Biomarkers Differ Between And Within Starters And Non-Starters Throughout A Collegiate Soccer Season

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PURPOSE: To observe differences in blood biomarkers (oxygen (O2) transport, immune, cardiovascular (CV) health and hematology) between starters (S) and non-starters (NS) over a full NCAA Division 1 collegiate men’s soccer season. METHODS: Biomarkers (n = 30) related to O2 transport (n = 9), immune function (n = 12), and CV and lipid profiles (n = 9) were collected at the start of pre-season (PS), in-season at weeks (W)1, 4, 8 and 12 in soccer players (n = 20, mean ± SD; age = 21 ± 1, height = 180 ± 6 cm, body mass = 78.19 ± 6.3 kg, body fat = 12.0 ± 2.6%, VO2max = 51.5 ± 5.1 ml·kg-1·min-1). A 2 x 5 (group x time) repeated measures ANOVA was used to identify differences between S (n = 10) and NS (n = 10). In the presence of a significant interaction effect (p<0.05), post-hoc one-way ANOVAs and paired tests were used to identify group and time differences with uncorrected alpha level set at p<0.05. RESULTS: A significant interaction effect (group x time) was found for 9 biomarkers (hematocrit [HCT], hemoglobin [HGB], red blood cells [RBC], total cholesterol [Total Chol], LDL cholesterol [LDL], Chol:HDL ratio, non-HDL cholesterol [non-HDL], direct LDL [dLDL] and apolipoprotein B [ApoB]). S demonstrated significant increases in RBC (W1) and Chol:HDL (W8), while NS demonstrated significant increases in HCT and HGB (W4); Chol:HDL (W4, 12). Within-group significant differences were found between PS and W1 for NS (HCT, HGB, RBC, Total Chol, LDL, Chol:HD, Non-HDL, ApoB) and for S (Chol:HDL, non-HDL, dLDL). HCT, HGB, RBC, LDL, Non-HDL, Direct LDL and Apo B were different in NS from W1 to W4, while only Apo B was different in S. From PS to W12, Total Chol, LDL, and non-HDL were significantly different for NS while HCT, HGB, Chol:HDL, and non-HDL were different in S. CONCLUSIONS: Our findings indicate that there are differences between and within S and NS for many biomarkers related to O2 transport, immune, CV health and hematology throughout a collegiate men’s soccer season. Thus, future analyses should account for playing status as a covariate. From a clinical perspective, while all biomarkers were within normal reference ranges, sports medicine personnel should account for playing status and inter-individual differences when tracking or diagnosing athletes who demonstrate signs of clinical pathologies associated with these biomarkers.