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International Journal of Interdisciplinary Research

Table 2 Effect of the total helmet weight on the muscle strain of the left splenius capitis during sitting, horizontal lifting and prone shooting described as changes in %MVC (N = 8)

From: Physiological and psychological neck load imposed by ballistic helmets during simulated military activities

Movements NH LH HH HH and NVD P value
 Sitting  
 %MVC 1.99 ± 1.26 2.21 ± 1.34 2.73 ± 1.38 2.60 ± 1.90
 ΔHEL 1.0 ± 0.0 1.24 ± 0.91 1.70 ± 1.67 1.42 ± 0.88
 ΔMOV 1.0 ± 0.0 1.0 ± 0.0 1.0 ± 0.0 1.0 ± 0.0
Horizontal lifting
 %MVC 3.81 ± 1.69 5.06 ± 2.46 4.97 ± 2.30 6.09 ± 2.80† 0.014
 ΔHEL 1.0 ± 0.0 1.19 ± 0.25 1.25 ± 0.29 1.57 ± 0.34  
 ΔMOV 2.7 ± 1.5 2.8 ± 1.5 2.4 ± 1.3 3.3 ± 2.2  
Prone shooting
 %MVC 7.07 ± 3.67 9.05 ± 3.98 8.97 ± 5.36 9.17 ± 3.50 0.919
 ΔHEL 1.0 ± 0.0 1.20 ± 0.58 1.29 ± 0.47 1.33 ± 0.60  
 ΔMOV 6.3 ± 5.4 5.4 ± 4.8 5.8 ± 5.9 5.1 ± 4.1  
P     
  1. %MVC muscle strain normalized by its maximal voluntary contraction activity, ΔHEL a mean of individual changes in %MVC in comparison with NH (in times), ΔMOV a mean of individual changes in %MVC compared to the sitting posture (in times), NH No Helmet, LH 1.15 kg helmet, HH 1.5 kg helmet, HH and NVD 1.5 kg helmet with a night vision device (total weight = 2.1 kg)
  2. The values represent the neck pain when each posture lasted for 8 min. Data are shown as the mean ± SD
  3. P < 0.05 indicates the helmet effects versus NH; Friedman test used for identifying the group differences using a Wilcoxon test as a post-hoc test