Abstract
[Purpose] This study was undertaken to quantify the effects of ankle joint position on unstable and stable surfaces during push up exercises on shoulder and trunk muscle activities. [Subjects] The study subjects were 45 healthy adults in their twenties with normal ranges of motion (ROM) and without disorders of the shoulder complex, musculoskeletal disease of the upper limbs, or low back pain. [Methods] Push-up exercises were performed under the following four conditions: (1) on an unstable surface created by placing a 65-cm diameter exercise ball under the ankle joints in full dorsiflexion; (2) on an unstable surface created by placing a 65-cm diameter exercise ball under the ankle joints in full plantarflexion; (3) on a stable surface created by placing a bench with a height of a 65-cm under the ankle joints in full dorsiflexion; and (4) on a stable surface created by placing a bench with a height of 65-cm under the ankle joints in full plantarflexion. To prevent bias, the exercise conditions were randomly arranged. [Results] Muscle activities were compared among the four different conditions. The erector spinae, rectus abdominis, external oblique abdominal, serratus anterior, deltoid middle fiber, and triceps brachii muscles showed significant differences among the four conditions. [Conclusion] These differences may have been resulted from increased trunk and shoulder muscle activations during push-up exercise with full ankle dorsiflexion on unstable ground.
