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Risk reduction
Isometric cervical muscle strength mitigates head impact severity
  1. Julianne Denice Schmidt1,*,
  2. Kevin M Guskiewicz1,2,
  3. Jason P Mihalik1
  1. 1Matthew A Gfeller Sport-Related Traumatic Brain Injury Research Center, Department of Exercise and Sport Science, University of North Carolina, Chapel Hill, North Carolina, USA
  2. 2Injury Prevention Research Center, University of North Carolina, Chapel Hill, North Carolina, USA


    Objective To compare the risk of sustaining a mild, moderate, and severe head impact between athletes with high and low isometric cervical strength.

    Design Prospective cohort.

    Setting Clinic/On-field.

    Participants Twenty-one collegiate American football players.

    Interventions Isometric strength was measured prior to the season using a handheld dynamometer in four directions: flexion, anterolateral-flexion, rotation, and posterolateral-extension. Participants completed three 3 s trials. We used the Head Impact Telemetry System to record head impact biomechanics (N=8649 head impacts) at practices and games.

    Main Outcome Measurements Peak force values were averaged across trials and sides and then normalised to body mass. Players were categorised as either high or low performers based on a 50th percentile cut-off separately for each direction and for composite strength (sum across each direction). Using previous values, each head impact was categorised as mild (linear acceleration ≤66 g), moderate (>66 g or <106 g), or severe (≥106 g). The risk of sustaining mild, moderate, and severe head impact between high- and low-strength athletes were computed using risk ratios.

    Results Players with low flexion, posterolateral-extension, and composite strength had a greater risk of sustaining moderate (RR=2.0, 1.8, 1.6, respectively) and severe (RR=1.6, 1.1, 1.2, respectively) impacts. Players with weaker anterolateral-flexors had a reduced risk of sustaining moderate (RR=0.8) and severe (RR=0.7) impacts.

    Conclusions The cervical musculature may play a role in mitigating head impact severity among collegiate football players. Sports medicine professionals and strength and conditioning coaches should continue exploring the potential benefits of cervical strengthening programmes on head injury prevention.

    Acknowledgements The authors thank Breton Asken for his assistance during data collection.

    Competing interests None.

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