Although much research has been devoted to gait analysis while walking or running, a surprising gap in knowledge is its relationship with upper body function, particularly core stability. The methods used to train and assess athletic locomotion are mainly focused on the lower limbs, while the upper body is often overlooked. Yet, proper body alignment from feet to head is essential for applying maximum force to the ground, thereby moving faster and more efficiently. It is believed that the core, which connects the upper and lower body, should be strong. The training of many athletes is therefore aimed at developing core muscle strength. However, for most of them, rigid core musculature associated with reduced spinal mobility may not be beneficial. Instead, core strength should be developed to the extent that allows race walkers and runners to optimize their performance. Accordingly, methods reflecting the functional nature of core strength, along with measures of postural alignment and lateral lumbopelvic stability, should be used to assess training effectiveness. To this end, a comprehensive head-to-toe approach to the assessment of athletic locomotion is recommended. Special emphasis should be placed on the role of postural and core stability in walking and running gait.