Abstract
This study examined the effects of different types of acute exercise on salivary expression levels of human herpesvirus 6 (HHV-6) and 7 (HHV-7). In a randomized crossover trial, 11 healthy untrained men performed a continuous exercise (CE) trial (20 min at 70% V̇O (2)max) and an interval exercise (IE) trial (20-min cycling: five sets of 2-min at 50% V̇O (2)max and 2-min at 90% V̇O (2)max). Salivary HHV-6 and HHV-7 DNA expression was measured using real-time PCR, and maximum voluntary contraction (MVC) of knee extensors was assessed after saliva collection. Salivary HHV-6 expression increased at post-0 min (p < 0.001) and post-30 min (p = 0.002) in IE compared with pre, and was higher in IE than CE at both time points (p = 0.002, p = 0.048 respectively), but salivary HHV-7 expression did not change between trials. Changes in serum IL-6 and blood lactate levels were significantly higher in IE than in CE at post (p < 0.001). The sum of time-dependent changes in MVC was significantly lower in IE than CE (p = 0.016). Change in salivary HHV-6 from pre to post-24 h was negatively correlated with change in MVC (r(s) = -0.349, p = 0.047). These results suggest that IE may increase salivary HHV-6 expression and that changes in salivary HHV-6 may reflect objective physical fatigue after acute IE.