Tennis movement can be characterized by primarily short lateral bursts over typically 3-4 m initiated by a reactive decision step. Lateral acceleration depends on unilateral movement, or specifically, the outside leg to enhance ground reaction force (GRF). Few studies have been conducted for the development of lateral speed with emphasis on unilateral training. A simple one-leg test for unilateral strength is presented. Exercises for improving lateral acceleration are presented.
The NASA Exploration Initiative provides a defining vision for the U.S. space program and an implementation of U.S. policy that will include a series of human and robotic missions to the Moon with a goal to thereby enabling ultimate exploration of Mars and other destinations. The success of this initiative will rest on the foundation of the initial lunar missions and the ability to develop the means for a sustained human presence on the moon.. These missions can be aided and enabled by a navigation and communication infrastructure that can evolve in capability to support lunar operations and data collection. This paper describes a system concept for evolving a lunar navigation/communication infrastructure (LNCI). The described approach uses small spacecraft that are capable of launch as auxiliary payloads. The mission concept is detailed, including spacecraft design, payload concepts and performance estimates for navigation precision and communications coverage. A complete lunar infrastructure would provide global, persistent highprecision navigation and full communications connectivity among lunar elements and the Earth. Detailed herein is an approach for implementation of a prototype LNCI system that would provide navigation and communication services to near-term RLEP missions (e.g., RLEP2 through RLEP4) and demonstrate the LNCI concept such that sustainment of the capability could be transitioned to NASA operational elements and/or industry. The system consists of four small, cost-effective spacecraft that provide radio frequency (RF)-based navigation and communication services from polar orbits. The system concept is designed to evolve by providing improved navigation accuracy and increased communication coverage and bandwidth as additional spacecraft supplement the infrastructure.
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