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The incidence of military training-related injuries in Chinese new recruits: a systematic review and meta-analysis
  1. Wei Hua1,
  2. Q Chen1,
  3. M Wan2,
  4. J Lu3 and
  5. L Xiong1
  1. 1 Department of Military Health Service, Second Military Medical University, Shanghai, China
  2. 2 Department of Orthopedics, PLA 422nd Hospital, Zhanjiang, China
  3. 3 Department of Training, Second Military Medical University, Shanghai, China
  1. Correspondence to Professor L Xiong, Department of Military Health Service, Second Military Medical University, Shanghai, CN 200433, China; xionglinping1962{at}sina.com

Abstract

Introduction Training-related injuries are the main reason for disability, long-term rehabilitation, functional impairment and premature discharge from military service. The aim of this study was to identify the incidence of injuries in the training of Chinese new recruits via a systematic review of the literature.

Method A systematic review and meta-analysis was conducted to evaluate the combined incidence of military training-related injuries in Chinese new recruits. The electronic databases of full-text journals were searched, and the Loney criteria were used to assess the quality of eligible articles. Summary estimates were obtained using random-effects models. Subgroup analyses and publication bias tests were performed.

Results Fifty-five eligible articles representing 109 611 Chinese new recruits met the inclusion criteria, of which 21 253 recruits were clinically diagnosed with military training-related injuries. The combined incidence of military training-related injuries in Chinese new recruits was found to be 21.04%.

Conclusions An increased incidence of training injuries was found in more recent years, underscoring the need for further research on the risk factors associated with their causation.

  • military training injuries
  • chinese army recruits
  • systematic review
  • meta-analysis

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Introduction

New military recruits are prone to training-related injuries, as they face a new living environment combined with high-intensity training. Training-related injuries are the main reason for disability, long-term rehabilitation, functional impairment and premature discharge from military service.1–5

During a 3-month period, the Chinese Army provides several intensive training courses for new recruits, which include running, loaded marches, shooting and drill moves. These courses are common and relatively fixed, unlike the special training and varied subjects received after entering the unit. During the past 25 years, several large-scale epidemiological studies have provided some data regarding training-related injuries in China. However, there has been no attempt to amalgamate these data. The aim of this study was to reveal the combined incidence of training-related injuries in Chinese new recruits according to injury type, character, injured body part and training subject via a systematic review and meta-analysis of previously published articles

Method

The methodology and reporting were conducted in accordance with meta-analysis of observation studies in epidemiology (MOOSE) guidelines.6

Search strategy

A literature search for relevant articles was performed using the MeSH terms ‘training’, ‘injuries’, and ‘new recruits’ in electronic databases for Chinese full-text journals (China biology medicine, China national knowledge infrastruture, ChongQing VIP and ChinaScience Periodical Database) from their inception to June 2016. The reference list of each published article was examined to identify additional relevant studies. In addition, a manual search of the references cited in all relevant original and review articles was conducted. For any articles that were not available, we attempted to obtain information from the authors by email. The literature search yielded a preliminary database of 4361 published articles, which were then reviewed for study eligibility.

Inclusion and exclusion criteria

In order to be eligible for inclusion in the meta-analysis, studies had to fulfil the following criteria: (1) the study was observational; (2) the study subjects were new recruits; (3) the main observation interval was the 3-month basic training period and the follow-up period was 1 year; (4) reported cases had military training-related injuries with a definite diagnosis; (5) the study reported the occurrence of military training-related injuries; and (6) the study reported the number of samples and cases, or the required values could be calculated according to the reported data. The exclusion criteria were as follows: (1) the study involved an investigation of training injuries in a single body region; (2) the study contained incomplete data; (3) the study included an intervention; (4) the article was a case report, review, comment or book chapter; and (5) duplicate published research.

Data abstraction and quality evaluation

Data abstraction was independently conducted by two investigators. Data retrieved from each eligible study included the following: the title, first author, year of study, geographical area and features of the study, services of the participants, sample size, number of injuries, injury type and character, injured body parts and training subjects. All information was collected using EpiData 3.0.

Quality assessment was conducted as recommended by Loney.7 The evaluation criteria consisted of eight items: (1) participants (random sample or population), (2) a description of the study procedure, (3) adequate sample size (≥300), (4) efficient diagnostic tools, (5) unbiased appraisal of the outcome, (6) adequate response rate, (7) subgroup analysis and (8) a detailed description of the participants. For each manuscript, the quality score was equal to the number of items satisfied (one point per item); thus, the score ranged from 0 to 8 points, with higher scores reflecting better quality.

In accordance with the diagnostic criteria and principles for the prevention and treatment of military training-related injuries published by the General Logistics Department of the People’s Liberation Army (PLA),8 military training-related injuries were divided into soft tissue, bone/joint and organ injuries. Soft tissue injuries mainly include brush burns (mainly refers to the skin), bruises (mainly refers to the muscle, including strain), tears (muscle, tendon, skin, not including a fracture), lower back injuries (acute or chronic injury, including prolapse of the lumbar intervertebral disc) and inflammation (tendonitis, muscle tissue inflammation, bursitis, and synovitis). Bone or joint injuries included fractures (acute or fatigue fractures), strains and dislocation. Soft tissue injuries are musculoskeletal injuries and can also be divided into acute or overuse injuries. Acute injuries included joint sprains, dislocation of the joint, bruises, brush burns, tears and acute lumbar muscle sprains. Overuse injuries included synovitis, fatigue periostitis, stress fractures, Achilles tendonitis, plantar fasciitis, chondromalacia of the patella, chronic lumbar strain and chronic aseptic inflammation. Injured body parts were divided into upper limbs, lower limbs, trunk, head, face and other. Training subjects were divided into running or loaded marches (long or short distances), tactical training, drill moves, shooting, gymnastics (horizontal bar, parallel bars, and horse-vaulting) and 400-m obstacle training.

Statistical analysis

The number of injuries and the total sample size were extracted from the original article for the calculation of the incidence of training-related injuries. A random-effects model,9 which assumes that the true underlying effect varies among the included studies, was used to estimate the incidence of training-related injuries, with a 95% CI. Heterogeneity was visually evaluated by means of the I2 statistic.10 The probability of publication bias was assessed using Egger’s regression test.11 Subgroups analyses according to service, geographical features (plateau vs cold regions), year of study (1992–2004 vs 2005–2015), injury type and characteristics, injured body part and training subject were performed using the χ2 test.

Analyses were conducted using Stata V.12.0 software (Stata, College Station, Texas). Subgroup comparisons were performed using the Statistical Package for the Social Sciences (SPSS) V.20.0 (IBM Corporation, Chicago, Illinois, USA). All statistical tests were two-tailed, and a P<0.05 was considered statistically significant.

Results

Search results and characteristics of the eligible articles

A total of 4361 relevant records were initially identified, from which 184 records were retained for further examination. An addition 63 records were excluded because of inaccurate data; 31 records were excluded because the injury prevalence could not be reasonably calculated; 10 records were excluded because the study objects included officers and other people; and 25 records were excluded for not having information regarding the sample size. Thus, 55 articles were determined to be eligible for inclusion.

The characteristics of the included studies are provided in the online supplementary table s1. The 55 eligible articles12–66 were all cross-sectional studies and represented the four services: the Army, Navy, Air Force and Armed Police Force. The main geographical features included the plateau and cold regions. In terms of quality assessment, 9 articles scored seven points, 31 articles scored six points, 13 articles scored five points and 2 articles scored four points.

Supplementary file 1

Combined incidence of military training-related injuries in Chinese new recruits

A total of 109 611 Chinese new recruits were represented in the meta-analysis, of which 21 253 had military training-related injuries that were clinically diagnosed. The incidence for military training-related injuries of the included studies ranged from 5.91% to 60.73%,7–61 with significant heterogeneity (I2=99.1%; P<0.001). Therefore, a random-effects model was used to assess the combined incidence, which was determined to be 21.04% (95% CI 18.73% to 23.35 %).

Due to incomplete data, the calculation of the combined incidence rates according to service and geographical features included only 46 articles and 9 articles, respectively. The incidence rates were significantly higher in the Air Force and Navy compared with that in the Army and Armed Police Force (P<0.05). The incidence rates for the plateau and cold regions were comparable (χ2=2.66, P=0.10), and both were lower than the total incidence rate (P<0.05). In addition, the incidence rate was higher in the more recent year group (2005–2015) compared with that in the less recent year group (1992 to 2004; χ2=112.98, P=0.00).

A publication bias was found in the total study sample, as well as in the army plateau and year of study subgroups. Details are provided in table 1.

Table 1

The combined incidence of military training-related injuries in Chinese new recruits

Combined incidence of military training-related injuries in new recruits by injury type and characteristics

The combined incidence rate for bone/joint injuries was significantly lower than that for soft tissue injuries (χ2=408.17; P=0.00), but significantly higher than that for organ injuries (χ2=314.95; P=0.00). In addition, the combined incidence rate for soft tissue injuries was significantly higher than that for organ injuries (χ2=496.73; P=0.00). Thus, the combined incidence of soft tissue injury was the highest among the three injury types. In addition, the combined incidence rate was higher for acute injuries compared with that for overuse injuries (χ2=562.62; P<0.001). Details are provided in tables 2 and 3.

Table 2

Combined incidence of military training-related injuries in new recruits by soft tissue, bone/joint and organ injuries

Table 3

Combined incidence of military training-related injuries in new recruits by acute and overuse injuries

Combined incidence of military training-related injuries in new recruits by injured body area and training subject

The combined incidence rate was significantly higher for the lower limbs compared with that for the upper limbs (χ2=3600.77; P<0.01), trunk (χ2=4749.86; P<0.01) and head, face and other body areas (χ2=4555.89; P<0.01). In addition, the combined incidence rate was significantly higher for running and loaded marches compared with that for tactical training (χ2=482.56; P<0.01), drill moves (χ2=1278.31; P<0.01), shooting (χ2=828.35; P<0.01), gymnastics (χ2=503.70; P<0.01) and 400 m obstacle training (χ2=245.40; P<0.01). Details are provided in tables 4 and 5.

Table 4

Combined incidence of military training-related injuries in new recruits by injured body area

Table 5

Combined incidence of military training-related injuries in new recruits by training subject

Discussion

The aim of this study was to conduct a meta-analysis of studies on military training-related injuries in Chinese new recruits published between 1992 and 2015. We identified 55 relevant studies, and the combined incidence was estimated to be 21.04%. Other countries have reported varying incidence rates for military training-related musculoskeletal injuries in recruits. For example, the incidence rate in the British Army during 26 weeks of training was reported to be 48.6%2; the incidence rate in the Finish Army during 6 months of training was reported to be 78%4; the incidence rate in the Norwegian Army during 6–10 weeks of training was reported to be 23.20%.5 Overall, musculoskeletal injuries have been the main study object regarding training-related injuries,1–5 and differences in the incidence rate between countries may be due to differences in the course duration, course content and intensity.

In the present study, brush burn, bruise, inflammation and lower back injuries were the most common soft tissue injuries, while stress fractures were the most common bone or joint injury. The high estimated incidence of soft tissue injury in the present study may be associated with the use of only two classification criteria for musculoskeletal injury; a number of training-induced pains and inflammation were considered soft tissue injuries. In contrast, dozens of injury categories are used in different diagnoses in other countries (eg, Norway). Furthermore, the subgroup analyses indicated that the combined incidence rate of acute injury was higher than that of overuse injury, which is inconsistent with results from other countries.4 Acute injuries are generally categorised as acute if there is a sudden onset involving known trauma, while overuse-related injuries have a gradual onset without known trauma67–69 or appear during physical activities in a previously symptomless body part.70 When an acute injury is not found or treated in time, it will develop into an overuse injury after a period of time. This may explain why the incidence rate of overuse injury in new recruits is higher with longer training durations. In addition, overuse-related injuries associated with excessive stress stimulation during the process of bone remodelling among military recruits are the result of high levels of physical activity during training.2 This phenomenon indicates that the Chinese Army pays more attention to training intensity and rhythm and less attention to avoiding sudden and accidental injuries. Thus, self-protection awareness must be strengthened in Chinese new recruits to reduce the high incidence of acute injury. In addition, the higher incidence rate in more recent years may be attributed to the poor entry-level physical quality of post-90 new recruits and underscores the need for further research on the risk factors associated with training-related injuries.

In Chinese new recruits, the majority of injuries occurred in the lower limbs, which is consistent with results from other countries. For example, a previous study reported that up to 82% of injuries in physical training occurred in the lower limbs.71 Another study involving Australian Defense Force recruits found that 48% of the injuries sustained during physical training occurred in the lower limbs.72 In addition, the majority of musculoskeletal disorders were found in the lower limbs in Norwegian (65%)5 and Finish new recruits (72%).1 As these reported statistics are percentages rather than incidence rates, they cannot be compared with the data in present study. However, it is clear that injuries are more common in the lower limbs than other body sites, which can be attributed to the strain on the lower limbs in most of the training activities.5

Among the training activities for the new recruits in China, running and loaded marches were found to cause the most injuries, which is in accordance with previous studies.71 73–75 This can be explained by a lack of physical fitness, long exercise duration, frequent exercise bouts and external loads that increase the damage to the leg, foot and knee.76 In China, numerous interventions have implemented (eg, traditional Chinese medicine, psychological training and control, health education, improvement in training methods and the use of protective equipment). Moreover, it has been indicated that the scientific arranging of training is an effective way to prevent injury.2 77 Thus, the Training-injury Prevention Research Centre of the PLA has proposed ‘Intensive cycle training,’ which has been successfully evaluated in randomised controlled trials. The method emphasises training cycles according to training intensity level (strong or weak), training location (indoor or outdoor) and body parts involved (upper or lower limbs).78

In the present study, the incidence of injury was higher in the Navy and Air Force than in the Army, which is different from the results of another study.5 There may be different levels of physical strain imposed in the different services; however, because of the heterogeneity and bias in the present study, this possibility should be viewed with caution. We also found that the incidence of injury is lower in cold regions compared with that in other regions, validating a relationship between environmental temperature and injury rate found by Knapik et al.79 The authors reported that the incidence of injury among US Army conscripts is higher in the summer than in the fall. In addition, another study pointed that snow may act like a cushion and may reduce both traumatic and overuse-related musculoskeletal disorders.1

We recognise that there are several potential limitations in the present meta-analysis. First, only cross-sectional studies were included, which can be prone to bias. Second, the standards of the PLA of China (2001) were used in the classification of training-related injuries, which is not unified with the international ICD-9 codes.80 81 Third, investigations of training-related injuries in the eligible articles lacked a unified format.

Acknowledgments

We are thankful to Editage for providing professional editing, and we thank all the authors whose articles contributed indispensable data for this meta-analysis.

References

Footnotes

  • Contributors WH and QC discussed and developed the research question for this review. WH and MW carried out the searches. WH and JL assessed the eligibility of the studies for inclusion, extracted data and carried out all analyses. All authors were involved in the interpretation and discussion of the results. WH wrote the first draft of this paper, which was reviewed by LPX, and all authors agreed on the final draft of this study. LPX is the guarantor.

  • Funding Work on this manuscript was supported by the Military Medicine Foundation of the Second Military Medical University, PLA (grant number 2014 JS21).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.