A plateau has trapped you. Losing weight, growing stronger, or improving strength stops. Repeating the same activity and expecting different outcomes is lunacy.
You get bored and find other things to do than workout. Doing the same thing over might be monotonous.
You have persistent pain or injury. Repeating a workout regimen might develop overuse problems. Overtraining can also result from excessive high-intensity activity without enough recuperation.
Exercise seems more like a duty than a pleasurable, leisurely pastime. We played for hours as kids because it was entertaining and offered new challenges.
You feel like you're always at the gym. Bodybuilder-style split routines target one body portion or muscle group.
Research suggests an alternative workout method that may yield better outcomes. Long, gradual distance training was the norm for cardiorespiratory exercise years ago.