quinta-feira, 16 de julho de 2015

Chronic Neck Pain


Chronic Neck Pain and Exercise Interventions: Frequency, Intensity, Time, and Type Principle


Cliona O'Riordan, BSccorrespondence
,
 Amanda Clifford, PhD
,
 Pepijn Van De Ven, PhD
,
 John Nelson, PhD

Department of Clinical Therapies, University of Limerick, Limerick, Ireland
Department of Electronic and Computer Engineering, University of Limerick, Limerick, Ireland
Published Online: December 13, 2013

Abstract

Objective

To identify the most effective components in an active exercise physiotherapy treatment intervention for chronic neck pain based on the frequency, intensity, time, and type (FITT) exercise method of tailoring physical activity recommendations to the individual needs and goals of patients.

Data Sources

Databases, including the Allied and Complementary Medicine Database, Cumulative Index to Nursing and Allied Health, MEDLINE, SPORTDiscus, Biomedical Reference Collection, and Academic Search Premier, were searched for relevant articles.

Study Selection

Quantitative design studies that included active exercise as part of a multimodal or stand-alone approach were selected. Only studies scoring ≥6 on the Physiotherapy Evidence Database Scale were included in the review because this reflected a good level of evidence.

Data Extraction

Study methodologies and relevant outcome measures, including isometric strength, Neck Disability Index scores, and pain scores, were extracted from relevant articles and grouped together for appraisal and synthesis.

Data Synthesis

Evidence from selected articles was synthesized according to the FITT exercise principal to determine the most effective exercise type, frequency, and intensity in the treatment of chronic neck pain.

Conclusions

Physiotherapy interventions using a multimodal approach appear to produce more beneficial outcomes in terms of increased strength, improved function, and health-related quality of life and reduced pain scores. Active strengthening exercises appear to be beneficial for all of these outcomes; the inclusion of additional stretching and aerobic exercise components appear to enhance the benefits of an exercise intervention.

Keywords:

Exercise, Neck pain, Physical therapy modalities, Rehabilitation

List of abbreviations:

FITT (frequency, intensity, time, and type), MVC (maximal voluntary contraction), PEDro (Physiotherapy Evidence Database)
Hudson and Ryan1 report that neck pain is one of the most prevalent and costly musculoskeletal conditions in Western society. It is estimated that up to 67% of adults will experience neck pain at some stage in their lives.2 In European populations, between 15% and 19% of cases will develop into a chronic state.3 Worldwide, this figure is up to 20% of the population reporting chronic neck problems at any one time.4 Those experiencing chronic pain are twice as likely to present to health care services compared with the general population.5 Compensation, health care service provision, and loss of productivity because of sick leave days accumulate to large amounts of money for states each year.2 Epidemiologic studies of chronic neck pain prevalence are limited in Ireland. A study by Raftery et al6 found that of the 13% of the population who suffer from chronic pain, 29.4% also suffered from neck pain. In 2008, an estimated €5.34 billion or 2.86% of the gross domestic product was spent on chronic pain in Ireland; second to lower back pain, chronic neck pain accounts for a large proportion of this expenditure. Data from the United States indicates that 14.3% of the population is experiencing chronic neck pain. Similar to this are Australian figures, which indicate that approximately 640,000 Australians experience chronic neck pain, costing the state almost $1.14 billion annually in associated health care.7National figures from The Netherlands indicated that $686 million was spent in 1996 on chronic neck pain.8 Data from the United Kingdom suggest that costs for private physiotherapy care for chronic neck pain amount to an approximated £296 per individual, with figures reaching upward of £1911 when referred to >1 service (eg, pain clinic and physiotherapy), which is commonly the case in chronic pain.9
For the purpose of this review, chronic pain is defined in accordance with the International Association for the Study of Pain and the American Pain Society as pain that persists beyond normative tissue healing time, which is defined as 3 months.10 Chronic neck pain for the purpose of this review includes pain experienced in the anatomic region of the cervical spine between C1 and C7 and surrounding musculature only, excluding the shoulders. Pain of insidious onset is discussed only because whiplash-associated disorders were excluded as a result of the psychosocial and medicolegal implications in such conditions.11 Mechanisms for the development of chronic pain are not fully understood; however, it is known that pain can become more complex in its pathophysiology than that of the original insult or injury.12 Chronic musculoskeletal pain usually develops as a result of an injury or insult followed by neurogenic inflammation, hyperalgesia, and allodynia.11 The transmission of repeated pain signals produces functional and structural changes in the nervous system and central sensitization occurs, followed by a loss of nociceptive control.13, 14
Evidence suggests that being a woman, white, and middle-aged increases the risks of neck pain becoming chronic.3, 15,16, 17 Ylinen,18 Webb,16 Guez,19 and colleagues report that the incidence of chronic neck pain in women ranges from 7% to 22% compared with 5% to 16% in men. A history of previous neck pain or, similarly, a whiplash-associated accident can increase the chances of developing chronic neck pain.20 However, personal societal and environmental factors can influence the development of a whiplash-associated disorder. Although a weaker correlation exists, occupation is a risk factor in the development of chronic neck pain.21 Sedentary lifestyles, office-based workplaces, and an ever-increasing reliance on technology has increased the prevalence of neck pain in recent years.22 Additionally, Manchikanti et al3 found that industrial workers and manual laborers were at an increased risk of developing/experiencing chronic pain; statistics indicate that 16% of manual laborers and 74% of crane operators experienced chronic neck pain.
With an increasing prevalence of chronic neck pain,22 it is important to determine physiotherapy treatment interventions that are cost effective, time efficient, and patient appropriate.20 A range of strategies to tackle chronic neck pain have been examined from single modalities to combination interventions.20 Single modality treatment approaches are deemed to be an inaccurate representation of clinical or best practice for individual patients.23 A large variety of physiotherapeutic interventions are available for the treatment of chronic neck pain, including manual therapy, spinal manipulations, passive therapies, relaxation techniques, electrotherapy and stress management, and active exercise.23, 24, 25 In 2008, a set of clinical guidelines published by the American Physical Therapy Association for the treatment of neck pain advocated participation in active exercise.25 Guidelines by Scholten-Peeters et al26 also recommend education and exercise therapy as key components of any multimodal treatment approach to encourage greater autonomy in managing pain and inhibiting pain transmission.
Active exercise is proposed to target the muscles that may be damaged during injury; resultant strains and tears of the stabilizing systems (including the deep muscles and ligaments) can result in dysfunctional movement patterns because of a lack of motor control at the cervical spine.22 Superficial neck muscles replace the actions of the deep muscles, resulting in early fatigue, overactivity, and pain; therefore, active exercise can work effectively to rehabilitate the injured musculoskeletal structures and correct movement patterns.22
In the same way as medication is prescribed in required dosages, applying a similar degree of precision to prescriptions of physical activity is required; hence the development of the frequency, intensity, time, and type (FITT) format. Despite the high incidence of chronic neck pain and the resounding evidence for the benefits of active exercise for the treatment of associated symptoms, there is a paucity of evidence to recommend a definitive FITT principle in this population. Through this method, exercise may be tailored to an individual's needs according to various aspects of activity—for example the type of exercise undertaken, at what level of exertion (intensity), how often, and for what duration.27
Therefore, it is the aim of this review to evaluate and present the research for active exercise in the treatment of chronic neck pain in an FITT format to identify which exercise interventions are associated with the most optimal outcomes and which other treatment modalities the exercise complements. We will also identify what further research may still be warranted for developing an effective intervention in a chronic neck pain population.

Methods

The following databases were searched between April and November 2012 for relevant articles: the Allied and Complementary Medicine Database, Cumulative Index to Nursing and Allied Health, MEDLINE, SPORTDiscus, Biomedical Reference Collection, and Academic Search Premier. Keywords search terms included chronic, neck, pain, and exercise as single words and in combinations. This identified 256 articles. Further studies were sourced via reference lists of appropriate articles. See the Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow diagram infigure 1 for full details.

Thumbnail image of Fig 1. Opens large image

Fig 1

Article retrieval process.
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The abstracts were read to ascertain relevance based on the following inclusion criteria: (1) published material; (2) research conducted between 2000 and 2012; (3) research examining the effects of active (where active was defined as an exercise in which the participant actively engages muscles of an affected limb/area to create motion or movement in direct contrast with a passive approach where a patient relies on an external stimulus to move a limb or limb segment) exercise in a chronic neck pain population where chronic neck pain was defined as the presence of pain for at least 3 months; (4) exercise that was used as part of a stand-alone or multimodal treatment approach to chronic neck pain to include advice/education as a component of treatment; (5) research that took the format of a randomized controlled trial, controlled trial, cross-sectional study, or pilot/feasibility trial; and (6) research that examined the effects of exercise on >1 outcome measure (eg, strength, pain, disability, health-related quality of life).
Articles were excluded if they were not published in English as a primary language, no form of active treatment was given, and there was no control or alternative therapy group for comparison.

Results

This search strategy identified 16 studies for inclusion in this literature review. Details of the included studies have been given in tabular form. Table 1 details the appraisal of evidence using the Physiotherapy Evidence Database (PEDro) Scale for each of the studies reviewed. The PEDro Scale is available online (http://www.pedro.org.au/english/downloads/pedro-scale/). Table 2 provides a description on the demographic details of included studies. Table 3 demonstrates the individual components of the exercise regimens used in each of the studies reviewed, and table 4 outlines the methodologic design and results of each of the studies reviewed.
Table 1Included studies assessed using the PEDro Scale
StudyRandomizedConcealed AllocationGroups Similar at BaselineBlinded (participants)Blinded (assessors)Blinded (therapists)Received Treatment/Control or Intention-to-TreatBetween Group Stats for at Least 1 OutcomeMeasure of at Least 1 Outcome From 85% of Original GroupPoint Measure of Variability for at Least 1 Key OutcomePEDro ScoreLevel of Evidence (Oxford Scale)
Falla et al31YesNoYesNoNoNoYesYesYesYes62
Hudson and Ryan1YesNoYesNoYesNoYesYesYesYes72
Häkkinen et al30YesNoYesNoNoNoYesYesYesYes62
Evans et al32YesNoYesNoNoNoYesYesYesYes62
Ylinen et al5YesNoYesNoYesNoYesYesYesYes72
Viljanen et al2YesNoYesNoYesNoYesYesYesYes72
Chiu et al43YesNoYesNoNoNoYesYesYesYes62
Stewart et al34YesNoYesNoYesNoYesYesYesYes72
Taimela et al44YesNoYesNoYesYesYesYesYesYes71
Salo et al29YesNoYesNoYesYesYesYesYesYes71
Jull et al45YesNoNoNoNoNoYesYesYesYes52
Ylinen16YesNoYesNoNoNoYesYesYesYes62
Waling et al39YesNoYesNoNoNoYesYesYesYes62
Chiu et al33YesNoYesNoNoNoYesYesYesYes62
Andersen et al35YesNoYesNoNoNoYesYesYesYes62
Bronfort et al4YesNoYesNoNoNoYesYesYesYes62
Table 2Participant demographics for included studies
StudySample Size (n)Symptom DurationSex Distribution (% female)Age (y)
Falla et al31587.90±6.40y100.0037.90±10.20
Hudson and Ryan1127.00±5.70y66.6642.70
Häkkinen et al301015.80±2.40y100.0040.00
Evans et al322709.40±9.10y77.0046.30±10.70
Ylinen et al51809.00±6.00y100.0046.00±6.00
Viljanen et al239311.00±5.70y100.0045.00±6.60
Chiu et al422181y66.7044.31±9.77
Stewart et al341349.00±2.40y89.0043.30±14.70
Taimela et al4476>3mo73.0047.00±16.80
Salo et al291015.8y90.0041.00±9.00
Jull et al454610.10±10.60y100.009.60±12.20
Ylinen181809.00±6.00y100.0046.00±6.00
Waling et al391036.75±3.51100.0038.10±6.10
Chiu et al 200533218>1y68.0045.00±6.00
Andersen et al35198>3mo12.1244.00±11.00
Bronfort et al41915y59.2045.00±10.50
NOTE. Values are mean ± SD or as otherwise indicated.
Table 3Individual study characteristics using the FITT principle
StudyFrequencyIntensityTimeTypeResults (effects on strength, pain, disability, other)Format
Falla et al31Twice daily12 repetition maximum10–20min daily over 6wkStrengthening/resistanceEG ↓ 1.1cm VAS

LLEG ↓ 0.9cm VAS

EG ↑ MVC 10.1±17.3N

LLEG ↑ 1.8±10.6N

P values not specified		Individual
Hudson and Ryan11d/wk for 1h with physiotherapy (MG) 20-min session with physiotherapy 5–8 times (UC)Undisclosed1h/wk for 6wkEG: strengthening/resistanceStatistically significant improvements in pain and disability (P<.01) pre- to postintervention, not statistically significant between groups (pain:P=.67, disability:P=.84). Pain: MG and UC ↓ 5/10 VAS

NDI score ↓ 12.3% (MG) and 7.4% (UC)		Individual
Häkkinen et al303t/wStrength group: 80% of MVC12moStrengthening/resistancePain (VAS) ↓ by 37mm in strength and stretching groups (95% CI, –44 to –30). Stretching only group ↓ –32mm (95% CI, –39 to –25mm). Complete pain relief by 51% of strength and stretch group, 42% of other. Insignificant change (P=.88; 95% CI, –7 to 7)

NDI score significantly lower at 12mo (P<.001), no discernible difference in change between 2 training groups

Isometric neck strength mean difference at 12mo, strength and stretch group increase of 9N (95% CI, 3–14), stretch only 9N (95% CI, 3–14,P=.88)		Group
Evans et al322t/wk (supervised or independent sessions)Partially individualized (load and repetitions) according to abilities of individual (eg, baseline 3 sets of 15–25 repetitions using variable head weights of 1.25–10lb [0.5–4.5kg])Hourly sessions for a 12wk treatment period (follow-up at 12mo)Strengthening↓ Pain (11 Box Numerical Rating Scale). Mean differences at 12wk from baseline.

Exercise vs exercise and manual therapy: –.19 (95% CI, –.89 to .51; P=1)

Exercise and manual therapy vs home exercise program: –1.27cm (95% CI, –1.96 to .58; P=.001)

Exercise vs home exercise program: –1.07cm (95% CI, –1.77 to .38;P=.001)

↓ NDI scores. Mean differences at 12 wk.

Exercise and manual therapy vs exercise: –2.26 (95% CI, –5.43 to .92; P=.265)

Exercise and manual therapy vs home exercise program: –4.66 (95% CI, –7.8 to –1.52; P=.001)

Exercise vs home exercise program: –2.4 (95% CI, –5.56 to .76;P=.001)		Supervised group and individual
Ylinen et al53–5t/wkStrengthening group 80% of MVC (individual)

Gravity for endurance group		12mo interventionStrengthening and endurance↓ Neck pain VAS

Controls: ↓ –16mm (95% CI, –22 to –9)

Endurance group: –35mm (95% CI, –42 to –28)

Strength group: –40mm (95% CI, –48 to –32)

P≤.001 (endurance vs control, strength vs control)

↓ NDI score

Control: –12 (95% CI, –15 to –81)

Endurance group: –22 (95% CI, –26 to –19)

Strength group: –23 (95% CI, –27 to –20)

P≤.001 (endurance vs control, strength vs control)

↑ Isometric strength

Strength group ↑ MVC 110% (flexion), 76% (rotation), 69% (extension)

Endurance group ↑ MVC 28% (flexion), 29% (rotation), 16% (extension)

Controls ↑MVC 10% (flexion), 10% (rotation), 7% (extension)		Individual
Viljanen et al23 exercise sessions a week or 5 relaxation sessions a weekLow-load intensity12wk treatment intervention

12mo follow-up period

Exercise sessions 30min in duration		Dynamic or relaxation therapyMean difference in pain reports as per VAS

At 3mo follow-up dynamic group vs control: .20 (95% CI, –.40 to 0.7)

At 12mo: 0.5 (95% CI, –7.6 to 0.3)

Mean difference in dynamic muscle strength

At 3mo DyG vs control: 0.1 (95% CI, –2.2 to 2.5)

At 12mo: –0.6 (95% CI, –3.2 to 2.1)

Mean difference in disability as per NDI score

At 3mo follow-up DyG vs control: 0.8 (95% CI, –1.9 to 3.6)

At 12mo: –0.1 (95% CI, –3 to 2.9)

P values are not given		Individual
Chiu et al432t/wk20% of 12 repetition maximum6wk treatment intervention

6mo follow-up

Exercise sessions 45min duration		6wk treatment period, 6mo follow-upPain: VPNS mean difference

Control: .30±2.48 (.475), TENS group: .60±2.54 (.027), exercise: 1.57±2.67 (<.001)

Disability NPQ mean difference

Control: .23±.63 (.003), TENS: .38±.60 (<.001), exercise: .39±.62 (<.001)

Neck muscle strength (N)

Control: 1.25±3.94 (.03), TENS: 1.42±3.9 (.02), exercise: 2.28±4.22 (<.001)

Control group differences were not maintained at 6mo follow-up		Individual
Stewart et al342t/wkDescribed in text as individualized, progressive, and submaximal6wk intervention, 1h exercise sessionsCombination therapy, strengthening, endurance, coordination

Aerobic		↓ Pain: VAS combination therapy vs advice/control: –1.1 (95% CI, –1.8 to 0.3; P=.005). Not significant at 12mo (P=.59)

NDI score

CombG vs advice: –2.7 (95% CI, –4.5 to .09; P=.004). Not significant at 12mo (P=.08)		Individual
Taimela et al441t/wkLow load and low progression12wk intervention

Follow-up at 12mo

1h sessions		Relaxation therapy, proprioceptive exercise, educationPain as per VAS

At baseline 55±21mm for both active exercise group and home exercise group (control group)

At 6wk, active mean VAS 22mm, home 23mm, control 39mm (P=.018)

No statistically significant difference between groups noted at 12mo follow-up; tendency in favor of home exercise group		Individual
Salo et al291–2t/wk80% of MVC of neck musculature12mo exercise interventionStrengthening/resistance, stretchingStatistically significant improvements in 5 out of the 8 health-related quality of life dimensions in the combined strengthening and stretching group, namely physical and social functioning, bodily pain and health perceptions, and role physical; for the strengthening group, improvements were seen in 4 of 8 of these dimensions

Bodily pain decreases increased week exercise adherence in the combined therapy group (P=.05; 95% CI, .00–.27)

Physical functioning improvements in the strengthening group resulted in increased weekly exercise adherence (P=.03; 95% CI, .03–.42)		Individual
Jull et al457t/wkLow load: against gravity

Strengthening group: individualized 12 repetition maximum, progressions based on 50% of 10 repetition maximum, 75% of 10 repetition maximum, 10 repetition maximum load		6wk exercise intervention (1h/wk with physiotherapy) and 10–20min of daily exerciseCCF training, proprioceptive training↓ EMG activity in superficial neck flexors in CCF training group (P<.001). Increase in deep neck flexor electromyographic activity in CCF group (P=.05)

↓ Pain scores as measured on VAS: CCF group (P<.001), strength group (P<.05). CCF group ↓ –2.8cm, proprioception training group ↓ –1.9cm

NDI score

CCF group –5.0±4.2, strength group –3.5±2.3

P=.05		Individual
Ylinen183–5t/wkStrengthening group 80% of MVC (individual)

Gravity for endurance group		12mo intervention3y follow-up from initial 2003 studyMedian VAS at 3y follow-up: 14 (95% CI, 4–39; P=.069)

Median NDI score value at 3y follow-up: 12 (95% CI, 4–22; P=.072)		Individual
Chiu et al332t/wkEG: 8–12 repetition maximum or 30% of MVC and increased by 5% when a set of 12 was achieved6wk exercise intervention

6mo follow-up		Strengthening/resistance

Education/advice		Pain scores as per VPNS after 6wk intervention

Mean difference control vs exercise: 1 (95% CI, 0.2–1.7; P=.01)

NPQ

Mean difference control vs exercise: 0.2 (95% CI, 0.0–0.4; P=.03)

Isometric strength

Significant increase (95% CI, 26.1–45.7; P<.01) in all 6 directions

At 6wk, significantly better improvements (mean difference: 0.4–2.2lb (0.5–1kg); P=.57–.00) in the exercise group compared with control group. Not significant at 6mo follow-up		Individual
Andersen et al355t/wkModerate to high based on elastic exercise band coloring red, green, and blue (red elastic exercise band=moderate for women, green=moderate for men etc)10wk exercise intervention

2–12min exercise sessions (total between 10 and 60min of exercise a week)		Strengthening/resistance (elastic exercise band training)NDI score (0–10) between group differences after 10wk

2min exercise group vs control: –1.4 (95% CI, –2.0 to .07; P<.001)

12min exercise group vs control: –1.9 (95% CI, –2.5 to –1.2; P<.001)

2min vs 12min exercise groups: 0.5 (95% CI, –0.3 to 1.3; P=.12)

↑ Muscle strength (Nm)

2min exercise vs control: 2 (95% CI, 0.5–3.5; P=.008)

12min vs control: 1.7 (95% CI, 0.2–3.3; P=.02)

2min vs 12min exercise group: 0.3 (95% CI, –1.3 to 1.8; P=.74)		Individual
Bronfort et al41 t/wkLow load individualized12wk exercise intervention

12mo follow-up

Maximum 45min exercise session duration		NAPain scores baseline to 11wk

Spinal manipulation and exercise (group 1): 56±15 to 23.6±18

MED X group (group 2): 57.1±15 to 24.1±19.7

Spinal manipulation (group 3): 56.6±12.8 to 31.3±21.8

Group 1 vs group 2: effect size, .03; 95% CI, .41–.35

Group 1 vs group 3: effect size, –.25; 95% CI, –.12 to –.61

Group 2 vs group 3: effect size, –.28; 95% CI, .10 to –.66

NDI score baseline to 11wk

Group 1: 26.4±8.5 to 14.1±8.7

Group 2: 26.7±10.4 to 12.4±9.9

Group 3: 27.8±10.3 to 15.8±12.3

Group 1 vs group 2: effect size, .16; 95% CI, .54 to –.22

Group 1 vs group 3: effect size, –.14; 95% CI, .22 to –.57

Group 2 vs group 3: effect size, –.27; 95% CI, .10–.65		Individual
Abbreviations: CCF, craniocervical flexion; CI, confidence interval; CombG, combination group; DyG, dynamic group; EG, exercise group; LLEG, low-load exercise group; MED X exercise group, one-to-one exercise supervision with physical therapist that included stretching, upper body strengthening, aerobic exercise, and dynamic progressive resistance exercises; MG, multimodal group; NA, not applicable; NDI, neck disability index; VPNS, verbal pain numerical scale; NPQ, Northwich Pain Questionnaire; TENS, transcutaneous electrical nerve stimulation; UC, usual care; VAS, visual analog scale.
Table 4Components of study exercise interventions
StudyResistance/StrengtheningEnduranceDynamicStretchingManual TherapyOther TrainingProprioception/Postural
Falla et al31√√XXXXX
Hudson and Ryan1√√XX√EducationX
Häkkinen et al30√XX√XXX
Evans et al32√XXX√EducationX
Ylinen et al5√√X√XAerobic exercise (controls)X
Viljanen et al2X√X√XRelaxation techniquesX
Chiu et al33√X√XXInfrared irradiationX
Stewart et al34√XXXXAerobic exercise, advice/educationX
Taimela et al44X√XXXAdvice, education, behavioral support, relaxation techniques√
Miller et al38√√X√√XX
Salo et al29√√X√XXX
Jull et al45XXXXXCraniocervical Flexion√
Ylinen18√√X√XXX
Chiu et al43√XXXXTranscutaneous electrical nerve stimulationX
Andersen et al35√XXXXAdvice/educationX
Bronfort et al4√XXX√Aerobic exerciseX
Waling et al39√√XXXAdvice, coordination trainingX
Abbreviations: √, yes; X, no.

Discussion

Research in the 1990s24 found inconclusive evidence for the effects of exercise on mechanical neck pain; this has been refuted by research over the last decade with resounding evidence for the benefits of active exercise in the treatment intervention above passive alternatives.4, 20, 28 For the purpose of this review, the studies included will be discussed in terms of the frequency with which the active exercise is undertaken, the intensity at which the exercise is conducted, the time spent exercising, and the type of exercise undertaken (the FITT principle).

Frequency

Exercise frequency varied among studies included in this review (see table 3) with interventions typically ranging from 3 sessions a week to daily sessions with benefits visible from all frequencies.1, 5, 29, 30, 31, 32, 33, 34, 35, 36 Positive outcomes were reported for pain intensity, isometric strength, health-related quality of life, and perceived disability in trials incorporating 3 exercise sessions a week.5, 18, 33, 35, 37, 38
Studies demonstrating significant increases in isometric strength used an exercise frequency of between 3 and 5 times a week.5, 31, 39 Programs that involved daily exercise over a 10-week period demonstrated beneficial effects for a reduction in neck pain and an increase in isometric strength.35 Falla et al31 found statistically significant increases of 10.1±17.3N in their endurance strength training group, whereas there were gains of 1.8N identified in participants of the low-load craniocervical flexor muscle group for the same frequency and intervention duration. Interventions of at least 3 sessions weekly produced gains in strength, which is in agreement with known resistance training benefits and its effects as established by the American College of Sports Medicine guidelines.40 Hudson,1 Evans,32 and colleagues reported beneficial outcomes; the most notable outcomes included reductions in pain intensity and perceived reductions in disability from lower-frequency exercise interventions (ie, 1–2 sessions/wk). Häkkinen et al30 reported statistically and clinically significant reductions in pain (37mm [51%] on a visual analog scale in the strengthening and stretching group and 32mm [42%] in a stretching group) from exercising 2.1 times a week and as little as 1.1 times in the fourth quarter of a 12-month intervention. Additionally, significant range of motion and isometric strength gains were visible in both groups for flexion-extension and lateral flexion. For further information, please see the PEDro Scale website (http://www.pedro.org.au/english/downloads/pedro-scale/).
Although an exercise frequency was determined per the study design (eg, 3 times/wk), adherence to the exercise protocol appeared to vary quite substantially.1, 5, 31 Although exercise frequency was, on average, 3 times a week, many studies, such as that of Viljanen et al,2 found that over a 12-week period, training adherence only ever reached approximately 39% (1.7 times/wk) of expected figures. Salo et al29 also reported significant benefits in health-related quality of life and an associated decrease in pain intensity from exercising as little as twice a week. Participation in an active exercise intervention appears to have positive effects on pain intensity and isometric strength, even when desired frequencies are not adhered to. This suggests that undertaking exercise as little as twice a week is beneficial, given the known benefits of exercise on general health and well-being in a chronic pain population.23 Many of the studies included in this review, such as Salo,29 Evans,32 and colleagues, incorporated education (see table 2) into their interventions as part of a multimodal approach; as such, it cannot be assumed that benefits seen were because of exercise alone because benefits may also be attributable to this. High-frequency exercise interventions are not deemed appropriate for a population with chronic neck pain because of adherence barriers. According to patient reports, training frequency decreased after the initial intervention had ended, with some decreasing from an expected 3 times a week to 1.9 times a week by the end of the first year.29
Findings, therefore, suggest that the most beneficial frequency of exercise to target pain, weakness, and quality of life in a population of people with chronic neck population with a varying age range is 3 times a week.

Intensity

Training intensity varied depending on the type of exercise being investigated, that is, resistance or endurance. Resistance regimens usually conducted exercises based on percentage values ranging between 20% and 70% of an individual's maximal voluntary contraction (MVC) (see table 3). For strength or resistance training, baseline measurements of MVC were determined using manual muscle testing methods with handheld dynamometers or purpose-built fixed-frame dynamometers, or as commonly seen, 1 repetition or 12 repetition maximums.5 Endurance training pertaining to the training of a larger group of muscles, that is, deep or superficial cervical muscles or larger shoulder muscles to increase muscular stamina, can be influenced by the ability of the cardiovascular system to provide oxygen rich blood to the area being exercised. These interventions were based on a lower intensity and primarily based on gravity, intending to increase physical muscular endurance.41 The mean age of participants across the studies in this review was mid-40s with age ranges spanning between 18 and 63 years. Therefore, to target the training needs of individual participants, exercise prescriptions were predominantly individualized. Minimum intensity thresholds were set at or above that at which participants were expected to work to induce strength benefits.5, 31, 33, 37 In a study by Ylinen et al,5 the resistance training group conducted multidirectional strengthening exercises (eg, flexion, lateral flexion, and rotation) using elastic exercise bands, whereas an endurance group conducted lower-intensity exercises against gravity. Both groups showed significant gains in strength (see table 3). Observed baseline levels of strength were so low in the sample population (such that 5 of the participants in the endurance training group struggled to lift their head from the bed) that strength gains were visible from exercising at an intensity as low as working against gravity. This finding strengthens the recommendation for individually tailoring exercise interventions; low-intensity exercise is defined as against gravity, and medium- to high-intensity exercise is defined as against gravity with further added resistance.35
In an attempt to combat adverse effects of training, such as delayed onset muscle soreness or an increase in pain, which may impact end results, a variety of studies reviewed here (see table 3) incorporated lower-intensity resistance training for some exercise sessions. For example, in a study by Ylinen et al,42 participants conducted exercise sessions at the prescribed intensity on day 1 of the exercise intervention; in the following exercise session, participants were only required to work at half that prescribed intensity. This was a measure taken to reduce excessive loading on musculoskeletal systems and aerobic endurance.
Progressive intensities are required to avoid plateauing and enable continued training gains.32, 43 For example, Chiu et al33 commenced training at 20% of MVC values; exercise intensity progressed in increments of 5% when an individual was able to conduct a set of 12 repetitions of flexion strengthening exercises (see table 3). Falla et al31 used an alternative approach by conducting a 2-phase strengthening program. Phase 1 consisted of a 12-repetition set (prescribed weight based on 12 repetition maximum weight) for the first 2 weeks. The remaining 4 weeks of the 6-week exercise intervention were then spent executing 15 repetitions per set. Because both had positive results, designing an exercise protocol that allows participants to become accustomed to an exercise before increasing the intensity is beneficial and positively effects outcomes.
Although high-dose/intensity exercise programs were seen to lead to reduction in neck pain,32 low-dose or low-load endurance exercise programs were still seen to have advantageous results.31 For endurance interventions, intensity was based on gravity, for example supine lying and lifting head against gravity.5 This surprising result has been hypothesized to be the result of the learning effect involved in the movement and the low-strength baseline values of participants. Therefore, from collating and reviewing the evidence, training intensity in a chronic neck pain population should be individually tailored based on baseline abilities as defined by their MVC values.

Time

The time spent exercising in an individual exercise session and the length of time the intervention lasted varied in length between studies (see table 3). It is difficult to ascertain the actual cumulative time spent exercising over the course of an intervention because of a lack of adherence by participants once an initial supervised exercise intervention was completed.18, 30, 32, 35 Single exercise bouts ranged from 10 minutes to 1 hour in duration in the studies reviewed; however, exercise interventions usually ranged from 6 to 12 weeks with follow-up at 3, 6, and 12 months.1, 5, 29, 30, 31, 32,33, 34, 35, 43 Benefits were seen from exercising for as little as 10 minutes a day 3 times a week.29, 33, 36 Because exercising a specific muscle group for an hour at a time may not be desirable for this particular population, a regimen which provides clinically significant results in the least time spent exercising should be used, that is between 2 and 20 minutes per session.32
The duration of exercise interventions varied with effective interventions ranging from 6 weeks to 3 years. Generally, interventions ranged between 6 to 12 weeks with follow-up occurring over a year-long period. Short duration interventions have been shown to produce immediate benefits in isometric strength, pain intensity, and perceived disability; however, long-term follow-up shows that if exercise is not conducted after the initial intervention is over, benefits are lost.2, 5, 18, 30, 32Outcomes found to be statistically significantly different immediately after an intervention were not found to be so 1 year later in most studies that conducted such follow-ups.2, 32, 33, 34 Therefore, it is important to take overall findings, including long-term benefits of exercise interventions, into consideration when formulating an optimal exercise intervention. Because episodes of chronic pain may be transient, it is important to maintain exercise levels beyond that of the initial scope of the study to maintain long-term benefits.4, 32 Strength or resistance training interventions need to be of a minimum 6-weeks duration to ensure there is sufficient opportunity for muscle hypertrophy to occur.5, 33, 40 Although interventions seen in this review were scheduled for a similar length in duration, the actual cumulative time spent exercising may have differed greatly. For example, Evans et al32 conducted an exercise intervention that lasted 12 months; however, during that time only 20 hours of supervised exercise were conducted. Salo et al29 provided an intervention of the same length of time but with a desired accumulative exercise duration of 156 hours over the course of the year (see table 3). Both methodologies had significantly desirable outcomes in their respective interventions; one must consider how likely an individual is to adhere fully to a year- long program or to attend 20 supervised physiotherapy sessions when formulating an optimally effective intervention. Salo29 aimed to have an accumulative exercise duration of approximately 156 hours over the course a year; however, according to exercise diaries kept by patients, the reality showed that by the final quarter of the trial period, approximately 1 hour of exercise, opposed to the desired 3 hours, was being performed by participants over a weekly period.
Therefore, when examining the time spent exercising and the duration of an exercise intervention to provide the most optimal results, it is recommended that interventions must last at least 6 weeks for physiological benefits to occur. Exercising between 12 and 45 minutes produces the best results with 30 to 45 minutes being a reasonable and largely attainable exercise session duration.

Type

Clinical guidelines by the orthopedic section of the American Physical Therapy Association25 detail that exercise should be part of a treatment intervention for chronic neck pain. Along with stretching, coordination, centralization procedures, nerve mobilizations, traction, manual therapy, patient education, and counseling, active exercise in the form of strengthening and/or endurance exercise are advocated. Though these guidelines formed similar conclusions to this review, the novelty of providing an exercise prescription in an FITT format makes this review clinically applicable.25
Although there has been much debate as to which form of exercise is most beneficial, a combination of both resistance and endurance exercise and stretching reaps the greatest benefits for participants.5, 29, 34, 38 These studies showed immediate and some long-term benefits in increased isometric strength, a desirable outcome from a physiotherapy perspective because it is widely postulated that the deep cervical flexor is substantially weaker in those with chronic neck pain. Endurance exercises are also of benefit; the stabilizing role of the deep neck flexors at the cervical spine is commonly affected in chronic neck pain, and these exercises help build the endurance required to maintain head postures over an extended period of time.22
Evaluation of the studies in this review demonstrate that resistance exercise made up approximately 50% of the interventions with the remainder being devoted to stretching, aerobic exercise, and/or education in order to target the known weaknesses that may occur in the cervical musculoskeletal system.1, 5, 32
It was rarely observed that both resistance and endurance exercise were part of the same exercise program; rather, the individual types of exercises were compared directly for their effectiveness. This may be because of the study methodology and aim to determine the benefits of any 1 active exercise form in a chronic neck pain population before combining different forms of exercise. According to this review and clinical guidelines, there is evidence for the beneficial effects of both forms of exercise. A combination of strengthening, stretching, and aerobic exercise appears to have the most beneficial effects on isometric strength and a reduction in pain intensity and disability with an overall increase in perceived well-being.25
The integration of aerobic exercise into many of the studies reviewed here5, 29, 32, 34 resulted in increased positive health-related quality of life perceptions29 and patient satisfaction and global perceived benefit.33 Though not commonly investigated, potential benefits from proprioceptive exercises and joint position training as studied by Jull et al45 found that joint position error was statistically significantly improved. There were also advantageous results seen for reduced pain and disability scores in the same training group when compared with a craniocervical flexion training regimen. Therefore, including ≥1 of these in an exercise intervention could produce favorable outcomes.1, 5

Barriers to exercise (adherence, adjuncts, delivery)

The importance of education in a chronic pain population has long been established, primarily in a chronic back pain population.12 Fear avoidance and a lack of understanding of exercise benefits are characteristics of those with chronic pain.24 These characteristics are postulated to be causative factors in the development of a chronic pain state.12 Studies intable 2 that included education as a component of a multimodal approach had beneficial results, such as reduced perceived levels of disability. A Cochrane review by Gross et al21 found evidence of varying quality, which suggests that education in chronic neck pain is beneficial for improvements in pain, function, quality of life, and exercise adherence; these results are further mirrored by studies in this review (see table 2).29 Therapeutic patient education should emphasize a patient-centered approach to specifically fit the needs of a patient.23
Adherence is predominantly only a superficially measured outcome in chronic pain population studies.32 The type of delivery of an intervention appears to affect adherence to a program, and designing what is perceived to be an optimal exercise intervention for a chronic neck pain population is of little significance if it is not going to be adhered to. Though it may be suggested that conducting exercise in a group setting would encourage participation because of the socialization and group dynamic factors, in fact, supervised group sessions offered little additional benefits from individual sessions.32
Exercise interventions reviewed here were largely conducted in home settings, community centers, or hospital settings; therefore, cost effectiveness must also be considered in the development and delivery of an optimal program. Viljanen2attempted to reproduce the beneficial effects found by Ylinen5 in a more cost-effective home-based setting. Though results were not of statistical or clinical significance, the availability for patients to conduct exercise in a more cost-effective manner than being supervised by a health professional is an important factor, particularly in current economic climates.
According to Ylinen,5 the potential barriers to adherence include the seasonal variation of symptoms. Pain is exacerbated in the autumn with some relief in the spring; therefore, the timing of an intervention may have a bearing on observed results. Studies in this review did not declare the time of year the interventions were undertaken, making it impossible to draw conclusions on what intervention had the best outcome based on time of year conducted.
Psychosocial factors, including depression and anxiety, are reported to affect between 20% to 50% of people with chronic pain.14 Experiencing such symptoms can effect a patient's ability to participate in their own self-care and pose difficulties in modulating pain because of altered neurotransmitter balance.14 The presence of such symptoms must be acknowledged when developing a treatment intervention for this population. Inclusion of psychosocial or counseling components as part of an intervention in parallel with education may be beneficial in increasing adherence in future studies.

Study limitations


Methodologic bias

Articles included and discussed in this review were critically appraised for their study methodology and resultant findings. Literature searches, article selection, data extraction, and synthesis were conducted by only 1 reviewer; this potentially creates a selection bias and should be considered when interpreting the conclusions drawn from this review. Articles retrieved were applied to previously outlined inclusion and exclusion criteria to determine suitability and were also assessed using the PEDro Scale to determine levels of evidence. Most studies reviewed were of good (score of 6 or 7) and not excellent (score ≥10) methodologic quality. Exercise interventions are difficult to blind from the participants because of the study nature. Therefore, it is possible that results seen in this review may have been biased. Therapist and assessor blinding, though not commonly seen in the studies here (see table 3), can strengthen findings and eliminate bias.6, 31

Multimodal approach

Many of the studies reviewed here were of multimodal approach; education or manual therapies were always given in conjunction with exercise. Therefore, it is important to consider this when interpreting the findings and recommendations outlined in this article because confounding variables cannot be ruled out.

Outcome assessment

Some studies discussed in this review (see table 3) used subjective outcomes as their primary evaluation method. Self-assessment can lead to bias and may not be a true indication of the results of an intervention. Objective measures are always more accurate.

Conclusions

The findings of the review are in agreement with the current guidelines for a chronic neck pain population, which state that programs should be multimodal to include active exercise and education. Exercising a minimum of 3 times a week for approximately 30 to 60 minutes at an intensity reaching up to 80% of MVC to induce strength gains and reduce pain and disability is recommended. Resistance exercises to increase isometric strength of the deep cervical flexors are warranted to ensure correct muscle recruitment and function.22 Endurance exercises incorporated into a regimen that uses gravity as resistance can increase the postural functioning of the deeper cervical muscles, which may reduce pain in a chronic neck pain population.46 Aerobic exercises can help induce an increased perceived feeling of global well-being and health-related quality of life.29 Effective interventions should last between 6 and 12 weeks with encouragement to continue life-long exercise to maintain long-term benefits and the longevity of alleviated pain-related symptoms. A combination of group and home-based exercises is optimal for increasing adherence and long-term motivation. Every effort should be made to make exercise facilities readily available for this population to aid adherence and ensure permanence of exercise benefits.

Clinical implications

This review has provided clinicians with an immediately clinically applicable physiotherapy intervention for a chronic neck pain population through the use of the FITT principle. It would be beneficial to incorporate or devise a future intervention trial for this clinical population using this proposed FITT principle and assess its effectiveness for outcomes, such as isometric strength, pain, neck disability, and health-related quality of life, to cement the findings of this review and further the level and scope of evidence for active exercise in a chronic neck pain population.

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