Promoting athlete health and performance : the role of haemostatic changes in response to exercise

\\(Background\\) Athletes are frequently exposed to training- and competition-induced risk factors that increase the risk of injury and illness, including venous thromboembolism (VTE). Whilst VTE is frequently associated with physical inactivity and non-athletic populations, approximately 1 in 1000 athletes will experience a post-exercise thrombotic episode, similar to that of the general population. \\(Aims\\) The overarching aim of the series of studies completed in this thesis was to investigate factors that may influence the overall haemostatic response, as demonstrated by activation of the coagulation and fibrinolytic systems in well-trained athletes. To investigate this aim, four studies were undertaken. The first study aimed to examine the validity of a new cycling ergometer, the Wahoo KICKR Power Trainer (KICKR). The second study aimed to investigate the reliability of a performance test, a 4km cycling time trial (TT). Once the ergometer was validated and TT performance test deemed to be reliable, a third study used both to investigate the influence of time of day on coagulation responses to a short-duration high-intensity bout of exercise, whilst investigating the potential existence of diurnal rhythms within markers of coagulation in well-trained cyclists. The final study aimed to investigate if sports compression clothing when worn during a longer bout of exercise could influence the haemostatic responses to exercise. \\(Results\\) Study One / Study Two: The KICKR displayed accurate measurements of power between 250 and 700 Watts (W) at cadences of 80-120 revolutions per minute (rpm), with an ergometer error/bias of -1.1% (95% Limits of Agreement (LoA): -3.6% to 1.4%). Average power was shown to be highly reliable within the 4km cycling TT, with an average Intraclass Correlation Coefficient (ICC) and typical error of measurement (CV) of 0.94 (95% Confidence Intervals [CI]: 0.85-0.98) and 3.4% (95%CI: 2.7-4.7%) respectively. These results indicate the KICKR is a suitable ergometer and a 4km TT a suitable performance test for the completion of further studies utilising well-trained cyclists. Study Three: A 4km TT was shown to significantly increase plasma concentrations of tissue factor (TF: p<0.0005), tissue factor pathway inhibitor (TFPI: p<0.0006), thrombin anti-thrombin complexes (TAT: p<0.0012) and D-Dimer (p<0.0003), regardless of the time of day the exercise was performed. A time of day response was observed in pre-exercise TF (p=0.004) and TFPI (p=0.031), with 0830 h higher than 1730 h (p<0.001), whilst levels at 1730 h were less than those at 2030 h (p=0.008). However, no significant effects for time of day for TAT (p=0.364) and D-Dimer (p=0.228) were reported. Study Four: When worn during a marathon, compression socks (SOCKS) significantly attenuated the post-exercise increase in D-Dimer compared to the control group (median (range) SOCK: +9.02, (-0.34 to 60.7) ng/mL, CONTROL: +25.48, (0.95 to 73.24) ng/mL, p=0.008). TF was increased following the marathon run (median (range), SOCK: +1.19, (-7.47 to 9.11) pg/mL, CONTROL: +3.47, (-5.01 to 38.56) pg/mL, p=0.001), but there was no significant difference between the compression and control groups. No significant post-exercise changes were observed for TAT and TFPI (p>0.05). \\(Conclusions\\) The major conclusions of this thesis are: 1. The KICKR is a valid ergometer for measuring cycling power output. 2. A 4km cycling TT, when completed on the KICKR, is a reliable performance test for well-trained cyclists. 3. A short-duration high-intensity TT significantly activates the coagulation and fibrinolytic systems in well-trained cyclists, regardless of the time of day the TT is performed. 4. TF and TFPI are influenced by time of day, suggesting an increased potential for coagulation activation in the morning. 5. When worn during a marathon, compression socks reduce exercise-associated fibrinolytic activity as reflected by lower D-Dimer concentrations. The significance of this series of studies is that they have demonstrated the duration of exercise and the time of day exercise is performed influence coagulation responses within a well-trained population. In addition, this thesis contributes to the scarce literature on the use of compression garments and haemostatic responses in endurance based exercise, establishing that the use of sports compression socks may be beneficial in the prevention of VTE. The findings of this thesis may assist coaches, sports scientists and the athletes themselves to consider preventative measures for VTE, especially in athletes who are genetically predisposed to hypercoagulability.