Introduction: Intermittent hypoxic training (IHT) has been used as a method of high level trained athletes in an attempt to improve their sport performance through higher-red cell maintenance and other adaptive physiological mechanisms induced at peripheral level to transport nutrients and oxygen (Hoppeler, 2008). For repeated long-term endurance exercises the parasympathetic tone usually increases with a decrease in resting heart rate (HRrest) and maximum (HRmx), the latter being a constraint for maximum performance. This adaptation justifies greater efficiency and positive response unless the HRmx decreases. Hypoxic states induce an increase in sympathetic-adrenal activation of glycolysis (Calbet, 2009) and a possible increase in HRmx (Gonzalez, 1998) that would justify an increase in maximal oxygen uptake (VO2max). Aim: To assess whether an IHT program is able to increase cardiac reserve and improve non-specific performance. Material and Methods: 22 firefighters (age: 33.7 ± 5.5 years, height: 179 ± 4 cm, weight: 81.3 ± 4.2 kg) divided into 2 groups: hypoxia (H) (n = 11) and control group (C) (n = 11). All of them underwent 4 sessions/week for two months, 60 minutes strength training (6×5 exercises of 30 repetitions; repetition rate 1/1 second) plus 30 minutes of interval exercise bike (3 minutes effort plus 2 minutes recover), for 8 weeks. The H group trained at 4000-5500m simulated altitude (first month: 4000-4500m; the second month: 5000-5500m) with normobaric hypoxia system (GO2Altitude) and group C trained in normoxia. Maximal test was performed in Concept-II rowing ergometer for 3 minutes before and after the intervention to obtain HRmx. The HRrest was measured lying in bed for 5 minutes at first time in the morning after waking and before breakfast. Cardiac reserve (CR = HRmx – HRrest) was measured before and after the intervention. Values are means±S.E.M., compared by ANOVA. Results: The CR increased in the H group (130±3 ppm vs. 139±5 ppm, p<0.022) compared with C group (132±4 ppm vs. 135±3 ppm, p=0.071) after the intervention. The H group improved performance in rowing ergometer (827.30±8.25 m vs. 889.18±9.79 m, p<0.019) compared with C group (868.11±6.35 m vs. 879.30±10,72 m, p=0.057). Conclusions: A IHT training program of 8 weeks between 4000-5500m increases HRmx and CR and final meters made in 3 minutes rowing ergometer (non-specific test). Increased non-specific enhancement of athletic performance may be justified by the increase in HRmx and CR. These stimuli can be interesting to decrease HRmx in periods of high volume training in endurance athletes.