Prevention of Injuries and Musculoskeletal Disorders in the Defence Forces
Condition: Musculoskeletal Injury
MeSH terms: Wounds and Injuries
Study type: Interventional

Summary: 
      The purpose of this study was to investigate the effect of an exercise-based
      injury-prevention program on the incidence of musculoskeletal injury, motor performance and
      psychosocial status. 36 Estonian Military Academy cadets were randomly assigned into either
      an intervention or control group. The intervention group followed a neuromuscular
      exercise-based injury-prevention warm-up program, 3 times per week for 6 months. The control
      group continued with the usual warm-up. The main outcome measure was injury incidence during
      the study period. Additionally, evaluation of isokinetic lower-extremity strength, postural
      sway, physical fitness and psychosocial status was included pre- and post-intervention.
    

Detailed description: 
      Injury incidence

      The primary outcome of interest in our study was incidence of musculoskeletal injury during
      the 6-month study period. Injury tracking was performed through the Estonian Defence Forces
      medical database. Since participants receive health care through the military health care
      system, any musculoskeletal condition severe enough to seek treatment from a medical provider
      is registered. Additionally, participants were asked to recall any musculoskeletal conditions
      at 3 and 6 months from the beginning of the study in order to catch potential injuries not
      reported to a military medical provider, or for which they might have obtained treatment from
      a nonmilitary medical care provider.

      Motor performance testing

      Prior to motor performance testing, baseline body mass (kg) and height (cm) were measured.
      Based on these body mass index (BMI) was calculated (BMI = weight (kg) / height (m)²). Before
      testing motor performance participants performed a 10-min individual warm-up - jogging, and
      range of motion and bodyweight strength exercises.

      Isokinetic muscle strength testing

      Strength parameters of the knee flexor and extensor muscles were recorded using a
      computerized dynamometer (CON-TREX® MJ, Physiomed Elektromedizin AG, Germany). Participants
      were seated upright with a hip flexion of 85°, the trunk stabilized with two 3-point seat
      belts and arms folded across the chest. The extremity to be tested was supported at the
      distal thigh with a Velcro strap. The distal shin adapter was attached 2-3 cm proximal to the
      lateral malleolus using a Velcro strap. The alignment of the rotational axis of the
      dynamometer was set so it would pass transversely through the femoral condyles, 1.5 finger
      width above joint space and vertical above head of fibula. The peak torque of knee flexion
      and extension was measured in concentric mode at an angular velocity of 60°/sec between a
      knee flexion of 10° and 90° (0° = full extension). For task-specific warm-up, the
      participants performed three submaximal knee flexion-extension movements. The test procedure
      included 3 maximal, consecutive flexion-extension movements. The participants were given
      verbal encouragement to flex and extend the leg as fast and forcefully as possible. Based on
      flexion-extension peak torque measurements hamstring/quadriceps ratio was calculated (H:Q =
      (flexion peak torque / extension peak torque) x 100%). Additionally, H:Q and peak torque
      differences between left and right lower extremity were calculated.

      Postural sway measurement

      A force platform (Kistler 9286A, Switzerland, dimensions 40 x 60cm) and biomechanical
      movement analysis system Elite Clinic with Sway software® (BTS S.p.A., Italy) were used to
      assess the equivalent area (EqArea) of the center of pressure sway. Participants were asked
      to maintain balance while standing on a single leg for 30 sec. For familiarization, the
      participants balanced 30 sec on each leg. Based on the measurements obtained, the difference
      of the EqArea between the left and right legs was calculated.

      Physical fitness test

      Participant physical fitness was assessed with a test consisting of a 2-min maximal-effort
      push-up event, a 2-min maximal-effort sit-up event and a 3.2 km timed run.

      Psychosocial status

      To assess participant psychosocial status, the RAND 36-item Health Survey 1.0 was used. All
      items in this survey are scored on a scale from 0 to 100, with a high score defining a more
      favorable health state. For analysis, the following subscales were used: physical
      functioning, role limitations due to physical health problems, role limitations due to
      personal or emotional problems, energy/fatigue, emotional well-being, social functioning,
      bodily pain and general health perception.

      Exercise intervention

      Participants in the INT group were asked to follow a prescribed injury-prevention program
      (PP) during warm-up before physical training for 6 months, 4 times per week. The PP was a
      structured warm-up routine, taking 20 min to finish. It was divided into 3 sequential parts:
      (1) whole-body range of motion and bodyweight strength exercises, (2) aerobic load - jogging,
      and (3) jump, balance and running exercises with a change of direction. A written PP
      description was provided. INT group participants were instructed on correct PP execution
      during a workshop led by a physical therapist. Also, detailed written instructions and online
      video materials were provided to ensure correct program execution. During the study period,
      no supervision on PP execution technique was provided. Participants in the CON group were
      asked to continue with their regular training and warm-up without any restrictions. The usual
      warm-up in the CON group involved a combination of aerobic exercises and range of motion
      exercises.

      Statistical analysis

      Descriptive statistics (mean, SD) in both groups were calculated. Differences between INT and
      CON groups were analyzed using an independent sample Student's t-test, and within-group
      differences between time points were analyzed using a dependent-sample paired t-test if the
      assumptions of a normal distribution and homogeneity of variances were satisfied. Normality
      of distribution was controlled using the Shapiro-Wilk test. Homogeneity of variances was
      controlled with Levene's test. If the previous assumptions for the t-test were not met, the
      between-group differences were analyzed with the non-parametric Wilcoxon test, and
      within-group differences between time points were analyzed using the dependent-sample paired
      Wilcoxon test. Bonferroni correction was applied to account for possible false positives due
      to the number of tests. Relative risk (RR) and 95% confidence intervals (95% CI) for
      between-group injury incidence were calculated. The level of significance was set at p <
      0.05. R version 4.1.1 and RStudio version 1.4.1717 were used for statistical analysis.
    

Intervention name(s): Neuromuscular exercise based injury-prevention program
Intervention type(s): Other
Intervention description(s): Neuromuscular exercise based injury-prevention program
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention