Table 4

Incidence per 1,000 person-days of different types of musculoskeletal injuries and hazard ratios for changes in incidence between the intervention and control companies during prestudy and study periods in moderately to highly fit conscriptsa,b

Variable

Company

Prestudy period

(n = 333/291)c

Study period

(n = 315/298)c

Age-adjusted HR

(95% CI)

HR adjusted modeld

(95% CI)

Number

Incidence

Number

Incidence


Acute injuries, all

Int

160

3.05

85

1.88

0.77 (0.49 to 1.22)

0.74 (0.46 to 1.18)

Ctrl

88

2.31

86

2.00

Lower extremity

Int

82

1.56

56

1.24

0.88 (0.51 to 1.51)

0.82 (0.46 to 1.45)

Ctrl

52

1.37

55

1.28

Knee

Int

27

0.51

26

0.57

1.18 (0.51 to 2.75)

1.22 (0.49 to 3.01)

Ctrl

22

0.58

21

0.49

Ankle

Int

17

0.32

12

0.26

0.53 (0.18 to 1.51)

0.50 (0.17 to 1.46)

Ctrl

12

0.32

20

0.46

Upper extremity

Int

37

0.70

16

0.35

0.43 (0.17 to 1.09)

0.37 (0.14 to 0.99)

Ctrl

15

0.39

20

0.46

Total number of off-duty dayse

Int

600

11.4

339

7.5

0.46

(0.22 to 0.97)

0.43 (0.19 to 0.97)f

Ctrl

218

5.7

424

9.8

Discharged from military serviceg

Int

10

0.19

19

0.42

1.06 (0.34 to 3.27)

1.13 (0.36 to 3.58)f

Ctrl

8

0.21

20

0.46

Follow-up days

Int

52,542

45,316

Ctrl

38,052

43,054


aHR, hazard ratio; 95% CI, 95% confidence interval; Int, intervention company; Ctrl, control company. HRs were calculated by using the Cox proportional hazard model if not otherwise mentioned. Statistical significance level was set at P < 0.05. HRs are based on the interaction term of each study group (intervention or control), and study period was entered into the model to analyse the difference in the change in incidence between the groups. bTwo highest tertiles of conscripts according to physical fitness (Conscript's physical fitness index > 14.04 points); cnumber of conscripts in the intervention and control companies per study period; dadjusted for age, urbanisation level of the home residence, smoking, alcohol intake, earlier musculoskeletal symptoms, orthopaedic surgeries, chronic disabilities due to earlier musculoskeletal injuries, school success, previous physical activity and waist circumference (n = 10 adjusting variables); ebecause of acute injuries, rate ratio was obtained from negative binomial model; fnot adjusted for waist circumference, since 15 discharged individuals had missing information; gafter the 2-week run-in period.

Parkkari et al. BMC Medicine 2011 9:35   doi:10.1186/1741-7015-9-35

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