AbstractSubconcussive head impacts (SHI), defined as impacts to the cranium that do not
result in concussion symptoms, are gaining traction as a major public health
concern. The contribution of physiological factors such as physical exertion and
muscle damage to SHI-dependent changes in neurological measures remains unknown.
A prospective longitudinal study examined the association between physiological
factors and SHI kinematics in 15 high school American football players over one
season. Players wore a sensor-installed mouthguard for all practices and games,
recording frequency and magnitude of all head impacts. Serum samples were
collected at 12 time points (pre-season, pre- and post-game for five in-season
games, and post-season) and were assessed for an isoenzyme of creatine kinase
(CK-MM) primarily found in skeletal muscle. Physical exertion was estimated in
the form of excess post-exercise oxygen consumption (EPOC) from heart rate data
captured during the five games. Mixed-effect regression models indicated that
head impact kinematics were significantly and positively associated with change
in CK-MM but not EPOC. There was a significant and positive association between
CK-MM and EPOC. These data suggest that when examining SHI, effects of skeletal
muscle damage should be considered when using outcome measures that may have an
interaction with muscle damage.
Factors influencing limb temperature during experiments on skeletal muscle
