The impact of 8-month training preparation for an Ironman distance triathlon on fitness and immune response in recreational athletes

Introduction: The popularity of extreme endurance events has grown over the past decade and recreationally trained athletes are more commonly undertaking extreme events, such as long distance triathlons. Few studies have investigated the effect of high volume triathlon training on illness risk; however, a high training load has been indicated as a predictor of increased risk of URTI symptoms in athletes (Gleeson et al, 2013). The aims of the current study were to examine the immune response and training adaptations to 8-months training for an ironman triathlon.
Methods: 12 recreational athletes (following an 8-month training plan to prepare for an Iron-distance triathlon) (IMM) and 12 recreationally active controls (CON) completed the study. At months 0, 2, 4, 6, and 8, participants completed a treadmill incremental exercise test to assess of maximal oxygen consumption (VO2max). Prior to the exercise test, a passive timed collection of saliva was undertaken, for subsequent analysis of secretory IgA (s-IgA) and salivary lysozyme using ELISA. Throughout the 8-month study period, participants completed bi-weekly nutrition diaries and weekly illness symptom and training diaries.
Results: There was a significant increase in VO2max in IMM between 0 and 2 months (48.1 ± 5.6 mL.-1kg. -1min-1, p=0.030); however, no subsequent changes. VO2max did not change in CON, although there was a significantly higher VO2max in IMM compared to CON at months 2, 4, 6 and 8. There was no significant difference in incidence of URTI or symptom score between months 0 and 8 in IMM. There was no difference in incidence of URTI between IMM and CON, except a significantly higher symptom score in IMM at month 6 (p=0.018).
Discussion: The increase in VO2max during the first two months of initiating triathlon training, indicates that adaptations occurred quickly; however after month 2 increasing training load did not affect VO2max. There was little difference in illness episodes scores, or incidence of URTI between time points or groups, this may have reflected the moderate and progressive training load undertaken by IMM; which did not increase the risk of URTI, predicted in elite athletes (Nieman, 1994). Analysis of s-IgA and s-lysozyme is required to examine the concomitant physiological response of the immune system and individual difference will be considered. However, it appears that 8 months of training for a long distance triathlon may not have a detrimental effect on the immune response in recreational athletes