Fibrinogen is negatively correlated with aerobic working capacity in football players.

While it is well established that blood viscosity is decreased in sportsmen and related to fitness, the involvement of fibrinogen in this relationship is less well defined. Relationships among fitness, rheology and fibrinogen were investigated in 32 football players (age 17-33 years: 19 professionals and 13 leisure players). A submaximal 25 min exercise-test was performed and allowed the calculation of aerobic working capacity. Aerobic working capacity (W170 and VO2 max) was negatively correlated to fibrinogen (r = -0.531, p < 0.01 and r = -0.623, p < 0.01), while on the whole sample the correlation to viscosity and erythrocyte aggregation was not significant. When subjects were divided into two subgroups according to their plasma fibrinogen concentration, the aerobic working capacity (either expressed as W170 or VO2 max) is higher when plasma fibrinogen level is lower than 2.7 g/l. Thus, there is a highly significant negative correlation between fibrinogen and fitness in these sportsmen, independent of blood rheology. These data suggest that rheology and fibrinogen are to some extent separate determinants of an individual's fitness.