Comparison of Countermovement Jump Strategy With and Without An Arm Swing

The countermovement jump (CMJ) is commonly used to assess both acute neuromuscular performance as well as adaptions to periods of training. Two methodologies are typically employed when performing the CMJ assessment. The first allows for the use of an arm swing (AS) to add a level of sport-specificity to the testing. The second restricts the movement of the arms (NAS) to allow for an assessment of the musculature of only the lower body. Thus, the purpose of this investigation was to examine differences in jump strategy between the two methodologies. Twenty-five female Division I collegiate athletes (volleyball = 13, beach volleyball = 12) participated in this investigation. Participants performed two CMJ in both the AS and NAS conditions. A paired samples t-test was used to evaluate differences in jump performance and jump strategy variables. During the braking phase of the CMJ statistical higher force values (p < 0.01) were seen in the NAS condition while longer phase durations were present in the AS condition (p < 0.001). No difference was seen in braking net impulse. During the propulsive phase statistically greater duration was seen in the AS condition (p < 0.001) leading to a greater propulsive net impulse (p < 0.001). The AS condition also displayed greater jump heights, countermovement depth and time to take off durations (p < 0.001) with no differences in reactive strength index modified. When performing CMJ assessments practitioners should consider which methodology they use carefully as the NAS assessment used a more force driven strategy while the AS used a time driven strategy.