The influence of baseline plasma fibrinogen on responses to an accumulative brisk walking intervention

Plasma fibrinogen (PF) is a commonly used marker of coagulation and inflammation, particularly in physical activity (PA) interventions, to assess change in cardiovascular disease risk. However, such studies have shown equivocal results. Since many physiological factors" baseline measures influence the potential for change due to exercise intervention, few of these studies have considered PF baseline measures.PURPOSE Therefore, the purpose of this study was to determine whether 24 weeks of accumulative brisk walking could decrease plasma fibrinogen and whether baseline PF affects the outcomes.METHODS 52 non-smoking sedentary males (54 ± 8.1 years), who were asymptomatic of cardiovascular disease and diabetes completed a 24-week randomised controlled walking trial. Participants were randomly allocated into one of the following three groups: control (CON); single bout of brisk walking per day (SBW); or accumulative bouts of brisk walking (ABW). Each walking group performed 30 minutes of walking ≥65% HRmax per day on 5 days of the week, with ABW accumulating their walking in 3×15 or 2×15 minute bouts. Pre- and post-intervention fasting blood samples were collected. The samples were assessed using a clotting technique and analysed using a one-way ANOVA and also two-way ANCOVA, with baseline plasma fibrinogen as a co-variate. One-way ANOVA was employed to assess differences between groups at baseline and Pearson"s correlations were used to assess the relationships.RESULTS There was a main effect of walking compared to CON on PF using one-way ANOVA (P=0.027) and ANCOVA (P=0.039). PF increased by 0.18 ± 0.66 g·L-1 in CON, but decreased by -0.34 ± 0.57 g·L-1 in SBW (P=0.268) and -0.30 ± 0.62 g·L-1 in ABW. However, when applying one-way ANOVA to the delta scores, the decrease in PF observed in SBW (P=0.052) approached significance, but not ABW (P=0.077), whereas applying an ANCOVA determined that ABW (P=0.040) significantly decreased PF but not SBW (P=0.268). Despite there being no significant differences between groups at baseline, Pearson's correlation demonstrate that those with higher baseline PF generally reduced PF greater than those with lower baseline PF.CONCLUSION The data suggest that baseline PF affects changes in PF and baseline PF should be considered when investigating the effect of interventions on PF.