Effects of Six Weeks of High-Intensity Functional Training on Physical Performance in Participants with Different Training Volumes and Frequencies

High-intensity functional training (HIFT) is characterized by presenting high volumes and training intensities with constantly varied exercises. The aim of this study was to analyze the internal training load and the effects of high-intensity functional training on physical performance in subjects with different training volumes and frequencies. A total of 31 volunteers involved in high-intensity functional training (14 men and 17 women) were divided according to their training volumes and frequencies (high training-volume and frequency—HTVF; ( n = 17) (nine women and eight men; age: 31.0 ± 6.3 years; height: 168.8 ± 8.1 cm, body weight: 73.6 ± 11.9 kg; BMI: 25.96 kg/m 2 ) and moderate training volume and frequency—MTVF; ( n = 14) (eight women and six men; age: 26.6 ± 4.7 years; height: 167.2 ± 8.6 cm, body weight: 75.8 ± 18.0 kg; BMI: 27.33 kg/m 2 )). The internal training load was determined using the session-rating of perceived exertion method. The monotony index (MI) and training strain (TS) were used to determine training variability during the training weeks. Countermovement vertical jump height, 20-m sprinting and handgrip strength were assessed at baseline and after six weeks of training. There was a time effect for MI ((F (5, 145) = 5.942; p = 0.0001)), TS ((F (5, 145) = 5.734; p = 0.0001)), weekly internal training load ((F (4.006, 116.87) = 4.188; p = 0.003)) and mean weekly internal training load ((F (4.006, 116.87) = 4.188; p = 0.003)). There was no increase in performance in either group for countermovement vertical jump height ((F (1,29) = 6.081; p = 0.050)), sprinting ((F (1,29) = 1.014; p = 0.322)), right handgrip strength ((F (1,29) = 2.522; p = 0.123)) or left handgrip strength ((F (1,29) = 2.550; p = 0.121)). The current findings suggest that six weeks of high-intensity functional training was not able to increase performance in either group. Therefore, different volumes and frequencies do not seem to influence the increase in physical performance of HIFT practitioners.