Variable, but not free-weight, loaded countermovement jump exercise potentiates jump performance following a comprehensive task-specific warm-up

IntroductionThe inclusion of maximal or sub-maximal muscle actions using elastic bands (EB) in combination with free-weight (FW) resistance can manipulate the loading characteristics of these actions. When performed during a warm-up, short-term increases in force production to further augment performance can occur, a state often referred to as post-activation potentiation. However, these improvements are often reported after limited or no warm-up was imposed. Our aim was to examine the influence of EB resistance following a comprehensive warm-up on subsequent countermovement jump (CMJ) performance.MethodsFifteen active men (age = 21.7 ± 1.1 y, height = 1.8 ± 0.1 m, mass = 77.6 ± 2.6 kg) volunteered for the study. On two separate occasions, participants performed a comprehensive warm-up of 5 min cycling, 10 continuous unloaded squats, 5 continuous CMJs at ~70% of maximum, then maximal jumps were performed every 30 s until 3 jumps were within 3% of maximum jump height. Participants then performed 5 repetitions of either EB- or FW-loaded CMJs at 50% 1-RM (35% of load generated from elastic resistance during EB). CMJs were then performed 30 s, 4 min, 8 min, and 12 min later. During CMJs, motion analysis and two force platforms recorded kinematic and kinetic data, with vastus lateralis, vastus medialis, gluteus maximus, and gastrocnemius medialis electromyograms (EMG) recorded simultaneously.ResultsSignificant increases in CMJ height (4.6-8.0%), net impulse (2.1-3.7%), peak power (3.9-5.0%), and peak eccentric kinetic energy (10.0-11.5%) were observed at 30 s and 4 min after EB; no changes were found at 8 min and 12 min. No difference in knee angular velocity, knee flexion angle, rate of force development or EMG activity were found at any time point. No changes were observed in FW.DiscussionThe lack of change in jump performance in FW suggests that the comprehensive warm-up potentiated the neuromuscular system such that subsequent FW contractions provide no further improvement in CMJ performance. Nonetheless, CMJ performance was significantly increased following EB at 30 s and 4 min, with increases in force production consistent with the changes in CMJ height. A number of mechanisms relating to stretch-shorten cycle efficiency may have contributed to the increase in CMJ height, including a more rapid muscle stretch resulting from force potentiation and greater elastic energy storage in the muscle. Regardless of the mechanism, elastic band use may enhance athletic performance even when a full warm-up is completed.