BACKGROUND: Swimming is a sport in which, at constant mean velocity, a balance must exist between propulsive forces (Fp) and resistive forces (Fd). However, measuring total propulsive force (Ft=Fp) and drag force (Fd) in swimming is rather complex. For this reason, this force balance has been previously assessed only in front crawl. The measurement of these forces is of fundamental importance for explaining variations in performance. Therefore, the aim is to quantify the force balance across the four competitive strokes and to examine the influence of sex and stroke technique on these forces.; METHODS: Swimmers performed: 4 full-tethered trials (one per each swimming stroke), 20 semi-tethered trials (five incremental loads per each swimming stroke) and 10 passive towing trials. Then Fd and Fp were calculated based on residual thrust method.; RESULTS: The main findings demonstrate experimentally that the balance of forces exists across swimming strokes and sexes, but this relation is affected by stroke frequency; CONCLUSIONS: The balance of forces was experimentally confirmed across swimming strokes. Since Fp are comparable, differences in swimming velocity can primarily be explained by the distinct hydrodynamic conditions experienced in each stroke
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