Purpose <p>The aim of this study was to determine whether lifting a weight with the left or right hand has a different effect on the right hemidiaphragm.</p> Methods <p>This study investigated the motion of the right hemidiaphragm during asymmetric lifting tasks using M-mode ultrasonography. Forty healthy adults (30 women and 10 men, aged 27.6 ± 5.4&#xa0;years) performed tidal breathing and loaded breathing, with the latter involving lifting a weight with either the left or right hand.</p> Results <p>Using one-way ANOVAs, significant differences were observed for the right hemidiaphragmatic position when holding the weight with the contralateral (left) hand for inspiration (<i>p</i> = .004) and total excursion (<i>p</i> &lt; 0.001), but not for expiration (p = 0.872) compared to tidal breathing. When tidal breathing positions were compared to holding the weight with the ipsilateral (right) hand, significant differences were observed for all three measures: inspiration (<i>p</i> = 0.005), expiration (<i>p</i> &lt; 0.001), and total excursion (<i>p</i> = 0.023). Comparison of the right hemidiaphragmatic position during contralateral and ipsilateral holds showed significant differences in expiration (<i>p</i> &lt; 0.001) and total excursion (<i>p</i> &lt; .001), but not for inspiration (p = 0.997).</p> Conclusion <p>The right hemidiaphragm showed different responses during one-handed weight lifting on the ipsilateral side compared to the contralateral side. Specifically, under ipsilateral loading, the expiratory position of the right hemidiaphragm was observed to be more caudal.</p>