Acute metformin intake on exercise performance in healthy participants during functional fitness training.

Background: The study aimed to assess whether prior intake of metformin enhances performance in the FRAN workout, a popular Functional Fitness Training protocol.

Methods: Fourteen men (mean±SD: 24.2±3.5 years; height: 173.3±7.8 cm; weight: 78.3±14.1 kg; body mass index: 25.9±3.0 kg/m²) participated. During the first visit, anthropometric measurements were taken, and participants performed the FRAN workout. After 72-96 hours, a retest was conducted to establish test-retest reliability. In the third and fourth visits, participants completed the FRAN workout under two conditions: metformin and placebo, using a crossover, counterbalanced, and double-blind design. The FRAN workout consisted of barbell thrusters (43.2 kg) and bodyweight butterfly pull-ups, performed in 21, 15, and 9 repetitions across three rounds.

Results: Significant differences were observed in partial times between rounds (F=28.91; P<0.01), but no significant differences were found between metformin and placebo conditions (F=0.08; P=0.77) or interaction effects (F=0.87; P=0.42). Similarly, total time differed significantly between rounds (F=158.04; P<0.01), with no significant differences between conditions (F=0.02; P=0.88) or interaction effects (F=0.30; P=0.73).

Conclusions: Acute metformin intake did not enhance FRAN workout performance, nor did it affect heart rate or perceived exertion. Coaches and athletes should consider that metformin's impact on exercise performance appears nonexistent, and its use in this context might not provide the desired ergogenic effect.