Stability balls (SB) are commonly used as substitutes for office chairs (OC) due to their potential benefits in preventing musculoskeletal issues. However, limited research has explored the specific impact of SB usage on energy expenditure (EE). This study investigated the effects of using various chairs, including SB, on energy metabolism, muscle activity, and subjective sensations during seated rest. Sixteen adults alternated randomly between four chair types, sitting on each for 10 min: OC with a backrest (OCcont), OC without a backrest, OC designed to promote proper posture, and SB. Expired gas and surface electromyogram (EMG) data were recorded. The integrated EMG (iEMG) was analyzed for two abdominal, two back, and two lower limb muscles. Oxygen consumption was significantly higher while sitting on SB (mean ± standard deviation, 13 ± 21% net increase) compared to OCcont. The combined iEMG for all six muscles showed a notable increase while sitting on SB (54.9 ± 45.6% net increase) versus OCcont, with rectus femoris activation being particularly prominent. These findings indicate that substituting a standard OC with an SB during office work induces small but significant physiological changes, potentially aiding in obesity and metabolic disorder prevention.