Effects of a Resistance and Stretching Training Program on Forward

Effects of a Resistance and Stretching Training Program on Forward Head and Protracted Shoulder Posture in Adolescents Rodrigo Miguel Ruivo, PhD, a Pedro Pezarat-Correia, PhD, a and Ana Isabel Carita, PhD b

ABSTRACT Objective: The purpose of this study was to evaluate the effects of a 16-week resistance and stretching training program applied in physical education (PE) classes on forward head posture and protracted shoulder posture in Portuguese adolescents. Methods: This prospective, randomized, controlled study was conducted in 2 secondary schools. One hundred and thirty adolescents (aged 15-17 years) with forward head and protracted shoulder posture were randomly assigned to a control or experimental group. Sagittal head, cervical, and shoulder angles were measured with photogrammetry and Postural Assessment Software. The American Shoulder and Elbow Surgeons Shoulder Assessment was used to assess shoulder pain, and neck pain during the last month was self-reported with a single question. These variables were assessed before and after a 16-week intervention period. The control group (n = 46) attended the PE classes, whereas the exercise group (n = 84) received a posture corrective exercise program in addition to PE classes. Results: A significant increase in cervical and shoulder angles was observed in the intervention group from pretest to posttest (P b .05). For the shoulder pain scores in both groups, there were no significant changes after the 16 weeks. Conclusions: A 16-week resistance and stretching training program decreased forward head and protracted shoulder postures in adolescents. (J Manipulative Physiol Ther 2017;40:1-10) Key Indexing Terms: Neck; Exercise; Posture; Rehabilitation

INTRODUCTION Epidemiological studies have reported a high prevalence of spinal postural deviations in children and adolescents, 1,2 with a high prevalence of self-reported upper quadrant musculoskeletal pain among adolescents. 3 Forward head posture (FHP) and protracted shoulders (PSs) are 2 of the most common postural deviations in people of all ages, including children and

a

Laboratory of Motor Behavior, Faculdade de Motricidade Humana, Universidade de Lisboa, CIPER, Lisbon, Portugal. b Secção Autónoma de Métodos Matemáticos, Faculdade de Motricidade Humana, Universidade de Lisboa, CIPER, Lisbon, Portugal. Corresponding author: Rodrigo Miguel Arsénio dos Santos Ruivo, PhD, Avenida Fernando Pessoa, lote 3.20.01, Bloco B, 4 A, 1990-102 Lisbon, Portugal. Tel.: +351 919996559; fax: +351 217507001. (e-mail: [email protected]). Paper submitted May 14, 2014; in revised form September 18, 2016; accepted September 27, 2016. 0161-4754 Copyright © 2016 by National University of Health Sciences. http://dx.doi.org/10.1016/j.jmpt.2016.10.005

adolescents of school age, 4 with the shoulder and neck regions being cited in many references as the areas of greatest discomfort in adults 5,6 and adolescents. 3,7 Forward head posture is characterized by hyperextension of the upper cervical spine (C1–C3) and flexion of the lower cervical spine (C4–C7), 8 and it is associated with shortening of the upper trapezius, posterior cervical extensor muscles (suboccipital, semispinalis, and splenii), sternocleidomastoideus, and levator scapulae muscles. 9 It is suggested that FHP leads to an increase in the compressive forces on the cervical apophyseal joints and posterior part of the vertebra and to changes in connective tissue length and strength resulting in pain. 10 A PS is a forward displacement of the acromion with reference to the seventh cervical spinous process and can be measured by the shoulder angle. It is frequently associated with a protracted, anteriorly tilted, and internally rotated scapula and with a tightness of the pectoralis minor muscle, 11 shoulder modifications that can be associated with pain. 12 To correct FHP, stretching of the shortened upper trapezius, sternocleidomastoid, and levator scapulae and strengthening of the deep cervical flexor muscles have been found to be effective, 9 whereas PS treatment most often is

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Ruivo et al Postural Correction Training

based on strengthening of the scapular stabilizers and rotator cuff muscles and stretching of the anterior musculature, namely, the pectoralis minor. 9,13,14 Interventions based on these premises have already produced good results. 9,15 To our knowledge, no study has attempted to correct posture through a training protocol involving flexibility and strength exercises with adolescents in a school context. The purpose of this study was to evaluate the effects of a 16-week resistance and stretching training program applied in physical education (PE) classes on Portuguese adolescents (15-17 years old) with FHP and PSs. Effects on neck and shoulder pain were also assessed. We hypothesized that measures of FHP and PSs, neck pain (NP), and shoulder pain and function would improve after the intervention.

METHODS Ethics The Research Ethics Committee of the Faculty of Human Kinetics of the Technical University of Lisbon approved the study, and all procedures were performed according to the Declaration of Helsinki. The clinical trial is recorded in the ClinicalTrials.gov Identifier with the following registration code: NCT02190331. The participation of all students was voluntary, and written informed consent was obtained from all participants and their parents or legal guardians prior to commencement of the study.

Participants A prospective, randomized, and controlled study was conducted over a 4-month period, starting in October 2012, with adolescents of two public secondary schools located in Lisbon, Portugal. At the beginning, a total of 275 adolescent students aged 15 to 17 years were evaluated with photogrammetry. We chose this age group to avoid the effects of a pubertal jump. The cervical and shoulder angles were measured using photogrammetry. If the cervical and shoulder angles were b50° and b52°, respectively, the adolescent was considered to have FHP and PSs and was referred to the study. Participants were excluded if their cervical and shoulder angles were ≥50° and ≥52°, respectively; if they had visual deficits, diagnosed balance disorders, or musculoskeletal pathologies (such as a history of shoulder surgery, or cervical or thoracic fractures); if they were nonambulatory; if they exhibited functional or structural scoliosis; or if they had excessive thoracic kyphosis. Thoracic kyphosis was calculated by an experienced investigator who has worked in musculoskeletal therapy for more than 10 years, using the Bioprint software and a validated and optimized estimation technique. 16 Given these criteria, 130 adolescents from 17 different classes (9 from the 10th grade, 7 from the 11th grade, and 1 from the 12th grade) met the inclusion criteria and were

Journal of Manipulative and Physiological Therapeutics January 2017

recruited for the study. They were randomly assigned to two groups, a control group and an exercise group. The randomization was generated using an arbitrary number table, and allocation to one of the two groups was concealed using sequentially numbered opaque envelopes held at a central location. The investigator responsible for the outcome assessments was blinded to group allocation. Participants were blinded to which intervention was considered therapeutic. After randomization, the intervention group, composed of 84 participants (50 female and 34 male; 15.5 ± 1.1 years), began a 16-week stretching and strengthening program that was performed in the last part of the PE classes. The control group, composed of 46 adolescents (32 female and 14 male; 15.9 ± 1.1 years), participated only in the PE classes. It must be emphasized that the numeric discrepancy between the control and intervention groups was justified because the intervention group would be split into two subgroups for future study purposes after the 4-month program. Figure 1 is a diagram of retention and randomization of patients throughout the study. One hundred thirty students fulfilled the inclusion criteria and were assessed at the beginning. After the 4-month period, 15 participants who were selected (7 from the control group and 8 from the experimental group) did not return for the second assessment because they were transferred from school or class, or were excluded because they missed practice for 2 consecutive weeks because they missed classes.

Testing Procedure: Posture Alignment Assessment Posture alignment assessment in both groups was performed at the beginning and after the 4-month training period. Standing cervical and shoulder posture was measured with a highly reliable photogrammetric method, 17-19 which allows quantitative assessment of postural alterations, 20 and Postural Assessment Software (PAS). This software had already proven to be valid and reliable. 21,22 Three angles were measured: sagittal head, cervical, and shoulder angles. We chose these angles because they had been used in previous studies and were found to be reliable, 23 enabling the comparison of results. The intrarater reliability of the researcher with computerized photogrammetry using the PAS for the angles studied was also confirmed by a separate preparatory study. 21 The angles in the sagittal view (Fig 2) were obtained as follows: Sagittal head angle: The angle formed at the intersection of a horizontal line through the tragus of the ear and a line joining the tragus of the ear and the lateral canthus of the eye. Cervical angle: The angle formed at the intersection of a horizontal line through the spinous process of C7 and a line to the tragus of the ear. If the cervical angle was less than 50°, the participant was considered to have FHP. Selection of 50° as a reference angle was guided by the studies of Diab and Moustafa 24 and Yip et al, 25 with the latter reporting 55.02° ± 2.86° as a normal range. As is well

Journal of Manipulative and Physiological Therapeutics Volume 40, Number 1


Fig 1. Flow of study participants. PE, physical education.

Fig 2. Adhesive marker placement and postural angles: A, sagittal head; B, cervical angle; C, shoulder angle. known, participants with FHP have a significantly smaller cervical angle compared with normal participants. 15 Shoulder angle: The angle formed at the intersection of the line between the midpoint of the humerus and the spinous process of C7 and the horizontal line through the midpoint of the humerus.

Based on the premise that participants with PSs have a significantly smaller shoulder angle when compared with normal participants 26 (Lewis et al 27 reported, for asymptomatic participants, a mean shoulder angle value of 61.9° ± 10.4°; Thigpen et al 28 reported, for 310 participants evaluated in a standing position, a normal range of 52.6° ± 15.3°; and Raine and Twomey 23 reported, for 160 participants evaluated in a standing position, a normal range of 53.7° ± 11.5°), we considered 52° as the reference angle. We considered an individual to have PSs if the angle was b52°. The same researcher who was experienced in the assessment of postural alignment and blinded to the group assignment of each student performed all measurements. Photography took place in the gymnasiums of the two secondary schools, with the areas arranged identically. Landmarks were placed on the floor to ensure the same positioning of all participants in front of the camera and to ensure that the participant was aligned perpendicular to the camera. A landmark was placed in front of a white wall to ensure a contrast of the participants against the background. One Canon Power Shot A4000 IS was supported on a Manfrotto tripod, Model 055 CLB, 3 m from the line marking the position of the participant. The height of the tripod was adjusted so that the middle of the objective lens was 130 cm above the ground. A calibration board was placed in the white wall in the field of view and aligned with the participant to

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Table 1. Description of Strengthening and Stretching Exercises Used During the Training Program Exercise

Principal Muscle

Description

Side-lying external rotation

Teres minor infraspinatus

Side lying with arm fully adducted to side and internally rotated with elbow flexed to 90°. Patients then externally rotate the shoulder with the hand moving in an arc away from the body.

Prone horizontal abduction with external rotation

Middle trapezius Lower trapezius Rhomboids Infraspinatus Teres minor

In a prone horizontal abduction position, the patient horizontally abducts the arm with the elbow extended and with external humeral rotation. The participant lifts the hand toward the ceiling keeping head/neck neutral and squeezing both shoulder blades together.

Y-to-I exercise

Middle trapezius Lower trapezius Serratus anterior

The patient retracts the scapulae with the arms abducted to 90°. As the patient advances, the shoulders are externally rotated with the elbows flexed to 90°, forming a Y. Then the patient moves into a position of full bilateral elevation with the elbow extension forming an I.

Chin tuck

Longus colli Longus capitis

This exercise targets the deep flexor muscles of the upper cervical region, the longus capitis and longus colli muscles. This is a low-load exercise51 that involves performing and holding inner range positions of craniocervical flexion that specifically activate and train the deep cervical flexor, rather than the superficial flexors muscles. This exercise is done in a supine lying position with the head in contact with the floor.

One-sided unilateral self-stretch exercise

Pectorals minor

The participant’s forearm is stabilized by a vertical plane before the trunk is rotated in the opposite direction. Therefore, the arm on the involved side is externally rotated and abducted to 90°.

One-sided unilateral self-stretch exercise

Pectorals minor

The participant’s forearm is stabilized by a vertical plane before the trunk is rotated in the opposite direction. Therefore, the arm on the involved side is externally rotated and abducted to 90°.

Static sternocleidomastoid stretch

Sternocleidomastoid

Start in optimal posture and place right arm behind body, depressing the shoulder. Draw abs in. Tuck chin and slowly draw left ear to the left shoulder. Continue by rotating the neck upward toward the ceiling until a slight stretch is felt on the right side. We can use the left hand to apply slight pressure and assist in lateral flexion and rotation. Switch sides and repeat.

Static levator scapulae stretch

Levator scapulae

Start in optimal posture and place right arm behind body, depressing the shoulder. Draw abs in. Tuck chin and slowly draw left ear to the left shoulder. Continue by rotating the neck downward toward the ceiling until a slight stretch is felt on the right side. We can use the left hand to apply slight pressure and assist in lateral flexion and rotation. Switch sides and repeat.

allow referencing of horizontal and vertical axes from the photographs. The calibration board also displayed each participant’s identification number. For positioning, the adolescent was instructed to stand comfortably in a normal standing position and to look straight ahead. Before photographing the student, the researcher placed reflective markers, polystyrene foam balls 20 mm in diameter, on the following anatomical points on the side of the participant’s body: tragus of the ear, lateral canthus of the eye, spinous process of C7, and midpoint of the humerus. With these markers, we were able to calculate the sagittal head, cervical, and shoulder angles. To enable precise positioning of the markers, we instructed participants to wear sleeveless T-shirts, with elastic for the hair when needed. The same researcher performed all procedures. To capture the participant’s natural head-on-trunk

and shoulder alignment, each person was asked to look straight ahead and to march on the spot five times before each picture was taken. 29 Each picture was taken 5 seconds after the marching sequence in a lateral view, with the right side of the participant photographed for right hand–dominant individuals and the left side for left hand– dominants. The dominant arm was defined as the one most used in daily activities. The photographic analysis was performed using PAS, which determined coordinates of the anatomical points on the photographs. The zoom was standardized at 200% to improve the accuracy of the analysis, and the angles were measured in degrees. One researcher undertook all scanning and digitizing to eliminate interexaminer error. Data were submitted to descriptive statistical analysis, and quantitative values for head and upper member angles were obtained.



Self-Assessment of Shoulder Pain and Function and NP The self-report section of the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) has already been validated and culturally adapted to the Portuguese language. 30,31 This Portuguese version was used to record the presence of shoulder pain and function in the participants. The questionnaire addressed self-evaluation of pain using a visual analogue scale and activities of daily living questionnaire. The maximum score is 100. A high total score indicates low perceived pain and low dysfunction in activities of daily living. After postural assessment and completion of the ASES questionnaire, students were asked about their 1-month experience of NP. The question was: Has your neck been painful in the last month? (“yes” or “no”). Straker et al used the same question in a previous study. 32 These procedures were repeated in the beginning and after the 4-month period.

Intervention Protocol After the testing protocol, adolescents in the intervention group began a 16-week stretching and strengthening program. Exercises were performed twice a week, in the last 15-20 minutes of each PE class, with the supervision and help of the PE teacher and the aid of an illustrated handout. Physical education classes for the control group did not include this specific protocol. Each PE teacher was responsible for approximately 20 students from the same class. The training protocol comprised four strengthening exercises and three stretching exercises (Table 1) and was designed based on the assumption that the use of therapeutic exercise is effective in the correction of specific neck and shoulder postures. 9,24,33-35 Strengthening exercises (Fig 3) are targeted to elicit activation of the rotator cuff,

namely, teres minor and infraspinatus, the scapula stabilizers such as the trapezius (mainly the medium trapezius and lower trapezius), the rhomboids, and the deep cervical flexor muscles. Stretching exercises (Fig 4) are directed to the pectoralis minor and the neck muscles, such as sternocleiomastoid and levator scapulae. Based on the training principles and considering the school calendar, we developed a long-term plan with an appropriate selection of training intensity, volume, rest interval between sets, velocity, and frequency. As the plan was to be performed in PE classes, the prescribed exercises were to be strictly followed in 2 nonconsecutive training days a week. For resistance training, we started with light loads and 2 sets of 15 repetitions for a general adaptation, and then we applied changes throughout 16 weeks, with periods with gradual and smooth increase in intensity and sets and/or repetitions, and other periods, after the Christmas holidays, with a lower intensity or volume. Briefly, the students performed 2 sets of 15 repetitions in October; in November they added 1 more set; and in December they maintained 3 sets, but now with 12 repetitions and N1 kg in the dumbbell exercises. In January, they did 3 sets of 10 and 12 repetitions, respectively, with a 0.5-kg increase from December to January. The rest interval between sets was 30 seconds. With these planned changes in program variables, we expected to maintain training-induced gains and prevent training plateaus, which are common in the first 8-12 weeks of resistance training. 36 In the three stretching exercises, we used the static stretching with a 30-second hold for 2 sets. 37 The all-interventional program took an average of 15 minutes to perform, and the order of the exercises was random.

Fig 3. Strengthening exercises.

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Fig 4. Stretching exercises. Table 2. Postural Angles and ASES Scores for Control and Intervention Participants, Pretest and Posttest Measure

Within Group Control (n = 39) Pretest Mean ± SD

Sagittal head tilt angle Cervical angle Shoulder angle ASES score Right Left

Posttest Mean ± SD

15.9 ± 7.1 13.4 ± 5.7

Experimental (n = 76) Paired t Test Mean Difference t

Pretest Mean ± SD

P a

Posttest Mean ± SD

Between-Group Independent t Test

Paired t Test Mean Difference t

P

Mean Score Change t

P

2.5

2.41 .021

45.7 ± 3.0 46.2 ± 3.5 –0.5

–0.93 .357

44.4 ± 3.5 46.8 ± 3.9 –2.5

–5.84 b.001 a 1.95

2.78 .006 b

45.5 ± 5.1 47.5 ± 5.2 –2.0

–3.06 .004 a 45.9 ± 4.9 49.8 ± 6.5 –3.9

–5.54 b.001 a 1.93

2.02 .046 b

95.3 ± 6.3 95.5 ± 5.1 –0.2 93.2 ± 7.2 94.0 ± 6.3 –0.8

–0.80 .845 –0.60 .553

–0.95 –1.03

0.45 .651 0.19 .852

18.6 ± 6.5 17.5 ± 5.7

1.2

93.2 ± 9.1 94.2 ± 6.6 –1.0 91.6 ± 9.4 92.8 ± 7.2 –1.1

1.72

.09

.347 .307

1.34

0.80 0.34

1.12 .265

ASES, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form; SD, standard deviation. a Statistically significant difference with Bonferroni correction (P b .025). b Statistically significant difference (P b .05).

Statistical Analysis All statistical analyses were performed using appropriate software (SPSS Version 22, IBM, Armonk, NY), and the statistical significance level was defined as P b .05. In both groups, data were analyzed using descriptive statistics such as mean, standard deviation, and percentage. The Shapiro– Wilk test was used to assess normality. Paired sample t tests were conducted to determine whether postural angles and ASES scores were significantly different before and after the 16 weeks for both groups, and independent sample t tests were conducted to compare for group differences between mean score difference and to compare postural angles and ASES scores in all participants with and without NP in the pretest. For within-subgroup comparisons, a Bonferroni adjustment for the correction of type 1 errors was performed.

RESULTS With respect to the preintervention comparison between groups, no significant difference was reported between genders or between those with and without NP.

Postural Angles and ASES scores Mean and SD values for the postural variables and ASES scores are listed in Table 2. Significant differences were observed in two postural angles in the intervention group from pretest to posttest, with an increase in the cervical angle (44.4° ± 3.5° vs 46.8° ± 3.9°) and shoulder angle (45.9° ± 4.9° vs 49.8° ± 6.5°) after the intervention. In the control group, the cervical angle (45.7° ± 3.0° vs 46.2° ± 3.5°) did not differ significantly from pretest



Table 3. Postural Angles and ASES Scores for All Participants With and Without Neck Pain in the Pretest Overall (n = 115) Preintervention

Cervical angle Shoulder angle ASES score Right Left

No NP a (n = 66)

NP a (n = 49)

Mean Score Change

T

P

95% CI

d

45.8 ± 3.0 45.4 ± 4.9

43.5 ± 3.5 46.4 ± 4.8

–2.3 1.0

–3.78 1.12

b.001 b .266

–3.5, –1.1 –0.7, 2.9

0.71 0.21

95.0 ± 7.8 93.3 ± 8.5

92.4 ± 8.8 90.7 ± 8.9

–2.5 –2.6

–1.63 –1.57

.106 .119

–5.6, 0.5 –5.8, 0.7

0.31 0.30

ASES, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form; CI, confidence interval; NP, neck pain. a Mean ± SD. b Statistically significant difference (P b .05).

to posttest, whereas we observed a significant decrease (15.9° ± 7.1° vs 13.4° ± 5.7°) in the sagittal head angle and a significant increase (45.5° ± 5.1° vs 47.5° ± 5.2°) in the shoulder angle. Considering the comparison between groups, we reported statistically significant results for the cervical and shoulder angles, with a P value b 0.05. There were no significant changes in ASES pain and function scores in both groups after the 16 weeks.

Postural Angles and NP In this study, we also compared the postural angles and ASES scores between the participants with and without NP, in the overall, in the preintervention (Table 3). For the postural angles, before the 16-week protocol intervention, the group with NP had statistically lower cervical angles compared with group without NP (43.5° ± 3.5° vs 45.8° ± 3.0°). In both groups, fewer participants reported NP after the 16 weeks (22 vs 12 in the control group and 34 vs 14 in the experimental group, representing 48% vs 31% and 41% vs 18%, respectively).

DISCUSSION This study indicates that a targeted exercise program, performed twice a week and integrated into PE classes over a 16-week period, can result in posture improvement, with increases in cervical and shoulder angles. To our knowledge, this is the first study examining the outcome of a physical program for postural correction, in a large sample, in a school. The fact that the program may be conducted in the school, which is a privileged place to apply changes to lifestyles, habits, and imbalances 38,39 and a place where children and adolescents spend much of their time, may favor the systematic realization of the training protocol. This factor may explain the relatively small number of study dropouts (15 of 130 adolescents with FHP and PS) in the 16-week period. The realization of this program in the school also has another benefit in that there is a PE teacher who can supervise technique.

In this study, the PE teachers were trained to correct postural alignment during the exercises, and there was a systematic concern to give useful corrective feedbacks to the students.

Postural Angles and ASES Scores After the 4-month period, there was a significant increase in cervical and shoulder angles in the intervention group, whereas in the control group, there were no significant differences in the cervical angle, suggesting that the targeted exercises contributed to improvement of posture. To correct FHP and PSs, this protocol was intended to restore the normal muscle balance between opposing muscle groups (agonists and antagonists) and work the elongation capacity of muscle groups that restrict the range of joint movements to which they are opposed. This concept has been supported by other studies. 9,40 To achieve the desired goal of PS and FHP correction, we aimed to actively stretch the sternocleidomastoid, levator scapulae, and pectoralis muscle group and to strengthen the rhomboids, lower and medium trapezius, and rotator cuff muscles. 24,41 Previous studies, performed in other contexts and populations, support our results of decreased FHP and PSs after an intervention training protocol. For example, Lynch et al. reported decreased PSs in elite swimmers after an 8-week intervention including stretching of the anterior musculature and strengthening of the scapula stabilizers. 9 With respect to FHP correction, Harman et al. reported that a 10-week home-based targeted exercise program improved postural alignment. 29 This program included the strengthening of deep cervical flexors and shoulder retractors and the stretching of cervical extensors and pectoralis muscles. As in the previously mentioned studies, the intervention protocol was designed on the basis of scientific evidence. We selected the exercises that have been reported to be the most effective in achieving the desired goal, based on electromyography research. For strengthening of the deep cervical flexor muscles, we selected the chin tuck exercise. 41 For rotator cuff muscles, which are crucial dynamic stabilizers of the

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glenohumeral joint in multiple shoulder positions contributing to its health, 42 we chose side-lying external rotation and prone horizontal abduction with external rotation. 43,44 Because the humerus, clavicle, and scapula move together in coordination during arm movements, 44 referred as scapulohumeral rhythm, we also prescribed two exercises for the scapula stabilizer muscles, the prone horizontal abduction with external rotation 43 and the Y-to-I exercise (described in Table 1). Both exercises highly activate the lower trapezius and middle trapezius with low activation of the upper trapezius. 44 In addition to the strength training exercises, we prescribed two stretching exercises for the sternocleidomastoid and levator scapulae 45 and one for the pectoralis minor, with the one-sided unilateral self-stretch exercise proving to be the most effective. 11 To optimize training results, we started with 2 sets of 15 repetitions with a relatively light or moderate load and moderate and controlled velocity and then, respecting individual abilities, we progressed to include an additional set, with heavier loads over time. For stretching exercises, we used static stretching with a 30-second hold for 2 sets. This has been recommended 37,41 and used successfully in other studies with the achievement of good results in the PS correction with the static stretching of pectoralis minor. 11,24 For postural angle analysis, we also reported a significant increase in the shoulder angle in the control group after 16 weeks. We hypothesized that this may be related to the fact, that by the second evaluation, students had experienced 4 months of physical activity in PE classes; this was not true of the first evaluation, which was performed after a long vacation period. This increase in exercise practice may have accounted for the increase in muscular strength of the scapular muscles and, therefore, in the better shoulder posture also seen in the control group. However, it must be pointed out that although the mean shoulder angles in the control group before and after the 4-month period differ significantly (45.5° ± 5.1° vs 47.5° ± 5.2°), the difference in the mean values of the intervention group is clearly higher (45.9° ± 4.9° vs 49.8° ± 6.5°). We hypothesized that participants in the intervention group would report higher ASES scores after the intervention, indicating a decrease in shoulder pain and an increase in function after the 16-week intervention. However, our results indicated no difference in ASES scores, in both groups, possibly because of the high initial score, relatively large minimal detectable change (9.7 points), and minimally clinically important difference (6.4 points). 46 Only 5 of the overall 115 participants experienced a clinically important difference in ASES scores. It must be added that ASES is an evaluative and discriminative instrument for patients with shoulder dysfunction and is characterized by its ability to distinguish between those patients who have improved and those who have not by identifying an external criterion indicative of clinically meaningfully change. 46 The presence of a huge majority of participants with no shoulder dysfunction or


functional limitations at the beginning of the training program may explain why the ASES score differences before and after the 4-month intervention prior were not significant.

Postural Angles and NP We reported, mainly at the beginning of the intervention, a high prevalence of self-reported upper quadrant musculoskeletal pain among adolescents. The same findings have been reported in other studies. 3 This can be attributed to several factors including psychosocial factors, 47 ergonomics, 48 strength imbalances, and neck and shoulder posture. 49 Results indicated that the group without NP had higher cervical angles with a between-group (NP vs no NP) difference of 2.3°. These results are in accordance with previous studies in which participants with NP had a significant smaller cervical angle when compared with normal participants. 15,17 It is believed that a sustained FHP, with a tightness of the sternocleidomastoid and the levator scapulae, may increase the loading on the noncontractile structures and place abnormal stress on the posterior cervical structures, leading to myofascial pain. 17 In terms of the clinical significance of the small differences between groups highlighted above (≤2.3°), the literature is still not consensual. For example, in accordance with our results, Silva et al. also reported that NP patients were found to have a significantly smaller angle between C7, the tragus, and the horizontal, and the mean difference between the NP group and the pain-free group was not greater than 3.2° (mean ± SD; NP, 45.4° ± 6.8°; pain-free, 48.6° ± 7.1°; P b .05). 10 On the other hand, Falla et al. reported that a change of 2.1° in the angle between C7, the tragus, and the horizontal in adults with NP did not result in greater pain improvement when compared with no change in FHP. 15 With respect to these opposite results and the possibility that a single angle is not adequate to capture the postural changes that might occur in adolescents with NP, 50 further studies are needed to ascertain whether FHP differs between adolescents with and without NP. Another relevant issue in our study is the fact that in the experimental group, the cervical angle improved, and in both groups, fewer participants reported NP after the 16 weeks. This may be due to the increased levels of physical activity and better condition of the adolescents as a consequence of the PE classes, or the postural correction protocol in the intervention group, or it may be derived from a different pain threshold in the two assessments.

Limitations Future investigations of the effectiveness of the protocol intervention should contemplate the use of a more detailed


and reliable NP and disability questionnaire instead of a simple self-designed question. Another limitation of this study is that it describes only the alignment of the spine and the shoulder girdle at rest; therefore, the findings cannot be generalized to alignment during functional tasks, especially when the upper limb is moving or loaded. This is also the case when activities are prolonged over time. Finally, it must be mentioned that, although we encouraged adolescents not to engage in any new activity or exercise program during the study period, we cannot guarantee that this did not occur.

CONCLUSION We found that a simple, targeted exercise program systematically incorporated into PE classes twice a week over a 16-week period can result in a posture improvement, with increases in the cervical and shoulder angles. Shoulder function and pain, measured with the ASES, did not change. In both groups, results indicated that participants with NP had a smaller cervical angle.

FUNDING SOURCES

AND

CONFLICTS

OF INTEREST

This study was supported by the Portuguese Foundation for Science and Technology (Grant SFRH/BD/77633/ 2011). No conflicts of interest were reported for this study.

CONTRIBUTORSHIP INFORMATION Concept development (provided idea for the research): R.R., P.P. Design (planned the methods to generate the results): R.R.

Practical Applications • A targeted exercise program incorporated into PE classes resulted in posture improvement. • Participants with NP had a smaller cervical angle after the intervention.

Supervision (provided oversight, responsible for organization and implementation, writing of the manuscript): R.R., P.P. Data collection/processing (responsible for experiments, patient management, organization, or reporting data): R.R. Analysis/interpretation (responsible for statistical analysis, evaluation, and presentation of the results): R.R., A.I.


Literature search (performed the literature search): R.R. Writing (responsible for writing a substantive part of the manuscript): R.R. Critical review (revised manuscript for intellectual content, this does not relate to spelling and grammar checking): R.R., P.P., A.I.

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