The proportion of non-responders (∼20%) predicted from their study of single-nucleotide polymorphism variation in DNA is close to the proportion of subjects showing no change in Pmax or การวัดประสิทธิภาพสูงสุดของร่างกายในการใช้อ็อกซิเจน in the present study (3/13×100=23%). Thus, the wide range of training responses apparent among the elderly subjects may well reflect DNA variation rather than an age-related change in adaptability to endurance training.