Effects of physical fatigue and cognitive challenges on the potential for low back injury

There is no question that the motor control system will adapt under fatiguing conditions; however, there is documented evidence showing that when fatigued or challenged, the motor control system will, on occasion, perform inappropriate muscle sequencing, increasing the risk of injury, or directly causing injury. Knowing that inappropriate muscle activations can lead to injury, the purpose of this study was to investigate motor patterns during cognitive and physical challenges. Rather than ensure change with severe challenges, milder challenges were purposefully chosen. Eight male subjects performed a low external load task performed near end ROM while in an unchallenged state, and while in three challenged states: passive tissue creep, muscle fatigue and cognitive distraction. Data were collected using EMG of the trunk muscles and angular displacement of the lumbar spine. Comparison of motor control patterns between the unchallenged state and each of the three challenged conditions showed no systematic differences. However, several random anomalies were observed. A case study of a single subject was chosen to show inappropriate motor control during one trial under the cognitive distraction conditions. The response of the motor control system is very individualized and does on occasion produce inappropriate motor patterns. This supports the notion that injury may also occur as the result of random motor control errors as well as predictable, systematic changes.