Introduction and Hypothesis <p>Exercise-based heavy lifting has been suggested to challenge pelvic organ support, yet no study has investigated this in women at risk of pelvic organ prolapse. This study aimed to investigate the immediate impact of heavy weightlifting on pelvic floor morphometry in premenopausal, vaginally parous women trained in exercise-based heavy lifting.</p> Methods <p>Participants without symptoms of vaginal bulge attended a heavy weightlifting session (heavy barbell back squats [5 × 5 repetitions at 80% one repetition maximum]). Pelvic floor morphometry was measured before and immediately after the session. Bladder neck and rectal ampulla positions, anorectal and levator plate angles, levator anteroposterior distance, and levator hiatal area were assessed using transperineal ultrasound at rest, during bearing down, and during pelvic floor muscle contraction, in supine and standing positions. The maximal vaginal descent was assessed using the Pelvic Organ Prolapse Quantification in supine.</p> Results <p>Thirty-seven women participated in the study. Compared to pre-lifting, immediately after lifting the anorectal angle at rest was larger in supine and standing (<i>p</i> ≤ 0.05); during pelvic floor muscle contraction the bladder neck was more caudal in supine (<i>p</i> &lt; 0.001) and the levator hiatal area was larger in standing (<i>p</i> = 0.02); during bearing down the levator plate angle was smaller in standing (<i>p</i> = 0.002) and the levator hiatal area was larger in supine (<i>p</i> = 0.01). No other significant pre–post changes were found.</p> Conclusions <p>In asymptomatic, trained, premenopausal, vaginally parous women, a single heavy lifting session may induce small immediate pelvic floor morphometric changes, with minor impact on organ support, as shown by stable bladder neck, rectal ampulla, and vaginal wall measures.</p>