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Table 4 Hazard ratios (HR) for any acute injury (AI) and severe acute injury (severe AI) incidence by physical fitness variables at baseline

From: Risk factors of acute and overuse musculoskeletal injuries among young conscripts: a population-based cohort study

Baseline variable Category Total number (% of experienced AI; % of experienced severe AI) HR for AI incidence (n = 386)* HR for AI incidence
(n = 386)**
HR for severe AI incidence (≥7 service days lost) (n = 89)* HR for severe AI incidence (≥7 service days lost) (n = 89)**
Self-assessed physical fitness1 Good or very good 323 (29; 6) 1 (Referent) 1 (Referent) 1 (Referent) 1 (Referent)
Average or inferior 1066 (27; 6) 1.0 (0.8–1.3) 0.9 (0.7–1.1) 1.2 (0.7–2.0) 0.8 (0.5–1.5)
Cooper’s test (12-min running test) Excellent (≥3000 m) 51 (22; 0) 1 (Referent) 1 (Referent) 1 (Referent) 1 (Referent)
Good (≥2600 m) 330 (26; 5) 1 (Referent) 1 (Referent) 1 (Referent) 1 (Referent)
  Fair good (≥2200 m) 630 (28; 7) 1.2 (0.9–1.5) 1.1 (0.8–1.4) 1.6 (0.9–2.9) 1.3 (0.7–2.3)
  Poor (<2200 m) 358 (28; 7) 1.3 (1.0–1.7) 1.2 (0.9–1.7) 1.9 (1.0–3.5) 1.3 (0.6–2.7)
Push-up test (repeats per 60 seconds) Excellent (≥38) 450 (26; 5) 1 (Referent) 1 (Referent) 1 (Referent) 1 (Referent)
Good (≥30) 312 (25; 4) 0.9 (0.7–1.3) 0.9 (0.7–1.2) 0.9 (0.4–1.7) 0.7 (0.4–1.5)
Fair good (≥22) 350 (28; 7) 1.1 (0.8–1.5) 1.0 (0.7–1.3) 1.4 (0.8–2.5) 0.9 (0.5–1.7)
  Poor (<22) 266 (32; 10) 1.4 (1.1–1.9) 1.2 (0.9–1.6) 2.2 (1.3–3.9) 1.7 (0.9–3.1)
Standing long jump test (two attempts, best result) Excellent (≥2,40 m) 241 (22; 3) 1 (Referent) 1 (Referent) 1 (Referent) 1 (Referent)
Good (≥2,20 m) 363 (28; 6) 1.3 (0.9–1.8) 1.2 (0.8–1.6) 1.8 (0.8–4.1) 1.6 (0.7–3.7)
Fair good (≥2,00 m) 442 (30; 6) 1.4 (1.0–1.9) 1.2 (0.9–1.7) 1.9 (0.9–4.2) 1.7 (0.7–3.8)
  Poor (<2,00 m) 332 (28; 9) 1.4 (1.0–2.0) 1.2 (0.9–1.8) 3.3 (1.5–7.1) 2.8 (1.2–6.4)
Conscript’s muscle fitness index 2 Excellent (13–15 points) 169 (21; 4) 1 (Referent) 1 (Referent) 1 (Referent) 1 (Referent)
Good (9–12 points) 361 (30; 6) 1.5 (1.0–2.2) 1.4 (1.0–2.1) 1.7 (0.7–4.3) 1.6 (0.6–4.0)
  Fair good (5–8 points) 472 (27; 6) 1.4 (0.9–2.0) 1.2 (0.8–1.8) 1.9 (0.8–4.6) 1.4 (0.6–3.6)
  Poor (0–4 points) 376 (29; 8) 1.6 (1.1–2.4) 1.3 (0.9–2.0) 2.6 (1.1–6.3) 1.8 (0.7–4.6)
Conscript’s physical fitness index3 Excellent (≥21,00) 69 (16; 0) 1 (Referent) 1 (Referent) 1 (Referent) 1 (Referent)
Good (17.00 − 20.99) 409 (29; 6) 1 (Referent) 1 (Referent) 1 (Referent) 1 (Referent)
  Fair good (13.00 − 16.99) 590 (27; 7) 1.0 (0.8–1.3) 0.9 (0.7–1.1) 1.5 (0.9–2.4) 1.1 (0.6–1.9)
  Poor (<13.00) 297 (29; 8) 1.2 (0.9–1.6) 1.0 (0.7–1.4) 1.9 (1.1–3.4) 1.3 (0.6–2.6)
Combination of standing long jump and push–up test Excellent4 144 (18; 2) 1 (Referent) 1 (Referent) 1 (Referent) 1 (Referent)
Good5 447 (30; 6) 1.7 (1.1–2.6) 1.4 (0.9–2.2) 3.0 (0.9–9.8) 2.5 (0.8–8.4)
Fair good6 650 (27; 6) 1.6 (1.1–2.4) 1.3 (0.8–2.0) 3.0 (0.9–9.6) 2.1 (0.6–6.9)
  Poor7 137 (33; 14) 2.5 (1.5–4.0) 1.8 (1.0–3.0) 8.8 (2.6–29.8) 5.9 (1.6–21.3)
Combination of standing long jump and Cooper’s test Excellent4 136 (21; 2) 1 (Referent) 1 (Referent) 1 (Referent) 1 (Referent)
Good 5 504 (28; 6) 1.4 (0.9–2.1) 1.4 (0.9–2.0) 3.0 (0.9–9.8) 2.7 (0.8–9.0)
Fair good6 550 (27; 6) 1.4 (0.9–2.1) 1.2 (0.8–1.9) 2.8 (0.9–9.2) 2.4 (0.7–8.1)
  Poor7 175 (31; 12) 1.9 (1.2–2.9) 1.7 (1.0–2.8) 7.0 (2.1–23.6) 5.8 (1.6–21.3)
  1. Variable distribution was charted in 1411 male conscripts during the first two weeks of military service and discharge outcomes were registered during the following 6-month military service.
  2. Statistically significant (p< 0.05) findings are indicated with bold type.
  3. *Adjusted for age (univariate).
  4. **Adjusted for age, company, smoking (previous or current smoker), frequency of drunkenness, baseline medical conditions (sum factor of earlier musculoskeletal symptoms, sports injury during the last month before entering the military), school success (educational level and grades combined), urbanisation level of the place of residence and waist circumference.
  5. 1Compared to age mates.
  6. 2Muscle fitness index is the sum of individual muscle fitness test results including push-up, sit-up, pull-up, standing long jump and back lift tests.
  7. 3Conscript's physical fitness index (CPFI) = (12-min running test result (m) + 100 × muscle fitness test points) / 200.
  8. 4Excellent or good result in Cooper's test and excellent result in selected muscular fitness test.
  9. 5Excellent result in selected muscular fitness test and fair good or poor result in Cooper's test; or excellent result in Cooper's test and good, fair good, or poor result in selected muscular fitness test.
  10. or good result in Cooper's test and good or fair good result in selected muscular fitness test; or fair good result in Cooper's test and good result in selected muscular fitness test.
  11. 6Poorer results than aforementioned, except the combination of poor results in both tests.
  12. 7Poor result in both tests.