Effect of Aerobic Exercise on Salivary Alpha-amylase and White Blood Cell Count among Sedentary Thais

Background and objectives : Physically and mentally stressful situations may arise during exercise, resulting in sympathetic activation and an increase in catecholamine secretion. This study aimed to examine sympathetic activation and immune function during aerobic exercise in sedentary Thais. Methods : Fifty sedentary subjects were divided into 2 groups: control (n = 25) and exercise groups (n = 25). All subjects were healthy, having no clinical evidence of cardiopulmonary disease. The exercise group was engaged in brisk marching (75to 80% HRmax) with 30 min/session, 3 to 5 sessions/week for 12 consecutive weeks.  Stressful condition was evaluated by measuring salivary alpha amylase (sAA) levels in order to investigate sympathetic activation. Additionally, immune function was evaluated by white blood cell (WBC) count: neutrophil (NE), lymphocyte (LY), monocyte (MO), eosinophil (EO) and basophil (BA). The mean, standard deviation, paired t-test; repeated ANOVA and ANCOVA were employed for data analysis. Results : In comparison to the pre-exercise, sAA levels were significantly increased following 4 and 8 weeks of brisk marching, 125.90 ± 13.31 kIU/l vs 196.46 ± 19.19 kIU/l (p < 0.05) and 177.69 ± 17.45 kIU/l (p < 0.05), respectively. Nevertheless, they were restored by week 12 (127.87 ± 16.89 kIU/l).  Moreover, significant differences in NE, LY, MO, EO and BA were not observed post- compared to pre-aerobic exercise (6.48 ± 2.40 vs 6.14 ± 1.78 10 3 /uL, 57.58 ± 10.12 vs 55.92 ± 8.42%, 31.94 ± 8.90 vs 33.74 ± 7.64%, 6.62 ± 1.93 vs 6.36 ± 1.35%, 3.36 ± 2.66 vs 3.41 ± 1.97% and 0.48 ± 0.18 vs 0.53 ± 0.17%, respectively. Conclusions : The present study suggests that aerobic exercise by brisk walking for 12 consecutive weeks may compromise a stressful situation induced earlier by aerobic exercise and maintain immune function. Therefore, prolonged exercise training should be recommended to sedentary individuals.