Recent studies have focused attention on the existence of physiological rhythms within the precise timing of the intervals between heart beats. This so called heart rate variability (HRV) has been reported to be related to autonomic function of the heart and differs among groups according to age, body position, fitness status, as well as acute levels of stress. Whether or not currently competitive athletes have a distinct autonomic response to stress is not well-established. PURPOSE: The purpose of the study was to examine the autonomic response as determined by HRV in active and inactive athletes during a mental workload. METHODS: Six currently competitive NCAA athletes (COL) and six ex-athletes (HS) of similar (p < .05) age (21.8 ± 2.3 yrs) and BMI (29.0 ± 5.9 kg·m2) served as subjects for this investigation. The Bassin Anticipation Timer (LaFayette Instrument Company, LaFayette, IN) was utilized to provide a repeated mild competitive stressor. To determine anticipatory timing (AT) subjects pushed a timed button anticipating the arrival of a light sequence that moved toward the athletes at 1.34 m-s1, increasing by 0.89 m-s1 each minute for 5 min. HRV was obtained and analyzed from 12-lead electrocardiogram (Welch Allyn, Inc., Skaneateles Falls, New York). Time domain measure of variability of intervals (SDNN, standard deviation of the interval between normal beats) was transformed to the frequency domain as 1) total power (TP, a measure of total variability of the intervals), and the normalized high frequency component of HRV (HFn, a measure of parasympathetic modulation). HRV was determined at rest (R) and during AT. RESULTS: Resting heart rates were 74 ± 9 and 60 ± 13bpmforHS and COL (p<.05) and remained unchanged (p>.05) during AT in both groups. A 2×2 repeated measures ANOVA revealed no change in SDNN (F(1,10)=0.33, p>.05) from R to AT, and no significant group interaction (F(1,10)=0.10, p>.05). TP remained unchanged from R to AT, 4909 and 4254 ms2 (F(1,10)=0.79, p>.05), respectively, and no group interaction (F(1,10)=0.10, p>.05). HFn was unchanged from R to AT, 40.8 and 49.7 (F(1,10)=2.49, p >.05), respectively, and no significant group interaction (F(1,10)=0.03, p>.05). CONCLUSION: Results of this investigation indicate that HRV is similar between active and inactive athletes during conditions of rest. Competitive participation in AT does not produce a detectable stressor as determined by HRV.