Scientific Papers

Summarizing the effects of different exercise types in chronic neck pain – a systematic review and meta-analysis of systematic reviews | BMC Musculoskeletal Disorders


Search results

The search results are summarized in Fig. 1. The literature search returned a total of 1,794 records. Following removal based on duplicates, a review of the titles and abstracts (n = 1,223) was performed, and 82 full texts were screened. Automatic de-duplication was based on the method described by Bramer et al. [35]. After checking against our inclusion and exclusion criteria, we included 25 SRs in the final review, which included a total of 221 randomized controlled trials (RCTs) in which 17,321participants were included (overlap not accounted for). Taking overlap into consideration, a total of 125 (original) studies were included in the 25 SRs. All included SRs were in English. A list of excluded SRs and reasons for exclusion is included in Additional file 4.

Fig. 1
figure 1

PRISMA chart for eligible study selection process. *Consider, if feasible to do so, reporting the number of records identified from each database or register searched (rather than the total number across all databases/registers)

Study characteristics

Our included SRs were published from 2010 to 2023. The majority (80%; 20 out of 25) were MAs, and most of the included patients were defined as having chronic neck pain for at least 12 weeks (Table 1).

Table 1 Description of the included systematic reviews; the number of original studies included, population, exercise intervention, and controls

The 25 included SRs were grouped into five exercise types: a) motor control exercise (MCE) with craniocervical flexion and including Pillar exercises, b) Pilates exercises, c) resistance training, d) traditional Chinese exercise (TCE) such as Tai Chi and Qigong, and e) yoga. A description of the exercise types is presented in Table 2. In four SRs [26, 42, 45, 58] several exercise types were studied and were reported for each exercise type studied separately (Table 5). All but one of the included SRs [43] reported effects on pain, and five did not report effects on disability [21, 26, 42, 54, 58]. In the short-term perspective, some SRs diverted from our definition of < 12 weeks and defined short-term as up to 24 weeks [42, 45, 50].

Table 2 Description of the exercise types

Quality of the included SRs

Based on the AMSTAR-2 ratings, we found five SRs with high quality [23, 26, 42, 51, 59], seven SRs with moderate quality [21, 32, 44,45,46,47, 57], eight SRs with low quality [22, 43, 48, 50, 53, 54, 56, 61], and five SRs with critically low quality [49, 52, 55, 58, 60]. The AMSTAR-2 ratings for all included publications are presented in Table 3. Of the six items that were identified as critical, most studies fulfilled these criteria, except for item 4 “Did the authors use a comprehensive literature search strategy?”, where only 13 out the of 25 SRs scored a “yes”. Concerning the remaining items, many studies lacked reporting on item 10 funding of the included studies (n = 23), and item 7 “Did not (or partially did not) include a list of excluded studies” (n = 20), and item 2 “Did not establish a protocol before the review” (n = 10).

Table 3 Summary of methodological quality assessment of included studies using AMSTAR-2

Summary results for exercises in chronic neck pain

The narrative analyses of the included SRs showed positive effects for all exercise types regarding pain in the short-term and when compared with non-exercise controls, and either varying or positive effects in the intermediate/long-term. For disability, all showed positive effects in the short-term compared to non-exercise controls, while compared with other exercise interventions there were no, varying, or positive effects. In the intermediate/long-term there were mainly no or varying results for pain as well as disability levels when compared to non-exercise controls as well as other exercise interventions. Our meta-analyses were based on fewer SRs (n = 16) but were mostly consistent with the narrative analyses. For yoga, no results concerning pain and disability in the intermediate/long-term were available.

In all, we found low- to high-quality evidence that the exercise types studied in this SR of SRs are effective for reducing pain and disability in the short-term compared to non-exercise controls, but we found conflicting results when compared to other exercises as well as in the long-term perspective (Table 4).

Table 4 Certainty of evidence (GRADE) for the exercise types (motor control (MCE), resistance training, traditional Chinese exercises (TCE) and yoga) compared with non-exercising and exercising control groups, for the outcomes pain and disability, at short and intermediate/long-term follow-up

Results for various exercise types

MCE and pillar exercises

Eight SRs were included, and these were based on 97 studies (Tables 1 and 5). In these studies, a total of 4,566 participants were included (overlap not accounted for). Taking overlap into consideration 38 original studies were included. The SRs investigated MCE mostly using a cranio-cervical flexion hold in patients suffering from chronic neck pain [21, 26, 42,43,44,45,46,47]. Pillar exercises, which are intended to develop the ability of the spine to maintain a neutral position during load, were investigated in one high-quality SR [26]. The included SRs were published between 2010 [43] and 2023 [45]. The last updated search in the SRs was on September 30, 2022 [45]. Six SRs [21, 42, 44,45,46,47] performed a MA. The quality of the included SRs varied from low [43], to moderate [21, 44,45,46,47], to high [26, 42], and there was a very high overlap with a CCA of 21%.

Table 5 Results of the different exercise types compared to control interventions for pain and disability

Seven SRs reported results on the effect of MCE on pain compared to various control treatments, including general exercises [21, 26, 45,46,47], strength and endurance exercises [21, 26, 42, 44, 45, 47, 53], manual therapy [26, 44], and minimal interventions such as usual care or education [26, 45, 53]. Most SRs investigated MCE in the short/intermediate perspective, while only one SR investigated the effect of the MCE in the long-term [47]. When MCE was compared to manual therapy, one high-quality SR reported that MCE was more effective in the short-term [26] while another SR with moderate quality reported no difference between MCE and manual therapy in the short/intermediate term [44]. One SR with high quality reported that MCE was more effective when compared with usual care in the short/intermediate term [26] and one SR with moderate quality showed positive results when compared to a true comparison group/minimal intervention [45]. Combining the two SRs [44, 45] that provided aggregated data using a non-exercising comparison group, we found significant positive effects for MCE on pain-intensity in the short-term (SMD = -1.69, 95%CI -2.73 to -0.64; I2 = 5%; Additional file 5). There was an inconsistency regarding the reported effect on pain for MCE compared to other exercise interventions, where four of the SRs with moderate to high quality reported positive effects in the short/intermediate-term [21, 44, 46, 47], while three SRs of medium and high quality [21, 44, 45] reported no results. However, combining the six SRs [21, 42, 44,45,46,47, 53] that provided aggregated data comparing MCE with other exercise interventions into a meta-analysis we found significant positive effects on pain-intensity in the short-term (SMD = -0.25, 95%CI -0.38 to -0.13; I2 = 0%; Additional file 5). There were no positive intermediate/long-term effects reported when comparing MCE to other exercises in one SR with moderate quality [47]. For Pillar exercises, one high-quality SR reported no effect on pain in the short/intermediate term compared with other exercise treatments, but a positive effect compared with education [26].

Six SRs reported results on disability, and of these three SRs compared MCE with a non-exercising control group in the short-term. One moderate-quality SR did not find significant results [44], while two moderate-quality SRs found positive results [26, 45]. The meta-analysis based on the two SRs that provided data [44, 45] showed significant positive effects for MCE (SMD = -2.26, 95%CI -3.13 to -1.39; I2 = 0%; Additional file 5). Four moderate-quality SRs [44,45,46,47] reported a positive effect of MCE compared to other exercises, while one low-quality SR [43] and one high-quality SR [26] reported no positive short-term effects. Our meta-analysis based on four SRs [44, 45, 47, 62] showed short-term positive effects of MCE compared to other exercises (SMD = -0.36, 95%CI -0.52 to -0.20; I2 = 0%; Additional file 5). In the intermediate-term, one moderate-quality SR reported no difference between MCE and other exercises [47], while MCE was found significantly inferior to Pillar exercises in a high-quality SR [26]. No effect was reported comparing MCE with manual therapy in the immediate term [44]. Regarding the effect of Pillar exercises, one high-quality SR showed that Pillar exercises had no positive effect compared with other exercises in the short/intermediate term, while a positive effect was reported for Pillar exercises compared to education in the short/intermediate term [26].

The GRADE analyses (Table 4) showed that there is a high certainty of evidence that there are positive effects of MCE but not of Pillar exercises on pain and disability compared to non-exercise controls in the short-term. Compared to other exercise types, there are positive results concerning the effect of MCE but not for Pillar exercises on pain and disability in the short-term. In the intermediate/long-term, there is a high certainty of evidence that MCE is more effective than non-exercise controls concerning disability, but not compared to exercise controls. Moreover, we found varying results if MCE compared to non-exercise in the intermediate/long-term as well as other exercise interventions for pain. Downgrading was mainly based on the inconsistency of the results.

Pilates

One high-quality SR (MA), based on 5 original studies was included [23]. In the study, a total of 224 participants with chronic neck pain were included. The included SR was published in 2022, and the search was done up until October 2021. The SR investigated Pilates interventions compared with other exercises such as stabilizing exercises, stretching, or strength training or in one of the studies with pharmacological intervention. The SR reported, based on their MA, a low certainty evidence, that the results for pain are not more positive than other exercises/treatments in the short term (SMD = 9.29, 95% CI -25.84; 7.26). The same refers to disability in the short term (SMD 3.20, 95% CI -7.70: 1.30). One of the original studies investigated Pilates in the intermediate term and reported that there is a moderate certainty evidence that Pilates is more effective than a pharmacological intervention for pain (SMD = 3.11, 95%CI 2.05; 0.17) and for disability (SMD = 11.21, 95%CI 5.58; 16.74).

Resistance training

Eight SRs were included, and these were based on a total of 74 studies (Tables 1 and 5). These studies included a total of 8,380 participants (overlap not accounted for) and investigated some form of isometric or dynamic resistance exercises in patients suffering from chronic neck pain [26, 45, 48,49,50,51,52,53]. Taking overlap into consideration 65 original studies were included. The included SRs were published between 2013 [48] and 2023 [45], and the last updated search in the SRs was performed in September 2022 [45]. Six out of the eight SRs performed an MA [26, 45, 48, 50, 51, 53]. The quality of the included SRs varied from critically low [49, 52], and low [48, 50, 53], to moderate [45] and high quality [26, 51]. There was nearly no overlap for resistance training (CCA = 2%). There was a large range in dosage, e.g., the number of treatment sessions, duration, number of sets and reps, and intensity. In most studies, external resistance such as dumbbells, resistance bands, or body weight were used for training specific neck and shoulder muscles. Six of the SRs included a comparison to a non-exercise control such as no treatment, education, or stretching [26, 45, 48,49,50, 52], and three included a comparison to another exercise-based control such as Thai Chi, aerobics, or general exercises [45, 50, 51].

Concerning pain, all six SRs that compared the effect of resistance training against a non-exercise control reported a positive effect at the short-term follow-up [26, 45, 48,49,50, 52]. Two SRs of moderate respective low quality [45, 48] provided data for a meta-analysis and our results showed significant short-term effects on pain-intensity in favour of resistance exercises compared to non-exercising controls (SMD = -0.75, 95%CI -1.41 to -0.09; I2 = 48%; Additional file 5). A low-quality SR [48] also reported positive effects in the intermediate term, but this was not confirmed by a high-quality SR [26]. Compared to a non-exercise control group, three SRs reported on long-term effects on pain, with one low-quality SR reporting positive effects of resistance training [50], one low-quality SR reporting no difference [48], and one critically low-quality SR reporting contradicting results [49]. The results were narratively found to be varying, and our meta-analysis based on two of the included SRs [48, 63] showed no positive results on pain in the intermediate/long-term for resistance training compared with non-exercise controls (SMD = -0.19, 95%CI -0.48 to 0.09; I2 = 70%; Additional file 5).

When narratively comparing resistance training to other exercise-based controls such as Thai Chi, aerobics, and general exercises, varying results were found in three SRs [26, 45, 51]. Our meta-analysis based on two SRs of moderate and high quality [45, 51] showed, however, no significant short-term effects for resistance exercises when compared to exercising controls SMD = -0.48 95%CI -1.11 to 0.15; I2 = 0%; Additional file 5). One high-quality SR reported positive effects in the intermediate term [51].

Concerning disability, two SRs with critically low and low quality that compared the effect of resistance training to non-exercise controls reported no effects at the short-term follow-up [48, 52], while one SR with moderate quality showed positive effects [45]. Our meta-analysis on two of these SRs [45, 48], showed no significant short-term effects on disability for resistance exercises when compared to non-exercising controls SMD = -0.91 95%CI -2.22 to 0.39; I2 = 70%; Additional file 5). Of the three SRs reporting intermediate/long-term effects, two SRs of low and critically low quality reported positive effects of resistance training [49, 50], and one low-quality SR reported no positive effect, all compared to non-exercising control groups [48]. Moreover, one high-quality SR compared a resistance intervention to other exercise-based controls and reported no positive effects in the intermediate-term follow-up [51]. Our meta-analysis based on two studies [48, 50] on the effects of resistance training in the intermediate/long-term on disability showed positive results when compared to non-exercise controls (SMD = -0.19, 95%CI -0.33 to -0.05; I2 = 0%; Additional file 5).

One low-quality SR (MA) [53] concluded that long-term isometric resistance exercises were effective for lowering both pain-intensity, but included mixed control groups, and did not report if the outcomes regarded short- or long-time outcomes and was therefore not included in our narrative synthesis or meta-analyses [53].

The GRADE analyses showed (Table 4) that there is moderate certainty of evidence that, compared to non-exercise controls, resistance training has a positive effect on pain in the short-term and that there is low certainty of evidence for a positive effect on disability in the intermediate/long-term. However, compared to exercise controls in the short- and intermediate/long-term, there is evidence of moderate certainty that resistance training is not better. The certainty of evidence was downgraded due to low study quality and inconsistent results.

TCE

Eight SRs were included, and these were based on 26 studies (Tables 1 and 5). The eight SRs included a total of 2,905 participants (overlap not accounted for) and investigated the effect of TCE (Qigong and Tai Chi) in patients suffering from chronic neck pain [32, 42, 54,55,56,57,58, 61]. Taking overlap into consideration 7 original studies were included. The included SRs were published between 2015 [54, 57] and 2022 [61], and the last updated search in the SRs was performed in January 2022 [61]. There was a very high overlap for TCE with a CCA of 41%. The quality of the included SRs varied from critically low [55, 58], low [54, 56, 61], moderate [32, 57] to high quality [42]. Both Qigong and Tai Chi interventions were included in the SRs. The type of Qigong varied and included Dantian, Neiyanggong, and Biyun Medical Qigong, but also included neck- and shoulder exercises and in addition moving and breathing exercises. Three SRs included Tai Chi based on the Yang style, all with different combinations of body posture, movement, breathing, meditation, relaxation, and self-massage [42, 56, 58]. Qigong was compared with other exercise types including softball and TheraBand exercises, strength and endurance training, flexibility/mobility exercises, proprioceptive exercises, neck-specific exercises, and cervical manipulation [55, 57, 58, 61]. However, most studies compared TCE to waiting list controls that received no or only minimal intervention [32, 54, 55, 57, 58, 61].

Six of the included SRs reported results on pain with a focus on Qigong and Tai Chi compared with non-exercising controls [32, 54,55,56,57,58]. TCE showed positive effects compared with wait-list controls in the short-term in three SRs, one (TCE) with low quality [54] and two (Qigong) with moderate quality [32, 57]. One SR (Qigong) with critically low study quality found no difference with the non-exercising control [55]. One SR, also with critically low study quality [58] showed varying results, in which Qigong was found to be no better than waiting list control, while Tai Chi showed positive results. Our meta-analysis of the available data in four of the included SRs [20, 54, 57, 61] showed significant positive short-term effects of TCE on pain compared with non-exercising controls (SMD = -0.63, 95%CI -0.95 to -0.32; I2 = 30%; Additional file 5). TCE was also found to be superior to non-exercising controls in the intermediate term in four SRs [32, 54, 57, 61] with SMD = -0.54, 95%CI -0.74 to -0.35; I2 = 3%; Additional file 5. Five SRs reported varying results on TCE compared with different exercise controls [42, 55,56,57,58]. Thai Chi showed positive effects compared with neck-specific exercises in the short-term in one SR with critically low study quality [58]. Compared with other exercise interventions, TCE did not show any positive effects in four SRs with critically low to moderate quality [55,56,57,58], while one SR with high study quality [42] reported that other exercise interventions were superior compared with TCE. Our meta-analysis based on data from 4 of the included SRs found non-significant results (SMD = 0.08, 95%CI -0.09 to 0.26; I2 = 19%; Additional file 5) [42, 56, 57, 61].

Five of the included SRs reported results on disability [32, 55,56,57, 61]. Qigong was found to be superior to non-exercising controls in the short-term in two SRs with moderate study quality [32, 57] while one SR [55] with low study quality found Qigong to be no better than waiting list controls. Based on data available from 2 SRs [32, 57], our meta-analysis showed significant positive short-term results on disability for TCE compared to non-exercising controls (SMD = -0.39, 95%CI -0.65 to -0.13; I2 = 0%; Additional file 5). In the intermediate term, Qigong was found to be superior to non-exercise controls in the intermediate term in one SR [55] while two SRs found Qigong to be no better than waiting list controls [32, 57] and our meta-analysis based on these SRs showed significant short-term effects on disability for TCE compared to non-exercise controls (SMD = -0.45, 95%CI -0.76 to -0.14, I2 = 52%; Additional file 5). Three SRs reported results on disability where TCE was compared with various exercising controls [55,56,57]. TCE was no better than exercise therapy in the short-term in one SR with low study quality [56] while Qigong was no better than exercise therapy in the short- as well as in the intermediate term [55, 57]. Based on data from two SRs with critically low to moderate study quality [55, 57] our meta-analysis showed no effects of short-term effects of TCE compared to exercise controls (SMD = 0.05, 95%CI -0.26 to 0.35, I2 = 0%; Additional file 5).

The GRADE analyses showed (Table 4) that there is low to moderate certainty of evidence that TCE with a focus on Qigong and/or Tai Chi has a positive effect on pain in short- and intermediate/long-term and on disability in the short-term compared to non-exercise controls. The level of evidence was downgraded due to low study quality and inconsistency. With low certainty of evidence, we found positive results for intermediate/long-term effects on disability compared to non-exercise controls. There is a moderate certainty of evidence that TCE is not effective compared to exercising controls on pain in the intermediate/long term and for disability in both the short- and long-term. The level of evidence was downgraded due to low study quality. Low certainty of evidence was found for varying results on pain when compared to exercising controls.

Yoga

Four SRs were included, and these were based on 10 studies (Tables 1 and 5). The SRs included a total of 1,246 participants (overlap not accounted for) and investigated some form of yoga in patients suffering from chronic neck pain [22, 58,59,60]. Taking overlap into consideration 10 original studies were included. The SRs were published between 2016 [60] and 2020 [58], and the last updated search in the SRs was in 2018 [22, 58]. Two of the four SRs performed an MA [22, 59]. The quality of the included SRs varied from critically low quality [58, 60], to low quality [22], to high quality [59]. There was a very high overlap with a CCA of 30%. No SR investigated the effect of yoga from a long-term perspective.

The SRs included different yoga styles, and these could include combinations of physical postures, breathing, and meditation with the aim of promoting well-being. The most-studied yoga style was Iyengar yoga (a Hata yoga, which implies a more physical-based style) which uses protocols that focus on postures (asanas) that lengthen and strengthen muscles in the neck and shoulders to improve stability, flexibility, alignment, and mobility in muscles, joints, and tendons combined with breathing regulation (pranayama) and relaxation (dyana). Some studies included Kriya and Kundalini yoga, in which one relies less on the asanas and more on energy management, meditation, and breathing techniques [59], but also lesser-known programs like the yogic mind sound resonance technique, which relies on relaxation techniques practiced in supine or sitting positions aiming to increase will power, concentration, and deep relaxation [64]. The yoga interventions were heterogeneous not only in style, but also in the length, frequency, and intensity of the sessions. The interventions were given for a period of between 10 days and 3 months and lasted between 20 min per day to 90 min a week. The control interventions were treatment such as physical therapy [58, 59], exercise [22, 60], or other active non-pharmacological control interventions, Pilates exercises, usual care, self-care information, and supine rest [58,59,60].

The narrative synthesis on pain intensity in the included SRs showed positive short-term post-intervention effects for yoga compared with no or only minimal intervention, while our meta-analysis based on two SRs with low respective high quality [22, 59] showed positive results (SMD = -1.32, 95%CI -1.84 to -0.80; I2 = 0%; Additional file 5) but there were varying results compared to general exercises [22, 58,59,60]. Narratively, two SRs with high and low quality [22, 59] showed positive effects. Regarding disability, there were short-term positive effects for yoga compared to no or only minimal intervention in our meta-analysis based on two SRs [22, 59] with low respective high quality (SMD = -1.00, 95%CI -1.47 to -0.54; I2 = 0%; Additional file 5), but not compared to general exercises [22, 58,59,60].

The GRADE analyses showed (Table 4) that there is a low certainty of evidence for positive effects in the short-term of yoga regarding pain and a moderate certainty of evidence for positive effects in the short-term of yoga regarding disability when compared to non-exercise controls. Compared to exercising controls, there was no effect with low to moderate certainty of evidence for pain and disability, respectively. The level of evidence was downgraded due to poor study quality and conflicting results. Long-term effects could not be analyzed due to a lack of studies.



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