Warming up

Athletes, singers, actors and others warm up before stressing their muscles.

For example, before running or playing an intensive sport, athletes might slowly jog to warm their muscles and increase their heart rate.

Stretching is part of some warm-up routines, although a study in 2013 indicates that it weakens muscles in that situation.

[1] There are 3 types of stretches: ballistic, dynamic, and static: Psychologists, educators, singers, and similar professionals use warm-ups in therapeutic or learning sessions before starting or after a break; these warm-ups can include vocal and physical exercises, interactive and improvisational games, role plays, etc.

[5] It has been suggested that it is specifically warm ups aimed at increasing body temperature, rather than targeting stretching, which can prevent injury.

Players of Legends Football League do a warm-up exercise, US
Swimmers perform squats prior to entering the pool in a U.S. military base, 2011
Steven Gerrard warming up prior to a football match in 2010.
A group of High School girls performing a ballistic stretch in a Physical Education session