Objective: To determine the association between variation in exercise load, immunoglobulin (Ig) status, and self-reported symptoms of upper respiratory tract infection (URTI) in ultramarathon runners.
Design: Longitudinal observational field study.
Setting: Four weeks before and 2 weeks after an 86.5-km Comrades Marathon, South Africa.
Participants: Fourteen randomly selected, amateur, male, ultramarathon runners.
Main Outcome Measures: Daily record of training and URTI symptom incidence. Salivary IgA and IgM at 28 days, 14 days, and 1 day (01PRE) before the race, immediately post race (IPR) and 1 (01 PR), 3, and 14 days post race. Serum cortisol, IgG, IgM, and IgA concentrations at 01PRE, IPR, and 01PR.
Results: Mean weekly training distance varied from 89.4 kilometers per week (28.9 kilometers per week) to 4.2 kilometers per week (6.7 kilometers per week). Absolute and relative mucosal IgA and IgM concentrations were unaffected by pre-race taper in training volume (P > 0.05). IgA and IgM secretion rates decreased post race (P = 0.018; 0.008), returning to baseline by 01PR. Blood leukocyte, serum cortisol, and serum IgG concentrations increased at IPR (P < 0.001, <0001) and 01PR (P = 0.009), respectively. Upper respiratory tract infection symptom incidence was highest at 28PRE and 7 to 14 days post race but not related to salivary IgA and IgM secretion rates. Eight subjects (57%) who reported URTI symptoms pre race also reported these during days 7 to 14 post race.
Conclusions: Upper respiratory tract infection symptom incidence was not associated with secretory Ig concentrations. Reactivation of pre-race viruses during the 2 weeks post race and exercise-induced inflammatory response are proposed as causes of the elevated URTI incidence at 28PRE and 7 to 14 days post race.