The oldest of active athletes retain greater muscle power than the average older person, though there is always the question of cause and effect: to what degree is this a consequence of the choice to continue as an athlete, accompanied by all that exercise, versus being a situation in which an individual can only continue to be an athlete because he or she happens to be more resilient. As this study demonstrates, the resistance to age-related loss of overall muscle power in these individuals is not due to suffering a lower level of the shared fundamental degeneration of capabilities in muscle fibers:
Elite runners do not experience the muscle weakening associated with aging as non-athletes do. Movement and strength come from the muscle fibers that make up a muscle group contracting and generating tension. Muscle weakening happens when the fibers contract slower and with less force. Muscle fiber samples were taken from the quadriceps of older elite runners and non-athlete adults in the same age range. "These are individuals in their 80s and 90s who actively compete in the world masters track and field championships. In the study, we had seven world champions, and everyone placed in the top four of their respective events."
The fibers' contraction speed and force were compared to fibers from 23-year-old non-athlete adults. Muscle fibers from older non-athletes contracted considerably slower and weaker than fibers from young non-athletes. To the researchers' surprise, the muscle fibers of masters athletes contracted at a speed and force similar to those of older non-athlete adults, not the young adults. Success in high-performance sports in old age does not appear to be due to maintained contraction capability of the fibers. This study suggests that aging is associated with decreased muscle quality regardless of physical activity status. However, other studies have shown that muscle fibers can be arranged in a variety of ways to optimize strength, speed and power of the whole muscle, so there are many structural ways to compensate for the reduced performance at the fiber level to maintain performance at the whole muscle level.