Final answer:
For muscular endurance improvements, you should focus on performing a greater number of repetitions at a lower intensity, targeting the mitochondrial-rich slow-twitch muscle fibers designed for sustained activity.
Step-by-step explanation:
For gains in muscular endurance, more reps are indicated at a lower intensity.
When working to increase muscular endurance, the goal is to perform a higher number of repetitions (reps) with lower weight, which equates to lower intensity. This approach leverages the characteristics of slow-twitch muscle fibers, which are more abundant in muscles that perform continuous and repetitive activities and are better suited for endurance. Slow-twitch fibers can sustain aerobic activity for an extended period as they are richer in capillaries, mitochondria, and myoglobin, allowing for more oxygen to be carried and utilized efficiently.
On the contrary, resistance training that focuses on muscular strength and hypertrophy requires fewer reps with heavier weights, targeting the fast-twitch muscle fibers known for providing powerful contractions during short, intense activities. Endurance training does not typically lead to significant increases in muscle size like resistance training, which can cause muscles to hypertrophy, or enlarge, through the addition of myofibrils and structural proteins.