of execution of each stretch sequence.
We followed the recommendations of Wilson et al. (25) regarding dietary control (food and beverages). We asked subjects to sleep at least 7 hours a day. The tests were carried out at the same time of day, always in the afternoon. We focused on the 2 joints that are most important for the activities of daily life in older people. Only flexion was measured as a result of time limitations for the number of subjects involved and because flexion movement was considered by the principal investigator to be the most common in everyday life. Measurement was carried out on the joint least affected by age and following the test recommendations.
The shoulder joint ROM test (9) was carried out before starting the shoulder joint training program and on completion (13th week). For this test, the subject lies in a prone position facing the side opposite the shoulder to be measured, which lies over the edge of the training table. The examiner was positioned at the side in such a way that their line of sight was at the height of the subject's shoulder. The subject's arm was taken at the elbow and the shoulder flexed. An electronic goniometer (Muscle Lab Ergotest Technology, Porsgrunn, Norway) was used to measure the range of movement in flexion of each joint. This was held in place at each end, and the subject's arm was raised passively until maximum flexion was reached. The hip joint flexion test (4) was performed before the start of the hip joint training program (13th week) and upon its completion (26th week). With the subject in the supine position, the primary examiner passively flexed the hip to 90° and zeroed the goniometer at the apex of the knee. The hip was then flexed until the opposite thigh began to rise off the table. The mean of the 3 measurements performed in each test was used for further analysis.
Mean ± SD of the data was calculated. Normal distribution and homogeneity of the parameters were checked with Shapiro-Wilk, and Levene's test. A 2 -way (group × time) analysis of variance was performed to identify differences in flexion angle between groups over time (pre/post). The null hypothesis of no difference between groups was rejected if the probability that the measured difference was due to chance was less than 5% (p < 0.05). Reliability of the dependent measures was assessed using single-measure intraclass correlations. In the current study, the measurements showed high reliability (intraclass correlation coefficients, r = 0.90–0.95). SPSS for Windows version 17.0 (SPSS, Inc., Chicago, IL, USA) was used for the statistical analysis.
All the variables were normally distributed. Levene's test showed no violation of homogeneity of variance. The mean flexion for shoulder and hip are displayed in Tables 1 and 2. The results show that flexion in the hip decreased 0.68% for the control group, increased 2.61% for the passive group, and increased 4.17% for the PNF group. In the shoulder, flexion decreased 2.83% for the control group, increased 7.27% for the passive group, and increased 7.62% for the PNF group.
A repeated-measures analysis of variance between groups was then conducted to examine the interaction between treatments and changes in ROM between pretest and posttest. For both the hip and shoulder, the interaction was significant (F = 26.08 and F = 12.44: p < 0.001 for the hip and shoulder, respectively). There were significant differences in posttest shoulder measurements between the control and passive groups (10.86°; p < 0.01) and the control and PNF groups (9.43°; p < 0.01) (Table 1).
In addition, significant differences were found between the control and passive groups (14.95°; p < 0.001) and control and PNF groups (14.20°; p < 0.001) in posttest hip measurements (Table 2). No significant differences were observed between groups in the pretest.
There was a significant increase in hip flexion (3.29°; p < 0.001) between pretest and posttest in the passive group. A considerable improvement (5.91°; p < 0.001) was observed between pretest and posttest in the PNF group. However, hip flexion in the control group showed a significant decrease (–2.57°; p < 0.01) between pretest and posttest (Table 1).
In the passive group, there was a significant increase in shoulder flexion (5.08°; p < 0.001) between pretest and posttest, and considerable improvement was also observed between pretest and posttest in the PNF group (4.52°; p < 0.001). In the control group, no significant changes were observed between pretest and posttest in shoulder flexion (Table 2).
This investigation compared hip and shoulder flexion over 13 weeks between 2 groups (passive and PNF stretch training) and a control group of healthy older subjects. It was based on the hypothesis that passive stretching and PNF are associated with an increase in hip and shoulder flexion and that there is no difference between the stretching methods used.
Our results show significant gains in hip and shoulder flexion in older people using PNF and passive stretching techniques during a 13-week flexibility training program. No significant differences between programs were found, thus confirming our hypotheses. Perhaps, a possible explanation to these results is the fact that this investigation used a similar dose of total daily stretch duration (30 seconds in passive vs. 27 seconds in PNF) and their participants had poor initial flexibility scores as a result of aging. These findings are important because flexibility training is widely used in general fitness programs to improve the health of older people (1,10). Gurjao et al. (10) investigated the acute effect of static stretching on both muscle activation and force output in 23 older women. The results showed that older women's capacity to produce muscular force decreased after their performance of static stretching exercises. Although it is difficult to compare the results with other studies, given the different joints measured and the different techniques used, one consistent finding is that stretching exercises are effective for enhancing ROM (24). Swank et al. (24) evaluated adding modest weight (0.45–1.35 kg) to a stretching exercise routine on joint ROM in 43 subjects aged between 55 and 83 years. The results showed that addition of weights to stretching routines for elderly people resulted in higher ROM.
Lucas and Koslow (14) found significant improvements in the flexibility of the hamstring-gastrocnemius muscle in college women using different stretching techniques (static, dynamic, and PNF) over a 7-week period. However, Chow and Ng (3) found no significant differences in a sample of 117 older people receiving total knee replacement due to knee osteoarthritis among active stretching, passive stretching, and PNF stretch training in the knee flexion range. These results agree with those of our study.
Several scientific studies have shown that PNF stretching techniques are more effective than simple passive-stretching techniques (13), which is in contrast to our findings. This could be because of the differences in the type of sample (physically older people vs. college students or athletes) used in other studies. Also, the ability to generalize responses is limited to healthy, active, older adults who may not represent the normal aging population (24). In this respect, Ninos (18) recommended that older people use long slow static stretches to achieve plastic changes in muscular and connective tissues and to make sure they stretched only to a point of stretch without pain.
Improvements in flexibility using the passive technique may be the result of an increase in ROM as a result of enhanced stretch tolerance (22). Passive stretching does not activate the stretch reflex; if this is activated, it causes the stretched muscle to contract instead of lengthening (17). During a passive stretch, reciprocal inhibition is accomplished by simultaneously contracting the muscle opposing the muscle being stretched. The tension in the contracting muscle stimulates the Golgi tendon organ and causes a simultaneous reflex relaxation in the opposite muscle (13). For the passive stretching group, it has been reported that the biomechanical effects of sustained stretching were because of the changes in the viscoelastic characteristics and stretch tolerance (15).
The results of our investigation are consistent with most studies affirming that passive stretching is an effective and time-efficient method for enhancing flexibility in most populations (8,23).
Funk et al. (8) compared 5 minutes of static stretching and PNF on hamstring flexibility performed with and without exercise in a sample of 40 undergraduate student athletes. Results demonstrated that PNF performed after exercise enhanced acute hamstring flexibility, and implementing a PNF stretching routine after exercise may augment current stretching practices among athletes.
Spernoga et al. (23) concluded that a sequence of 5 modified hold-relax stretches produced significantly increased hamstring flexibility that lasted 6 minutes after the stretching protocol ended in 30 subjects (aged 18–23 years). However, it is necessary to take into account that the participants in this study had limited hamstring flexibility in the right lower extremity.
Improvements in flexibility using the PNF technique could also be the result of the inhibitory effect of the Golgi tendon organs after resisted isometric contraction (13,19). Although several mechanisms have been reported to explain acute flexibility gains using PNF stretching (2,18), the mechanisms explaining the more long-term improvements when this technique is performed have not been elucidated (12). Funk et al. (8) demonstrated the efficacy of performing PNF stretching after exercise to optimize flexibility outcomes for college-aged athletes. However, in this study, no significant differences were observed with static stretching. The findings of Funk et al. (8) coincide with our results in that no significant differences were found between stretching techniques, although the populations and treatments used were different from those of our study.
It is interesting that a practically and statistically significant improvement in joint ROM is achievable using both passive and PNF methods but that when differences observed between the 2 treatment groups were compared, there were no significant differences in improvements between passive and PNF methods. Static (or passive) stretches have some benefits but may not work as good as PNF stretches.
The daily and weekly flexibility volume performed in our study was consistent with the recommendations of Riewald (20), the American College of Sports Medicine (1), and Roberts and Wilson (21). In our study, subjects maintained the stretch for 10 seconds, then relaxed for 5 seconds for 2 minutes in passive stretching. Riewald (20) affirms that a passive stretch held for 15-30 seconds is all that is needed to improve flexibility and that a single bout of stretching can increase flexibility for up to 90 minutes. Roberts and Wilson (21) found significant improvements in both active and passive ROM (5 or 15 seconds) in the lower extremity during a 5-week flexibility training program. In our study, the change in flexion was 5° in the shoulder and 3.3° in the hip, results that confirm the efficacy shown by the studies cited. Improvements in flexion were different compared with other studies. Sainz de Baranda and Ayala (22) found improvements of 14.5° to 21° in passive hip flexion after 12 weeks of a stretching training program in recreationally active young adult university students. It should be taken into consideration that in this study, the training frequency was 3 days per week, whereas in our study, it was 2 days per week.
In relation to the PNF technique, in the study by Funk et al. (8), subjects maximally contracted the hamstring against resistance for 30 seconds and repeated this until completion of the 5-minute time. In our study, the PNF technique consisted of 6 seconds of passive stretching, 3 seconds of muscular contractions, and 2 seconds of relaxation, and this sequence being repeated 3 times. Several studies indicate that one repetition of PNF is sufficient to increase ROM with an expected change in ROM from anywhere between 3° and 9°, depending on the joint (6,14). In our study, the change in ROM in flexion was 5° in the shoulder and 6° in the hip, results that confirm the efficacy shown in the studies cited.
In conclusion, no significant differences were found between PNF and passive stretching techniques after a 13-week flexibility training program in older people, but significant improvements were found in hip and shoulder flexion with both training programs.
The information of this research would be useful to coaches and athletes as recommendations regarding the optimal stretching methods to improve hip and shoulder flexion in older people. The main finding was that the ability of physically active older people to increase hip and shoulder flexion in response to a passive technique (3 sets of 10 seconds of stretching and 5 seconds of relaxation) and a PNF stretching technique (3 sets of 6 seconds of passive stretching, 3 seconds of muscular contractions, and 2 seconds of relaxation) was similar in both groups, at least within the 13-week training period (2 times per week) used here. However, any practical application requires careful implementation and individual experimentation in older people. An older individual could therefore choose either the passive or PNF technique to maintain the same gains in flexibility. Improvements in flexibility in the older adult may enhance the ability to perform daily living and recreational activities. For example, increased ROM at the shoulder complex may be related to activities such as reaching overhead to a shelf, and improved knee flexion and extension would be associated with an increased ability to climb stairs or rise from a chair (23). Strength and conditioning specialists are encouraged to use passive stretching techniques with older people because it is easy to administer and it is comfortably performed.
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