Bands reduce the release of force during the deadlift
Multi-joint exercises with free weights for large muscles, such as deadlifts and bench presses, provide constant resistance during the movement, but athletes may release more force at the end of the range of motion due to an increased mechanical advantage. Many athletes use bands and chains to increase resistance at the end of the range of motion of these exercises.
Andrew Galpin and colleagues from California State University, Fullerton studied strength and power during deadlifts with and without bands. Bands increased power and speed during the deadlift, but reduced strength. Bands are appropriate during deadlifts if the goal is to increase power, but free weights without bands would be more appropriate if the goal is to develop maximal strength.
Vertical jumps and 10 and 30 meter sprints look strongly related to pulling strength, which is why most power athletes should stick with traditional deadlifting.
(Journal Strenght Conditioning Research, 29: 3271 - 3278, 2016)