Serum S-100B protein levels in young amateur soccer players after controlled heading and normal exercise

Repeated impacts by heading might lead to significant head injuries in soccer players comparable to those of patients with accidental minor traumatic brain injury (TBI). The neuroprotein S-100B released into the circulation is suggested to be a reliable marker indicating brain damage. The objective was to evaluate the neuroprotein S-100B serum levels in young amateur soccer players early after controlled heading compared to early measurements after normal exercise as well as in other patients after minor TBI.

Sixty-one male amateur soccer players (median age 15.3 years) performed controlled heading aimed at the forehead for 55 minutes. Data were compared to 58 male amateur soccer players (15.9 years) performing 61 minutes of normal exercise training without head contact and 81 young male patients early after TBI who underwent computed tomography (CCT) for detection of intracranial lesions. First venous blood samples were drawn before the training sessions, second and third samples 60 and 360 minutes after heading or 64 and 355 minutes after exercise, respectively, 65 and 366 minutes after TBI.

Median S-100B serum levels of the heading group only slightly increased from 0.15 ng/ml to 0.18 ng/ml 60 minutes after end of training. Within 360 minutes S-100B values decreased again to 0.15 ng/ml reaching the initial values. S-100B serum values of the exercise group showed a similar transient increase exhibiting significant lower levels before exercise (0.10 ng/ml) as well as 64 minutes (0.11 ng/ml) and 355 minutes after exercise (0.09 ng/ml) compared to the heading group. According to age stratification in the heading group, starting median S-100B levels were significantly higher in subjects with 12-13 years (0.22 ng/ml) and 14-15 years (0.17 ng/ml) compared to those with 16-17 years of age (0.06 ng/ml). None of the subcollectives did reach median S-100B levels of the CCT+ group (n = 20) at admission (0.62 ng/ml) or 366 minutes later (0.32 ng/ml), which were significantly elevated compared to those of the CCT group (n = 61) at admission (0.10 ng/ml) or 370 minutes later (0.08 ng/ml).

Controlled repetitive heading in young amateur soccer players leads to a transient increase between 60 to 360 min after training, but does not appear to evoke a longer lasting S-100B release into serum indicating cellular brain damage. After heading S-100B levels are significantly elevated compared to normal exercise. Although soccer players with 12-13 years and 14-15 years revealed significantly higher S-100B values than with 16-17 years of age, the transient increase is independent of the age-related starting values. However, since brain damage due to abrupt heading a ball of high speed or accidental trauma during regular soccer games cannot be excluded, S-100B measurements in soccer players are initiated during video-controlled soccer games.