How many leg curls should I do to achieve optimal muscle hypertrophy, considering both my current fitness level and my overarching training goals? Should I be focusing on an elevated number of repetitions to enhance muscular endurance, or would a lower repetition scheme with greater load be more efficacious for strength development? Furthermore, in the context of my overall lower body workout regimen, how do leg curls integrate with other exercises aimed at targeting various muscle groups, such as squats and lunges? Additionally, taking into account the frequency of my workouts, how can I best gauge the appropriate volume of leg curls to prevent overtraining while still ensuring progressive overload? Should I consider variables such as age, body weight, and specific athletic objectives when determining this number? Ultimately, what guidelines or frameworks exist to assist in delineating a precise answer to this question, thereby facilitating a structured and beneficial leg curl routine?