What is the result of resistance training on muscle fiber types?

Resistance training primarily affects muscle fiber types by promoting adaptations that can enhance performance but does not lead to a complete transformation of fiber types in the way option B suggests. While Type II A fibers, known for their capacity to generate power and strength, can enhance their functional capabilities with resistance training, the dominant pathway actually involves Type II A fibers developing more characteristics of Type II B fibers under certain conditions, such as heavy resistance training.

However, it’s more accurate to say that intense training can enhance the metabolic and contractile properties of Type II A fibers, allowing them to perform more like Type II B fibers, which are more geared toward short bursts of speed and power. This plasticity allows Type II A fibers to better meet the demands of resistance training. Thus, the training doesn't lead to a conversion in the traditional sense but rather an enhancement of specific performance capacities.

Ultimately, rather than converting Type II A fibers into Type II B fibers, the adaptations from resistance training often support the development of these muscle fibers to work more efficiently within their existing type boundaries while increasing overall muscle strength and hypertrophy.