Play is a range of intrinsically motivated activities done for recreational pleasure and enjoyment.Play is commonly associated with children and juvenile-level activities, but play occurs at any life stage, and among other higher-functioning animals as well, most notably mammals.
Many prominent researchers in the field of psychology, including Melanie Klein, Jean Piaget, William James, Sigmund Freud, Carl Jung and Lev Vygotsky have viewed play as confined to the human species, believing play was important for human development .
The TRX System, also known as Total Resistance Exercises, refers to a specialized form of suspension training that utilizes equipment developed by former U.S. Navy SEAL Randy Hetrick. TRX is a form of suspension training that uses body weight exercises to develop strength, balance, flexibility and core stability simultaneously. It requires the use of the TRX Suspension Trainer, a performance training tool that leverages gravity and the user’s body weight to complete the exercises. TRX's designers claim that it draws on research from the military, pro sports, and academic institutions along with experience gathered from the TRX team, who work "with thousands of athletes, coaches, trainers, first responders, subject matter experts, professors, and service members in all branches.
Supporters of TRX Training claim that it can improve mobility and stability, increase metabolic results, build lean muscle, and develop functional strength. Other advocates of the system say that you can't help but use your core for stabilization.