Effect of Training Status on Muscle Length Change During Jumping

The purpose of this investigation was to utilize a novel technique involving the insertion of a Fiber Bragg Grading (FBG) sensor through the patellar tendon to determine changes in tendon length. It has been speculated that muscle tendon unit (MTU) function differs between trained and untrained individuals, effecting concentric performance. One trained and one untrained individual reported to the laboratory one time. Each subject performed three individual CMJ before and after 20 sequential jumps to determine changes in MTU function due to fatigue. A visual ultrasound was used to determine muscle length and a FBG sensor was used to determine tendon length. The trained subject had an 11.2% increase in peak force, a 2.3% increase in jump height, a 25% decrease in tendon length change, and a 50% increase in muscle length change after 20 CMJ. The untrained subject had a 3.4% decrease in peak force, a 7.5% decrease in jump height, a 94% decrease in tendon length change, and a 50% decrease in muscle length change after 20 CMJ. This indicates that a trained individual is better able to maintain muscle length during jumping, influencing performance. Training status may influence performance by varying the function of the MTU.