Final answer:
According to the sliding filament model of muscle contraction, skeletal muscles contract as thin actin filaments slide past thick myosin filaments within the sarcomeres. The repeated attachment and pulling of myosin heads on actin filaments causes the sarcomeres to shorten.
Step-by-step explanation:
According to the sliding filament model of muscle contraction, skeletal muscle fibers contract as the thin actin filaments slide past the thick myosin filaments within the sarcomeres. This sliding is caused by the repeated attachment and pulling of myosin heads on actin filaments. As a result, the sarcomeres shorten, leading to the contraction of the muscle fiber.