This is the 14576th most frequent German word.
lockert
"Lockert" means "loosens" or "relaxes" in English.
Here, 'lockert' conveys the act of 'making less strict or stringent', applied to rules or guidelines. It shows the action performed by the coach.
Der Trainer lockert die Regeln, damit die Spieler mehr Freiheit haben.
The coach relaxes the rules so that the players have more freedom.
In this example, 'lockert' pertains to the easing or relaxation of tension, specifically the tension in a muscle.
Nach der Arbeit lockert sich der Muskel dank der Massage.
After work, the muscle relaxes thanks to the massage.
This usage of 'lockert' refers to 'making a grip less tight or firm', indicating a physical interaction.