## 2 Materials and Methods
### Procedures  
The study comprised two sessions in one week. The first session was for familiarization with the equipment and the second session was for registering the external workload during the dance class. The first session allowed the participants to become familiar with the equipment during the activity.  
Firstly, the participants arrived 30 min previous to the start of the dance class to attach the inertial devices in six anatomical locations: (1) scapulae (in the T2-T4 vertebrae), (2) lower back (L2-L4 vertebrae), (3 and 4) knees (one to the right (RK) and the other to the left (LK) of the vastus lateralis muscle insertion point), and (5 and 6) ankles (3 cm above the right (RA) and left (LA) peroneal malleolus). The lower back sensor was placed at L3 due to this region having been recommended for capturing representative kinematics and loadingduring dynamic activities [26; 27] and not being influenced by the rotational movements of the sacrum [28].  
The devices were secured using fitted tops and leggings with pockets designed to prevent unwanted vibrations or device movements during testing [24] (see Figure 1a,b). Before device placement, the accelerometers were calibrated per the manufacturer's (RealTrack Systems, Almeria, Spain) recommendations to avoid four potential sources of error: offset error, scaling error, orthogonal error, and random error [29]. Additionally, to ensure correct data collection at device initiation, three key recommendations from [PERSON] et al. [24] were followed: (1) leave the device motionless for 30 s, (2) on a flat surface, and (3) away from magnetic devices.  
Then, the 60 min dance class was performed. The dance class consisted of group choreographies and movements performed individually, without the need for partner work or couple dances. This allowed all 30 participants (28 women and 2 men) to perform the same movements and follow the instructor's guidance without being paired up. This session was designed by an expert in dance and physical activity with older people, as well as followed the recommendations for aerobic fitness and safety provided by [PERSON] et al. [30]. This class was composed of 16 songs with a great variety of Latin rhythms and an Angolan rhythms (kizomba, for the first song as a warm-up). Dance movements included walking forward and backward, side-to-side steps, turns, pivots, foot drags, small jumps, and knee flexions. The dance routine was pre-recorded and edited to standardize the intervention session across all participants. The routine was projected in TV screens to enable proper viewing and the execution of the moves. The television screens were positioned to be clearly visible and to allow the music to be heard adequately. Table 1 shows the description of the order of songs, duration, and dance rhythms.  
At the conclusion of each session, the inertial device data were downloaded to a computer and imported into the SPROTM analysis software (version 989, RealTrack Systems, Almeria, Spain). This software enabled the configuration of impact intensity thresholds. It also allowed for the data extraction of impacts for each participant, anatomical location, and individual song. The aggregated data were compiled into an Excel spreadsheet formatted as a database. To enable comparisons of workload between songs with varying durations, the absolute impact counts extracted for each song were normalized by expressing them relative to the song length as impacts per minute.  
Figure 1: Inertial device placement. (**a**) 1: Scapulae, 2: lower back, 3: left knee, 4: right knee, 5: left ankle, and 6: right ankle. (**b**) Fixing system of the inertial devices to avoid movement during the assessments.