Upper Respiratory Tract Infection and Neutrophil Degranulation during an Arduous Military Training Programme

Abstract

1748 PURPOSE: The aim of the present study was to determine the effects of a 20-week military training programme on upper respiratory tract infection (URTI) incidence and neutrophil degranulation. METHODS: Participants were 14 UK Parachute Regiment recruits (PARA) entering into training in mid-January and 12 recreationally active controls (CONTROL) who were not undertaking training. Venous blood samples were collected every 2 weeks during training, and before and after Easter leave (weeks 11 and 12), at between 0500 and 0700 h after an overnight fast. On a daily basis, participants recorded the incidence and severity of URTI. Elastase release from bacterial-stimulated neutrophils (degranulation) and serum cortisol were determined using ELISA. RESULTS: There were no significant differences between groups for the number or duration of URTI during the 20-weeks. A significant increase in URTI incidence, typical for the time of year (early-mid February), occurred at weeks 2 and 3 for PARA and week 4 for CONTROL compared with week 0 (P< 0.05). Incidence of URTI was greater in PARA compared with CONTROL at week 2 only (P < 0.05). Neutrophil counts were unaffected by training (PARA week 0: 3.6 ± 0.4; week 20: 3.5 ± 0.2 × 109 cells.l−1, mean ± SEM). A significant increase in neutrophil degranulation occurred at weeks 4, 11, 12 and 16 for PARA compared with week 0 (P <0.01). A significant decrease in neutrophil degranulation occurred in CONTROL at weeks 2, 4 and 16 compared with week 0 (P< 0.01). At weeks 4, 12 and 16 neutrophil degranulation was greater in PARA compared with CONTROL (P <0.01). Greater neutrophil degranulation in PARA at week 4 coincided with peaks in URTI incidence and serum cortisol (P< 0.01). CONCLUSIONS: These results show a limited effect of Parachute Regiment training on URTI incidence. Additionally, Parachute Regiment training does not appear to suppress neutrophil degranulation. This work was supported by the Ministry of Defence (Army).