Background <p>The Elevation Training Mask 2.0 (ETM) is a respiratory muscle device, designed to simulate altitude training. It works by reducing airflow through a valve system. During exercise, ETM could restore respiratory damage from post-infection phase of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), allowing ventilatory restriction that works as resistance training for respiratory muscles.</p> Aim <p>To comparatively evaluate the spirometry parameters in CrossFit^® practitioners training using ETM (EG), compared to a control group (CG).</p> Methods <p>In a single-blind randomized clinical trial, following the Consolidated Standards of Reporting Trials (CONSORT) recommendations, 20 trained male athletes were randomly assigned to an EG and a CG using simulated ETM device. Both groups completed 12 weeks of CrossFit^® training after 1 month of finishing SARS-CoV-2 symptoms. Pre- (T1) and post-training (T2) testing included assessment of lung function and respiratory muscle strength.</p> Results <p>No significant differences (<i>p</i> &gt; 0.05) were observed comparing EG and CG in any of spirometry parameters evaluated. Nevertheless, significant differences (<i>p</i> &lt; 0.05) in behavior were observed throughout the 36 training sessions for maximum voluntary ventilation (MVV) and maximum inspiratory pressure (MIP) with a strong effect (η²<i>p</i> = 0.693). In addition, significant improvements (<i>p</i> &lt; 0.05) were observed in MIP and MVV exclusively in the EG when comparing T1 vs. T2.</p> Conclusion <p>The findings suggest that the inclusion of ETM in a 12-week CrossFit^® training program, in athletes returning to exercise post-SARS-CoV-2 infection, may have modest benefits compared to CG on lung function and respiratory muscle strength.</p> Protocol registration <p>ClinicalTrials.gov, identifier (ID NCT06806124). 25/01/2025 retrospectively registered.</p>