Cardiac Indicators During Half And Full Ironman Competition: A Comparative Analysis

Ultra-endurance triathlon competitions and participants have increased in number worldwide over recent years with little research focused on cardiac performance or risk during competition. Though relatively rare, anecdotal reports of athlete death during triathlon competition continue to emerge, most commonly a result of sudden adverse cardiac events. PURPOSE: To investigate how relative time in heart rate zones (HRZ) differs among half and full Ironman (IM) athletes, as well as maximal heart rate variability (HRV) and pre-competition somatic anxiety. METHODS: Participants (n = 15) were recruited from ultra-endurance triathlon races including the Tri-Cities, WA (half IM) and Kona, HI Ironman World Championships (full IM). Participants were equipped with a portable two-lead electrocardiogram to monitor cardiac performance throughout both races. Pre-competition somatic anxiety (day prior to race) was assessed via survey using the Competitive State Anxiety Inventory-2 (CSAI-2). Independent samples T-tests were used to compare study variables of interest between half and full IM participants. RESULTS: Half IM athletes spent more time in HRZ 5 (55.0% of race) compared to full IM athletes (26.5% of race). In contrast, full IM athletes spent more time in HRZ 4 (41.0% of race) compared to half IM athletes (34.5% of race). Pre-competition somatic anxiety scores were higher for half IM athletes (18.8 ± 4.3) compared to full IM athletes (15.6 ± 0.7). For half IM athletes, significant correlations were found for pre-competition somatic anxiety and time spent in HRZ 4 (r = 0.671, p = 0.048) and HRZ 5 (r = -0.724, p = 0.027) during the race. However, this trend was not found with full IM athletes. Max HRV (Mv) during the race was higher for full IM (95.5 ± 34.6) compared to half IM athletes (80.4 ± 35.6). CONCLUSION: Half IM athletes appear to spend more time at higher intensities compared to full IM athletes, as indicated by several cardiac indicators. Preliminary data infers that high pre-competition somatic anxiety may be a product of anticipated higher intensity, rather than volume. These findings provide a basis for future examinations of competition intensity and anxiety seeking to understand mechanisms of adverse cardiac events in triathlons.