<![CDATA[Micro, Small, and Medium Enterprises (MSMEs) heavily rely on manual labor, which frequently leads to severe physical fatigue. This condition is often exacerbated by non-ergonomic working postures, repetitive movements, and extreme environmental temperatures, placing a dual burden on the workers' cardiovascular systems. This study aims to objectively evaluate the physical workload of manual workers at UD. Barokah by analyzing the interaction between mechanical load and thermal stress to formulate comprehensive ergonomic improvements. A quantitative descriptive approach with an observational design was employed in this study. Primary physiological data were collected directly by measuring the Resting Heart Rate and Working Heart Rate of workers across different age groups (30 and 60 years old) using an oximeter during their daily shifts. The physiological workload was analyzed using the Cardiovascular Load (%CVL) method and cross-validated with net energy consumption estimations derived from heart rate fluctuations. The field measurements indicated a high environmental temperature exposure reaching 33.1°C. Consequently, the %CVL values for the observed workers reached 33.93% and 40.70%, indicating a moderate cardiovascular strain that requires immediate system improvement. In stark contrast, the net energy consumption was classified as extremely light, at only 2.60 kcal/min and 2.22 kcal/min. This significant discrepancy confirms that the workers' physiological fatigue is not primarily driven by muscular mechanical exertion but rather by dominant thermal stress forcing the cardiovascular system to overwork for body thermoregulation. These findings critically correct the common assumption in the informal sector that manual fatigue is strictly proportional to caloric expenditure. Therefore, recommended ergonomic interventions must prioritize physical environment engineering, such as improved ventilation and rehydration facilities, alongside proportional work-rest schedules over mere load reduction.]]>
