###### Abstract  
The purpose of this non-randomized study was to determine the effect of strength training and aerobic interval training on the anaerobic and aerobic power and endurance of young men (assessed by determination of the second ventilatory threshold (VT2)) in non-trained men. Participants (n = 45) were recruited into three groups of 15 each. The first group performed strength training (ST), the second performed aerobic interval training (AIT), and the third group was the control group (CON). In each group, somatic measurements and tests of aerobic (graded test with VT2 determination) and anaerobic capacity (Wingate test) were performed twice (before and after the exercise intervention in the training groups). In the graded test, the level of maximal load (Pmax), maximal oxygen uptake (VO\({}_{2}\)max) and intensity and oxygen uptake at VT2 were determined. In the Wingate test, peak power (PP) and mean power (MP) were determined. The exercise intervention in the ST and AIT groups lasted 6 weeks, with three workouts per week. Training in the ST and AIT groups resulted in significant increase in absolute Pmax (\(p\) < 0.001, ES = 0.52 and \(p\) < 0.05, ES = 0.36), VO\({}_{2}\)max (\(p\) < 0.001, ES = 0.50 and \(p\) = 0.02, ES = 0.55) in the participants. Only AIT was significantly effective in improving oxygen uptake at VT2 (\(p\) < 0.04, ES = 0.64), and ST in improving PP. Strength training can be an effective training method in training aerobic and anaerobic capacity (significantly increases Pmax, VO\({}_{2}\)max, and PP), while it does not significantly affect work intensity at VT2. Our results suggest that, particularly in anaerobic-aerobic sports, strength training may be a training method that can simultaneously improve both anaerobic power and maximal oxygen uptake. It can also complement endurance training. strength; anaerobic; aerobic; power; endurance; training; intervals Article  
1  
<ccs2012>  
improvements in endurance, as assessed by running economy, were observed after resistance training [10; 11; 12; 13]. Another study [7] showed that strength training using free weights improved both aerobic and anaerobic capacity in female soccer players. Lower lactate concentration was also observed after such training in comparison to aerobic training [8]. It has also been proven that 20-week ST has the effect of increasing blood indices, such as mean red blood cell volume, hematocrit and red blood cell count [14]. The authors [14] suggest that resistance training affects fluctuations in blood morphology parameters, causing an increase in red blood cell-related indices. It may counteract sports anemia, which often occurs among people who perform endurance training. Another study [15] showed that ST significantly improves, in a similar way to long-term aerobic training, cardiovascular function in obese individuals; after training, there was not only a significant increase in VO2 max, but also improved endothelial function in blood vessels, an increase in PGC-1\(\alpha\), a protein responsible for regulating liver function during gluconeogenesis or mitochondrial biogenesis, and increased transport of calcium ions involved in muscle contraction. In addition, a decrease in LDL lipoprotein levels was noted in the subjects [15]. The above-reported changes occurring under the influence of strength training may also have a beneficial effect on aerobic capacity and suggest that strength training may also be at least a complement or alternative to endurance training. One of the physiological indicators of aerobic endurance is VO2 max, the intensity of work at metabolic thresholds (first and second ventilatory threshold: VT1 and VT2), maximal steady state and economy of movement [16; 17; 18]. As intensity increases to maximal, energy metabolism changes. Once the first ventilatory threshold is exceeded, compensated metabolic acidosis occurs [19].