Reducing music volume by approximately 3 A-weighted decibels in group fitness classes met a prespecified noninferiority threshold for perceived exercise intensity compared with louder sessions, according to a comparative effectiveness study.
The researchers surveyed 189 participants who attended 1-hour group fitness classes at a Los Angeles studio from February 1 to 28, 2025. The participants completed 239 postclass surveys following sessions held under standard- or reduced-volume conditions. Twenty-one participants completed surveys following both louder and quieter classes.
The researchers reported that the mean sound levels were 91.4 A-weighted decibels (dBA) during louder classes and 88.5 dBA during quieter classes. Across all sessions, measured levels ranged from 84.1 to 95.0 dBA.
Perceived exertion was measured with the Borg Category-Ratio–10 scale, which ranges from 0 for rest to 10 for maximal exertion. In a multivariable mixed-effects linear regression model that accounted for repeated measurements and included age, education level, class size, and instructor, estimated mean Borg Category-Ratio–10 scores were 6.61 units in louder classes and 5.96 units in quieter classes. The adjusted difference was −0.66 units.
The researchers predefined the noninferiority margin as a lower confidence boundary above −1.5 units. Because the lower boundary did not cross that threshold, quieter classes were considered noninferior to louder classes for perceived exertion.
A sensitivity analysis modeling sound intensity continuously showed that each 1-dBA reduction corresponded to a 0.18-unit lower Borg Category-Ratio–10 score. Noninferiority was maintained for reductions up to 4 dBA but could not be concluded at a 5-dBA reduction.
The median age of the participants was 28 years, and about 87% of them were female. According to the researchers, 44% reported attending three to five group fitness classes per week, and 33% of them had attended such classes for more than 5 years.
Hearing protection use was uncommon. For instance, just 2% (n = 4) of the participants reported using hearing protection during fitness classes, three of whom reported using it most of the time. Among the participants who did not use hearing protection, 11% (n = 20) said they would consider using it. Further, 15% (n = 28) reported ever experiencing tinnitus following class, and 13% (n = 24) were unsure.
The participants’ subjective loudness ratings varied across similar measured sound levels. The median measured level among those who rated the music as “just right” was 88.7 dBA. The loudest measured level was 95 dBA, which the researchers noted exceeded National Institute for Occupational Safety and Health recommended limits for 1 hour of exposure.
The researchers assessed perceived exertion rather than objective physiologic exercise measures and did not evaluate hearing outcomes directly. They noted that the observational, partially repeated measures design limited causal interpretation. Louder and quieter classes occurred sequentially rather than through randomization, and the instructors were aware of the reduced-volume phase. The single-studio sample of mostly younger adults may also limit generalizability.
Additional limitations included the voluntary participatory nature of the study, lack of data on otologic history or baseline hearing health knowledge, modest sound reduction, persistent high sound levels even in quieter classes, total room sound measurement rather than personal exposure measurement, instructor-specific playlists and routines, and reliance on a self-reported exertion scale.
“[L]owering sound levels in group fitness classes did not diminish participants’ perceived workout intensity, supporting the feasibility of creating safer auditory environments without compromising workout effectiveness,” wrote lead study author Kaitlin Hori, BS, of the Keck School of Medicine at the University of Southern California (USC), and colleagues.
The study was supported by grants from the National Center for Advancing Translational Science of the National Institutes of Health. Senior study author Janet S. Choi, MD, MPH, reported receiving grant funding outside the submitted work from the USC/University of California, Los Angeles Center on Biodemography and Population Health and the Southern California Clinical and Translational Science Institute. The study authors reported no other conflicts of interest.
