There are no studies in the literature to validate equations that predict maximum heart rate (HRmax) in children and adolescents. To analyze the validity of the HRmax predictive equations "220 - age" and "208 - (0.7 x age)" in boys aged 10 and 16. A progressive maximal exertion test was carried out in 69 apparently healthy boys aged 10 to 16. The initial test velocity was 9 km/h, with 1-km/h increments every three minutes. The test was maintained until maximum voluntary exertion was achieved, considering HRmax as the highest heart rate attained during the test. The measured HRmax was compared with the values predicted by the "220 - age" and "208 - (0.7 x age)" equations, using ANOVA for repeated measures. The mean values of HRmax (bpm) were: 200.2 ± 8.0 (measured), 207.4 ± 1.5 ("220 - age") and 199.2 ± 1.1 ("208 - (0.7 x age)"). The HRmax predicted by the "220 - age" equation was significantly higher (p < 0.001) than the measured HRmax and the HRmax predicted by the ("208 - (0.7 x age)") equation. The correlation between the measured HRmax and age was not statistically significant (r = 0.096; p > 0.05). The "220 - age" equation overestimated the measured HRmax and was not valid for this population. The "208 - (0.7 x age)" equation was valid for this population, showing results that were quite similar to those of measured HRmax. Future studies with larger sample sizes can verify whether the HRmax does not depend on age for this population, a situation in which the constant 200 bpm value would be more appropriate for HRmax.

The objective of this study was to analyze the effect of two different high-intensity interval training (HIT) programs on selected aerobic physiological indices and 1500 and 5000 m running performance in well-trained runners. The following tests were completed (n = 17): (i) incremental treadmill test to determine maximal oxygen uptake (VO_{2 max}), running velocity associated with VO_{2 max} (vVO_{2 max}), and the velocity corresponding to 3.5 mmol/L of blood lactate concentration (vOBLA); (ii) submaximal constant-intensity test to determine running economy (RE); and (iii) 1500 and 5000 m time trials on a 400 m track. Runners were then randomized into 95% vVO_{2 max} or 100% vVO_{2 max} groups, and undertook a 4 week training program consisting of 2 HIT sessions (performed at 95% or 100% vVO_{2 max}, respectively) and 4 submaximal run sessions per week. Runners were retested on all parameters at the completion of the training program. The VO_2 max values were not different after training for both groups. There was a significant increase in post-training vVO_{2 max}, RE, and 1500 m running performance in the 100% vVO_{2 max} group. The vOBLA and 5000 m running performance were significantly higher after the training period for both groups. We conclude that vOBLA and 5000 m running performance can be significantly improved in well-trained runners using a 4 week training program consisting of 2 HIT sessions (performed at 95% or 100% vVO_{2 max}) and 4 submaximal run sessions per week. However, the improvement in vVO_{2 max}, RE, and 1500 m running performance seems to be dependent on the HIT program at 100% vVO_{2 max}.

The objective of this study was to compare the effect of different strength training protocols added to endurance training on running economy (RE). Sixteen well-trained runners (27.4 ± 4.4 years; 62.7 ± 4.3 kg; 166.1 ± 5.0 cm), were randomized into two groups: explosive strength training (EST) (n = 9) and heavy weight strength training (HWT) (n = 7) group. They performed the following tests before and after 4 weeks of training: 1) incremental treadmill test to exhaustion to determine of peak oxygen uptake and the velocity corresponding to 3.5 mM of blood lactate concentration; 2) submaximal constant-intensity test to determine RE; 3) maximal countermovement jump test and; 4) one repetition maximal strength test in leg press. After the training period, there was an improvement in RE only in the HWT group (HWT = 47.3 ± 6.8 vs. 44.3 ± 4.9 ml · kg⁻¹ · min⁻¹; EST = 46.4 ± 4.1 vs. 45.5 ± 4.1 ml · kg⁻¹ · min⁻¹). In conclusion, a short period of traditional strength training can improve RE in well-trained runners, but this improvement can be dependent on the strength training characteristics. When comparing to explosive training performed in the same equipment, heavy weight training seems to be more efficient for the improvement of RE.