The typical macroeconomic model is based on an aggregate production function that is unbounded from above and increasing with respect to labor and capital. Hence, given this function, it is possible for output to increase rapidly as long as the labor input increases sufficiently.
In a similar vein, aggregate models of physical capital accumulation typically assume that the future capital stock is an unbounded and increasing function of physical investment. According to this formulation, it is possible for the capital stock to rise rapidly, as long as physical investment increases sufficiently.