<p>The objective of this paper is to explore methodologies used to estimate the mechanical cost of locomotion and evaluate their validity as indicators of metabolic cost within rehabilitation contexts. Aging societies face rising healthcare costs and fewer workers. Remote monitoring of rehabilitation progress may help address these challenges. Because locomotion mechanics are easier to measure than metabolic cost, understanding whether mechanical cost of transport can serve as a surrogate is of interest. We conducted a systematic search for studies on mechanical work or power and metabolic energy consumption in adults under physical rehabilitation contexts. Abstract, full text screening, and data extraction were performed. Ten articles were included. We found no direct relationship between mechanical cost and metabolic cost in the included studies. However, consistent trends were observed: interventions that provided net positive work generally reduced both mechanical and metabolic costs. Similar trends were found in wheelchair propulsion, where mechanical advantage and power assistance reduced both mechanical cost and metabolic demand for wheelchair users. Rehabilitation progress can be monitored using metabolic cost, and given the observed parallel trends, mechanical cost may also serve as a practical indicator, although further research is needed to establish its validity as a surrogate.</p>