Abstract
BackgroundThe suitability of corticomotor inhibition and corticospinal excitability to measure brain health outcomes and recovery of sport-related head impact (concussion and subconcussion) depends on good inter-day reliability, which is evaluated in this study. Transcranial magnetic stimulation (TMS) reliability in soccer players is assessed by comparing soccer players, for whom reliability on this measure may be reduced due to exposure to head impacts, to generally active individuals not engaged in contact sport.MethodsTMS-derived corticomotor inhibition and corticospinal excitability were recorded from the rectus femoris muscle during two testing sessions, spaced 1–2 weeks apart in 19 soccer players (SOC—age 22 ± 3 years) and 20 generally active (CON—age 24 ± 4 years) healthy volunteers. Inter-day reliability between the two time points was quantified by using intra-class correlation coefficients (ICC). Intra-group reliability and group differences on actual measurement values were also explored.ResultsGood inter-day reliability was evident for corticomotor inhibition (ICCSOC = 0.61; ICCCON = 0.70) and corticospinal excitability (ICCSOC = 0.59; ICCCON = 0.70) in both generally active individuals and soccer players routinely exposed to sport-related head impacts. Corticomotor inhibition showed lower coefficients of variation than excitability for both groups (InhibSOC = 15.2%; InhibCON = 9.7%; ExcitabSOC = 41.6%; ExcitabCON = 39.5%). No group differences between soccer players and generally active individuals were found on the corticomotor inhibition value (p > 0.05), but levels of corticospinal excitability were significantly lower in soccer players (45.1 ± 20.8 vs 85.4 ± 6.2%Mmax, p < 0.0001). Corticomotor inhibition also showed excellent inter-rater reliability (ICC = 0.87).ConclusionsCorticomotor inhibition and corticospinal excitability are stable and maintain good degrees of reliability when assessed over different days in soccer players, despite their routine exposure to head impacts. However, based on intra-group reliability and group differences of the levels of excitability, we conclude that corticomotor inhibition is best suited for the evaluation of neuromuscular alterations associated with head impacts in contact sports.
Highlights
IntroductionInjuries of a concussive (and more recently subconcussive) nature have been at the center of attention for researchers, clinicians and sporting bodies alike
Injuries of a concussive nature have been at the center of attention for researchers, clinicians and sporting bodies alike
The sequelae of repetitive impacts to the head in soccer and other contact sports are increasingly becoming a cause for concern
Summary
Injuries of a concussive (and more recently subconcussive) nature have been at the center of attention for researchers, clinicians and sporting bodies alike Such injuries have been shown to be associated with both acute and chronic impairments to cognitive function [1,2,3], motor control [4,5,6] and brain structure [1, 7]. Our research group has shown that corticomotor inhibition is acutely and transiently modulated following a bout of soccer ball heading, suggesting increased GABA-ergic activity [14]; we are unaware of any studies examining TMS reliability in this particular population or in any other contact sport. Transcranial magnetic stimulation (TMS) reliability in soccer players is assessed by comparing soccer players, for whom reliability on this measure may be reduced due to exposure to head impacts, to generally active individuals not engaged in contact sport
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