From: Risk factors for injuries in female soldiers: a systematic review
References study type | Population | Risk factor | Key findings | Â | Score* (%) |
---|---|---|---|---|---|
1. Altarac et al. [23] cohort study | 915 female US Army recruits in 8-week basic training. Smoking history captured by self-reported survey prior to training, injuries collected via medical record review | Smoking in 1Â month prior to enlisting | Smoking vs not smoking | Â | 92 |
 |  |  | Any injury | aOR 1.61 [95% CI = 1.19–2.17] |  |
 |  |  | Traumatic | aOR 1.05 [95% CI = 0.67–1.64] |  |
 |  |  | Overuse | aOR = 1.71 [95% CI = 1.26–2.31] |  |
 |  |  |  ≥ 1 days lost injury | aOR = 1.44 [95% CI = 1.02–2.02] |  |
 |  |  |  ≥ 6 days lost | aOR = 1.75 [95% CI = 1.21–2.51] |  |
2. Anderson et al. [34] cross-sectional study | 363 female enlisted US Army soldiers from two light infantry brigades. Data collected via self-reported survey over 12 months | Age | 22–26 years (57% injured), 27–30 years (43% injured), ≥ 31 years (48% injured) |  | 60 |
 |  | BF % | ≤ 19.28% | REFERENCE |  |
 |  |  | 19.29–23.37% | RR = 0.74 [95% CI = 0.30–1.80] |  |
 |  |  | ≥ 23.38% | RR = 0.88 [95% CI = 0.53–1.47] |  |
 |  | APFT push-ups | ≥ 72 reps | REFERENCE |  |
 |  |  | 58–71 reps | RR = 1.05 [95% CI = 0.32–3.48] |  |
 |  |  | ≤ 57 reps | RR = 1.30 [95% CI = 0.44–3.82] |  |
 |  | Sit-ups | ≥ 74 reps | REFERENCE |  |
 |  |  | 63-73reps | RR = 1.09 [95% CI = 0.78–1.54] |  |
 |  |  | ≤ 62 reps | RR 1.35 [95% CI = 1.01–1.80] p = 0.03 |  |
 |  | 2-mile run time | ≤ 14.13 min | REFERENCE |  |
 |  |  | 14.14–15.67 min | RR = 0.92 [95% CI = 0.35–2.41] |  |
 |  |  | ≥ 15.68 min | RR = 1.32 [95% CI = 0.61–2.85] |  |
3. Bedno et al. [3] cohort study | All 37,413 new enlisted female US Army soldiers from Jan 2011–Jan 2014 (lower extremity ICD = 9 musculoskeletal injuries captured from inpatient or outpatient visits) | Age | 17–23 years | REF | 83 |
 |  |  | 24–28 years | OR = 1.05 [1.01–1.10] p = 0.008 |  |
 |  |  | 29–35 years | OR = 1.18 [1.11–1.26] p < 0.001 |  |
 |  |  | ≥ 36 years | OR = 1.47 [1.27–1.69] p < 0.001 |  |
 |  | BMI | Normal | REFERENCE |  |
 |  |  | Underweight | OR = 1.16 [0.99–1.36] p = 0.07 |  |
 |  |  | Overweight | OR = 1.04 [1.00–1.08] p = 0.09 |  |
 |  |  | Obese | OR = 1.03 [0.90–1.18] p = 0.68 |  |
 |  | APFT |  > 270 | REFERENCE |  |
 |  |  | 240–269 | OR = 1.11 [95% CI = 1.03–1.20] p = 0.006 |  |
 |  |  | 215–239 | OR = 1.17 [95% CI = 1.09–1.27] p < 0.001 |  |
 |  |  |  < 215 | OR = 1.45 [95% CI = 1.35–1.57] p < 0.001 |  |
 |  | Current smoking (Y/N) | (Y) | OR = 1.30 [1.23–1.36] |  |
 |  | Deployment | none | REFERENCE |  |
 |  |  | 1 | OR = 0.65 [95% CI = 0.58–0.72] p < 0.001 |  |
 |  |  | 2 | OR 0.73 [95% CI = 0.43–1.25] p = 0.258 |  |
4. Bijur et al. [9] cohort study | 85 female West Point Cadets. Data collected via medical records | Height | N/S | Â | 92 |
 |  | Mean Run time per mile | 7.2 min 42.1 injuries /100 cadets, 8.1 min 66.7 injuries /100 cadets, 8.7 min 76.2 injuries /100 cadets, 9.8 min 126.3 injuries/100 cadets |  |  |
5. Grier et al. [24] cohort study | 3856 women prior to ordinance AIT after recently finishing BCT. All data collected via self-reported survey | Age | 17–19 years | REFERENCE | 70 |
 |  |  | 20–24 years | OR = 1.29 [95% CI = 1.07–1.56] |  |
 |  |  | 25–29years | OR = 1.29 [95% CI = 0.96–1.74] |  |
 |  |  | ≥ 30 years | OR = 2.02 [95% CI = 1.43–2.87] |  |
 |  | Smoking | Non-smokers | REFERENCE |  |
 |  |  | Occasional | OR = 1.01 [95% CI = 0.74–1.39] p = 0.95 |  |
 |  |  | Frequent | OR = 0.96 [95% CI = 0.80–1.15] p = 0.65 |  |
 |  | Number of Cigarettes | None | REFERENCE |  |
 |  |  | ≤ 10 | OR = 1.04 [95% CI = 0.80–1.34] p = 0.77 |  |
 |  |  | 20-Oct | OR = 0.91 [95% CI = 0.71–1.18] p = 0.48 |  |
 |  |  | > 20 | OR = 0.89 [95% CI = 0.61–1.30] p = 0.55 |  |
6. Grier et al. [35] cross-sectional study | 498 Women at US Army Ordinance School. Physical performance data collected via military records; injuries collected via self-reported survey | Age | 17–19 years | REFERENCE | 83 |
 |  |  | 20–24 years | HR = 0.89 [95% CI = 0.68–1.16) p = 0.39 |  |
 |  |  | 25+ years | HR = 1.18 [95% CI = 0.86–1.63] p = 0.32 |  |
 |  | Smoking | Non-smokers | REFERENCE |  |
 |  |  | Occasional | HR = 1.08 [95% CI = 0.67–1.73] p = 0.77 |  |
 |  |  | Frequent | HR = 1.27 [95% CI = 0.98–1.63] p = 0.07 |  |
 |  | Number of Cigarettes | None | REFERENCE |  |
 |  |  |  ≤ 10 | HR = 1.03 [95% CI = 0.71–1.49] p = 0.89 |  |
 |  |  | 20-Oct | HR = 1.37 [95% CI = 0.95–1.97] p = 0.09 |  |
 |  |  |  > 20 | HR = 1.71 [95% CI = 1.12–2.59] p = 0.01 |  |
 |  | Injury (Y/N) | Y | HR = 1.67 [95% CI = 1.21–2.30] p < 0.01 |  |
 |  | Push-ups | 0–23 reps | HR = 1.47 [95% CI = 1.03–2.09] p = 0.03 |  |
 |  |  | 24–30 reps | HR = 1.44 [95% CI = 1.02–2.04] p = 0.04 |  |
 |  |  | 31–36 reps | HR = 1.04 [95% CI = 0.71–1.53] p = 0.84 |  |
 |  |  | 37 + reps | REFERENCE |  |
 |  | Sit-ups | 0–53 reps | HR = 1.28 [95% CI = 0.91–1.76] p = 0.16 |  |
 |  |  | 54–60 reps | HR = 1.17 [95% CI = 0.83–1.66] p = 0.36 |  |
 |  |  | 61–67 reps | HR = 1.04 [95% CI = 0.73–1.48] p = 0.82 |  |
 |  |  | 68 + reps | REFERENCE |  |
 |  | 2 Mile Run | 0–17.00 min | REFERENCE |  |
 |  |  | 17.01–18.08 min | HR = 1.46 [95% CI = 1.02–2.08] p = 0.04 |  |
 |  |  | 18.09–19.38 min | HR = 1.27 [95% CI = 0.88–1.83] p = 0.21 |  |
 |  |  | 19.39 + mins | HR = 2.04 [95% CI = 1.45–2.88] p < 0.01 |  |
7. Heller et al. [25] cohort study | 227 British Army basic training recruits. Run times collected via military records, injuries collected via medical records | 1.5 mile run time | Mean injury free time = 12min13sec, Mean Injured time = 12min43sec, Every 10 s increase in time = 8.3% greater injury risk |  | 75 |
8. Henderson et al. [36] cross-sectional study | 287 US Combat Medic Trainees. Previous injury, smoking and activity collected via self-reported survey; all other data collected via medical records | Age | < 20 years Injury Incidence 31.2% | REFERENCE | 75 |
 |  |  | 20–25 years Injury Incidence 21.3% | aOR = 0.7 [95% CI = 0.4–1.3] |  |
 |  |  | > 25 years Injury Incidence 52.9% | aOR = 3.5 [95% CI = 1.5–8.1] |  |
 |  | Previous Injury | Y Injury incidence 29.5%, N Injury Incidence 37.4% |  |  |
 |  | BMI | 17.5–21.0 kg/m2 Injury Incidence 22.1% |  |  |
 |  |  | 22.0–23.5 kg/m2 Injury Incidence 29.0% |  |  |
 |  |  | 23.6–25.3 kg/m2 Injury Incidence 27.9% |  |  |
 |  |  | 25.4–31.2 kg/m2 Injury Incidence 36.8% |  |  |
 |  |  | n/s p = 0.305 |  |  |
 |  | Body Mass | 46-57 kg Injury Incidence 22.4% | REFERENCE |  |
 |  |  | 58-63 kg Injury Incidence 30.9% | aOR = 1.5 [95% CI = 0.7–2.3] |  |
 |  |  | 64-68 kg Injury Incidence 22.2% | aOR = 1.1 [95% CI = 0.5–2.5] |  |
 |  |  | 69-95 kg Injury Incidence 41.8% | aOR = 2.4 [95% CI = 1.1–5.0] |  |
 |  | Smoking (Y/N) |  |  |  |
 |  | Activity Prior to BCT |  |  |  |
 |  | Frequency of Activity prior to BCT | Yes—Injury Incidence 23.6%, No—Injury Incidence 31.8% (n/s p = 0.190) |  |  |
 |  |  | More than most—Injury Incidence 41.9%, Somewhat more than most—Injury Incidence 25.6%, as active as most—Injury Incidence 29.5%, Less active than most—Injury Incidence 25.0% (p = 0.243) |  |  |
 |  |  | 0/week—Injury Incidence 36.4% |  |  |
 |  |  | 1–2/week– Injury Incidence 25.3% |  |  |
 |  |  | 3–4/week– Injury Incidence 31.0% |  |  |
 |  |  | 5–7/week– Injury Incidence 30.9% (p = 0.623) |  |  |
9. Jones et al. [26] cohort study | 186 women Army trainees during basic training. Previous activity self-reported via survey, all other data via medical records, | Height | Shorter 25% women at greater risk than taller 75% | RR 1.7 [95% CI = 1.2–2.4] p = 0.02 | 83 |
 |  | Body Fat % | N/S |  |  |
 |  | Body mass | N/S |  |  |
 |  | BMI | N/S |  |  |
 |  | Push-ups | N/S |  |  |
 |  | Sit-ups | N/S |  |  |
 |  | Self-reported previous activity | N/S |  |  |
 |  | Run Time | Q1 | RR = 1.16 [95% CI = 0.5–2.7] |  |
 |  |  | Q2 | RR = 1.0 |  |
 |  |  | Q3 | RR = 2.40 [95% CI = 1.2–4.8] p = 0.028 |  |
 |  |  | Q4 | RR = 2.18 [95% CI = 1.1–5.0] p = 0.063 |  |
 |  | Slow vs Fast Runners | Any injury | RR = 1.69 [95% CI = 1.2–2.4] p = 0.004 |  |
 |  |  | Lower body injury | RR = 1.78 [95% CI = 1.2–2.6] p = 0.004 |  |
 |  |  | Time loss injury | RR = 2.12 [95% CI = 1.2–3.7] p = 0.0007 |  |
 |  |  | Stress Fracture | RR = 2.54 [95% CI = 1.0–6.6] p = 0.05 |  |
10. Jones et al. [27] cohort study | 41 727 women in US Army Basic Training. Data collected via military database; injuries collected via surveillance system | 2-mile Run time | Q1 (Fastest) injury risk = 26.5% | REFERENCE | 83 |
 |  |  | Q2 Injury risk = 35% | RR = 1.3 [95% CI = 1.3–1.4] |  |
 |  |  | Q3 Injury risk = 39.3% | RR = 1.5 [95% CI = 1.4–1.5] |  |
 |  |  | Q4 Injury risk = 44.6% | RR = 1.7 [95% CI = 1.6–1.8] |  |
 |  |  | Q5 (Slowest) Injury risk = 56.0% | RR = 2.1 [95% CI = 2.0–2.2] |  |
 |  | BMI | Q1 (Lowest) Injury risk = 41.9% | RR = 1.1 [95% CI = 1.02–1.1] |  |
 |  |  | Q2 Injury risk = 39.1% | RR = 1.0 [95% CI = 0.9–1.0] |  |
 |  |  | Q3 Injury risk = 39.5% | REFERENCE |  |
 |  |  | Q4 Injury risk = 39.6% | RR = 1.0 [95% CI = 0.9–1.1] |  |
 |  |  | Q5 (Highest) Injury risk = 41.2% | RR = 1.04 [95% CI = 1.01–1.08] |  |
 |  | Slow run time and low BMI | Injury risk 63.1% | RR = 2.6 [95% CI = 2.3–2.8], p < 0.00001 |  |
 |  | Push-ups | Low vs High 48.8% to 31.6% | RR = 1.5 [95% CI = 1.49–1.61] p < 0.00001 |  |
 |  | Low BMI & Low Push-ups | Injury risk 50% | RR = 1.7 [95% CI = 1.6–1.9] |  |
11. Knapik et al. [28] cohort study | 474 women in US Army Basic Training. Smoking and physical activity history self-reported, all other data collected via medical records | Age | 17–20 years | REFERENCE | 92 |
 |  |  | 20–25 years | RR = 1.0 [95% CI = 0.8–1.3] |  |
 |  |  | 25–35 years | RR = 1.3 [95% CI = 0.9–1.9] |  |
 |  | Height | 58–62in | REFERENCE |  |
 |  |  | 63–64in | RR = 1.0 [95% CI = 0.7–1.4] p = 0.89 |  |
 |  |  | 65–66in | RR = 1.3 [95% CI = 0.9–1.9] p = 0.22 |  |
 |  |  | 67–74in | RR = 1.0 [95% CI = 0.7–0.4] p = 0.85 |  |
 |  | Mass | 90–119lbs | REFERENCE |  |
 |  |  | 120–134lbs | RR = 1.0 [95% CI = 0.7–1.4] p = 0.93 |  |
 |  |  | 135–150lbs | RR = 1.0 [95% CI = 0.7–1.5] p = 0.84 |  |
 |  |  | 151–239lbs | RR = 1.1 [95% CI = 0.8–1.6] p = 0.47 |  |
 |  | BMI | 15.81–20.54 m/kg2 | REFERENCE |  |
 |  |  | 20.55–22.98 m/kg2 | RR = 1.3[95% CI = 0.9–1.9] p = 0.15 |  |
 |  |  | 22.99–25.01 m/kg2 | RR = 0.9 [95% CI = 0.7–1.4] p = 0.78 |  |
 |  |  | 25.02–33.21 m/kg2 | RR = 1.3 [95% CI = 0.9–1.9] p = 0.10 |  |
 |  | 3.2 km Run time | 13.00–19.48 min | REFERENCE |  |
 |  |  | 19.49–21.65 min | RR = 1.5 [95% CI = 1.0–2.3] p = 0.06 |  |
 |  |  | 21.66–23.48 min | RR = 1.6 [95% CI = 1.0–2.3] p = 0.04 |  |
 |  |  | 23.49–28.68 min | RR = 1.9 [95% CI = 1.2–2.8] p < 0.01 |  |
 |  | Push-ups | 0–2 reps | RR = 1.6 [95% CI = 1.1–2.5] p = 0.02 |  |
 |  |  | 3–5 reps | RR = 1.6 [95% CI = 1.1–2.3] p = 0.02 |  |
 |  |  | 6–13 reps | RR = 1.6 [95% CI = 1.1–2.4] p = 0.02 |  |
 |  |  | 14–50 reps | REFERENCE |  |
 |  | Sit-ups | 0–22 reps | RR = 1.3 [95% CI = 0.9–2.0] p = 0.14 |  |
 |  |  | 23–33 reps | RR = 1.2 [95% CI = 0.8–1.8] p = 0.29 |  |
 |  |  | 34–44 reps | RR = 1.1 [95% CI = 0.7–1.6] p = 0.66 |  |
 |  |  | 45–80 reps | REFERENCE |  |
 |  | Smoking (Y/N) | Y | RR = 2.0 [95% CI = 12–3.5] p = 0.01 |  |
 |  |  |  > 20 Cigarettes/day | RR = 1.4 [95% CI = 1.9–10.0] p < 0.01 |  |
 |  | VO2max | 29.9–37.0 ml/kg/min | RR = 2.8 [95% CI = 1.4–5.6] p < 0.01 |  |
12. Knapik et al. [29] cohort Study | 451 women in US Army Basic Training. Smoking, injury, and activity history collected via self-reported survey; injuries collected via surveillance system | Age | 17.0–19.9 years | REFERENCE | 100 |
 |  |  | 20.0–24.9 years | HR = 1.02 [95% CI = 0.85–1.23] p = 0.84 |  |
 |  |  | 25.0–29.9 years | HR = 1.30 [95% CI = 1.01–1.66] p = 0.04 |  |
 |  |  | ≥ 30 years | HR = 1.43 [95% CI = 1.12–1.84] p < 0.01 |  |
 |  | Previous injury (Y/N) | (Y) | HR = 1.41 [95% CI = 1.13–1.75] p < 0.01 |  |
 |  | BMI | 15.20–22.12 kg/m2 | REFERENCE |  |
 |  |  | 21.30–23.80 kg/m2 | HR = 0.89 [95% CI = 0.71–1.11] p = 0.30 |  |
 |  |  | 23.81–25.97 kg/m2 | HR = 0.91 [95% CI = 0.73–1.13] p = 0.40 |  |
 |  |  | 25.98–34.02 kg/m2 | HR = 0.89 [95% CI = 0.71–1.11] p = 0.28 |  |
 |  | Push-ups | 0–4 reps | HR = 1.92 [95% CI = 1.41–2.59] p < 0.01 |  |
 |  |  | 5–13 reps | HR = 1.36 [95% CI = 0.99–1.86] p = 0.06 |  |
 |  |  | 14–22 reps | HR = 1.20 [95% CI = 0.87–1.65] p = 0.27 |  |
 |  |  | 23–62 reps | REFERENCE |  |
 |  | Sit-ups | 0–20 reps | HR = 1.75 [95% CI = 1.29–2.37] p < 0.01 |  |
 |  |  | 21–33 reps | HR = 1.34 [95% CI = 0.98–1.83] p = 0.07 |  |
 |  |  | 34–46 reps | HR = 1.10 [95% CI = 0.79–1.51] p = 0.58 |  |
 |  |  | 47–89 reps | REFERENCE |  |
 |  | 2 Mile Run | 12.3–19.4 min | REFERENCE |  |
 |  |  | 19.5–22.1 min | HR = 0.99 [95% CI = 0.71–1.38] p = 0.94 |  |
 |  |  | 22.2–24.7 min | HR = 1.14 [95% CI = 0.82–1.59] p = 0.43 |  |
 |  |  | 24.8–31.3 min | HR = 2.18 [95% CI = 1.60–2.98] p < 0.01 |  |
 |  | Smoking | 0 | REFERENCE |  |
 |  |  | 1–9/day | HR = 1.44 [95% CI = 1.19–1.73] p < 0.01 |  |
 |  |  | 10–19/day | HR = 1.47 [95% CI = 1.17–1.89] p < 0.01 |  |
 |  |  | ≥ 20/day | HR = 1.90 [95% CI = 1.34–2.68] p < 0.01 |  |
 |  | Frequency of ex before BCT | ≤ 1/week | HR 1.41 [95% CI = 1.09–1.82p p < 0.01 |  |
 |  | Frequency of running before BCT | ≤ 1/week | HR = 1.62 [95% CI = 1.16–2.27] p < 0.01 |  |
13. Kodesh et al. [30] cohort study | 158 females on IDF Combat Fitness Instructor Course. All data collected via medical records | Power Performance including 10 m sprint, single leg triple hop drop jump, CMJ | All power tests n/s except, L triple hop (cm) 418 (254–559) vs 446.5 (199–584) p = 0.029, R triple hop distance (cm) 434 (287–536) vs 460 (263–546) p = 0.047) |  | 67 |
 |  | Body Fat % | BF% 23.7 (20.5–29.2) vs 22.5 (14.9–31.5) p = 0.047 |  |  |
 |  | BMI | BMI 21.14 [18.06–25.79) injured vs 20.70 [16.16–32.03] not injured |  |  |
 |  | FMS | FMS n/s |  |  |
 |  | 2 km Run | 258 (578–776) sec vs 640 (488–804) sec p = 0.044 |  |  |
14. Krauss et al. [31] cohort study | 1900 US Army recruits during first 183 days of service from six locations in the US. Data collected via military and medical records | Fit vs unfit | Non stress fracture | IRR = 1.32 [95% CI = 1.14–1.53] | 75 |
 |  |  | Stress fracture | IRR = 1.62 [95% CI = 1.19–2.21] |  |
 |  |  | Non stress fracture | IRR = 1.27 [95% CI = 1.07–1.50] |  |
 |  | Fit (high % BF vs low % BF) | Stress fracture | IRR = 0.79 [95% CI = 0.49–1.28] |  |
15. Rappole et al. [1] cohort study | 369 US female Army Soldiers from Combat Arms, Combat Support and Combat Service Support. Injury data collected via medical records, other data via self-reported survey | Age | n/s | Â | 67 |
 |  | 2-mile run | n/s |  |  |
 |  | Push-ups | n/s |  |  |
 |  | Sit-ups | n/s (at 0.05) |  |  |
 |  | Unit PT resistance training | ≥ 1/week | OR 1.96 [95% CI = 1.20–3.21] p < 0.01 |  |
 |  | Personal PT run distance | > 1 mile | OR 1.57 [95% CI = 0.98–2.52] p = 0.06 |  |
 |  | Personal PT interval freq | None/ < 1/week | OR 1.64 [95% CI = 1.00–2.71] p = 0.05 |  |
16. Roy et al. [2] cohort study | 625 US Army female soldiers within three brigade combat teams Injuries collected via self-reported survey | Deployment | 0 | RR = 1.48 [95% CI = 1.02–1.71] | 75 |
 |  |  | 1 | RR = 1.22 [95% CI = 0.84–1.78] |  |
 |  |  | ≥ 2 | REFERENCE |  |
 |  | Injury History (Y/N) | (Y) | RR = 2.6 [95% CI = 2.06–3.28] |  |
 |  | 2-mile Run time | ≤ 17 min | REFERENCE |  |
 |  |  | 17.01–18.0 | RR = 1.71 [95% CI = 1.07–2.73] |  |
 |  |  | > 18 min | RR = 1.41 [95% CI = 0.90–2.19] |  |
 |  | Unit Runs/week | 0 | RR = 1.526 [95% CI = 1.07–2.19] |  |
 |  | Pers. PT/week | 0 | REFERENCE |  |
 |  |  | 2-Jan | RR = 1.42 [95% CI = 1.08–1.87] |  |
 |  |  | ≥ 3 | RR = 1.31 [95% CI = 0.94–1.83] |  |
 |  | APFT score | < 220 | RR = 1.74 [95% CI = 1.01–3.02] |  |
 |  |  | 220–249 | RR = 2.01 [95% CI = 1.19–3.38] |  |
 |  |  | 250–289 | RR = 1.7 [95% CI = 1.02–2.86] |  |
 |  |  | ≥ 290 | REFERENCE |  |
17. Roy et al. [32] cohort study | 57 female soldiers from US infantry or support battalions on deployment in Afghanistan in 2012. Data collected by self-reported survey | Work type | Physically demanding | RR = 6.0 [95% CI = 1.50–23.99] | 67 |
 |  | Miles walked/day | > 4 | RR = 3.0 [95% CI = 1.52–5.93] |  |
 |  | Avg worn load | > 30 lb | RR = 2.44 [95% CI = 1.7–4.36] |  |
 |  | Weight of avg lifted object | > 50 lb | RR = 2.3 [95% CI = 1.19–4.45] |  |
18. Roy et al. [33] cohort study | 160 female soldiers from three brigade combat teams deployed to Afghanistan for nine months. Data collected via self-reported survey | Wearing load | > 10% body weight | RR = 2.0 [95% CI = 1.31–3.06] | 100 |
 |  |  | Heaviest load > 15% | RR = 5.83 [95% CI = 1.51–22.50] |  |
 |  | Wearing armour | 1–4 h | RR = 1.62 [95% CI = 1.002–2.62] |  |
 |  |  | > 4 h | RR = 1.84 [95% CI = 1.03–3.27] |  |
 |  | Wearing backpack | Y | RR = 1.85 [95% CI = 1.23–2.80] |  |
 |  | Occupational tasks | Lifting > 22.68 kg | RR = 1.96 [95% CI = 1.08–2.97] |  |
 |  |  | Lifting objects 1–2 × day | RR = 1.73 [95% CI = 1.002–2.97] |  |
 |  |  | Carrying objects > 7.62 m | RR = 2.01 [95% CI = 1.19–3.42] |  |
 |  | Y balance score | < 95.23 | RR = 1.71 [95% CI = 1.13–2.60] |  |