What type of training involves muscles developing tension without changing length?

Isometric training is characterized by muscle contractions that occur without any change in the length of the muscle. During isometric exercises, the muscle generates tension while remaining in a static position, meaning that there is no movement of the joint. This type of training is effective for building strength and endurance, particularly in a specific position.

For instance, exercises like wall sits or plank holds exemplify isometric training, as the muscles are actively engaged to hold a position but do not elongate or shorten during the process. This unique aspect makes isometric training beneficial for improving stability and strength in certain postures, which can enhance overall performance in various activities and sports.

The other training types listed do not fit this definition. Aerobic training is centered on activities that build cardiovascular fitness and typically involve rhythmic movements that lengthen and shorten muscles. Plyometric training emphasizes explosive movements that involve both eccentric (lengthening) and concentric (shortening) muscle actions, while flexibility training focuses on increasing the range of motion in muscles and joints through movements that involve changes in length.