Karpouzi C, Kosmidis I, Petridou A, Bogdanis G, Mougios V (2023). EFFECTS OF PROTEIN SUPPLEMENTATION COMBINED WITH HIGH-INTENSITY FUNCTIONAL TRAINING ON PHYSICAL PERFORMANCE

High-intensity functional training (HIFT) is an effective form of training including multijoint aerobic and resistance exercises. Although protein supplementation has been extensively investigated in resistance training, there is limited evidence regarding its effectiveness in HIFT. Hence, the aim of this study was to examine the effects of protein supplementation, combined with HIFT, on physical performance in trained
individuals. Thirty trained volunteers (20 men and 10 women), aged 23-55, underwent 6 weeks of HIFT while receiving 0.6g/kg/day of egg white protein, whey protein, or maltodextrin (placebo) in a single-blinded, randomized, triple-crossover, and counterbalanced design, with 2 weeks of washout between supplements.

Participants received isoenergetic dietary plans providing 1 g/kg/day of protein. VO2max, maximal strength (1RM) and force-velocity relationship of shoulder press, peak torque and strength endurance of knee extensors and flexors, strength endurance of core muscles, and body composition through dual X-ray absorptiometry were measured pre- and post-supplementation. Data were analyzed by 3-way ANOVA and Pearson correlation. Regardless of protein supplementation, 1RM of shoulder press and strength endurance of core muscles increased (p < 0.001), whereas peak torque of knee flexors decreased with training (p < 0.05). The change in core endurance correlated positively with the change in lean soft trunk mass (r = 0.218, p = 0.039). In conclusion, short-term HIFT increased upper-body and core strength of trained men and women, while lower-body strength was not maintained. Protein supplementation did not affect these adaptations.